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author | Josh Poimboeuf <jpoimboe@redhat.com> | 2018-01-30 07:00:39 +0300 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-02-07 22:12:21 +0300 |
commit | a358df03279e806f8f4217eacf813c5b6c3578ee (patch) | |
tree | bb466fd3593554e940d8e46491f91b59baa12820 /tools | |
parent | 92f4b68ed14c7731cadd5bf7501a98da5302c093 (diff) | |
download | linux-a358df03279e806f8f4217eacf813c5b6c3578ee.tar.xz |
objtool: Improve retpoline alternative handling
commit a845c7cf4b4cb5e9e3b2823867892b27646f3a98
Currently objtool requires all retpolines to be:
a) patched in with alternatives; and
b) annotated with ANNOTATE_NOSPEC_ALTERNATIVE.
If you forget to do both of the above, objtool segfaults trying to
dereference a NULL 'insn->call_dest' pointer.
Avoid that situation and print a more helpful error message:
quirks.o: warning: objtool: efi_delete_dummy_variable()+0x99: unsupported intra-function call
quirks.o: warning: objtool: If this is a retpoline, please patch it in with alternatives and annotate it with ANNOTATE_NOSPEC_ALTERNATIVE.
Future improvements can be made to make objtool smarter with respect to
retpolines, but this is a good incremental improvement for now.
Reported-and-tested-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/819e50b6d9c2e1a22e34c1a636c0b2057cc8c6e5.1517284349.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'tools')
-rw-r--r-- | tools/objtool/check.c | 36 |
1 files changed, 16 insertions, 20 deletions
diff --git a/tools/objtool/check.c b/tools/objtool/check.c index f40d46e24bcc..bc3490d929ff 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -543,18 +543,14 @@ static int add_call_destinations(struct objtool_file *file) dest_off = insn->offset + insn->len + insn->immediate; insn->call_dest = find_symbol_by_offset(insn->sec, dest_off); - /* - * FIXME: Thanks to retpolines, it's now considered - * normal for a function to call within itself. So - * disable this warning for now. - */ -#if 0 - if (!insn->call_dest) { - WARN_FUNC("can't find call dest symbol at offset 0x%lx", - insn->sec, insn->offset, dest_off); + + if (!insn->call_dest && !insn->ignore) { + WARN_FUNC("unsupported intra-function call", + insn->sec, insn->offset); + WARN("If this is a retpoline, please patch it in with alternatives and annotate it with ANNOTATE_NOSPEC_ALTERNATIVE."); return -1; } -#endif + } else if (rela->sym->type == STT_SECTION) { insn->call_dest = find_symbol_by_offset(rela->sym->sec, rela->addend+4); @@ -648,6 +644,8 @@ static int handle_group_alt(struct objtool_file *file, last_new_insn = insn; + insn->ignore = orig_insn->ignore_alts; + if (insn->type != INSN_JUMP_CONDITIONAL && insn->type != INSN_JUMP_UNCONDITIONAL) continue; @@ -729,10 +727,6 @@ static int add_special_section_alts(struct objtool_file *file) goto out; } - /* Ignore retpoline alternatives. */ - if (orig_insn->ignore_alts) - continue; - new_insn = NULL; if (!special_alt->group || special_alt->new_len) { new_insn = find_insn(file, special_alt->new_sec, @@ -1089,11 +1083,11 @@ static int decode_sections(struct objtool_file *file) if (ret) return ret; - ret = add_call_destinations(file); + ret = add_special_section_alts(file); if (ret) return ret; - ret = add_special_section_alts(file); + ret = add_call_destinations(file); if (ret) return ret; @@ -1720,10 +1714,12 @@ static int validate_branch(struct objtool_file *file, struct instruction *first, insn->visited = true; - list_for_each_entry(alt, &insn->alts, list) { - ret = validate_branch(file, alt->insn, state); - if (ret) - return 1; + if (!insn->ignore_alts) { + list_for_each_entry(alt, &insn->alts, list) { + ret = validate_branch(file, alt->insn, state); + if (ret) + return 1; + } } switch (insn->type) { |