asan: Add --param=asan-kernel-mem-intrinsic-prefix= [PR108777]

While in the -fsanitize=address case libasan overloads memcpy, memset,
memmove and many other builtins, such that they are always instrumented,
Linux kernel for -fsanitize=kernel-address recently changed or is changing,
such that memcpy, memset and memmove actually aren't instrumented because
they are often used also from no_sanitize ("kernel-address") functions
and wants __{,hw,}asaN_{memcpy,memset,memmove} to be used instead
for the instrumented calls.  See e.g. the https://lkml.org/lkml/2023/2/9/1182
thread.  Without appropriate support on the compiler side, that will mean
any time a kernel-address instrumented function (most of them) calls
memcpy/memset/memmove, they will not be instrumented and thus won't catch
kernel bugs.  Apparently clang 15 has a param for this.

The following patch implements the same (except it is a usual GCC --param,
not -mllvm argument) on the GCC side.  I know this isn't a regression
bugfix, but given that -fsanitize=kernel-address has a single project that
uses it which badly wants this I think it would be worthwhile to make an
exception and get this into GCC 13 rather than waiting another year, it
won't affect non-kernel code, nor even the kernel unless the new parameter
is used.

2023-02-14  Jakub Jelinek  <jakub@redhat.com>

	PR sanitizer/108777
	* params.opt (-param=asan-kernel-mem-intrinsic-prefix=): New param.
	* asan.h (asan_memfn_rtl): Declare.
	* asan.cc (asan_memfn_rtls): New variable.
	(asan_memfn_rtl): New function.
	* builtins.cc (expand_builtin): If
	param_asan_kernel_mem_intrinsic_prefix and function is
	kernel-{,hw}address sanitized, emit calls to
	__{,hw}asan_{memcpy,memmove,memset} rather than
	{memcpy,memmove,memset}.  Use sanitize_flags_p (SANITIZE_ADDRESS)
	instead of flag_sanitize & SANITIZE_ADDRESS to check if
	asan_intercepted_p functions shouldn't be expanded inline.

	* gcc.dg/asan/pr108777-1.c: New test.
	* gcc.dg/asan/pr108777-2.c: New test.
	* gcc.dg/asan/pr108777-3.c: New test.
	* gcc.dg/asan/pr108777-4.c: New test.
	* gcc.dg/asan/pr108777-5.c: New test.
	* gcc.dg/asan/pr108777-6.c: New test.
	* gcc.dg/completion-3.c: Adjust expected multiline output.

1 files changed, 40 insertions, 0 deletions

diff --git a/gcc/asan.cc b/gcc/asan.cc
index 57834b7..f56d084 100644
--- a/gcc/asan.cc
+++ b/gcc/asan.cc
@@ -391,6 +391,46 @@ asan_memintrin (void)
 }
 
 
+/* Support for --param asan-kernel-mem-intrinsic-prefix=1.  */
+static GTY(()) rtx asan_memfn_rtls[3];
+
+rtx
+asan_memfn_rtl (tree fndecl)
+{
+  int i;
+  const char *f, *p;
+  char buf[sizeof ("__hwasan_memmove")];
+
+  switch (DECL_FUNCTION_CODE (fndecl))
+    {
+    case BUILT_IN_MEMCPY: i = 0; f = "memcpy"; break;
+    case BUILT_IN_MEMSET: i = 1; f = "memset"; break;
+    case BUILT_IN_MEMMOVE: i = 2; f = "memmove"; break;
+    default: gcc_unreachable ();
+    }
+  if (asan_memfn_rtls[i] == NULL_RTX)
+    {
+      tree save_name = DECL_NAME (fndecl);
+      tree save_assembler_name = DECL_ASSEMBLER_NAME (fndecl);
+      rtx save_rtl = DECL_RTL (fndecl);
+      if (flag_sanitize & SANITIZE_KERNEL_HWADDRESS)
+	p = "__hwasan_";
+      else
+	p = "__asan_";
+      strcpy (buf, p);
+      strcat (buf, f);
+      DECL_NAME (fndecl) = get_identifier (buf);
+      DECL_ASSEMBLER_NAME_RAW (fndecl) = NULL_TREE;
+      SET_DECL_RTL (fndecl, NULL_RTX);
+      asan_memfn_rtls[i] = DECL_RTL (fndecl);
+      DECL_NAME (fndecl) = save_name;
+      DECL_ASSEMBLER_NAME_RAW (fndecl) = save_assembler_name;
+      SET_DECL_RTL (fndecl, save_rtl);
+    }
+  return asan_memfn_rtls[i];
+}
+
+
 /* Checks whether section SEC should be sanitized.  */
 
 static bool