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authorPeter Zijlstra <peterz@infradead.org>2022-03-22 12:33:31 +0100
committerPeter Zijlstra <peterz@infradead.org>2022-04-05 10:24:40 +0200
commitd139bca4b824ffb9731763c31b271a24b595948a (patch)
tree616c3ebbe255cf44d23b8172f062e5ef193af3ea /tools/objtool
parent9ce02f0fc68326dd1f87a0a3a4c6ae7fdd39e6f6 (diff)
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.c19
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);
}