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| author | Josh Poimboeuf <jpoimboe@redhat.com> | 2020-04-01 21:23:25 +0300 |
|---|---|---|
| committer | Borislav Petkov <bp@suse.de> | 2020-04-14 12:55:09 +0300 |
| commit | bd841d6154f5f41f8a32d3c1b0bc229e326e640a (patch) | |
| tree | 6349f1956da0f00695f145f48a801496232cc3bf | |
| parent | 8f3d9f354286745c751374f5f1fcafee6b3f3136 (diff) | |
| download | linux-bd841d6154f5f41f8a32d3c1b0bc229e326e640a.tar.xz | |
objtool: Fix CONFIG_UBSAN_TRAP unreachable warnings
CONFIG_UBSAN_TRAP causes GCC to emit a UD2 whenever it encounters an
unreachable code path. This includes __builtin_unreachable(). Because
the BUG() macro uses __builtin_unreachable() after it emits its own UD2,
this results in a double UD2. In this case objtool rightfully detects
that the second UD2 is unreachable:
init/main.o: warning: objtool: repair_env_string()+0x1c8: unreachable instruction
We weren't able to figure out a way to get rid of the double UD2s, so
just silence the warning.
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/6653ad73c6b59c049211bd7c11ed3809c20ee9f5.1585761021.git.jpoimboe@redhat.com
| -rw-r--r-- | tools/objtool/check.c | 17 |
1 files changed, 15 insertions, 2 deletions
diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 8dd01f986fbb..481132539384 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -2364,14 +2364,27 @@ static bool ignore_unreachable_insn(struct instruction *insn) !strcmp(insn->sec->name, ".altinstr_aux")) return true; + if (!insn->func) + return false; + + /* + * CONFIG_UBSAN_TRAP inserts a UD2 when it sees + * __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). + */ + if (list_prev_entry(insn, list)->dead_end && + (insn->type == INSN_BUG || + (insn->type == INSN_JUMP_UNCONDITIONAL && + insn->jump_dest && insn->jump_dest->type == INSN_BUG))) + return true; + /* * Check if this (or a subsequent) instruction is related to * CONFIG_UBSAN or CONFIG_KASAN. * * End the search at 5 instructions to avoid going into the weeds. */ - if (!insn->func) - return false; for (i = 0; i < 5; i++) { if (is_kasan_insn(insn) || is_ubsan_insn(insn)) |