linux.git/arch/powerpc/kernel/trace, branch v6.12.80

ftrace: Make ftrace_regs abstract from direct use

2026-03-04T12:19:36+00:00

[ Upstream commit 7888af4166d4ab07ba51234be6ba332b7807e901 ]

ftrace_regs was created to hold registers that store information to save
function parameters, return value and stack. Since it is a subset of
pt_regs, it should only be used by its accessor functions. But because
pt_regs can easily be taken from ftrace_regs (on most archs), it is
tempting to use it directly. But when running on other architectures, it
may fail to build or worse, build but crash the kernel!

Instead, make struct ftrace_regs an empty structure and have the
architectures define __arch_ftrace_regs and all the accessor functions
will typecast to it to get to the actual fields. This will help avoid
usage of ftrace_regs directly.

Link: https://lore.kernel.org/all/20241007171027.629bdafd@gandalf.local.home/

Cc: "linux-arch@vger.kernel.org" 
Cc: "x86@kernel.org" 
Cc: Mathieu Desnoyers 
Cc: Mark Rutland 
Cc: Will Deacon 
Cc: Huacai Chen 
Cc: WANG Xuerui 
Cc: Michael Ellerman 
Cc: Nicholas Piggin 
Cc: Christophe Leroy 
Cc: Naveen N Rao 
Cc: Madhavan Srinivasan 
Cc: Paul  Walmsley 
Cc: Palmer Dabbelt 
Cc: Albert Ou 
Cc: Heiko Carstens 
Cc: Vasily Gorbik 
Cc: Alexander Gordeev 
Cc: Christian Borntraeger 
Cc: Sven Schnelle 
Cc: Thomas  Gleixner 
Cc: Ingo Molnar 
Cc: Borislav  Petkov 
Cc: Dave Hansen 
Link: https://lore.kernel.org/20241008230628.958778821@goodmis.org
Acked-by: Catalin Marinas 
Signed-off-by: Steven Rostedt (Google) 
Acked-by: Masami Hiramatsu (Google) 
Acked-by: Heiko Carstens  # s390
Signed-off-by: Steven Rostedt (Google) 
Stable-dep-of: aea251799998 ("x86/fgraph,bpf: Switch kprobe_multi program stack unwind to hw_regs path")
Signed-off-by: Sasha Levin

powerpc/ftrace: Ignore ftrace locations in exit text sections

2024-02-14T03:24:06+00:00

Michael reported that we are seeing an ftrace bug on bootup when KASAN
is enabled and we are using -fpatchable-function-entry:

  ftrace: allocating 47780 entries in 18 pages
  ftrace-powerpc: 0xc0000000020b3d5c: No module provided for non-kernel address
  ------------[ ftrace bug ]------------
  ftrace faulted on modifying
  [] 0xc0000000020b3d5c
  Initializing ftrace call sites
  ftrace record flags: 0
   (0)
   expected tramp: c00000000008cef4
  ------------[ cut here ]------------
  WARNING: CPU: 0 PID: 0 at kernel/trace/ftrace.c:2180 ftrace_bug+0x3c0/0x424
  Modules linked in:
  CPU: 0 PID: 0 Comm: swapper Not tainted 6.5.0-rc3-00120-g0f71dcfb4aef #860
  Hardware name: IBM pSeries (emulated by qemu) POWER9 (raw) 0x4e1202 0xf000005 of:SLOF,HEAD hv:linux,kvm pSeries
  NIP:  c0000000003aa81c LR: c0000000003aa818 CTR: 0000000000000000
  REGS: c0000000033cfab0 TRAP: 0700   Not tainted  (6.5.0-rc3-00120-g0f71dcfb4aef)
  MSR:  8000000002021033   CR: 28028240  XER: 00000000
  CFAR: c0000000002781a8 IRQMASK: 3
  ...
  NIP [c0000000003aa81c] ftrace_bug+0x3c0/0x424
  LR [c0000000003aa818] ftrace_bug+0x3bc/0x424
  Call Trace:
   ftrace_bug+0x3bc/0x424 (unreliable)
   ftrace_process_locs+0x5f4/0x8a0
   ftrace_init+0xc0/0x1d0
   start_kernel+0x1d8/0x484

