6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Josh Poimboeuf jpoimboe@kernel.org
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.174348153... Closes: https://lore.kernel.org/314f8809-cd59-479b-97d7-49356bf1c8d1@infradead.org/ Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- tools/objtool/check.c | 22 ++++++++++++++++------ 1 file changed, 16 insertions(+), 6 deletions(-)
--- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -1552,6 +1552,8 @@ static int add_jump_destinations(struct 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 } 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 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 /* * 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 * 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; } }