From cef0c0bb13e2953b41caca0506ab1d41c56f29de Mon Sep 17 00:00:00 2001
From: Alexander Monakov <amonakov@ispras.ru>
Date: Thu, 19 Jan 2023 19:25:04 +0300
Subject: [PATCH] do not tailcall __sanitizer_cov_trace_pc [PR90746]
When instrumentation is requested via -fsanitize-coverage=trace-pc, GCC
emits calls of __sanitizer_cov_trace_pc callback in each basic block.
This callback is supposed to be implemented by the user, and should be
able to identify the containing basic block by inspecting its return
address. Tailcalling the callback prevents that, so disallow it.
gcc/ChangeLog:
PR sanitizer/90746
* calls.cc (can_implement_as_sibling_call_p): Reject calls
to __sanitizer_cov_trace_pc.
gcc/testsuite/ChangeLog:
PR sanitizer/90746
* gcc.dg/sancov/basic0.c: Verify absence of tailcall.
---
gcc/calls.cc | 10 ++++++++++
gcc/testsuite/gcc.dg/sancov/basic0.c | 4 +++-
2 files changed, 13 insertions(+), 1 deletion(-)
diff --git a/gcc/calls.cc b/gcc/calls.cc
index 4d7f6c3d2912..1c9abccef681 100644
--- a/gcc/calls.cc
+++ b/gcc/calls.cc
@@ -2541,6 +2541,16 @@ can_implement_as_sibling_call_p (tree exp,
return false;
}
+ /* __sanitizer_cov_trace_pc is supposed to inspect its return address
+ to identify the caller, and therefore should not be tailcalled. */
+ if (fndecl && DECL_BUILT_IN_CLASS (fndecl) == BUILT_IN_NORMAL
+ && DECL_FUNCTION_CODE (fndecl) == BUILT_IN_SANITIZER_COV_TRACE_PC)
+ {
+ /* No need for maybe_complain_about_tail_call here:
+ the call is synthesized by the compiler. */
+ return false;
+ }
+
/* If the called function is nested in the current one, it might access
some of the caller's arguments, but could clobber them beforehand if
the argument areas are shared. */
diff --git a/gcc/testsuite/gcc.dg/sancov/basic0.c b/gcc/testsuite/gcc.dg/sancov/basic0.c
index af69b2d12ed2..dfdaea848020 100644
--- a/gcc/testsuite/gcc.dg/sancov/basic0.c
+++ b/gcc/testsuite/gcc.dg/sancov/basic0.c
@@ -1,9 +1,11 @@
/* Basic test on number of inserted callbacks. */
/* { dg-do compile } */
-/* { dg-options "-fsanitize-coverage=trace-pc -fdump-tree-optimized" } */
+/* { dg-options "-fsanitize-coverage=trace-pc -fdump-tree-optimized -fdump-rtl-expand" } */
void foo(void)
{
}
/* { dg-final { scan-tree-dump-times "__builtin___sanitizer_cov_trace_pc \\(\\)" 1 "optimized" } } */
+/* The built-in should not be tail-called: */
+/* { dg-final { scan-rtl-dump-not "call_insn/j" "expand" } } */
--
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