With CONFIG_FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY=y and
CONFIG_KASAN=y, compiler emits nops in functions that it generates for
registering and unregistering global variables (unlike with -pg and
-mprofile-kernel where calls to _mcount() are not generated in those
functions). Those functions then end up in INIT_TEXT and EXIT_TEXT
respectively. We don't expect to see any profiled functions in
EXIT_TEXT, so ftrace_init_nop() assumes that all addresses that aren't
in the core kernel text belongs to a module. Since these functions do
not match that criteria, we see the above bug.

Address this by having ftrace ignore all locations in the text exit
sections of vmlinux.

Fixes: 0f71dcfb4aef ("powerpc/ftrace: Add support for -fpatchable-function-entry")
Cc: stable@vger.kernel.org # v6.6+
Reported-by: Michael Ellerman 
Signed-off-by: Naveen N Rao 
Reviewed-by: Benjamin Gray 
Signed-off-by: Michael Ellerman 
Link: https://msgid.link/20240213175410.1091313-1-naveen@kernel.org

Merge tag 'powerpc-6.8-1' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux

2024-01-09T00:22:47+00:00

Pull powerpc updates from Michael Ellerman:

 - Add initial support to recognise the HeXin C2000 processor.

 - Add papr-vpd and papr-sysparm character device drivers for VPD &
   sysparm retrieval, so userspace tools can be adapted to avoid doing
   raw firmware calls from userspace.

 - Sched domains optimisations for shared processor partitions on
   P9/P10.

 - A series of optimisations for KVM running as a nested HV under
   PowerVM.

 - Other small features and fixes.

Thanks to Aditya Gupta, Aneesh Kumar K.V, Arnd Bergmann, Christophe
Leroy, Colin Ian King, Dario Binacchi, David Heidelberg, Geoff Levand,
Gustavo A. R. Silva, Haoran Liu, Jordan Niethe, Kajol Jain, Kevin Hao,
Kunwu Chan, Li kunyu, Li zeming, Masahiro Yamada, Michal Suchánek,
Nathan Lynch, Naveen N Rao, Nicholas Piggin, Randy Dunlap, Sathvika
Vasireddy, Srikar Dronamraju, Stephen Rothwell, Vaibhav Jain, and
Zhao Ke.

* tag 'powerpc-6.8-1' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux: (96 commits)
  powerpc/ps3_defconfig: Disable PPC64_BIG_ENDIAN_ELF_ABI_V2
  powerpc/86xx: Drop unused CONFIG_MPC8610
  powerpc/powernv: Add error handling to opal_prd_range_is_valid
  selftests/powerpc: Fix spelling mistake "EACCESS" -> "EACCES"
  powerpc/hvcall: Reorder Nestedv2 hcall opcodes
  powerpc/ps3: Add missing set_freezable() for ps3_probe_thread()
  powerpc/mpc83xx: Use wait_event_freezable() for freezable kthread
  powerpc/mpc83xx: Add the missing set_freezable() for agent_thread_fn()
  powerpc/fsl: Fix fsl,tmu-calibration to match the schema
  powerpc/smp: Dynamically build Powerpc topology
  powerpc/smp: Avoid asym packing within thread_group of a core
  powerpc/smp: Add __ro_after_init attribute
  powerpc/smp: Disable MC domain for shared processor
  powerpc/smp: Enable Asym packing for cores on shared processor
  powerpc/sched: Cleanup vcpu_is_preempted()
  powerpc: add cpu_spec.cpu_features to vmcoreinfo
  powerpc/imc-pmu: Add a null pointer check in update_events_in_group()
  powerpc/powernv: Add a null pointer check in opal_powercap_init()
  powerpc/powernv: Add a null pointer check in opal_event_init()
  powerpc/powernv: Add a null pointer check to scom_debug_init_one()
  ...

powerpc/ftrace: Remove nops after the call to ftrace_stub

2023-12-13T10:49:22+00:00

ftrace_stub is within the same CU, so there is no need for a subsequent
nop instruction.

