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| author | Jiri Olsa <jolsa@kernel.org> | 2022-09-03 15:11:54 +0200 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2022-09-16 22:23:20 +0200 |
| commit | ceea991a019c57a1fb0edd12a5f836a0fa431aee (patch) | |
| tree | a7f8c1564646e0e153392ddaf5369ae1135b9781 /arch/x86/Kconfig | |
| parent | 9440155ccb948f8e3ce5308907a2e7378799be60 (diff) | |
| download | linux-ceea991a019c57a1fb0edd12a5f836a0fa431aee.tar.bz2 | |
bpf: Move bpf_dispatcher function out of ftrace locations
The dispatcher function is attached/detached to trampoline by
dispatcher update function. At the same time it's available as
ftrace attachable function.
After discussion [1] the proposed solution is to use compiler
attributes to alter bpf_dispatcher_##name##_func function:
- remove it from being instrumented with __no_instrument_function__
attribute, so ftrace has no track of it
- but still generate 5 nop instructions with patchable_function_entry(5)
attribute, which are expected by bpf_arch_text_poke used by
dispatcher update function
Enabling HAVE_DYNAMIC_FTRACE_NO_PATCHABLE option for x86, so
__patchable_function_entries functions are not part of ftrace/mcount
locations.
Adding attributes to bpf_dispatcher_XXX function on x86_64 so it's
kept out of ftrace locations and has 5 byte nop generated at entry.
These attributes need to be arch specific as pointed out by Ilya
Leoshkevic in here [2].
The dispatcher image is generated only for x86_64 arch, so the
code can stay as is for other archs.
[1] https://lore.kernel.org/bpf/20220722110811.124515-1-jolsa@kernel.org/
[2] https://lore.kernel.org/bpf/969a14281a7791c334d476825863ee449964dd0c.camel@linux.ibm.com/
Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/bpf/20220903131154.420467-3-jolsa@kernel.org
Diffstat (limited to 'arch/x86/Kconfig')
| -rw-r--r-- | arch/x86/Kconfig | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index f9920f1341c8..089c20cefd2b 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -284,6 +284,7 @@ config X86 select PROC_PID_ARCH_STATUS if PROC_FS select HAVE_ARCH_NODE_DEV_GROUP if X86_SGX imply IMA_SECURE_AND_OR_TRUSTED_BOOT if EFI + select HAVE_DYNAMIC_FTRACE_NO_PATCHABLE config INSTRUCTION_DECODER def_bool y |