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commit 2decad92f4731fac9755a083fcfefa66edb7d67d upstream.
The entry from EL0 code checks the TFSRE0_EL1 register for any
asynchronous tag check faults in user space and sets the
TIF_MTE_ASYNC_FAULT flag. This is not done atomically, potentially
racing with another CPU calling set_tsk_thread_flag().
Replace the non-atomic ORR+STR with an STSET instruction. While STSET
requires ARMv8.1 and an assembler that understands LSE atomics, the MTE
feature is part of ARMv8.5 and already requires an updated assembler.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Fixes: 637ec831ea4f ("arm64: mte: Handle synchronous and asynchronous tag check faults")
Cc: <stable@vger.kernel.org> # 5.10.x
Reported-by: Will Deacon <will@kernel.org>
Cc: Will Deacon <will@kernel.org>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20210409173710.18582-1-catalin.marinas@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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[ Upstream commit 1d676673d665fd2162e7e466dcfbe5373bfdb73e ]
Currently we advertise the ID_AA6DFR0_EL1.TRACEVER for the guest,
when the trace register accesses are trapped (CPTR_EL2.TTA == 1).
So, the guest will get an undefined instruction, if trusts the
ID registers and access one of the trace registers.
Lets be nice to the guest and hide the feature to avoid
unexpected behavior.
Even though this can be done at KVM sysreg emulation layer,
we do this by removing the TRACEVER from the sanitised feature
register field. This is fine as long as the ETM drivers
can handle the individual trace units separately, even
when there are differences among the CPUs.
Cc: Will Deacon <will@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210323120647.454211-2-suzuki.poulose@arm.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
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[ Upstream commit 141f8202cfa4192c3af79b6cbd68e7760bb01b5a ]
The ppos points to a position in the old kernel memory (and in case of
arm64 in the crash kernel since elfcorehdr is passed as a segment). The
function should update the ppos by the amount that was read. This bug is
not exposed by accident, but other platforms update this value properly.
So, fix it in ARM64 version of elfcorehdr_read() as well.
Signed-off-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Fixes: e62aaeac426a ("arm64: kdump: provide /proc/vmcore file")
Reviewed-by: Tyler Hicks <tyhicks@linux.microsoft.com>
Link: https://lore.kernel.org/r/20210319205054.743368-1-pasha.tatashin@soleen.com
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
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commit c607ab4f916d4d5259072eca34055d3f5a795c21 upstream.
We recently converted arm64 to use arch_stack_walk() in commit:
5fc57df2f6fd ("arm64: stacktrace: Convert to ARCH_STACKWALK")
The core stacktrace code expects that (when tracing the current task)
arch_stack_walk() starts a trace at its caller, and does not include
itself in the trace. However, arm64's arch_stack_walk() includes itself,
and so traces include one more entry than callers expect. The core
stacktrace code which calls arch_stack_walk() tries to skip a number of
entries to prevent itself appearing in a trace, and the additional entry
prevents skipping one of the core stacktrace functions, leaving this in
the trace unexpectedly.
We can fix this by having arm64's arch_stack_walk() begin the trace with
its caller. The first value returned by the trace will be
__builtin_return_address(0), i.e. the caller of arch_stack_walk(). The
first frame record to be unwound will be __builtin_frame_address(1),
i.e. the caller's frame record. To prevent surprises, arch_stack_walk()
is also marked noinline.
While __builtin_frame_address(1) is not safe in portable code, local GCC
developers have confirmed that it is safe on arm64. To find the caller's
frame record, the builtin can safely dereference the current function's
frame record or (in theory) could stash the original FP into another GPR
at function entry time, neither of which are problematic.
Prior to this patch, the tracing code would unexpectedly show up in
traces of the current task, e.g.
| # cat /proc/self/stack
| [<0>] stack_trace_save_tsk+0x98/0x100
| [<0>] proc_pid_stack+0xb4/0x130
| [<0>] proc_single_show+0x60/0x110
| [<0>] seq_read_iter+0x230/0x4d0
| [<0>] seq_read+0xdc/0x130
| [<0>] vfs_read+0xac/0x1e0
| [<0>] ksys_read+0x6c/0xfc
| [<0>] __arm64_sys_read+0x20/0x30
| [<0>] el0_svc_common.constprop.0+0x60/0x120
| [<0>] do_el0_svc+0x24/0x90
| [<0>] el0_svc+0x2c/0x54
| [<0>] el0_sync_handler+0x1a4/0x1b0
| [<0>] el0_sync+0x170/0x180
After this patch, the tracing code will not show up in such traces:
| # cat /proc/self/stack
| [<0>] proc_pid_stack+0xb4/0x130
| [<0>] proc_single_show+0x60/0x110
| [<0>] seq_read_iter+0x230/0x4d0
| [<0>] seq_read+0xdc/0x130
| [<0>] vfs_read+0xac/0x1e0
| [<0>] ksys_read+0x6c/0xfc
| [<0>] __arm64_sys_read+0x20/0x30
| [<0>] el0_svc_common.constprop.0+0x60/0x120
| [<0>] do_el0_svc+0x24/0x90
| [<0>] el0_svc+0x2c/0x54
| [<0>] el0_sync_handler+0x1a4/0x1b0
| [<0>] el0_sync+0x170/0x180
Erring on the side of caution, I've given this a spin with a bunch of
toolchains, verifying the output of /proc/self/stack and checking that
the assembly looked sound. For GCC (where we require version 5.1.0 or
later) I tested with the kernel.org crosstool binares for versions
5.5.0, 6.4.0, 6.5.0, 7.3.0, 7.5.0, 8.1.0, 8.3.0, 8.4.0, 9.2.0, and
10.1.0. For clang (where we require version 10.0.1 or later) I tested
with the llvm.org binary releases of 11.0.0, and 11.0.1.
