diff options
| author | Daniel Micay <danielmicay@gmail.com> | 2015-02-05 21:53:16 -0500 |
|---|---|---|
| committer | alk3pInjection <webmaster@raspii.tech> | 2021-09-27 21:17:05 +0800 |
| commit | 2780434e17939a9bbda1212f44a0ab655c539f6a (patch) | |
| tree | c7b9cd415914274a207c8b63d68d6872f1b7ff52 | |
| parent | 3a003876ad043c5280e0fbb334e8d17c3d941bfc (diff) | |
[GrapheneOS] add a real explicit_bzero implementation
Clang, GCC and other compilers special-case standard C functions like
memset. Calls to memset will be optimized out.
OpenBSD provides explicit_bzero to work around this but Android simply
defines it as memset so nothing prevents it from being optimized away.
This implementation uses a memory read constraint via empty inline
assembly rather than something that may be broken via link-time
optimization in the future.
Change-Id: I6005d65a2afd4bd54aacfdfa633d215a58e9907a
| -rw-r--r-- | libc/Android.bp | 1 | ||||
| -rw-r--r-- | libc/bionic/explicit_bzero.cpp | 7 | ||||
| -rw-r--r-- | libc/include/string.h | 1 | ||||
| -rw-r--r-- | libc/libc.map.txt | 1 | ||||
| -rw-r--r-- | libc/upstream-openbsd/android/include/openbsd-compat.h | 2 |
5 files changed, 10 insertions, 2 deletions
diff --git a/libc/Android.bp b/libc/Android.bp index ce714054a..49108bf35 100644 --- a/libc/Android.bp +++ b/libc/Android.bp @@ -1047,6 +1047,7 @@ cc_library_static { "bionic/error.cpp", "bionic/eventfd.cpp", "bionic/exec.cpp", + "bionic/explicit_bzero.cpp", "bionic/faccessat.cpp", "bionic/fchmod.cpp", "bionic/fchmodat.cpp", diff --git a/libc/bionic/explicit_bzero.cpp b/libc/bionic/explicit_bzero.cpp new file mode 100644 index 000000000..b06daa138 --- /dev/null +++ b/libc/bionic/explicit_bzero.cpp @@ -0,0 +1,7 @@ +#include <string.h> + +void* explicit_bzero(void* s, size_t n) { + void *ptr = memset(s, 0, n); + __asm__ __volatile__("" : : "r"(ptr) : "memory"); + return ptr; +} diff --git a/libc/include/string.h b/libc/include/string.h index 0cc5611aa..befffd082 100644 --- a/libc/include/string.h +++ b/libc/include/string.h @@ -56,6 +56,7 @@ void* mempcpy(void* __dst, const void* __src, size_t __n) __INTRODUCED_IN(23); #endif void* memmove(void* __dst, const void* __src, size_t __n); void* memset(void* __dst, int __ch, size_t __n); +void* explicit_bzero(void *s, size_t n); void* memmem(const void* __haystack, size_t __haystack_size, const void* __needle, size_t __needle_size) __attribute_pure__; char* strchr(const char* __s, int __ch) __attribute_pure__; diff --git a/libc/libc.map.txt b/libc/libc.map.txt index 4bfb8a232..36803984e 100644 --- a/libc/libc.map.txt +++ b/libc/libc.map.txt @@ -332,6 +332,7 @@ LIBC { execvp; execvpe; # introduced=21 exit; + explicit_bzero; # introduced=30 faccessat; fallocate; # introduced=21 fallocate64; # introduced=21 diff --git a/libc/upstream-openbsd/android/include/openbsd-compat.h b/libc/upstream-openbsd/android/include/openbsd-compat.h index 878f71cec..79a260425 100644 --- a/libc/upstream-openbsd/android/include/openbsd-compat.h +++ b/libc/upstream-openbsd/android/include/openbsd-compat.h @@ -53,8 +53,6 @@ extern const char* __progname; /* OpenBSD has this, but we can't really implement it correctly on Linux. */ #define issetugid() 0 -#define explicit_bzero(p, s) memset(p, 0, s) - /* OpenBSD has these in <sys/param.h>, but "ALIGN" isn't something we want to reserve. */ #define ALIGNBYTES (sizeof(uintptr_t) - 1) #define ALIGN(p) (((uintptr_t)(p) + ALIGNBYTES) &~ ALIGNBYTES) |