Signed-off-by: Naveen N Rao 
Signed-off-by: Michael Ellerman 
Link: https://msgid.link/8ee5ec520e37d5523654bb2cd65a17512fb774e2.1702045299.git.naveen@kernel.org

powerpc/ftrace: Fix stack teardown in ftrace_no_trace

2023-12-05T03:14:12+00:00

Commit 41a506ef71eb ("powerpc/ftrace: Create a dummy stackframe to fix
stack unwind") added use of a new stack frame on ftrace entry to fix
stack unwind. However, the commit missed updating the offset used while
tearing down the ftrace stack when ftrace is disabled. Fix the same.

In addition, the commit missed saving the correct stack pointer in
pt_regs. Update the same.

Fixes: 41a506ef71eb ("powerpc/ftrace: Create a dummy stackframe to fix stack unwind")
Cc: stable@vger.kernel.org # v6.5+
Signed-off-by: Naveen N Rao 
Signed-off-by: Michael Ellerman 
Link: https://msgid.link/20231130065947.2188860-1-naveen@kernel.org

Merge tag 'powerpc-6.6-1' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux

2023-08-31T19:43:10+00:00

Pull powerpc updates from Michael Ellerman:

 - Add HOTPLUG_SMT support (/sys/devices/system/cpu/smt) and honour the
   configured SMT state when hotplugging CPUs into the system

 - Combine final TLB flush and lazy TLB mm shootdown IPIs when using the
   Radix MMU to avoid a broadcast TLBIE flush on exit

 - Drop the exclusion between ptrace/perf watchpoints, and drop the now
   unused associated arch hooks

 - Add support for the "nohlt" command line option to disable CPU idle

 - Add support for -fpatchable-function-entry for ftrace, with GCC >=
   13.1

 - Rework memory block size determination, and support 256MB size on
   systems with GPUs that have hotpluggable memory

 - Various other small features and fixes

Thanks to Andrew Donnellan, Aneesh Kumar K.V, Arnd Bergmann, Athira
Rajeev, Benjamin Gray, Christophe Leroy, Frederic Barrat, Gautam
Menghani, Geoff Levand, Hari Bathini, Immad Mir, Jialin Zhang, Joel
Stanley, Jordan Niethe, Justin Stitt, Kajol Jain, Kees Cook, Krzysztof
Kozlowski, Laurent Dufour, Liang He, Linus Walleij, Mahesh Salgaonkar,
Masahiro Yamada, Michal Suchanek, Nageswara R Sastry, Nathan Chancellor,
Nathan Lynch, Naveen N Rao, Nicholas Piggin, Nick Desaulniers, Omar
Sandoval, Randy Dunlap, Reza Arbab, Rob Herring, Russell Currey, Sourabh
Jain, Thomas Gleixner, Trevor Woerner, Uwe Kleine-König, Vaibhav Jain,
Xiongfeng Wang, Yuan Tan, Zhang Rui, and Zheng Zengkai.

* tag 'powerpc-6.6-1' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux: (135 commits)
  macintosh/ams: linux/platform_device.h is needed
  powerpc/xmon: Reapply "Relax frame size for clang"
  powerpc/mm/book3s64: Use 256M as the upper limit with coherent device memory attached
  powerpc/mm/book3s64: Fix build error with SPARSEMEM disabled
  powerpc/iommu: Fix notifiers being shared by PCI and VIO buses
  powerpc/mpc5xxx: Add missing fwnode_handle_put()
  powerpc/config: Disable SLAB_DEBUG_ON in skiroot
  powerpc/pseries: Remove unused hcall tracing instruction
  powerpc/pseries: Fix hcall tracepoints with JUMP_LABEL=n
  powerpc: dts: add missing space before {
  powerpc/eeh: Use pci_dev_id() to simplify the code
  powerpc/64s: Move CPU -mtune options into Kconfig
  powerpc/powermac: Fix unused function warning
  powerpc/pseries: Rework lppaca_shared_proc() to avoid DEBUG_PREEMPT
  powerpc: Don't include lppaca.h in paca.h
  powerpc/pseries: Move hcall_vphn() prototype into vphn.h
  powerpc/pseries: Move VPHN constants into vphn.h
  cxl: Drop unused detach_spa()
  powerpc: Drop zalloc_maybe_bootmem()
  powerpc/powernv: Use struct opal_prd_msg in more places
  ...