Fixes: 5fc57df2f6fd ("arm64: stacktrace: Convert to ARCH_STACKWALK")
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chen Jun <chenjun102@huawei.com>
Cc: Marco Elver <elver@google.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Will Deacon <will@kernel.org>
Cc: <stable@vger.kernel.org> # 5.10.x
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20210319184106.5688-1-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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[ Upstream commit 7ba8f2b2d652cd8d8a2ab61f4be66973e70f9f88 ]
52-bit VA kernels can run on hardware that is only 48-bit capable, but
configure the ID map as 52-bit by default. This was not a problem until
recently, because the special T0SZ value for a 52-bit VA space was never
programmed into the TCR register anwyay, and because a 52-bit ID map
happens to use the same number of translation levels as a 48-bit one.
This behavior was changed by commit 1401bef703a4 ("arm64: mm: Always update
TCR_EL1 from __cpu_set_tcr_t0sz()"), which causes the unsupported T0SZ
value for a 52-bit VA to be programmed into TCR_EL1. While some hardware
simply ignores this, Mark reports that Amberwing systems choke on this,
resulting in a broken boot. But even before that commit, the unsupported
idmap_t0sz value was exposed to KVM and used to program TCR_EL2 incorrectly
as well.
Given that we already have to deal with address spaces being either 48-bit
or 52-bit in size, the cleanest approach seems to be to simply default to
a 48-bit VA ID map, and only switch to a 52-bit one if the placement of the
kernel in DRAM requires it. This is guaranteed not to happen unless the
system is actually 52-bit VA capable.
Fixes: 90ec95cda91a ("arm64: mm: Introduce VA_BITS_MIN")
Reported-by: Mark Salter <msalter@redhat.com>
Link: http://lore.kernel.org/r/20210310003216.410037-1-msalter@redhat.com
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20210310171515.416643-2-ardb@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
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commit 7bb8bc6eb550116c504fb25af8678b9d7ca2abc5 upstream.
Commit 0fdf1bb75953 ("arm64: perf: Avoid PMXEV* indirection") changed
armv8pmu_read_evcntr() to return a u32 instead of u64. The result is
silent truncation of the event counter when using 64-bit counters. Given
the offending commit appears to have passed thru several folks, it seems
likely this was a bad rebase after v8.5 PMU 64-bit counters landed.
Cc: Alexandru Elisei <alexandru.elisei@arm.com>
Cc: Julien Thierry <julien.thierry.kdev@gmail.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: <stable@vger.kernel.org>
Fixes: 0fdf1bb75953 ("arm64: perf: Avoid PMXEV* indirection")
Signed-off-by: Rob Herring <robh@kernel.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Alexandru Elisei <alexandru.elisei@arm.com>
Link: https://lore.kernel.org/r/20210310004412.1450128-1-robh@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit a2c42bbabbe260b7626d8459093631a6e16ee0ee upstream.
The Spectre-v4 workaround is re-configured when resuming from suspend,
as the firmware may have re-enabled the mitigation despite the user
previously asking for it to be disabled.
Enabling or disabling the workaround can result in an undefined
instruction exception on CPUs which implement PSTATE.SSBS but only allow
it to be configured by adjusting the SPSR on exception return. We handle
this by installing an 'undef hook' which effectively emulates the access.
