[compiler-rt] r300889 - [asan] Optimize strchr for strict_string_checks=false
Ahmed Bougacha via llvm-commits
llvm-commits at lists.llvm.org
Thu Apr 20 18:19:25 PDT 2017
Hey Vitaly,
I saw your fixes in r300906 and r300935, but this fails differently
for me on Darwin:
ASAN:DEADLYSIGNAL
=================================================================
==52312==ERROR: AddressSanitizer: BUS on unknown address
0x00010affd000 (pc 0x7fff999a7168 bp 0x7fff57e31270 sp 0x7fff57e31270
T0)
#0 0x7fff999a7167 in strlen (libsystem_c.dylib:x86_64+0x1167)
#1 0x107dee5bb in wrap_strchr sanitizer_common_interceptors.inc:578
#2 0x107dceaa5 in main strchr.c:29
#3 0x7fff970345ac in start (libdyld.dylib:x86_64+0x35ac)
==52312==Register values:
....
AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: BUS (libsystem_c.dylib:x86_64+0x1167) in strlen
==52312==ABORTING
Does that ring a bell?
Thanks!
-Ahmed
On Thu, Apr 20, 2017 at 1:59 PM, Vitaly Buka via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
> Author: vitalybuka
> Date: Thu Apr 20 15:59:37 2017
> New Revision: 300889
>
> URL: http://llvm.org/viewvc/llvm-project?rev=300889&view=rev
> Log:
> [asan] Optimize strchr for strict_string_checks=false
>
> Summary:
> strchr interceptor does not need to call strlen if strict_string_checks is not
> enabled. Unnecessary strlen calls affect python parser performance.
>
> Reviewers: eugenis, kcc
>
> Subscribers: llvm-commits, kubamracek
>
> Differential Revision: https://reviews.llvm.org/D32264
>
> Added:
> compiler-rt/trunk/test/asan/TestCases/Posix/strchr.c
> Modified:
> compiler-rt/trunk/lib/sanitizer_common/sanitizer_common_interceptors.inc
>
> Modified: compiler-rt/trunk/lib/sanitizer_common/sanitizer_common_interceptors.inc
> URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/sanitizer_common/sanitizer_common_interceptors.inc?rev=300889&r1=300888&r2=300889&view=diff
> ==============================================================================
> --- compiler-rt/trunk/lib/sanitizer_common/sanitizer_common_interceptors.inc (original)
> +++ compiler-rt/trunk/lib/sanitizer_common/sanitizer_common_interceptors.inc Thu Apr 20 15:59:37 2017
> @@ -139,12 +139,9 @@ bool PlatformHasDifferentMemcpyAndMemmov
> #define COMMON_INTERCEPTOR_NOTHING_IS_INITIALIZED (0)
> #endif
>
> -#define COMMON_INTERCEPTOR_READ_STRING_OF_LEN(ctx, s, len, n) \
> - COMMON_INTERCEPTOR_READ_RANGE((ctx), (s), \
> - common_flags()->strict_string_checks ? (len) + 1 : (n) )
> -
> #define COMMON_INTERCEPTOR_READ_STRING(ctx, s, n) \
> - COMMON_INTERCEPTOR_READ_STRING_OF_LEN((ctx), (s), REAL(strlen)(s), (n))
> + COMMON_INTERCEPTOR_READ_RANGE((ctx), (s), \
> + common_flags()->strict_string_checks ? (REAL(strlen)(s)) + 1 : (n) )
>
> #ifndef COMMON_INTERCEPTOR_ON_DLOPEN
> #define COMMON_INTERCEPTOR_ON_DLOPEN(filename, flag) \
> @@ -450,8 +447,7 @@ static inline void StrstrCheck(void *ctx
> const char *s2) {
> uptr len1 = REAL(strlen)(s1);
> uptr len2 = REAL(strlen)(s2);
> - COMMON_INTERCEPTOR_READ_STRING_OF_LEN(ctx, s1, len1,
> - r ? r - s1 + len2 : len1 + 1);
> + COMMON_INTERCEPTOR_READ_STRING(ctx, s1, r ? r - s1 + len2 : len1 + 1);
> COMMON_INTERCEPTOR_READ_RANGE(ctx, s2, len2 + 1);
> }
> #endif
> @@ -577,10 +573,11 @@ INTERCEPTOR(char*, strchr, const char *s
> return internal_strchr(s, c);
> COMMON_INTERCEPTOR_ENTER(ctx, strchr, s, c);
> char *result = REAL(strchr)(s, c);
> - uptr len = internal_strlen(s);
> - uptr n = result ? result - s + 1 : len + 1;
> - if (common_flags()->intercept_strchr)
> - COMMON_INTERCEPTOR_READ_STRING_OF_LEN(ctx, s, len, n);
> + if (common_flags()->intercept_strchr) {
> + // Keep strlen as macro argument, as macro may ignore it.
