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authorPeter Zijlstra <peterz@infradead.org>2022-03-23 23:35:01 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2022-04-13 19:27:42 +0200
commit53a4a15dd6d2b6d014ee49d9adc1f9b520ad23de (patch)
treed9e225d30d3fa1026329429bf7d801acb43bafca /tools
parent4c250bba3233ca709608f67c42ec6f6b203cc37d (diff)
objtool: Fix SLS validation for kcov tail-call replacement
commit 7a53f408902d913cd541b4f8ad7dbcd4961f5b82 upstream. Since not all compilers have a function attribute to disable KCOV instrumentation, objtool can rewrite KCOV instrumentation in noinstr functions as per commit: f56dae88a81f ("objtool: Handle __sanitize_cov*() tail calls") However, this has subtle interaction with the SLS validation from commit: 1cc1e4c8aab4 ("objtool: Add straight-line-speculation validation") In that when a tail-call instrucion is replaced with a RET an additional INT3 instruction is also written, but is not represented in the decoded instruction stream. This then leads to false positive missing INT3 objtool warnings in noinstr code. Instead of adding additional struct instruction objects, mark the RET instruction with retpoline_safe to suppress the warning (since we know there really is an INT3). Fixes: 1cc1e4c8aab4 ("objtool: Add straight-line-speculation validation") Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20220323230712.GA8939@worktop.programming.kicks-ass.net Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'tools')
-rw-r--r--tools/objtool/check.c11
1 files changed, 11 insertions, 0 deletions
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 7c33ec67c4a9..3470813daf4a 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1090,6 +1090,17 @@ static void annotate_call_site(struct objtool_file *file,
: arch_nop_insn(insn->len));
insn->type = sibling ? INSN_RETURN : INSN_NOP;
+
+ if (sibling) {
+ /*
+ * We've replaced the tail-call JMP insn by two new
+ * insn: RET; INT3, except we only have a single struct
+ * insn here. Mark it retpoline_safe to avoid the SLS
+ * warning, instead of adding another insn.
+ */
+ insn->retpoline_safe = true;
+ }
+
return;
}