Installing this hook requires us to take a couple of spinlocks both to
avoid corrupting the internal list of hooks but also to ensure that we
don't run into an unhandled exception. Unfortunately, when resuming from
suspend, we haven't yet called rcu_idle_exit() and so lockdep gets angry
about "suspicious RCU usage". In doing so, it tries to print a warning,
which leads it to get even more suspicious, this time about itself:
| rcu_scheduler_active = 2, debug_locks = 1
| RCU used illegally from extended quiescent state!
| 1 lock held by swapper/0:
| #0: (logbuf_lock){-.-.}-{2:2}, at: vprintk_emit+0x88/0x198
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| Call trace:
| dump_backtrace+0x0/0x1d8
| show_stack+0x18/0x24
| dump_stack+0xe0/0x17c
| lockdep_rcu_suspicious+0x11c/0x134
| trace_lock_release+0xa0/0x160
| lock_release+0x3c/0x290
| _raw_spin_unlock+0x44/0x80
| vprintk_emit+0xbc/0x198
| vprintk_default+0x44/0x6c
| vprintk_func+0x1f4/0x1fc
| printk+0x54/0x7c
| lockdep_rcu_suspicious+0x30/0x134
| trace_lock_acquire+0xa0/0x188
| lock_acquire+0x50/0x2fc
| _raw_spin_lock+0x68/0x80
| spectre_v4_enable_mitigation+0xa8/0x30c
| __cpu_suspend_exit+0xd4/0x1a8
| cpu_suspend+0xa0/0x104
| psci_cpu_suspend_enter+0x3c/0x5c
| psci_enter_idle_state+0x44/0x74
| cpuidle_enter_state+0x148/0x2f8
| cpuidle_enter+0x38/0x50
| do_idle+0x1f0/0x2b4
Prevent these splats by running __cpu_suspend_exit() with RCU watching.
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Saravana Kannan <saravanak@google.com>
Suggested-by: "Paul E . McKenney" <paulmck@kernel.org>
Reported-by: Sami Tolvanen <samitolvanen@google.com>
Fixes: c28762070ca6 ("arm64: Rewrite Spectre-v4 mitigation code")
Cc: <stable@vger.kernel.org>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Acked-by: Marc Zyngier <maz@kernel.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20210218140346.5224-1-will@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit d47422d953e258ad587b5edf2274eb95d08bdc7d upstream.
As stated in linux/errno.h, ENOTSUPP should never be seen by user programs.
When we set up uprobe with 32-bit perf and arm64 kernel, we would see the
following vague error without useful hint.
The sys_perf_event_open() syscall returned with 524 (INTERNAL ERROR:
strerror_r(524, [buf], 128)=22)
Use EOPNOTSUPP instead to indicate such cases.
Signed-off-by: He Zhe <zhe.he@windriver.com>
Link: https://lore.kernel.org/r/20210223082535.48730-1-zhe.he@windriver.com
Cc: <stable@vger.kernel.org>
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 656d1d58d8e0958d372db86c24f0b2ea36f50888 upstream.
in function create_dtb(), if fdt_open_into() fails, we need to vfree
buf before return.
Fixes: 52b2a8af7436 ("arm64: kexec_file: load initrd and device-tree")
Cc: stable@vger.kernel.org # v5.0
Signed-off-by: qiuguorui1 <qiuguorui1@huawei.com>
Link: https://lore.kernel.org/r/20210218125900.6810-1-qiuguorui1@huawei.com
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit c0b15c25d25171db4b70cc0b7dbc1130ee94017d upstream.
The erratum 1024718 affects Cortex-A55 r0p0 to r2p0. However
we apply the work around for r0p0 - r1p0. Unfortunately this
won't be fixed for the future revisions for the CPU. Thus
extend the work around for all versions of A55, to cover
for r2p0 and any future revisions.
Cc: stable@vger.kernel.org
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: James Morse <james.morse@arm.com>
Cc: Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20210203230057.3961239-1-suzuki.poulose@arm.com
[will: Update Kconfig help text]
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit df84fe94708985cdfb78a83148322bcd0a699472 upstream.
Since commit f086f67485c5 ("arm64: ptrace: add support for syscall
emulation"), if system call number -1 is called and the process is being
traced with PTRACE_SYSCALL, for example by strace, the seccomp check is
skipped and -ENOSYS is returned unconditionally (unless altered by the
tracer) rather than carrying out action specified in the seccomp filter.
The consequence of this is that it is not possible to reliably strace
a seccomp based implementation of a foreign system call interface in
which r7/x8 is permitted to be -1 on entry to a system call.
Also trace_sys_enter and audit_syscall_entry are skipped if a system
call is skipped.
Fix by removing the in_syscall(regs) check restoring the previous
behaviour which is like AArch32, x86 (which uses generic code) and
everything else.
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Catalin Marinas<catalin.marinas@arm.com>
Cc: <stable@vger.kernel.org>
Fixes: f086f67485c5 ("arm64: ptrace: add support for syscall emulation")
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
Tested-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Timothy E Baldwin <T.E.Baldwin99@members.leeds.ac.uk>
Link: https://lore.kernel.org/r/90edd33b-6353-1228-791f-0336d94d5f8c@majoroak.me.uk
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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[ Upstream commit 9d41053e8dc115c92b8002c3db5f545d7602498b ]
Although there has been a bit of back and forth on the subject, it
appears that invalidating TLBs requires an ISB instruction when FEAT_ETS
is not implemented by the CPU.
