linux.git/arch/mips/kernel/traps.c, branch v4.4.187

MIPS: Fix FCSR Cause bit handling for correct SIGFPE issue

2018-11-10T15:41:36+00:00

[ Upstream commit 5a1aca4469fdccd5b74ba0b4e490173b2b447895 ]

Sanitize FCSR Cause bit handling, following a trail of past attempts:

* commit 4249548454f7 ("MIPS: ptrace: Fix FP context restoration FCSR
regression"),

* commit 443c44032a54 ("MIPS: Always clear FCSR cause bits after
emulation"),

* commit 64bedffe4968 ("MIPS: Clear [MSA]FPE CSR.Cause after
notify_die()"),

* commit b1442d39fac2 ("MIPS: Prevent user from setting FCSR cause
bits"),

* commit b54d2901517d ("Properly handle branch delay slots in connection
with signals.").

Specifically do not mask these bits out in ptrace(2) processing and send
a SIGFPE signal instead whenever a matching pair of an FCSR Cause and
Enable bit is seen as execution of an affected context is about to
resume.  Only then clear Cause bits, and even then do not clear any bits
that are set but masked with the respective Enable bits.  Adjust Cause
bit clearing throughout code likewise, except within the FPU emulator
proper where they are set according to IEEE 754 exceptions raised as the
operation emulated executed.  Do so so that any IEEE 754 exceptions
subject to their default handling are recorded like with operations
executed by FPU hardware.

Signed-off-by: Maciej W. Rozycki 
Cc: Paul Burton 
Cc: James Hogan 
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/14460/
Signed-off-by: Ralf Baechle 
Signed-off-by: Sasha Levin

MIPS: Call dump_stack() from show_regs()

2018-07-22T12:25:53+00:00

commit 5a267832c2ec47b2dad0fdb291a96bb5b8869315 upstream.

The generic nmi_cpu_backtrace() function calls show_regs() when a struct
pt_regs is available, and dump_stack() otherwise. If we were to make use
of the generic nmi_cpu_backtrace() with MIPS' current implementation of
show_regs() this would mean that we see only register data with no
accompanying stack information, in contrast with our current
implementation which calls dump_stack() regardless of whether register
state is available.

In preparation for making use of the generic nmi_cpu_backtrace() to
implement arch_trigger_cpumask_backtrace(), have our implementation of
show_regs() call dump_stack() and drop the explicit dump_stack() call in
arch_dump_stack() which is invoked by arch_trigger_cpumask_backtrace().

This will allow the output we produce to remain the same after a later
patch switches to using nmi_cpu_backtrace(). It may mean that we produce
extra stack output in other uses of show_regs(), but this:

  1) Seems harmless.
  2) Is good for consistency between arch_trigger_cpumask_backtrace()
     and other users of show_regs().
  3) Matches the behaviour of the ARM & PowerPC architectures.

Marked for stable back to v4.9 as a prerequisite of the following patch
"MIPS: Call dump_stack() from show_regs()".

Signed-off-by: Paul Burton 
Patchwork: https://patchwork.linux-mips.org/patch/19596/
Cc: James Hogan 
Cc: Ralf Baechle 
Cc: Huacai Chen 
Cc: linux-mips@linux-mips.org
Cc: stable@vger.kernel.org # v4.9+
Signed-off-by: Huacai Chen 
Signed-off-by: Greg Kroah-Hartman

MIPS: Avoid accidental raw backtrace

2017-07-05T12:37:15+00:00

commit 854236363370995a609a10b03e35fd3dc5e9e4a1 upstream.

Since commit 81a76d7119f6 ("MIPS: Avoid using unwind_stack() with
usermode") show_backtrace() invokes the raw backtracer when
cp0_status & ST0_KSU indicates user mode to fix issues on EVA kernels
where user and kernel address spaces overlap.

However this is used by show_stack() which creates its own pt_regs on
the stack and leaves cp0_status uninitialised in most of the code paths.
This results in the non deterministic use of the raw back tracer
depending on the previous stack content.

show_stack() deals exclusively with kernel mode stacks anyway, so
explicitly initialise regs.cp0_status to KSU_KERNEL (i.e. 0) to ensure
we get a useful backtrace.