> + COMMON_INTERCEPTOR_READ_STRING(ctx, s,
> + (result ? result - s : REAL(strlen)(s)) + 1);
> + }
> return result;
> }
> #define INIT_STRCHR COMMON_INTERCEPT_FUNCTION(strchr)
> @@ -609,9 +606,8 @@ INTERCEPTOR(char*, strrchr, const char *
> if (COMMON_INTERCEPTOR_NOTHING_IS_INITIALIZED)
> return internal_strrchr(s, c);
> COMMON_INTERCEPTOR_ENTER(ctx, strrchr, s, c);
> - uptr len = internal_strlen(s);
> if (common_flags()->intercept_strchr)
> - COMMON_INTERCEPTOR_READ_STRING_OF_LEN(ctx, s, len, len + 1);
> + COMMON_INTERCEPTOR_READ_RANGE(ctx, s, REAL(strlen)(s) + 1);
> return REAL(strrchr)(s, c);
> }
> #define INIT_STRRCHR COMMON_INTERCEPT_FUNCTION(strrchr)
>
> Added: compiler-rt/trunk/test/asan/TestCases/Posix/strchr.c
> URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/test/asan/TestCases/Posix/strchr.c?rev=300889&view=auto
> ==============================================================================
> --- compiler-rt/trunk/test/asan/TestCases/Posix/strchr.c (added)
> +++ compiler-rt/trunk/test/asan/TestCases/Posix/strchr.c Thu Apr 20 15:59:37 2017
> @@ -0,0 +1,36 @@
> +// Test strchr for strict_string_checks=false does not look beyond necessary
> +// char.
> +// RUN: %clang_asan %s -o %t
> +// RUN: %env_asan_opts=strict_string_checks=false %run %t 2>&1
> +// RUN: %env_asan_opts=strict_string_checks=true not %run %t 2>&1 | FileCheck %s
> +
> +#include <assert.h>
> +#include <stdint.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <sys/mman.h>
> +#include <unistd.h>
> +
> +int main(int argc, char **argv) {
> + size_t page_size = sysconf(_SC_PAGE_SIZE);
> + size_t size = 2 * page_size;
> + char *s = (char *)mmap(0, size, PROT_READ | PROT_WRITE,
> + MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
> + assert(s);
> + assert(((uintptr_t)s & (page_size - 1)) == 0);
> + memset(s, 'o', size);
> + s[size - 1] = 0;
> +
> + char *p = s + page_size - 1;
> + *p = 'x';
> +
> + if (mprotect(p + 1, 1, PROT_NONE))
> + return 1;
> + char *r = strchr(s, 'x');
> + // CHECK: AddressSanitizer: SEGV on unknown address
> + // CHECK: The signal is caused by a READ memory access
> + // CHECK: strchr.c:[[@LINE-3]]
> + assert(r == p);
> +
> + return 0;
> +}
>
>
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