From the bible:
| In an implementation that does not implement FEAT_ETS, a TLB
| maintenance instruction executed by a PE, PEx, can complete at any
| time after it is issued, but is only guaranteed to be finished for a
| PE, PEx, after the execution of DSB by the PEx followed by a Context
| synchronization event
Add the missing ISB in __primary_switch, just in case.
Fixes: 3c5e9f238bc4 ("arm64: head.S: move KASLR processing out of __enable_mmu()")
Suggested-by: Will Deacon <will@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20210224093738.3629662-3-maz@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
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commit 68d54ceeec0e5fee4fb8048e6a04c193f32525ca upstream.
The ptrace(PTRACE_PEEKMTETAGS) implementation checks whether the user
page has valid tags (mapped with PROT_MTE) by testing the PG_mte_tagged
page flag. If this bit is cleared, ptrace(PTRACE_PEEKMTETAGS) returns
-EIO.
A newly created (PROT_MTE) mapping points to the zero page which had its
tags zeroed during cpu_enable_mte(). If there were no prior writes to
this mapping, ptrace(PTRACE_PEEKMTETAGS) fails with -EIO since the zero
page does not have the PG_mte_tagged flag set.
Set PG_mte_tagged on the zero page when its tags are cleared during
boot. In addition, to avoid ptrace(PTRACE_PEEKMTETAGS) succeeding on
!PROT_MTE mappings pointing to the zero page, change the
__access_remote_tags() check to (vm_flags & VM_MTE) instead of
PG_mte_tagged.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Fixes: 34bfeea4a9e9 ("arm64: mte: Clear the tags when a page is mapped in user-space with PROT_MTE")
Cc: <stable@vger.kernel.org> # 5.10.x
Cc: Will Deacon <will@kernel.org>
Reported-by: Luis Machado <luis.machado@linaro.org>
Tested-by: Luis Machado <luis.machado@linaro.org>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Link: https://lore.kernel.org/r/20210210180316.23654-1-catalin.marinas@arm.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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[ Upstream commit df06824767cc9a32fbdb0e3d3b7e169292a5b5fe ]
All EL0 returns go via ret_to_user(), which masks IRQs and notifies
lockdep and tracing before calling into do_notify_resume(). Therefore,
there's no need for do_notify_resume() to call trace_hardirqs_off(), and
the comment is stale. The call is simply redundant.
In ret_to_user() we call exit_to_user_mode(), which notifies lockdep and
tracing the IRQs will be enabled in userspace, so there's no need for
el0_svc_common() to call trace_hardirqs_on() before returning. Further,
at the start of ret_to_user() we call trace_hardirqs_off(), so not only
is this redundant, but it is immediately undone.
In addition to being redundant, the trace_hardirqs_on() in
el0_svc_common() leaves lockdep inconsistent with the hardware state,
and is liable to cause issues for any C code or instrumentation
between this and the call to trace_hardirqs_off() which undoes it in
ret_to_user().
This patch removes the redundant tracing calls and associated stale
comments.
Fixes: 23529049c684 ("arm64: entry: fix non-NMI user<->kernel transitions")
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Will Deacon <will@kernel.org>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20210107145310.44616-1-mark.rutland@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
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commit 45ba7b195a369f35cb39094fdb32efe5908b34ad upstream.
Commit d82755b2e781 ("KVM: arm64: Kill off CONFIG_KVM_ARM_HOST") deletes
CONFIG_KVM_ARM_HOST option, it should use CONFIG_KVM instead.
Just remove CONFIG_KVM_ARM_HOST here.
Fixes: d82755b2e781 ("KVM: arm64: Kill off CONFIG_KVM_ARM_HOST")
Signed-off-by: Shannon Zhao <shannon.zhao@linux.alibaba.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/1609760324-92271-1-git-send-email-shannon.zhao@linux.alibaba.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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[ Upstream commit 929c1f3384d7e5cd319d03242cb925c3f91236f7 ]
Previously we were always returning a tag inclusion mask of zero via
PR_GET_TAGGED_ADDR_CTRL if TCF0 was set to NONE. Fix it by making
the code for the NONE case match the others.
Signed-off-by: Peter Collingbourne <pcc@google.com>
Link: https://linux-review.googlesource.com/id/Iefbea66cf7d2b4c80b82f9639b9ea7f33f7fac53
Fixes: af5ce95282dc ("arm64: mte: Allow user control of the generated random tags via prctl()")
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20201203075110.2781021-1-pcc@google.com
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux
Pull arm64 fixes from Will Deacon:
"I'm sad to say that we've got an unusually large arm64 fixes pull for
rc7 which addresses numerous significant instrumentation issues with
our entry code.
