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[PATCH] Limit removal of UBSAN_NULL checks


This patch limits optimizing UBSAN_NULL checks a bit, so that we
don't lose diagnostics.
If we know we're on a path where segv would have already occured,
we can drop further checks (e.g. dereferencing a NULL pointer - we
can't recover from that).  Also if we're not recovering or using
-fsanitize-undefined-trap-on-error we can clear checks that are
dominated.  Furthermore, if we have more checks for the same location,
there's no point in keeping all of them.

Bootstrap-ubsan/regtest passed on x86_64-linux, ok for trunk?

2014-11-05  Marek Polacek  <polacek@redhat.com>

	* sanopt.c (sanopt_optimize_walker): Limit removal of the checks.
testsuite/
	* c-c++-common/ubsan/align-2.c: Add dg-output.
	* c-c++-common/ubsan/align-4.c: Likewise.
	* c-c++-common/ubsan/align-6.c: New test.
	* c-c++-common/ubsan/align-7.c: New test.
	* c-c++-common/ubsan/align-8.c: New test.
	* g++.dg/ubsan/null-1.C: Add dg-output.
	* g++.dg/ubsan/null-2.C: Likewise.
	* g++.dg/ubsan/null-3.C: New test.
	* g++.dg/ubsan/null-4.C: New test.
	* g++.dg/ubsan/null-5.C: New test.

