4.15-stable review patch. If anyone has any objections, please let me know.
------------------
From: Josh Poimboeuf jpoimboe@redhat.com
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... Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- tools/objtool/check.c | 36 ++++++++++++++++-------------------- 1 file changed, 16 insertions(+), 20 deletions(-)
--- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -543,18 +543,14 @@ static int add_call_destinations(struct 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 objto
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(stru 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 objtoo 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 objtoo
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) {