Without these patches, lockdep is hopelessly unreliable in some
configurations [1,2] and syzkaller is therefore not a lot of use
because it's so noisy.
Although much of this has always been broken, it appears to have been
exposed more readily by other changes such as 044d0d6de9f5 ("lockdep:
Only trace IRQ edges") and general lockdep improvements around IRQ
tracing and NMIs.
Fixing this properly required moving much of the instrumentation hooks
from our entry assembly into C, which Mark has been working on for the
last few weeks. We're not quite ready to move to the recently added
generic functions yet, but the code here has been deliberately written
to mimic that closely so we can look at cleaning things up once we
have a bit more breathing room.
Having said all that, the second version of these patches was posted
last week and I pushed it into our CI (kernelci and cki) along with a
commit which forced on PROVE_LOCKING, NOHZ_FULL and
CONTEXT_TRACKING_FORCE. The result? We found a real bug in the
md/raid10 code [3].
Oh, and there's also a really silly typo patch that's unrelated.
Summary:
- Fix numerous issues with instrumentation and exception entry
- Fix hideous typo in unused register field definition"
[1] https://lore.kernel.org/r/CACT4Y+aAzoJ48Mh1wNYD17pJqyEcDnrxGfApir=-j171TnQXhw@mail.gmail.com
[2] https://lore.kernel.org/r/20201119193819.GA2601289@elver.google.com
[3] https://lore.kernel.org/r/94c76d5e-466a-bc5f-e6c2-a11b65c39f83@redhat.com
* tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux:
arm64: mte: Fix typo in macro definition
arm64: entry: fix EL1 debug transitions
arm64: entry: fix NMI {user, kernel}->kernel transitions
arm64: entry: fix non-NMI kernel<->kernel transitions
arm64: ptrace: prepare for EL1 irq/rcu tracking
arm64: entry: fix non-NMI user<->kernel transitions
arm64: entry: move el1 irq/nmi logic to C
arm64: entry: prepare ret_to_user for function call
arm64: entry: move enter_from_user_mode to entry-common.c
arm64: entry: mark entry code as noinstr
arm64: mark idle code as noinstr
arm64: syscall: exit userspace before unmasking exceptions
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In debug_exception_enter() and debug_exception_exit() we trace hardirqs
on/off while RCU isn't guaranteed to be watching, and we don't save and
restore the hardirq state, and so may return with this having changed.
Handle this appropriately with new entry/exit helpers which do the bare
minimum to ensure this is appropriately maintained, without marking
debug exceptions as NMIs. These are placed in entry-common.c with the
other entry/exit helpers.
In future we'll want to reconsider whether some debug exceptions should
be NMIs, but this will require a significant refactoring, and for now
this should prevent issues with lockdep and RCU.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marins <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20201130115950.22492-12-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
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Exceptions which can be taken at (almost) any time are consdiered to be
NMIs. On arm64 that includes:
* SDEI events
* GICv3 Pseudo-NMIs
* Kernel stack overflows
* Unexpected/unhandled exceptions
... but currently debug exceptions (BRKs, breakpoints, watchpoints,
single-step) are not considered NMIs.
As these can be taken at any time, kernel features (lockdep, RCU,
ftrace) may not be in a consistent kernel state. For example, we may
take an NMI from the idle code or partway through an entry/exit path.
While nmi_enter() and nmi_exit() handle most of this state, notably they
don't save/restore the lockdep state across an NMI being taken and
handled. When interrupts are enabled and an NMI is taken, lockdep may
see interrupts become disabled within the NMI code, but not see
interrupts become enabled when returning from the NMI, leaving lockdep
believing interrupts are disabled when they are actually disabled.
The x86 code handles this in idtentry_{enter,exit}_nmi(), which will
shortly be moved to the generic entry code. As we can't use either yet,
we copy the x86 approach in arm64-specific helpers. All the NMI
entrypoints are marked as noinstr to prevent any instrumentation
handling code being invoked before the state has been corrected.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20201130115950.22492-11-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
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There are periods in kernel mode when RCU is not watching and/or the
scheduler tick is disabled, but we can still take exceptions such as
interrupts. The arm64 exception handlers do not account for this, and
it's possible that RCU is not watching while an exception handler runs.
The x86/generic entry code handles this by ensuring that all (non-NMI)
kernel exception handlers call irqentry_enter() and irqentry_exit(),
which handle RCU, lockdep, and IRQ flag tracing. We can't yet move to
the generic entry code, and already hadnle the user<->kernel transitions
elsewhere, so we add new kernel<->kernel transition helpers alog the
lines of the generic entry code.
Since we now track interrupts becoming masked when an exception is
taken, local_daif_inherit() is modified to track interrupts becoming
re-enabled when the original context is inherited. To balance the
entry/exit paths, each handler masks all DAIF exceptions before
exit_to_kernel_mode().
