This is a note to let you know that I've just added the patch titled
objtool: Fix noreturn detection for ignored functions
to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
objtool-fix-noreturn-detection-for-ignored-functions.patch
and it can be found in the queue-4.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 7dd971d22ed262952967151a08ef9295718d4e05
Author: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Date: Thu Sep 10 10:24:57 2020 -0500
objtool: Fix noreturn detection for ignored functions
[ Upstream commit db6c6a0df840e3f52c84cc302cc1a08ba11a4416 ]
When a function is annotated with STACK_FRAME_NON_STANDARD, objtool
doesn't validate its code paths. It also skips sibling call detection
within the function.
But sibling call detection is actually needed for the case where the
ignored function doesn't have any return instructions. Otherwise
objtool naively marks the function as implicit static noreturn, which
affects the reachability of its callers, resulting in "unreachable
instruction" warnings.
Fix it by just enabling sibling call detection for ignored functions.
The 'insn->ignore' check in add_jump_destinations() is no longer needed
after
e6da9567959e ("objtool: Don't use ignore flag for fake jumps").
Fixes the following warning:
arch/x86/kvm/vmx/vmx.o: warning: objtool: vmx_handle_exit_irqoff()+0x142: unreachable instruction
which triggers on an allmodconfig with CONFIG_GCOV_KERNEL unset.
Reported-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Acked-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/5b1e2536cdbaa5246b60d7791b76130a74082c62.1599751464.git.jpoimboe@xxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 247fbb5f6a389..2c8e2dae17016 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -502,7 +502,7 @@ static int add_jump_destinations(struct objtool_file *file)
insn->type != INSN_JUMP_UNCONDITIONAL)
continue;
- if (insn->ignore || insn->offset == FAKE_JUMP_OFFSET)
+ if (insn->offset == FAKE_JUMP_OFFSET)
continue;
rela = find_rela_by_dest_range(insn->sec, insn->offset,
