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| author | Peter Zijlstra <peterz@infradead.org> | 2022-10-28 21:08:19 +0200 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2022-11-01 13:44:09 +0100 |
| commit | b341b20d648bb7e9a3307c33163e7399f0913e66 (patch) | |
| tree | 4e17b455af51640eec3f16b30821e6dc35a33b80 | |
| parent | 9f2899fe36a623885d8576604cb582328ad32b3c (diff) | |
x86: Add prefix symbols for function padding
When code is compiled with:
-fpatchable-function-entry=${PADDING_BYTES},${PADDING_BYTES}
functions will have PADDING_BYTES of NOP in front of them. Unwinders
and other things that symbolize code locations will typically
attribute these bytes to the preceding function.
Given that these bytes nominally belong to the following symbol this
mis-attribution is confusing.
Inspired by the fact that CFI_CLANG emits __cfi_##name symbols to
claim these bytes, use objtool to emit __pfx_##name symbols to do
the same when CFI_CLANG is not used.
This then shows the callthunk for symbol 'name' as:
__pfx_##name+0x6/0x10
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Yujie Liu <yujie.liu@intel.com>
Link: https://lkml.kernel.org/r/20221028194453.592512209@infradead.org
| -rw-r--r-- | arch/x86/Kconfig | 4 | ||||
| -rw-r--r-- | scripts/Makefile.lib | 1 |
2 files changed, 5 insertions, 0 deletions
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index b52ad13f0f44..32818aa1dca4 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -2471,6 +2471,10 @@ config CALL_THUNKS def_bool n select FUNCTION_ALIGNMENT_16B +config PREFIX_SYMBOLS + def_bool y + depends on CALL_THUNKS && !CFI_CLANG + menuconfig SPECULATION_MITIGATIONS bool "Mitigations for speculative execution vulnerabilities" default y diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib index 85f02756dc9c..2e03bcbf2b9b 100644 --- a/scripts/Makefile.lib +++ b/scripts/Makefile.lib @@ -265,6 +265,7 @@ objtool-args-$(CONFIG_STACK_VALIDATION) += --stackval objtool-args-$(CONFIG_HAVE_STATIC_CALL_INLINE) += --static-call objtool-args-$(CONFIG_HAVE_UACCESS_VALIDATION) += --uaccess objtool-args-$(CONFIG_GCOV_KERNEL) += --no-unreachable +objtool-args-$(CONFIG_PREFIX_SYMBOLS) += --prefix=$(CONFIG_FUNCTION_PADDING_BYTES) objtool-args = $(objtool-args-y) \ $(if $(delay-objtool), --link) \ |