From fc0bb9915bce0c333f918ca76958d804ccd79f89 Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Thu, 23 Apr 2026 15:53:17 -0700 Subject: 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 Signed-off-by: Josh Poimboeuf --- scripts/Makefile.lib | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) (limited to 'scripts') 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) \ -- cgit v1.2.3