objtool fixes
Linus,
Please pull the latest core-urgent-for-linus git tree from:
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git core-urgent-for-linus
# HEAD: c2bb9e32e2315971a8535fee77335c04a739d71d objtool: Fix Makefile to properly see if libelf is supported
A handful of objtool fixes: two improvements to how warnings are printed plus a false positive warning fix, and build environment fix.
Thanks,
Ingo
------------------>
Josh Poimboeuf (2):
objtool: Add workaround for GCC switch jump table bug
objtool: Detect falling through to the next function
Steven Rostedt (1):
objtool: Fix Makefile to properly see if libelf is supported
Makefile | 3 +- tools/objtool/Documentation/stack-validation.txt | 38 +++++++--- tools/objtool/builtin-check.c | 97 ++++++++++++++++++------ 3 files changed, 103 insertions(+), 35 deletions(-)
Makefile +2 -1
@@ -1008,7 +1008,8 @@ prepare0: archprepare FORCE prepare: prepare0 prepare-objtool ifdef CONFIG_STACK_VALIDATION - has_libelf := $(shell echo "int main() {}" | $(HOSTCC) -xc -o /dev/null -lelf - &> /dev/null && echo 1 || echo 0) + has_libelf := $(call try-run,\ + echo "int main() {}" | $(HOSTCC) -xc -o /dev/null -lelf -,1,0) ifeq ($(has_libelf),1) objtool_target := tools/objtool FORCE else
tools/objtool/Documentation/stack-validation.txt +29 -9
@@ -299,18 +299,38 @@ they mean, and suggestions for how to fix them. Errors in .c files ------------------ -If you're getting an objtool error in a compiled .c file, chances are -the file uses an asm() statement which has a "call" instruction. An -asm() statement with a call instruction must declare the use of the -stack pointer in its output operand. For example, on x86_64: +1. c_file.o: warning: objtool: funcA() falls through to next function funcB() - register void *__sp asm("rsp"); - asm volatile("call func" : "+r" (__sp)); + This means that funcA() doesn't end with a return instruction or an + unconditional jump, and that objtool has determined that the function + can fall through into the next function. There could be different + reasons for this: -Otherwise the stack frame may not get created before the call. + 1) funcA()'s last instruction is a call to a "noreturn" function like + panic(). In this case the noreturn function needs to be added to + objtool's hard-coded global_noreturns array. Feel free to bug the + objtool maintainer, or you can submit a patch. -Another possible cause for errors in C code is if the Makefile removes --fno-omit-frame-pointer or adds -fomit-frame-pointer to the gcc options. + 2) funcA() uses the unreachable() annotation in a section of code + that is actually reachable. + + 3) If funcA() calls an inline function, the object code for funcA() + might be corrupt due to a gcc bug. For more details, see: + https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70646 + +2. If you're getting any other objtool error in a compiled .c file, it + may be because the file uses an asm() statement which has a "call" + instruction. An asm() statement with a call instruction must declare + the use of the stack pointer in its output operand. For example, on + x86_64: + + register void *__sp asm("rsp"); + asm volatile("call func" : "+r" (__sp)); + + Otherwise the stack frame may not get created before the call. + +3. Another possible cause for errors in C code is if the Makefile removes + -fno-omit-frame-pointer or adds -fomit-frame-pointer to the gcc options. Also see the above section for .S file errors for more information what the individual error messages mean.
tools/objtool/builtin-check.c +72 -25
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