Re: libsanitizer merge from upstream r208536

[Jakub Jelinek <jakub at redhat dot com>]

On Fri, May 23, 2014 at 04:11:48PM +0400, Konstantin Serebryany wrote:
> >> 2) it doesn't still deal with unaligned power of two accesses properly,
> >>    but neither does llvm (at least not 3.4).  Am not talking about
> >>    undefined behavior cases where the compiler isn't told the access
> >>    is misaligned, but e.g. when accessing struct S { int x; }
> >>    __attribute__((packed)) and similar (or aligned(1)).  Supposedly
> >>    we could force __asan_report_*_n for that case too, because
> >>    normal wider check assumes it is aligned
> >
> > Yep, we don't do it.
> Now we do: http://llvm.org/viewvc/llvm-project?rev=209508&view=rev

Here is the GCC side of the thing, ok for trunk if it bootstraps/regtests?
(on top of the earlier posted two patches).

Note, I think some work is needed on the library side, 
ERROR: AddressSanitizer: unknown-crash on address 0xffc439cf at pc 0x804898e bp 0xffc438d8 sp 0xffc438cc
READ of size 4 at 0xffc439cf thread T0
    #0 0x804898d in foo /usr/src/gcc/gcc/testsuite/c-c++-common/asan/misalign-1.c:10
    #1 0x8048746 in main /usr/src/gcc/gcc/testsuite/c-c++-common/asan/misalign-1.c:34
    #2 0x49e39b72 in __libc_start_main (/lib/libc.so.6+0x49e39b72)
    #3 0x8048848 (/usr/src/gcc/obj2/gcc/testsuite/gcc/misalign-1.exe+0x8048848)

Address 0xffc439cf is located in stack of thread T0 at offset 175 in frame
    #0 0x804868f in main /usr/src/gcc/gcc/testsuite/c-c++-common/asan/misalign-1.c:27

  This frame has 3 object(s):
    [32, 36) 'v'
    [96, 100) 'w'
    [160, 176) 't' <== Memory access at offset 175 partially overflows this variable
HINT: this may be a false positive if your program uses some custom stack unwind mechanism or swapcontext
      (longjmp and C++ exceptions *are* supported)
SUMMARY: AddressSanitizer: unknown-crash /usr/src/gcc/gcc/testsuite/c-c++-common/asan/misalign-1.c:10 foo
Shadow bytes around the buggy address:
  0x3ff886e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x3ff886f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x3ff88700: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x3ff88710: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x3ff88720: 00 00 00 00 f1 f1 f1 f1 04 f4 f4 f4 f2 f2 f2 f2
=>0x3ff88730: 04 f4 f4 f4 f2 f2 f2 f2 00[00]f4 f4 f3 f3 f3 f3
  0x3ff88740: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x3ff88750: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x3ff88760: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x3ff88770: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x3ff88780: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07 
  Heap left redzone:       fa
  Heap right redzone:      fb
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack partial redzone:   f4
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  ASan internal:           fe

is just too ugly (I mean, it shouldn't print unknown-crash).
It is true that the first byte of the __asan_report_load_n range
corresponds to shadow byte 0, but for _n you should either check
it for all bytes in that range, or at least the first and last byte
(which would correspond to what the caller of __asan_report_*_n
actually does right now).

2014-05-23  Jakub Jelinek  <jakub@redhat.com>

	* asan.c (report_error_func): Add SLOW_P argument, use
	BUILT_IN_ASAN_*_N if set.
	(build_check_stmt): Likewise.
	(instrument_derefs): If T has insufficient alignment,
	force same handling as for odd sizes.

	* c-c++-common/asan/misalign-1.c: New test.
	* c-c++-common/asan/misalign-2.c: New test.

--- gcc/asan.c.jj	2014-05-23 17:17:46.000000000 +0200
+++ gcc/asan.c	2014-05-23 18:14:08.630807014 +0200
@@ -1319,7 +1319,7 @@ asan_protect_global (tree decl)
    IS_STORE is either 1 (for a store) or 0 (for a load).  */
 
