86 lines
3.3 KiB
Diff
86 lines
3.3 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Daniel Micay <danielmicay@gmail.com>
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Date: Thu, 5 Feb 2015 21:53:16 -0500
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Subject: [PATCH] add a real explicit_bzero implementation
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Clang, GCC and other compilers special-case standard C functions like
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memset. Calls to memset will be optimized out.
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OpenBSD provides explicit_bzero to work around this but Android simply
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defines it as memset so nothing prevents it from being optimized away.
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This implementation uses a memory read constraint via empty inline
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assembly rather than something that may be broken via link-time
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optimization in the future.
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---
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libc/Android.bp | 1 +
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libc/bionic/explicit_bzero.cpp | 7 +++++++
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libc/include/string.h | 1 +
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libc/libc.map.txt | 1 +
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libc/upstream-openbsd/android/include/openbsd-compat.h | 2 --
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5 files changed, 10 insertions(+), 2 deletions(-)
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create mode 100644 libc/bionic/explicit_bzero.cpp
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diff --git a/libc/Android.bp b/libc/Android.bp
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index 1599d5ed9..d7c066890 100644
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--- a/libc/Android.bp
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+++ b/libc/Android.bp
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@@ -1056,6 +1056,7 @@ cc_library_static {
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"bionic/error.cpp",
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"bionic/eventfd.cpp",
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"bionic/exec.cpp",
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+ "bionic/explicit_bzero.cpp",
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"bionic/faccessat.cpp",
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"bionic/fchmod.cpp",
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"bionic/fchmodat.cpp",
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diff --git a/libc/bionic/explicit_bzero.cpp b/libc/bionic/explicit_bzero.cpp
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new file mode 100644
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index 000000000..b06daa138
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--- /dev/null
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+++ b/libc/bionic/explicit_bzero.cpp
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@@ -0,0 +1,7 @@
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+#include <string.h>
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+
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+void* explicit_bzero(void* s, size_t n) {
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+ void *ptr = memset(s, 0, n);
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+ __asm__ __volatile__("" : : "r"(ptr) : "memory");
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+ return ptr;
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+}
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diff --git a/libc/include/string.h b/libc/include/string.h
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index 0cc5611aa..befffd082 100644
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--- a/libc/include/string.h
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+++ b/libc/include/string.h
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@@ -56,6 +56,7 @@ void* mempcpy(void* __dst, const void* __src, size_t __n) __INTRODUCED_IN(23);
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#endif
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void* memmove(void* __dst, const void* __src, size_t __n);
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void* memset(void* __dst, int __ch, size_t __n);
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+void* explicit_bzero(void *s, size_t n);
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void* memmem(const void* __haystack, size_t __haystack_size, const void* __needle, size_t __needle_size) __attribute_pure__;
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char* strchr(const char* __s, int __ch) __attribute_pure__;
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diff --git a/libc/libc.map.txt b/libc/libc.map.txt
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index 4bfb8a232..36803984e 100644
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--- a/libc/libc.map.txt
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+++ b/libc/libc.map.txt
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@@ -332,6 +332,7 @@ LIBC {
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execvp;
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execvpe; # introduced=21
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exit;
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+ explicit_bzero; # introduced=30
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faccessat;
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fallocate; # introduced=21
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fallocate64; # introduced=21
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diff --git a/libc/upstream-openbsd/android/include/openbsd-compat.h b/libc/upstream-openbsd/android/include/openbsd-compat.h
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index 878f71cec..79a260425 100644
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--- a/libc/upstream-openbsd/android/include/openbsd-compat.h
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+++ b/libc/upstream-openbsd/android/include/openbsd-compat.h
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@@ -53,8 +53,6 @@ extern const char* __progname;
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/* OpenBSD has this, but we can't really implement it correctly on Linux. */
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#define issetugid() 0
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-#define explicit_bzero(p, s) memset(p, 0, s)
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-
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/* OpenBSD has these in <sys/param.h>, but "ALIGN" isn't something we want to reserve. */
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#define ALIGNBYTES (sizeof(uintptr_t) - 1)
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#define ALIGN(p) (((uintptr_t)(p) + ALIGNBYTES) &~ ALIGNBYTES)
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