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20201130115950.22492-10-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
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When built with PROVE_LOCKING, NO_HZ_FULL, and CONTEXT_TRACKING_FORCE
will WARN() at boot time that interrupts are enabled when we call
context_tracking_user_enter(), despite the DAIF flags indicating that
IRQs are masked.
The problem is that we're not tracking IRQ flag changes accurately, and
so lockdep believes interrupts are enabled when they are not (and
vice-versa). We can shuffle things so to make this more accurate. For
kernel->user transitions there are a number of constraints we need to
consider:
1) When we call __context_tracking_user_enter() HW IRQs must be disabled
and lockdep must be up-to-date with this.
2) Userspace should be treated as having IRQs enabled from the PoV of
both lockdep and tracing.
3) As context_tracking_user_enter() stops RCU from watching, we cannot
use RCU after calling it.
4) IRQ flag tracing and lockdep have state that must be manipulated
before RCU is disabled.
... with similar constraints applying for user->kernel transitions, with
the ordering reversed.
The generic entry code has enter_from_user_mode() and
exit_to_user_mode() helpers to handle this. We can't use those directly,
so we add arm64 copies for now (without the instrumentation markers
which aren't used on arm64). These replace the existing user_exit() and
user_exit_irqoff() calls spread throughout handlers, and the exception
unmasking is left as-is.
Note that:
* The accounting for debug exceptions from userspace now happens in
el0_dbg() and ret_to_user(), so this is removed from
debug_exception_enter() and debug_exception_exit(). As
user_exit_irqoff() wakes RCU, the userspace-specific check is removed.
* The accounting for syscalls now happens in el0_svc(),
el0_svc_compat(), and ret_to_user(), so this is removed from
el0_svc_common(). This does not adversely affect the workaround for
erratum 1463225, as this does not depend on any of the state tracking.
* In ret_to_user() we mask interrupts with local_daif_mask(), and so we
need to inform lockdep and tracing. Here a trace_hardirqs_off() is
sufficient and safe as we have not yet exited kernel context and RCU
is usable.
* As PROVE_LOCKING selects TRACE_IRQFLAGS, the ifdeferry in entry.S only
needs to check for the latter.
* EL0 SError handling will be dealt with in a subsequent patch, as this
needs to be treated as an NMI.
Prior to this patch, booting an appropriately-configured kernel would
result in spats as below:
| DEBUG_LOCKS_WARN_ON(lockdep_hardirqs_enabled())
| WARNING: CPU: 2 PID: 1 at kernel/locking/lockdep.c:5280 check_flags.part.54+0x1dc/0x1f0
| Modules linked in:
| CPU: 2 PID: 1 Comm: init Not tainted 5.10.0-rc3 #3
| Hardware name: linux,dummy-virt (DT)
| pstate: 804003c5 (Nzcv DAIF +PAN -UAO -TCO BTYPE=--)
| pc : check_flags.part.54+0x1dc/0x1f0
| lr : check_flags.part.54+0x1dc/0x1f0
| sp : ffff80001003bd80
| x29: ffff80001003bd80 x28: ffff66ce801e0000
| x27: 00000000ffffffff x26: 00000000000003c0
| x25: 0000000000000000 x24: ffffc31842527258
| x23: ffffc31842491368 x22: ffffc3184282d000
| x21: 0000000000000000 x20: 0000000000000001
| x19: ffffc318432ce000 x18: 0080000000000000
| x17: 0000000000000000 x16: ffffc31840f18a78
| x15: 0000000000000001 x14: ffffc3184285c810
| x13: 0000000000000001 x12: 0000000000000000
| x11: ffffc318415857a0 x10: ffffc318406614c0
| x9 : ffffc318415857a0 x8 : ffffc31841f1d000
| x7 : 647261685f706564 x6 : ffffc3183ff7c66c
| x5 : ffff66ce801e0000 x4 : 0000000000000000
| x3 : ffffc3183fe00000 x2 : ffffc31841500000
| x1 : e956dc24146b3500 x0 : 0000000000000000
| Call trace:
| check_flags.part.54+0x1dc/0x1f0
| lock_is_held_type+0x10c/0x188
| rcu_read_lock_sched_held+0x70/0x98
| __context_tracking_enter+0x310/0x350
| context_tracking_enter.part.3+0x5c/0xc8
| context_tracking_user_enter+0x6c/0x80
| finish_ret_to_user+0x2c/0x13cr
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20201130115950.22492-8-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
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In preparation for reworking the EL1 irq/nmi entry code, move the
existing logic to C. We no longer need the asm_nmi_enter() and
asm_nmi_exit() wrappers, so these are removed. The new C functions are
marked noinstr, which prevents compiler instrumentation and runtime
probing.
In subsequent patches we'll want the new C helpers to be called in all
cases, so we don't bother wrapping the calls with ifdeferry. Even when
the new C functions are stubs the trivial calls are unlikely to have a
measurable impact on the IRQ or NMI paths anyway.