 static tree
-report_error_func (bool is_store, HOST_WIDE_INT size_in_bytes)
+report_error_func (bool is_store, HOST_WIDE_INT size_in_bytes, bool slow_p)
 {
   static enum built_in_function report[2][6]
     = { { BUILT_IN_ASAN_REPORT_LOAD1, BUILT_IN_ASAN_REPORT_LOAD2,
@@ -1329,7 +1329,8 @@ report_error_func (bool is_store, HOST_W
 	  BUILT_IN_ASAN_REPORT_STORE4, BUILT_IN_ASAN_REPORT_STORE8,
 	  BUILT_IN_ASAN_REPORT_STORE16, BUILT_IN_ASAN_REPORT_STORE_N } };
   if ((size_in_bytes & (size_in_bytes - 1)) != 0
-      || size_in_bytes > 16)
+      || size_in_bytes > 16
+      || slow_p)
     return builtin_decl_implicit (report[is_store][5]);
   return builtin_decl_implicit (report[is_store][exact_log2 (size_in_bytes)]);
 }
@@ -1508,7 +1509,8 @@ build_shadow_mem_access (gimple_stmt_ite
 
 static void
 build_check_stmt (location_t location, tree base, gimple_stmt_iterator *iter,
-		  bool before_p, bool is_store, HOST_WIDE_INT size_in_bytes)
+		  bool before_p, bool is_store, HOST_WIDE_INT size_in_bytes,
+		  bool slow_p = false)
 {
   gimple_stmt_iterator gsi;
   basic_block then_bb, else_bb;
@@ -1522,9 +1524,15 @@ build_check_stmt (location_t location, t
   HOST_WIDE_INT real_size_in_bytes = size_in_bytes;
   tree sz_arg = NULL_TREE;
 
-  if ((size_in_bytes & (size_in_bytes - 1)) != 0
-      || size_in_bytes > 16)
-    real_size_in_bytes = 1;
+  if (size_in_bytes == 1)
+    slow_p = false;
+  else if ((size_in_bytes & (size_in_bytes - 1)) != 0
+	   || size_in_bytes > 16
+	   || slow_p)
+    {
+      real_size_in_bytes = 1;
+      slow_p = true;
+    }
 
   /* Get an iterator on the point where we can add the condition
      statement for the instrumentation.  */
@@ -1582,8 +1590,8 @@ build_check_stmt (location_t location, t
       t = gimple_assign_lhs (gimple_seq_last (seq));
       gimple_seq_set_location (seq, location);
       gsi_insert_seq_after (&gsi, seq, GSI_CONTINUE_LINKING);
-      /* For weird access sizes, check first and last byte.  */
-      if (real_size_in_bytes != size_in_bytes)
+      /* For weird access sizes or misaligned, check first and last byte.  */
+      if (slow_p)
 	{
 	  g = gimple_build_assign_with_ops (PLUS_EXPR,
 					    make_ssa_name (uintptr_type, NULL),
@@ -1626,7 +1634,7 @@ build_check_stmt (location_t location, t
 
