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authorIlie Halip <ilie.halip@gmail.com>2020-09-19 09:41:18 +0300
committerJosh Poimboeuf <jpoimboe@redhat.com>2020-09-21 18:20:10 +0300
commit14db1f0a93331d0958e90da522c429ff0890d2d6 (patch)
tree09eb8e56cbb22665bd0c55c61d865969a933cf6e /tools/objtool
parent2b232a22d8225df419a92ca69ddeeb4e5fe902f7 (diff)
downloadlinux-14db1f0a93331d0958e90da522c429ff0890d2d6.tar.xz
objtool: Ignore unreachable trap after call to noreturn functions
With CONFIG_UBSAN_TRAP enabled, the compiler may insert a trap instruction after a call to a noreturn function. In this case, objtool warns that the UD2 instruction is unreachable. This is a behavior seen with Clang, from the oldest version capable of building the mainline x64_64 kernel (9.0), to the latest experimental version (12.0). Objtool silences similar warnings (trap after dead end instructions), so so expand that check to include dead end functions. Cc: Nick Desaulniers <ndesaulniers@google.com> Cc: Rong Chen <rong.a.chen@intel.com> Cc: Marco Elver <elver@google.com> Cc: Philip Li <philip.li@intel.com> Cc: Borislav Petkov <bp@alien8.de> Cc: kasan-dev@googlegroups.com Cc: x86@kernel.org Cc: clang-built-linux@googlegroups.com BugLink: https://github.com/ClangBuiltLinux/linux/issues/1148 Link: https://lore.kernel.org/lkml/CAKwvOdmptEpi8fiOyWUo=AiZJiX+Z+VHJOM2buLPrWsMTwLnyw@mail.gmail.com Suggested-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Tested-by: Nick Desaulniers <ndesaulniers@google.com> Reported-by: kbuild test robot <lkp@intel.com> Signed-off-by: Ilie Halip <ilie.halip@gmail.com> Tested-by: Sedat Dilek <sedat.dilek@gmail.com> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Diffstat (limited to 'tools/objtool')
-rw-r--r--tools/objtool/check.c10
1 files changed, 7 insertions, 3 deletions
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index a4796e32bbd1..2df9f769412e 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -2638,9 +2638,10 @@ static bool is_ubsan_insn(struct instruction *insn)
"__ubsan_handle_builtin_unreachable"));
}
-static bool ignore_unreachable_insn(struct instruction *insn)
+static bool ignore_unreachable_insn(struct objtool_file *file, struct instruction *insn)
{
int i;
+ struct instruction *prev_insn;
if (insn->ignore || insn->type == INSN_NOP)
return true;
@@ -2668,8 +2669,11 @@ static bool ignore_unreachable_insn(struct instruction *insn)
* __builtin_unreachable(). The BUG() macro has an unreachable() after
* the UD2, which causes GCC's undefined trap logic to emit another UD2
* (or occasionally a JMP to UD2).
+ *
+ * It may also insert a UD2 after calling a __noreturn function.
*/
- if (list_prev_entry(insn, list)->dead_end &&
+ prev_insn = list_prev_entry(insn, list);
+ if ((prev_insn->dead_end || dead_end_function(file, prev_insn->call_dest)) &&
(insn->type == INSN_BUG ||
(insn->type == INSN_JUMP_UNCONDITIONAL &&
insn->jump_dest && insn->jump_dest->type == INSN_BUG)))
@@ -2796,7 +2800,7 @@ static int validate_reachable_instructions(struct objtool_file *file)
return 0;
for_each_insn(file, insn) {
- if (insn->visited || ignore_unreachable_insn(insn))
+ if (insn->visited || ignore_unreachable_insn(file, insn))
continue;
WARN_FUNC("unreachable instruction", insn->sec, insn->offset);