Prototypes are added to <asm/exception.h> as otherwise (in some
configurations) GCC will complain about the lack of a forward
declaration. We already do this for existing function, e.g.
enter_from_user_mode().
The new helpers are marked as noinstr (which prevents all
instrumentation, tracing, and kprobes). Otherwise, there should be no
functional change as a result of this patch.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20201130115950.22492-7-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
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|
In a subsequent patch ret_to_user will need to make a C function call
(in some configurations) which may clobber x0-x18 at the start of the
finish_ret_to_user block, before enable_step_tsk consumes the flags
loaded into x1.
In preparation for this, let's load the flags into x19, which is
preserved across C function calls. This avoids a redundant reload of the
flags and ensures we operate on a consistent shapshot regardless.
There should be no functional change as a result of this patch. At this
point of the entry/exit paths we only need to preserve x28 (tsk) and the
sp, and x19 is free for this use.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20201130115950.22492-6-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
|
|
In later patches we'll want to extend enter_from_user_mode() and add a
corresponding exit_to_user_mode(). As these will be common for all
entries/exits from userspace, it'd be better for these to live in
entry-common.c with the rest of the entry logic.
This patch moves enter_from_user_mode() into entry-common.c. As with
other functions in entry-common.c it is marked as noinstr (which
prevents all instrumentation, tracing, and kprobes) but there are no
other functional changes.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20201130115950.22492-5-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
|
|
Functions in entry-common.c are marked as notrace and NOKPROBE_SYMBOL(),
but they're still subject to other instrumentation which may rely on
lockdep/rcu/context-tracking being up-to-date, and may cause nested
exceptions (e.g. for WARN/BUG or KASAN's use of BRK) which will corrupt
exceptions registers which have not yet been read.
Prevent this by marking all functions in entry-common.c as noinstr to
prevent compiler instrumentation. This also blacklists the functions for
tracing and kprobes, so we don't need to handle that separately.
Functions elsewhere will be dealt with in subsequent patches.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20201130115950.22492-4-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
|
|
Core code disables RCU when calling arch_cpu_idle(), so it's not safe
for arch_cpu_idle() or its calees to be instrumented, as the
instrumentation callbacks may attempt to use RCU or other features which
are unsafe to use in this context.
Mark them noinstr to prevent issues.
The use of local_irq_enable() in arch_cpu_idle() is similarly
problematic, and the "sched/idle: Fix arch_cpu_idle() vs tracing" patch
queued in the tip tree addresses that case.
Reported-by: Marco Elver <elver@google.com>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20201130115950.22492-3-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
|
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In el0_svc_common() we unmask exceptions before we call user_exit(), and
so there's a window where an IRQ or debug exception can be taken while
RCU is not watching. In do_debug_exception() we account for this in via
debug_exception_{enter,exit}(), but in the el1_irq asm we do not and we
call trace functions which rely on RCU before we have a guarantee that
RCU is watching.
Let's avoid this by having el0_svc_common() exit userspace before
unmasking exceptions, matching what we do for all other EL0 entry paths.
We can use user_exit_irqoff() to avoid the pointless save/restore of IRQ
flags while we're sure exceptions are masked in DAIF.
The workaround for Cortex-A76 erratum 1463225 may trigger a debug
exception before this point, but the debug code invoked in this case is
safe even when RCU is not watching.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20201130115950.22492-2-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking fixes from Thomas Gleixner:
"Two more places which invoke tracing from RCU disabled regions in the
idle path.
Similar to the entry path the low level idle functions have to be
non-instrumentable"
* tag 'locking-urgent-2020-11-29' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
intel_idle: Fix intel_idle() vs tracing
sched/idle: Fix arch_cpu_idle() vs tracing
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We call arch_cpu_idle() with RCU disabled, but then use
local_irq_{en,dis}able(), which invokes tracing, which relies on RCU.
Switch all arch_cpu_idle() implementations to use
raw_local_irq_{en,dis}able() and carefully manage the
lockdep,rcu,tracing state like we do in entry.