diff --git gcc/sanopt.c gcc/sanopt.c
index 4483ff7..cb172d3 100644
--- gcc/sanopt.c
+++ gcc/sanopt.c
@@ -130,7 +130,27 @@ sanopt_optimize_walker (basic_block bb, struct sanopt_ctx *ctx)
 			  /* At this point we shouldn't have any statements
 			     that aren't dominating the current BB.  */
 			  tree align = gimple_call_arg (g, 2);
-			  remove = tree_int_cst_le (cur_align, align);
+			  int kind = tree_to_shwi (gimple_call_arg (g, 1));
+			  /* If this is a NULL pointer check where we had segv
+			     anyway, we can remove it.  */
+			  if (integer_zerop (align)
+			      && (kind == UBSAN_LOAD_OF
+				  || kind == UBSAN_STORE_OF
+				  || kind == UBSAN_MEMBER_ACCESS))
+			    remove = true;
+			  /* Otherwise remove the check in non-recovering
+			     mode, or if the stmts have same location.  */
+			  else if (integer_zerop (align))
+			    remove = !(flag_sanitize_recover & SANITIZE_NULL)
+				     || flag_sanitize_undefined_trap_on_error
+				     || gimple_location (g)
+					== gimple_location (stmt);
+			  else if (tree_int_cst_le (cur_align, align))
+			    remove = !(flag_sanitize_recover
+				       & SANITIZE_ALIGNMENT)
+				     || flag_sanitize_undefined_trap_on_error
+				     || gimple_location (g)
+					== gimple_location (stmt);
 			  break;
 			}
 		    }
diff --git gcc/testsuite/c-c++-common/ubsan/align-2.c gcc/testsuite/c-c++-common/ubsan/align-2.c
index 02a26e2..071de8c 100644
--- gcc/testsuite/c-c++-common/ubsan/align-2.c
+++ gcc/testsuite/c-c++-common/ubsan/align-2.c
@@ -51,4 +51,6 @@ main ()
 /* { dg-output "\.c:(13|16):\[0-9]*: \[^\n\r]*store to misaligned address 0x\[0-9a-fA-F]* for type 'int', which requires 4 byte alignment.*" } */
 /* { dg-output "\.c:23:\[0-9]*: \[^\n\r]*member access within misaligned address 0x\[0-9a-fA-F]* for type 'struct S', which requires \[48] byte alignment.*" } */
 /* { dg-output "\.c:(29|30):\[0-9]*: \[^\n\r]*member access within misaligned address 0x\[0-9a-fA-F]* for type 'struct S', which requires \[48] byte alignment.*" } */
+/* { dg-output "\.c:30:\[0-9]*: \[^\n\r]*member access within misaligned address 0x\[0-9a-fA-F]* for type 'struct S', which requires \[48] byte alignment.*" } */
+/* { dg-output "\.c:31:\[0-9]*: \[^\n\r]*member access within misaligned address 0x\[0-9a-fA-F]* for type 'struct S', which requires \[48] byte alignment.*" } */
 /* { dg-output "\.c:37:\[0-9]*: \[^\n\r]*load of misaligned address 0x\[0-9a-fA-F]* for type 'long long int', which requires \[48] byte alignment" } */
diff --git gcc/testsuite/c-c++-common/ubsan/align-4.c gcc/testsuite/c-c++-common/ubsan/align-4.c
index f010589..3252595 100644
--- gcc/testsuite/c-c++-common/ubsan/align-4.c
+++ gcc/testsuite/c-c++-common/ubsan/align-4.c
@@ -9,4 +9,6 @@
 /* { dg-output "\[^\n\r]*\.c:(13|16):\[0-9]*: \[^\n\r]*store to misaligned address 0x\[0-9a-fA-F]* for type 'int', which requires 4 byte alignment.*" } */
 /* { dg-output "\[^\n\r]*\.c:23:\[0-9]*: \[^\n\r]*member access within misaligned address 0x\[0-9a-fA-F]* for type 'struct S', which requires \[48] byte alignment.*" } */
 /* { dg-output "\[^\n\r]*\.c:(29|30):\[0-9]*: \[^\n\r]*member access within misaligned address 0x\[0-9a-fA-F]* for type 'struct S', which requires \[48] byte alignment.*" } */
+/* { dg-output "\[^\n\r]*\.c:30:\[0-9]*: \[^\n\r]*member access within misaligned address 0x\[0-9a-fA-F]* for type 'struct S', which requires \[48] byte alignment.*" } */
+/* { dg-output "\[^\n\r]*\.c:31:\[0-9]*: \[^\n\r]*member access within misaligned address 0x\[0-9a-fA-F]* for type 'struct S', which requires \[48] byte alignment.*" } */
 /* { dg-output "\[^\n\r]*\.c:37:\[0-9]*: \[^\n\r]*load of misaligned address 0x\[0-9a-fA-F]* for type 'long long int', which requires \[48] byte alignment" } */
diff --git gcc/testsuite/c-c++-common/ubsan/align-6.c gcc/testsuite/c-c++-common/ubsan/align-6.c
index e69de29..5521292 100644
--- gcc/testsuite/c-c++-common/ubsan/align-6.c
+++ gcc/testsuite/c-c++-common/ubsan/align-6.c
@@ -0,0 +1,33 @@
+/* Limit this to known non-strict alignment targets.  */