Fixes: 81a76d7119f6 ("MIPS: Avoid using unwind_stack() with usermode")
Signed-off-by: James Hogan 
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/16656/
Signed-off-by: Ralf Baechle 
Signed-off-by: Greg Kroah-Hartman

MIPS: Avoid using unwind_stack() with usermode

2016-06-08T01:14:30+00:00

commit 81a76d7119f63c359750e4adeff922a31ad1135f upstream.

When showing backtraces in response to traps, for example crashes and
address errors (usually unaligned accesses) when they are set in debugfs
to be reported, unwind_stack will be used if the PC was in the kernel
text address range. However since EVA it is possible for user and kernel
address ranges to overlap, and even without EVA userland can still
trigger an address error by jumping to a KSeg0 address.

Adjust the check to also ensure that it was running in kernel mode. I
don't believe any harm can come of this problem, since unwind_stack() is
sufficiently defensive, however it is only meant for unwinding kernel
code, so to be correct it should use the raw backtracing instead.

Signed-off-by: James Hogan 
Reviewed-by: Leonid Yegoshin 
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/11701/
Signed-off-by: Ralf Baechle 
(cherry picked from commit d2941a975ac745c607dfb590e92bb30bc352dad9)
Signed-off-by: Greg Kroah-Hartman

MIPS: MSA: Fix a link error on `_init_msa_upper' with older GCC

2016-06-08T01:14:30+00:00

commit e49d38488515057dba8f0c2ba4cfde5be4a7281f upstream.

Fix a build regression from commit c9017757c532 ("MIPS: init upper 64b
of vector registers when MSA is first used"):

arch/mips/built-in.o: In function `enable_restore_fp_context':
traps.c:(.text+0xbb90): undefined reference to `_init_msa_upper'
traps.c:(.text+0xbb90): relocation truncated to fit: R_MIPS_26 against `_init_msa_upper'
traps.c:(.text+0xbef0): undefined reference to `_init_msa_upper'
traps.c:(.text+0xbef0): relocation truncated to fit: R_MIPS_26 against `_init_msa_upper'

to !CONFIG_CPU_HAS_MSA configurations with older GCC versions, which are
unable to figure out that calls to `_init_msa_upper' are indeed dead.
Of the many ways to tackle this failure choose the approach we have
already taken in `thread_msa_context_live'.

[ralf@linux-mips.org: Drop patch segment to junk file.]

Signed-off-by: Maciej W. Rozycki 
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/13271/
Signed-off-by: Ralf Baechle 
Signed-off-by: Greg Kroah-Hartman

MIPS: traps: Fix SIGFPE information leak from `do_ov' and `do_trap_or_bp'

2016-03-09T23:34:55+00:00

commit e723e3f7f9591b79e8c56b3d7c5a204a9c571b55 upstream.

Avoid sending a partially initialised `siginfo_t' structure along SIGFPE
signals issued from `do_ov' and `do_trap_or_bp', leading to information
leaking from the kernel stack.

Signed-off-by: Maciej W. Rozycki 
Signed-off-by: Ralf Baechle 
Signed-off-by: Greg Kroah-Hartman

Merge branch '4.3-fixes' into mips-for-linux-next

2015-11-12T10:36:03+00:00

MIPS: add nmi_enter() + nmi_exit() to nmi_exception_handler()

2015-11-09T08:56:56+00:00

We need to enter NMI context when NMI interrupt fires.

Signed-off-by: Petri Gynther 
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/11323/
Signed-off-by: Ralf Baechle

MIPS: traps: tidy up ebase calculation

2015-10-26T08:49:44+00:00

Rather than #ifdef on CONFIG_KVM_GUEST & redefine the guest kseg0 base
locally, make use of the CAC_BASE macro which has the correct value in
both cases.

Signed-off-by: Paul Burton 
Cc: James Hogan 
Cc: linux-mips@linux-mips.org
Cc: Leonid Yegoshin 
Cc: Maciej W. Rozycki 
Cc: linux-kernel@vger.kernel.org
Cc: Markos Chandras 
Patchwork: https://patchwork.linux-mips.org/patch/11183/
Signed-off-by: Ralf Baechle

MIPS: Add uprobes support.

2015-09-03T10:08:05+00:00

Signed-off-by: Ralf Baechle