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| author | Josh Poimboeuf <jpoimboe@kernel.org> | 2026-04-23 15:53:17 -0700 |
|---|---|---|
| committer | Josh Poimboeuf <jpoimboe@kernel.org> | 2026-05-04 21:16:07 -0700 |
| commit | fc0bb9915bce0c333f918ca76958d804ccd79f89 (patch) | |
| tree | 4623f5e23f16b8d185f7a59b1f61c625947594c7 /scripts/Makefile.lib | |
| parent | cca84cb12908f1cfcecaef80a7692017e2d6a945 (diff) | |
objtool: Grow __cfi_* prefix symbols for all CFI+CALL_PADDING
For all CONFIG_CFI+CONFIG_CALL_PADDING configs, for C functions, the
__cfi_ symbols only cover the 5-byte kCFI type hash. After that there
also N bytes of NOP padding between the hash and the function entry
which aren't associated with any symbol.
The NOPs can be replaced with actual code at runtime. Without a symbol,
unwinders and tooling have no way of knowing where those bytes belong.
Grow the existing __cfi_* symbols to fill that gap.
Note that assembly functions with SYM_TYPED_FUNC_START() aren't affected
by this issue, their __cfi_ symbols also cover the padding.
Also, CONFIG_PREFIX_SYMBOLS has no reason to exist: CONFIG_CALL_PADDING
is what causes the compiler to emit NOP padding before function entry
(via -fpatchable-function-entry), so it's the right condition for
creating prefix symbols.
Remove CONFIG_PREFIX_SYMBOLS, as it's no longer needed. Simplify the
LONGEST_SYM_KUNIT_TEST dependency accordingly. Rework objtool's
arguments a bit to handle the variety of prefix/cfi-related cases.
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Diffstat (limited to 'scripts/Makefile.lib')
| -rw-r--r-- | scripts/Makefile.lib | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib index 0718e39cedda..7e216d82e988 100644 --- a/scripts/Makefile.lib +++ b/scripts/Makefile.lib @@ -187,7 +187,11 @@ objtool-args-$(CONFIG_HAVE_JUMP_LABEL_HACK) += --hacks=jump_label objtool-args-$(CONFIG_HAVE_NOINSTR_HACK) += --hacks=noinstr objtool-args-$(CONFIG_MITIGATION_CALL_DEPTH_TRACKING) += --hacks=skylake objtool-args-$(CONFIG_X86_KERNEL_IBT) += --ibt -objtool-args-$(CONFIG_FINEIBT) += --cfi +objtool-args-$(CONFIG_CALL_PADDING) += --prefix=$(CONFIG_FUNCTION_PADDING_BYTES) +ifdef CONFIG_CALL_PADDING +objtool-args-$(CONFIG_CFI) += --cfi +objtool-args-$(CONFIG_FINEIBT) += --fineibt +endif objtool-args-$(CONFIG_FTRACE_MCOUNT_USE_OBJTOOL) += --mcount ifdef CONFIG_FTRACE_MCOUNT_USE_OBJTOOL objtool-args-$(CONFIG_HAVE_OBJTOOL_NOP_MCOUNT) += --mnop @@ -200,7 +204,6 @@ objtool-args-$(CONFIG_STACK_VALIDATION) += --stackval objtool-args-$(CONFIG_HAVE_STATIC_CALL_INLINE) += --static-call objtool-args-$(CONFIG_HAVE_UACCESS_VALIDATION) += --uaccess objtool-args-$(or $(CONFIG_GCOV_KERNEL),$(CONFIG_KCOV)) += --no-unreachable -objtool-args-$(CONFIG_PREFIX_SYMBOLS) += --prefix=$(CONFIG_FUNCTION_PADDING_BYTES) objtool-args-$(CONFIG_OBJTOOL_WERROR) += --werror objtool-args = $(objtool-args-y) \ |