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author | Peter Zijlstra <peterz@infradead.org> | 2022-03-22 12:33:31 +0100 |
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committer | Peter Zijlstra <peterz@infradead.org> | 2022-04-05 10:24:40 +0200 |
commit | d139bca4b824ffb9731763c31b271a24b595948a (patch) | |
tree | 616c3ebbe255cf44d23b8172f062e5ef193af3ea /tools/objtool | |
parent | 9ce02f0fc68326dd1f87a0a3a4c6ae7fdd39e6f6 (diff) | |
download | linux-d139bca4b824ffb9731763c31b271a24b595948a.tar.gz linux-d139bca4b824ffb9731763c31b271a24b595948a.tar.bz2 linux-d139bca4b824ffb9731763c31b271a24b595948a.zip |
objtool: Fix IBT tail-call detection
Objtool reports:
arch/x86/crypto/poly1305-x86_64.o: warning: objtool: poly1305_blocks_avx() falls through to next function poly1305_blocks_x86_64()
arch/x86/crypto/poly1305-x86_64.o: warning: objtool: poly1305_emit_avx() falls through to next function poly1305_emit_x86_64()
arch/x86/crypto/poly1305-x86_64.o: warning: objtool: poly1305_blocks_avx2() falls through to next function poly1305_blocks_x86_64()
Which reads like:
0000000000000040 <poly1305_blocks_x86_64>:
40: f3 0f 1e fa endbr64
...
0000000000000400 <poly1305_blocks_avx>:
400: f3 0f 1e fa endbr64
404: 44 8b 47 14 mov 0x14(%rdi),%r8d
408: 48 81 fa 80 00 00 00 cmp $0x80,%rdx
40f: 73 09 jae 41a <poly1305_blocks_avx+0x1a>
411: 45 85 c0 test %r8d,%r8d
414: 0f 84 2a fc ff ff je 44 <poly1305_blocks_x86_64+0x4>
...
These are simple conditional tail-calls and *should* be recognised as
such by objtool, however due to a mistake in commit 08f87a93c8ec
("objtool: Validate IBT assumptions") this is failing.
Specifically, the jump_dest is +4, this means the instruction pointed
at will not be ENDBR and as such it will fail the second clause of
is_first_func_insn() that was supposed to capture this exact case.
Instead, have is_first_func_insn() look at the previous instruction.
Fixes: 08f87a93c8ec ("objtool: Validate IBT assumptions")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20220322115125.811582125@infradead.org
Diffstat (limited to 'tools/objtool')
-rw-r--r-- | tools/objtool/check.c | 19 |
1 files changed, 14 insertions, 5 deletions
diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 6de5085e3e5a..b848e1ddd5d8 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -1239,11 +1239,20 @@ static bool same_function(struct instruction *insn1, struct instruction *insn2) return insn1->func->pfunc == insn2->func->pfunc; } -static bool is_first_func_insn(struct instruction *insn) +static bool is_first_func_insn(struct objtool_file *file, struct instruction *insn) { - return insn->offset == insn->func->offset || - (insn->type == INSN_ENDBR && - insn->offset == insn->func->offset + insn->len); + if (insn->offset == insn->func->offset) + return true; + + if (ibt) { + struct instruction *prev = prev_insn_same_sym(file, insn); + + if (prev && prev->type == INSN_ENDBR && + insn->offset == insn->func->offset + prev->len) + return true; + } + + return false; } /* @@ -1327,7 +1336,7 @@ static int add_jump_destinations(struct objtool_file *file) insn->jump_dest->func->pfunc = insn->func; } else if (!same_function(insn, insn->jump_dest) && - is_first_func_insn(insn->jump_dest)) { + is_first_func_insn(file, insn->jump_dest)) { /* internal sibling call (without reloc) */ add_call_dest(file, insn, insn->jump_dest->func, true); } |