4.15-stable review patch. If anyone has any objections, please let me know.
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From: Josh Poimboeuf jpoimboe@redhat.com
commit 17bc33914bcc98ba3c6b426fd1c49587a25c0597
Now that the previous patch gave objtool the ability to read retpoline alternatives, it shows a new warning:
arch/x86/entry/entry_64.o: warning: objtool: .entry_trampoline: don't know how to handle alternatives at end of section
This is due to the JMP_NOSPEC in entry_SYSCALL_64_trampoline().
Previously, objtool ignored this situation because it wasn't needed, and it would have required a bit of extra code. Now that this case exists, add proper support for it.
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: Guenter Roeck linux@roeck-us.net 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/2a30a3c2158af47d891a76e69bb1ef347e0443fd.1517284349... Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- tools/objtool/check.c | 53 +++++++++++++++++++++++++++++--------------------- 1 file changed, 31 insertions(+), 22 deletions(-)
--- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -594,7 +594,7 @@ static int handle_group_alt(struct objto struct instruction *orig_insn, struct instruction **new_insn) { - struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump; + struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump = NULL; unsigned long dest_off;
last_orig_insn = NULL; @@ -610,28 +610,30 @@ static int handle_group_alt(struct objto last_orig_insn = insn; }
- if (!next_insn_same_sec(file, last_orig_insn)) { - WARN("%s: don't know how to handle alternatives at end of section", - special_alt->orig_sec->name); - return -1; - } - - fake_jump = malloc(sizeof(*fake_jump)); - if (!fake_jump) { - WARN("malloc failed"); - return -1; + if (next_insn_same_sec(file, last_orig_insn)) { + fake_jump = malloc(sizeof(*fake_jump)); + if (!fake_jump) { + WARN("malloc failed"); + return -1; + } + memset(fake_jump, 0, sizeof(*fake_jump)); + INIT_LIST_HEAD(&fake_jump->alts); + clear_insn_state(&fake_jump->state); + + fake_jump->sec = special_alt->new_sec; + fake_jump->offset = -1; + fake_jump->type = INSN_JUMP_UNCONDITIONAL; + fake_jump->jump_dest = list_next_entry(last_orig_insn, list); + fake_jump->ignore = true; } - memset(fake_jump, 0, sizeof(*fake_jump)); - INIT_LIST_HEAD(&fake_jump->alts); - clear_insn_state(&fake_jump->state); - - fake_jump->sec = special_alt->new_sec; - fake_jump->offset = -1; - fake_jump->type = INSN_JUMP_UNCONDITIONAL; - fake_jump->jump_dest = list_next_entry(last_orig_insn, list); - fake_jump->ignore = true;
if (!special_alt->new_len) { + if (!fake_jump) { + WARN("%s: empty alternative at end of section", + special_alt->orig_sec->name); + return -1; + } + *new_insn = fake_jump; return 0; } @@ -654,8 +656,14 @@ static int handle_group_alt(struct objto continue;
dest_off = insn->offset + insn->len + insn->immediate; - if (dest_off == special_alt->new_off + special_alt->new_len) + if (dest_off == special_alt->new_off + special_alt->new_len) { + if (!fake_jump) { + WARN("%s: alternative jump to end of section", + special_alt->orig_sec->name); + return -1; + } insn->jump_dest = fake_jump; + }
if (!insn->jump_dest) { WARN_FUNC("can't find alternative jump destination", @@ -670,7 +678,8 @@ static int handle_group_alt(struct objto return -1; }
- list_add(&fake_jump->list, &last_new_insn->list); + if (fake_jump) + list_add(&fake_jump->list, &last_new_insn->list);
return 0; }