+/* { dg-do run { target { i?86-*-linux* x86_64-*-linux* } } } */
+/* { dg-options "-O -fsanitize=alignment -fsanitize-recover=alignment" } */
+
+struct S { int a; char b; long long c; short d[10]; };
+struct T { char a; long long b; };
+struct U { char a; int b; int c; long long d; struct S e; struct T f; } __attribute__((packed));
+struct V { long long a; struct S b; struct T c; struct U u; } v;
+
+__attribute__((noinline, noclone)) int
+foo (struct S *p)
+{
+  volatile int i;
+  i = p->a;
+  i = p->a;
+  i = p->a;
+  i = p->a;
+  return p->a;
+}
+
+int
+main ()
+{
+  if (foo (&v.u.e))
+    __builtin_abort ();
+  return 0;
+}
+
+/* { dg-output "\.c:14:\[0-9]*: \[^\n\r]*member access within misaligned address 0x\[0-9a-fA-F]* for type 'struct S', which requires \[48] byte alignment.*" } */
+/* { dg-output "\.c:15:\[0-9]*: \[^\n\r]*member access within misaligned address 0x\[0-9a-fA-F]* for type 'struct S', which requires \[48] byte alignment.*" } */
+/* { dg-output "\.c:16:\[0-9]*: \[^\n\r]*member access within misaligned address 0x\[0-9a-fA-F]* for type 'struct S', which requires \[48] byte alignment.*" } */
+/* { dg-output "\.c:17:\[0-9]*: \[^\n\r]*member access within misaligned address 0x\[0-9a-fA-F]* for type 'struct S', which requires \[48] byte alignment.*" } */
+/* { dg-output "\.c:18:\[0-9]*: \[^\n\r]*member access within misaligned address 0x\[0-9a-fA-F]* for type 'struct S', which requires \[48] byte alignment.*" } */
diff --git gcc/testsuite/c-c++-common/ubsan/align-7.c gcc/testsuite/c-c++-common/ubsan/align-7.c
index e69de29..4a18d8d 100644
--- gcc/testsuite/c-c++-common/ubsan/align-7.c
+++ gcc/testsuite/c-c++-common/ubsan/align-7.c
@@ -0,0 +1,32 @@
+/* Limit this to known non-strict alignment targets.  */
+/* { dg-do run { target { i?86-*-linux* x86_64-*-linux* } } } */
+/* { dg-options "-O -fsanitize=alignment -fno-sanitize-recover=alignment -fdump-tree-sanopt-details" } */
+/* { dg-shouldfail "ubsan" } */
+
+struct S { int a; char b; long long c; short d[10]; };
+struct T { char a; long long b; };
+struct U { char a; int b; int c; long long d; struct S e; struct T f; } __attribute__((packed));
+struct V { long long a; struct S b; struct T c; struct U u; } v;
+
+__attribute__((noinline, noclone)) int
+foo (struct S *p)
+{
+  volatile int i;
+  i = p->a;
+  i = p->a;
+  i = p->a;
+  i = p->a;
+  return p->a;
+}
+
+int
+main ()
+{
+  if (foo (&v.u.e))
+    __builtin_abort ();
+  return 0;
+}
+
+/* { dg-output "\.c:15:\[0-9]*: \[^\n\r]*member access within misaligned address 0x\[0-9a-fA-F]* for type 'struct S', which requires \[48] byte alignment.*" } */
+/* { dg-final { scan-tree-dump-times "Optimizing" 4 "sanopt"} } */
+/* { dg-final { cleanup-tree-dump "sanopt" } } */
diff --git gcc/testsuite/c-c++-common/ubsan/align-8.c gcc/testsuite/c-c++-common/ubsan/align-8.c
index e69de29..b930162 100644
--- gcc/testsuite/c-c++-common/ubsan/align-8.c
+++ gcc/testsuite/c-c++-common/ubsan/align-8.c
@@ -0,0 +1,31 @@
+/* Limit this to known non-strict alignment targets.  */
+/* { dg-do run { target { i?86-*-linux* x86_64-*-linux* } } } */
+/* { dg-options "-O -fsanitize=alignment -fsanitize-undefined-trap-on-error -fdump-tree-sanopt-details" } */
+/* { dg-shouldfail "ubsan" } */
+
+struct S { int a; char b; long long c; short d[10]; };
+struct T { char a; long long b; };
+struct U { char a; int b; int c; long long d; struct S e; struct T f; } __attribute__((packed));
+struct V { long long a; struct S b; struct T c; struct U u; } v;
+
+__attribute__((noinline, noclone)) int
+foo (struct S *p)
+{
+  volatile int i;
+  i = p->a;
+  i = p->a;
+  i = p->a;
+  i = p->a;
+  return p->a;
+}
+
+int
+main ()
+{
+  if (foo (&v.u.e))
+    __builtin_abort ();
+  return 0;
+}
+
+/* { dg-final { scan-tree-dump-times "Optimizing" 4 "sanopt"} } */
+/* { dg-final { cleanup-tree-dump "sanopt" } } */
diff --git gcc/testsuite/g++.dg/ubsan/null-1.C gcc/testsuite/g++.dg/ubsan/null-1.C
index 83b3033..e1524b1 100644
--- gcc/testsuite/g++.dg/ubsan/null-1.C
+++ gcc/testsuite/g++.dg/ubsan/null-1.C
@@ -25,4 +25,6 @@ main (void)
 }
 
