samsung_sm8750/android_kernel_samsung_sm8750
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

objtool: Ignore end-of-section jumps for KCOV/GCOV

Browse Source 
commit 0d7597749f5a3ac67851d3836635d084df15fb66 upstream.

When KCOV or GCOV is enabled, dead code can be left behind, in which
case objtool silences unreachable and undefined behavior (fallthrough)
warnings.

Fallthrough warnings, and their variant "end of section" warnings, were
silenced with the following commit:

  6b023c784204 ("objtool: Silence more KCOV warnings")

Another variant of a fallthrough warning is a jump to the end of a
function.  If that function happens to be at the end of a section, the
jump destination doesn't actually exist.

Normally that would be a fatal objtool error, but for KCOV/GCOV it's
just another undefined behavior fallthrough.  Silence it like the
others.

Fixes the following warning:

  drivers/iommu/dma-iommu.o: warning: objtool: iommu_dma_sw_msi+0x92: can't find jump dest instruction at .text+0x54d5

Fixes: 6b023c784204 ("objtool: Silence more KCOV warnings")
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/08fbe7d7e1e20612206f1df253077b94f178d93e.1743481539.git.jpoimboe@kernel.org
Closes: https://lore.kernel.org/314f8809-cd59-479b-97d7-49356bf1c8d1@infradead.org/
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Josh Poimboeuf
2025-03-31 21:26:37 -07:00
committed by Greg Kroah-Hartman
parent 26084aa1a1
commit 014a761be0
1 changed files with 16 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files

22
tools/objtool/check.c
View File

@@ -1552,6 +1552,8 @@ static int add_jump_destinations(struct objtool_file *file)
unsigned long dest_off;
for_each_insn(file, insn) {
struct symbol *func = insn_func(insn);
if (insn->jump_dest) {
/*
* handle_group_alt() may have previously set
@@ -1575,7 +1577,7 @@ static int add_jump_destinations(struct objtool_file *file)
} else if (reloc->sym->return_thunk) {
add_return_call(file, insn, true);
continue;
} else if (insn_func(insn)) {
} else if (func) {
/*
* External sibling call or internal sibling call with
* STT_FUNC reloc.
@@ -1608,6 +1610,15 @@ static int add_jump_destinations(struct objtool_file *file)
continue;
}
/*
* GCOV/KCOV dead code can jump to the end of the
* function/section.
*/
if (file->ignore_unreachables && func &&
dest_sec == insn->sec &&
dest_off == func->offset + func->len)
continue;
WARN_INSN(insn, "can't find jump dest instruction at %s+0x%lx",
dest_sec->name, dest_off);
return -1;
@@ -1616,8 +1627,7 @@ static int add_jump_destinations(struct objtool_file *file)
/*
* Cross-function jump.
*/
if (insn_func(insn) && insn_func(jump_dest) &&
insn_func(insn) != insn_func(jump_dest)) {
if (func && insn_func(jump_dest) && func != insn_func(jump_dest)) {
/*
* For GCC 8+, create parent/child links for any cold
@@ -1634,10 +1644,10 @@ static int add_jump_destinations(struct objtool_file *file)
* case where the parent function's only reference to a
* subfunction is through a jump table.
*/
if (!strstr(insn_func(insn)->name, ".cold") &&
if (!strstr(func->name, ".cold") &&
strstr(insn_func(jump_dest)->name, ".cold")) {
insn_func(insn)->cfunc = insn_func(jump_dest);
insn_func(jump_dest)->pfunc = insn_func(insn);
func->cfunc = insn_func(jump_dest);
insn_func(jump_dest)->pfunc = func;
}
}