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objtool: Detect jumps to retpoline thunks

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A direct jump to a retpoline thunk is really an indirect jump in
disguise.  Change the objtool instruction type accordingly.

Objtool needs to know where indirect branches are so it can detect
switch statement jump tables.

This fixes a bunch of warnings with CONFIG_RETPOLINE like:

  arch/x86/events/intel/uncore_nhmex.o: warning: objtool: nhmex_rbox_msr_enable_event()+0x44: sibling call from callable instruction with modified stack frame
  kernel/signal.o: warning: objtool: copy_siginfo_to_user()+0x91: sibling call from callable instruction with modified stack frame
  ...

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: gnomes@lxorguk.ukuu.org.uk
Cc: Rik van Riel <riel@redhat.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: thomas.lendacky@amd.com
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Kees Cook <keescook@google.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@linux-foundation.org>
Cc: Paul Turner <pjt@google.com>
Link: https://lkml.kernel.org/r/1515707194-20531-2-git-send-email-dwmw@amazon.co.uk
This commit is contained in:
Josh Poimboeuf 2018-01-11 21:46:23 +00:00 committed by Thomas Gleixner
parent 445b69e3b7
commit 39b735332c
1 changed files with 7 additions and 0 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

7
tools/objtool/check.c
View file

@ -456,6 +456,13 @@ static int add_jump_destinations(struct objtool_file *file)
} else if (rela->sym->sec->idx) {
dest_sec = rela->sym->sec;
dest_off = rela->sym->sym.st_value + rela->addend + 4;
} else if (strstr(rela->sym->name, "_indirect_thunk_")) {
/*
* Retpoline jumps are really dynamic jumps in
* disguise, so convert them accordingly.
*/
insn->type = INSN_JUMP_DYNAMIC;
continue;
} else {
/* sibling call */
insn->jump_dest = 0;