 // { dg-output "reference binding to null pointer of type 'int'(\n|\r\n|\r)" }
+// { dg-output "\[^\n\r]*reference binding to null pointer of type 'int'(\n|\r\n|\r)" }
 // { dg-output "\[^\n\r]*reference binding to null pointer of type 'const L'(\n|\r\n|\r)" }
+// { dg-output "\[^\n\r]*reference binding to null pointer of type 'int'(\n|\r\n|\r)" }
diff --git gcc/testsuite/g++.dg/ubsan/null-2.C gcc/testsuite/g++.dg/ubsan/null-2.C
index 0230c7c..88f387e 100644
--- gcc/testsuite/g++.dg/ubsan/null-2.C
+++ gcc/testsuite/g++.dg/ubsan/null-2.C
@@ -35,3 +35,5 @@ main (void)
 
 // { dg-output "\.C:26:\[0-9]*:\[\^\n\r]*member call on null pointer of type 'struct U'.*" }
 // { dg-output "\.C:29:\[0-9]*:\[\^\n\r]*member call on null pointer of type 'struct V'.*" }
+// { dg-output "\.C:31:\[0-9]*:\[\^\n\r]*member call on null pointer of type 'struct V'.*" }
+// { dg-output "\.C:33:\[0-9]*:\[\^\n\r]*member call on null pointer of type 'struct V'" }
diff --git gcc/testsuite/g++.dg/ubsan/null-3.C gcc/testsuite/g++.dg/ubsan/null-3.C
index e69de29..cd3716b 100644
--- gcc/testsuite/g++.dg/ubsan/null-3.C
+++ gcc/testsuite/g++.dg/ubsan/null-3.C
@@ -0,0 +1,20 @@
+// { dg-do run }
+// { dg-options "-fsanitize=null" }
+
+int
+main (void)
+{
+  int *p = 0;
+
+  int &r1 = *p;
+  int &r2 = *p;
+  int &r3 = *p;
+  int &r4 = *p;
+  int &r5 = *p;
+}
+
+// { dg-output "reference binding to null pointer of type 'int'(\n|\r\n|\r)" }
+// { dg-output "\[^\n\r]*reference binding to null pointer of type 'int'(\n|\r\n|\r)" }
+// { dg-output "\[^\n\r]*reference binding to null pointer of type 'int'(\n|\r\n|\r)" }
+// { dg-output "\[^\n\r]*reference binding to null pointer of type 'int'(\n|\r\n|\r)" }
+// { dg-output "\[^\n\r]*reference binding to null pointer of type 'int'(\n|\r\n|\r)" }
diff --git gcc/testsuite/g++.dg/ubsan/null-4.C gcc/testsuite/g++.dg/ubsan/null-4.C
index e69de29..9cb04ef 100644
--- gcc/testsuite/g++.dg/ubsan/null-4.C
+++ gcc/testsuite/g++.dg/ubsan/null-4.C
@@ -0,0 +1,19 @@
+// { dg-do run }
+// { dg-options "-O -fsanitize=null -fno-sanitize-recover=null -fdump-tree-sanopt-details" }
+// { dg-shouldfail "ubsan" }
+
+int
+main (void)
+{
+  int *p = 0;
+
+  int &r1 = *p;
+  int &r2 = *p;
+  int &r3 = *p;
+  int &r4 = *p;
+  int &r5 = *p;
+}
+
+// { dg-output "reference binding to null pointer of type 'int'(\n|\r\n|\r)" }
+// { dg-final { scan-tree-dump-times "Optimizing" 4 "sanopt"} }
+// { dg-final { cleanup-tree-dump "sanopt" } }
diff --git gcc/testsuite/g++.dg/ubsan/null-5.C gcc/testsuite/g++.dg/ubsan/null-5.C
index e69de29..d8e4a68 100644
--- gcc/testsuite/g++.dg/ubsan/null-5.C
+++ gcc/testsuite/g++.dg/ubsan/null-5.C
@@ -0,0 +1,18 @@
+// { dg-do run }
+// { dg-options "-O -fsanitize=null -fsanitize-undefined-trap-on-error -fdump-tree-sanopt-details" }
+// { dg-shouldfail "ubsan" }
+
+int
+main (void)
+{
+  int *p = 0;
+
+  int &r1 = *p;
+  int &r2 = *p;
+  int &r3 = *p;
+  int &r4 = *p;
+  int &r5 = *p;
+}
+
+// { dg-final { scan-tree-dump-times "Optimizing" 4 "sanopt"} }
+// { dg-final { cleanup-tree-dump "sanopt" } }

	Marek


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