From: Naveen N Rao <naveen@kernel.org>
To: Christophe Leroy <christophe.leroy@csgroup.eu>,
"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH 16/17] powerpc/ftrace: Add support for -fpatchable-function-entry
Date: Wed, 28 Jun 2023 13:10:44 +0530 [thread overview]
Message-ID: <1687937905.1es5lckagj.naveen@kernel.org> (raw)
In-Reply-To: <66372e0f-a5e0-d883-e9b3-a837a17cd593@csgroup.eu>
Christophe Leroy wrote:
>
>
> Le 19/06/2023 à 11:47, Naveen N Rao a écrit :
>> 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 <naveen@kernel.org>
>
> Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
>
> Nit below
>
>> ---
>> arch/powerpc/Kconfig | 14 +++++++---
>> arch/powerpc/Makefile | 5 ++++
>> arch/powerpc/include/asm/ftrace.h | 6 +++--
>> arch/powerpc/include/asm/vermagic.h | 4 ++-
>> arch/powerpc/kernel/module_64.c | 2 +-
>> arch/powerpc/kernel/trace/ftrace.c | 14 ++++++++--
>> arch/powerpc/kernel/trace/ftrace_entry.S | 2 ++
>> .../gcc-check-fpatchable-function-entry.sh | 26 +++++++++++++++++++
>> 8 files changed, 64 insertions(+), 9 deletions(-)
>> create mode 100755 arch/powerpc/tools/gcc-check-fpatchable-function-entry.sh
>>
>> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
>> index bff5820b7cda14..9352d8e68152e1 100644
>> --- a/arch/powerpc/Kconfig
>> +++ b/arch/powerpc/Kconfig
>> @@ -187,6 +187,7 @@ config PPC
>> select DYNAMIC_FTRACE if FUNCTION_TRACER
>> select EDAC_ATOMIC_SCRUB
>> select EDAC_SUPPORT
>> + select FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY if ARCH_USING_PATCHABLE_FUNCTION_ENTRY
>> select GENERIC_ATOMIC64 if PPC32
>> select GENERIC_CLOCKEVENTS_BROADCAST if SMP
>> select GENERIC_CMOS_UPDATE
>> @@ -227,8 +228,8 @@ config PPC
>> select HAVE_DEBUG_KMEMLEAK
>> select HAVE_DEBUG_STACKOVERFLOW
>> select HAVE_DYNAMIC_FTRACE
>> - select HAVE_DYNAMIC_FTRACE_WITH_ARGS if MPROFILE_KERNEL || PPC32
>> - select HAVE_DYNAMIC_FTRACE_WITH_REGS if MPROFILE_KERNEL || PPC32
>> + select HAVE_DYNAMIC_FTRACE_WITH_ARGS if ARCH_USING_PATCHABLE_FUNCTION_ENTRY || MPROFILE_KERNEL || PPC32
>> + select HAVE_DYNAMIC_FTRACE_WITH_REGS if ARCH_USING_PATCHABLE_FUNCTION_ENTRY || MPROFILE_KERNEL || PPC32
>
> ARCH_USING_PATCHABLE_FUNCTION_ENTRY defaults to y if PPC32, so you can
> remove PPC32 from the condition here.
ARCH_USING_PATCHABLE_FUNCTION_ENTRY also depends on compiler support for
-fpatchable-function-entry, and gcc v5.x doesn't support that. So, we
need to retain PPC32 here.
- Naveen
>
>> select HAVE_EBPF_JIT
>> select HAVE_EFFICIENT_UNALIGNED_ACCESS
>> select HAVE_FAST_GUP
>> @@ -256,7 +257,7 @@ config PPC
>> select HAVE_MOD_ARCH_SPECIFIC
>> select HAVE_NMI if PERF_EVENTS || (PPC64 && PPC_BOOK3S)
>> select HAVE_OPTPROBES
>> - select HAVE_OBJTOOL if PPC32 || MPROFILE_KERNEL
>> + select HAVE_OBJTOOL if ARCH_USING_PATCHABLE_FUNCTION_ENTRY || MPROFILE_KERNEL || PPC32
>
> Same
>
>> select HAVE_OBJTOOL_MCOUNT if HAVE_OBJTOOL
>> select HAVE_PERF_EVENTS
>> select HAVE_PERF_EVENTS_NMI if PPC64
>> @@ -550,6 +551,13 @@ config MPROFILE_KERNEL
>> depends on PPC64 && CPU_LITTLE_ENDIAN && FUNCTION_TRACER
>> def_bool $(success,$(srctree)/arch/powerpc/tools/gcc-check-mprofile-kernel.sh $(CC) -I$(srctree)/include -D__KERNEL__)
>>
>> +config ARCH_USING_PATCHABLE_FUNCTION_ENTRY
>> + depends on FUNCTION_TRACER && (PPC32 || PPC64_ELF_ABI_V2)
>> + depends on $(cc-option,-fpatchable-function-entry=2)
>> + def_bool y if PPC32
>> + def_bool $(success,$(srctree)/arch/powerpc/tools/gcc-check-fpatchable-function-entry.sh $(CC) -mlittle-endian) if PPC64 && CPU_LITTLE_ENDIAN
>> + def_bool $(success,$(srctree)/arch/powerpc/tools/gcc-check-fpatchable-function-entry.sh $(CC) -mbig-endian) if PPC64 && CPU_BIG_ENDIAN
>> +
...