powerpc/ftrace: Add support for -fpatchable-function-entry

2023-08-21T14:09:06+00:00

GCC v13.1 updated support for -fpatchable-function-entry on ppc64le to
emit nops after the local entry point, rather than before it. This
allows us to use this in the kernel for ftrace purposes. A new script is
added under arch/powerpc/tools/ to help detect if nops are emitted after
the function local entry point, or before the global entry point.

With -fpatchable-function-entry, we no longer have the profiling
instructions generated at function entry, so we only need to validate
the presence of two nops at the ftrace location in ftrace_init_nop(). We
patch the preceding instruction with 'mflr r0' to match the
-mprofile-kernel ABI for subsequent ftrace use.

This changes the profiling instructions used on ppc32. The default -pg
option emits an additional 'stw' instruction after 'mflr r0' and before
the branch to _mcount 'bl _mcount'. This is very similar to the original
-mprofile-kernel implementation on ppc64le, where an additional 'std'
instruction was used to save LR to its save location in the caller's
stackframe. Subsequently, this additional store was removed in later
compiler versions for performance reasons. The same reasons apply for
ppc32 so we only patch in a 'mflr r0'.

Signed-off-by: Naveen N Rao 
Reviewed-by: Christophe Leroy 
Signed-off-by: Michael Ellerman 
Link: https://msgid.link/68586d22981a2c3bb45f27a2b621173d10a7d092.1687166935.git.naveen@kernel.org

powerpc/ftrace: Implement ftrace_replace_code()

2023-08-21T14:09:06+00:00

Implement ftrace_replace_code() to consolidate logic from the different
ftrace patching routines: ftrace_make_nop(), ftrace_make_call() and
ftrace_modify_call(). Note that ftrace_make_call() is still required
primarily to handle patching modules during their load time. The other
two routines should no longer be called.

This lays the groundwork to enable better control in patching ftrace
locations, including the ability to nop-out preceding profiling
instructions when ftrace is disabled.

Signed-off-by: Naveen N Rao 
Reviewed-by: Christophe Leroy 
Signed-off-by: Michael Ellerman 
Link: https://msgid.link/c28f852225646b0561bbf3c1d22d03f041ace8e0.1687166935.git.naveen@kernel.org

powerpc/ftrace: Replace use of ftrace_call_replace() with ftrace_create_branch_inst()

2023-08-21T14:09:06+00:00

ftrace_create_branch_inst() is clearer about its intent than
ftrace_call_replace().

Signed-off-by: Naveen N Rao 
Reviewed-by: Christophe Leroy 
Signed-off-by: Michael Ellerman 
Link: https://msgid.link/953513b88fa922ba7a66d772dc1310710efe9177.1687166935.git.naveen@kernel.org

powerpc/ftrace: Simplify ftrace_modify_call()

2023-08-21T14:09:06+00:00

Now that we validate the ftrace location during initialization in
ftrace_init_nop(), we can simplify ftrace_modify_call() to patch-in the
updated branch instruction without worrying about the instructions
surrounding the ftrace location. Note that we continue to ensure we
have the expected branch instruction at the ftrace location before
patching it with the updated branch destination.

Signed-off-by: Naveen N Rao 
Reviewed-by: Christophe Leroy 
Signed-off-by: Michael Ellerman 
Link: https://msgid.link/06275720939f8ee4c2f61c9e9a3e89b1fa3c441d.1687166935.git.naveen@kernel.org