   /* Generate call to the run-time library (e.g. __asan_report_load8).  */
   gsi = gsi_start_bb (then_bb);
-  g = gimple_build_call (report_error_func (is_store, size_in_bytes),
+  g = gimple_build_call (report_error_func (is_store, size_in_bytes, slow_p),
 			 sz_arg ? 2 : 1, base_addr, sz_arg);
   gimple_set_location (g, location);
   gsi_insert_after (&gsi, g, GSI_NEW_STMT);
@@ -1722,8 +1730,31 @@ instrument_derefs (gimple_stmt_iterator
   base = build_fold_addr_expr (t);
   if (!has_mem_ref_been_instrumented (base, size_in_bytes))
     {
+      bool slow_p = false;
+      if (size_in_bytes > 1)
+	{
+	  if ((size_in_bytes & (size_in_bytes - 1)) != 0
+	      || size_in_bytes > 16)
+	    slow_p = true;
+	  else
+	    {
+	      unsigned int align = get_object_alignment (t);
+	      if (align < size_in_bytes * BITS_PER_UNIT)
+		{
+		  /* On non-strict alignment targets, if
+		     16-byte access is just 8-byte aligned,
+		     this will result in misaligned shadow
+		     memory 2 byte load, but otherwise can
+		     be handled using one read.  */
+		  if (size_in_bytes != 16
+		      || STRICT_ALIGNMENT
+		      || align < 8 * BITS_PER_UNIT)
+		    slow_p = true;
+		}
+	    }
+	}
       build_check_stmt (location, base, iter, /*before_p=*/true,
-			is_store, size_in_bytes);
+			is_store, size_in_bytes, slow_p);
       update_mem_ref_hash_table (base, size_in_bytes);
       update_mem_ref_hash_table (t, size_in_bytes);
     }
--- gcc/testsuite/c-c++-common/asan/misalign-1.c.jj	2014-05-23 18:03:40.400842565 +0200
+++ gcc/testsuite/c-c++-common/asan/misalign-1.c	2014-05-23 18:29:42.899264340 +0200
@@ -0,0 +1,42 @@
+/* { dg-do run { target { ilp32 || lp64 } } } */
+/* { dg-options "-O2" } */
+/* { dg-shouldfail "asan" } */
+
+struct S { int i; } __attribute__ ((packed));
+
+__attribute__((noinline, noclone)) int
+foo (struct S *s)
+{
+  return s->i;
+}
+
+__attribute__((noinline, noclone)) int
+bar (int *s)
+{
+  return *s;
+}
+
+__attribute__((noinline, noclone)) struct S
+baz (struct S *s)
+{
+  return *s;
+}
+
+int
+main ()
+{
+  struct T { char a[3]; struct S b[3]; char c; } t;
+  int v = 5;
+  struct S *p = t.b;
+  asm volatile ("" : "+rm" (p));
+  p += 3;
+  if (bar (&v) != 5) __builtin_abort ();
+  volatile int w = foo (p);
+  return 0;
+}
+
+/* { dg-output "ERROR: AddressSanitizer:\[^\n\r]*on address\[^\n\r]*" } */
+/* { dg-output "0x\[0-9a-f\]+ at pc 0x\[0-9a-f\]+ bp 0x\[0-9a-f\]+ sp 0x\[0-9a-f\]+\[^\n\r]*(\n|\r\n|\r)" } */
+/* { dg-output "\[^\n\r]*READ of size 4 at 0x\[0-9a-f\]+ thread T0\[^\n\r]*(\n|\r\n|\r)" } */
+/* { dg-output "    #0 0x\[0-9a-f\]+ (in _*foo(\[^\n\r]*misalign-1.c:10|\[^\n\r]*:0)|\[(\])\[^\n\r]*(\n|\r\n|\r)" } */
+/* { dg-output "    #1 0x\[0-9a-f\]+ (in _*main (\[^\n\r]*misalign-1.c:34|\[^\n\r]*:0)|\[(\]).*(\n|\r\n|\r)" } */
--- gcc/testsuite/c-c++-common/asan/misalign-2.c.jj	2014-05-23 18:07:59.820594400 +0200
+++ gcc/testsuite/c-c++-common/asan/misalign-2.c	2014-05-23 18:29:51.808220759 +0200
@@ -0,0 +1,42 @@
+/* { dg-do run { target { ilp32 || lp64 } } } */
+/* { dg-options "-O2" } */
+/* { dg-shouldfail "asan" } */
+
+struct S { int i; } __attribute__ ((packed));
+
+__attribute__((noinline, noclone)) int
+foo (struct S *s)
+{
+  return s->i;
+}
+
+__attribute__((noinline, noclone)) int
+bar (int *s)
+{
+  return *s;
+}
+
+__attribute__((noinline, noclone)) struct S
+baz (struct S *s)
+{
+  return *s;
+}
+
+int
+main ()
+{
+  struct T { char a[3]; struct S b[3]; char c; } t;
+  int v = 5;
+  struct S *p = t.b;
+  asm volatile ("" : "+rm" (p));
+  p += 3;
+  if (bar (&v) != 5) __builtin_abort ();
+  volatile struct S w = baz (p);
+  return 0;
+}
+
+/* { dg-output "ERROR: AddressSanitizer:\[^\n\r]*on address\[^\n\r]*" } */
+/* { dg-output "0x\[0-9a-f\]+ at pc 0x\[0-9a-f\]+ bp 0x\[0-9a-f\]+ sp 0x\[0-9a-f\]+\[^\n\r]*(\n|\r\n|\r)" } */
+/* { dg-output "\[^\n\r]*READ of size 4 at 0x\[0-9a-f\]+ thread T0\[^\n\r]*(\n|\r\n|\r)" } */
+/* { dg-output "    #0 0x\[0-9a-f\]+ (in _*baz(\[^\n\r]*misalign-2.c:22|\[^\n\r]*:0)|\[(\])\[^\n\r]*(\n|\r\n|\r)" } */
+/* { dg-output "    #1 0x\[0-9a-f\]+ (in _*main (\[^\n\r]*misalign-2.c:34|\[^\n\r]*:0)|\[(\]).*(\n|\r\n|\r)" } */


	Jakub