(XXX: we really should change arch_cpu_idle() to not return with
interrupts enabled)
Reported-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lkml.kernel.org/r/20201120114925.594122626@infradead.org
|
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull perf fixes from Thomas Gleixner:
"A set of fixes for perf:
- A set of commits which reduce the stack usage of various perf
event handling functions which allocated large data structs on
stack causing stack overflows in the worst case
- Use the proper mechanism for detecting soft interrupts in the
recursion protection
- Make the resursion protection simpler and more robust
- Simplify the scheduling of event groups to make the code more
robust and prepare for fixing the issues vs. scheduling of
exclusive event groups
- Prevent event multiplexing and rotation for exclusive event groups
- Correct the perf event attribute exclusive semantics to take
pinned events, e.g. the PMU watchdog, into account
- Make the anythread filtering conditional for Intel's generic PMU
counters as it is not longer guaranteed to be supported on newer
CPUs. Check the corresponding CPUID leaf to make sure
- Fixup a duplicate initialization in an array which was probably
caused by the usual 'copy & paste - forgot to edit' mishap"
* tag 'perf-urgent-2020-11-15' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
perf/x86/intel/uncore: Fix Add BW copypasta
perf/x86/intel: Make anythread filter support conditional
perf: Tweak perf_event_attr::exclusive semantics
perf: Fix event multiplexing for exclusive groups
perf: Simplify group_sched_in()
perf: Simplify group_sched_out()
perf/x86: Make dummy_iregs static
perf/arch: Remove perf_sample_data::regs_user_copy
perf: Optimize get_recursion_context()
perf: Fix get_recursion_context()
perf/x86: Reduce stack usage for x86_pmu::drain_pebs()
perf: Reduce stack usage of perf_output_begin()
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git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux
Pull arm64 fixes from Will Deacon:
- Spectre/Meltdown safelisting for some Qualcomm KRYO cores
- Fix RCU splat when failing to online a CPU due to a feature mismatch
- Fix a recently introduced sparse warning in kexec()
- Fix handling of CPU erratum 1418040 for late CPUs
- Ensure hot-added memory falls within linear-mapped region
* tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux:
arm64: cpu_errata: Apply Erratum 845719 to KRYO2XX Silver
arm64: proton-pack: Add KRYO2XX silver CPUs to spectre-v2 safe-list
arm64: kpti: Add KRYO2XX gold/silver CPU cores to kpti safelist
arm64: Add MIDR value for KRYO2XX gold/silver CPU cores
arm64/mm: Validate hotplug range before creating linear mapping
arm64: smp: Tell RCU about CPUs that fail to come online
arm64: psci: Avoid printing in cpu_psci_cpu_die()
arm64: kexec_file: Fix sparse warning
arm64: errata: Fix handling of 1418040 with late CPU onlining
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QCOM KRYO2XX Silver cores are Cortex-A53 based and are
susceptible to the 845719 erratum. Add them to the lookup
list to apply the erratum.
Signed-off-by: Konrad Dybcio <konrad.dybcio@somainline.org>
Link: https://lore.kernel.org/r/20201104232218.198800-5-konrad.dybcio@somainline.org
Signed-off-by: Will Deacon <will@kernel.org>
|
|
KRYO2XX silver (LITTLE) CPUs are based on Cortex-A53
and they are not affected by spectre-v2.
Signed-off-by: Konrad Dybcio <konrad.dybcio@somainline.org>
Link: https://lore.kernel.org/r/20201104232218.198800-4-konrad.dybcio@somainline.org
Signed-off-by: Will Deacon <will@kernel.org>
|
|
QCOM KRYO2XX gold (big) silver (LITTLE) CPU cores are based on
Cortex-A73 and Cortex-A53 respectively and are meltdown safe,
hence add them to kpti_safe_list[].
Signed-off-by: Konrad Dybcio <konrad.dybcio@somainline.org>
Link: https://lore.kernel.org/r/20201104232218.198800-3-konrad.dybcio@somainline.org
Signed-off-by: Will Deacon <will@kernel.org>
|
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Commit ce3d31ad3cac ("arm64/smp: Move rcu_cpu_starting() earlier") ensured
that RCU is informed early about incoming CPUs that might end up calling
into printk() before they are online. However, if such a CPU fails the
early CPU feature compatibility checks in check_local_cpu_capabilities(),
then it will be powered off or parked without informing RCU, leading to
an endless stream of stalls:
| rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
| rcu: 2-O...: (0 ticks this GP) idle=002/1/0x4000000000000000 softirq=0/0 fqs=2593
| (detected by 0, t=5252 jiffies, g=9317, q=136)
| Task dump for CPU 2:
| task:swapper/2 state:R running task stack: 0 pid: 0 ppid: 1 flags:0x00000028
| Call trace:
| ret_from_fork+0x0/0x30
Ensure that the dying CPU invokes rcu_report_dead() prior to being powered
off or parked.
Cc: Qian Cai <cai@redhat.com>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Suggested-by: Qian Cai <cai@redhat.com>
Link: https://lore.kernel.org/r/20201105222242.GA8842@willie-the-truck
Link: https://lore.kernel.org/r/20201106103602.9849-3-will@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
|
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cpu_psci_cpu_die() is called in the context of the dying CPU, which
will no longer be online or tracked by RCU. It is therefore not generally
safe to call printk() if the PSCI "cpu off" request fails, so remove the
pr_crit() invocation.
Cc: Qian Cai <cai@redhat.com>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20201106103602.9849-2-will@kernel.org
Signed-off-by: Will D |