next prev parent reply other threads:[~2023-06-28 7:42 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-19 9:47 [PATCH 00/17] powerpc/ftrace: refactor and add support for -fpatchable-function-entry Naveen N Rao
2023-06-19 9:47 ` [PATCH 01/17] powerpc/ftrace: Fix dropping weak symbols with older toolchains Naveen N Rao
2023-06-23 5:10 ` Christophe Leroy
2023-06-19 9:47 ` [PATCH 02/17] powerpc/module: Remove unused .ftrace.tramp section Naveen N Rao
2023-06-23 5:12 ` Christophe Leroy
2023-06-19 9:47 ` [PATCH 03/17] powerpc64/ftrace: Move ELFv1 and -pg support code into a separate file Naveen N Rao
2023-06-23 5:13 ` Christophe Leroy
2023-06-19 9:47 ` [PATCH 04/17] powerpc/ftrace: Simplify function_graph support in ftrace.c Naveen N Rao
2023-06-23 5:14 ` Christophe Leroy
2023-06-19 9:47 ` [PATCH 05/17] powerpc/ftrace: Use FTRACE_REGS_ADDR to identify the correct ftrace trampoline Naveen N Rao
2023-06-23 5:15 ` Christophe Leroy
2023-06-19 9:47 ` [PATCH 06/17] powerpc/ftrace: Extend ftrace support for large kernels to ppc32 Naveen N Rao
2023-06-23 5:21 ` Christophe Leroy
2023-06-19 9:47 ` [PATCH 07/17] powerpc/ftrace: Consolidate ftrace support into fewer files Naveen N Rao
2023-06-23 5:25 ` Christophe Leroy
2023-06-28 7:32 ` Naveen N Rao
2023-06-19 9:47 ` [PATCH 08/17] powerpc/ftrace: Refactor ftrace_modify_code() Naveen N Rao
2023-06-23 5:27 ` Christophe Leroy
2023-06-19 9:47 ` [PATCH 09/17] powerpc/ftrace: Stop re-purposing linker generated long branches for ftrace Naveen N Rao
2023-06-23 5:28 ` Christophe Leroy
2023-06-19 9:47 ` [PATCH 10/17] powerpc/ftrace: Add separate ftrace_init_nop() with additional validation Naveen N Rao
2023-06-23 5:29 ` Christophe Leroy
2023-06-19 9:47 ` [PATCH 11/17] powerpc/ftrace: Simplify ftrace_make_nop() Naveen N Rao
2023-06-23 5:30 ` Christophe Leroy
2023-06-19 9:47 ` [PATCH 12/17] powerpc/ftrace: Simplify ftrace_make_call() Naveen N Rao
2023-06-23 5:30 ` Christophe Leroy
2023-06-19 9:47 ` [PATCH 13/17] powerpc/ftrace: Simplify ftrace_modify_call() Naveen N Rao
2023-06-23 5:31 ` Christophe Leroy
2023-06-19 9:47 ` [PATCH 14/17] powerpc/ftrace: Replace use of ftrace_call_replace() with ftrace_create_branch_inst() Naveen N Rao
2023-06-23 5:32 ` Christophe Leroy
2023-06-19 9:47 ` [PATCH 15/17] powerpc/ftrace: Implement ftrace_replace_code() Naveen N Rao
2023-06-23 5:32 ` Christophe Leroy
2023-06-19 9:47 ` [PATCH 16/17] powerpc/ftrace: Add support for -fpatchable-function-entry Naveen N Rao
2023-06-23 5:37 ` Christophe Leroy
2023-06-28 7:40 ` Naveen N Rao [this message]
2023-06-19 9:47 ` [PATCH 17/17] powerpc/ftrace: Create a dummy stackframe to fix stack unwind Naveen N Rao
2023-06-23 5:40 ` Christophe Leroy
2023-06-28 7:43 ` Naveen N Rao
2023-08-23 11:55 ` [PATCH 00/17] powerpc/ftrace: refactor and add support for -fpatchable-function-entry Michael Ellerman
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