mirror of
https://github.com/Divested-Mobile/DivestOS-Build.git
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93 lines
3.4 KiB
Diff
93 lines
3.4 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: anupritaisno1 <www.anuprita804@gmail.com>
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Date: Wed, 13 Oct 2021 12:30:25 +0300
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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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Signed-off-by: anupritaisno1 <www.anuprita804@gmail.com>
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Change-Id: Ia021e30f86ee4b998d541fbf7262110f9d1d6fbf
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Signed-off-by: anupritaisno1 <www.anuprita804@gmail.com>
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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 | 2 ++
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libc/libc.map.txt | 1 +
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libc/upstream-openbsd/android/include/openbsd-compat.h | 4 ----
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5 files changed, 11 insertions(+), 4 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 a5f87c3a2..bc5b16a22 100644
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--- a/libc/Android.bp
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+++ b/libc/Android.bp
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@@ -850,6 +850,7 @@ cc_library_static {
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"bionic/eventfd.cpp",
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"bionic/exec.cpp",
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"bionic/execinfo.cpp",
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+ "bionic/explicit_bzero.cpp",
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"bionic/exit.cpp",
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"bionic/faccessat.cpp",
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"bionic/fchmod.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..dd43f9c00
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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* _Nonnull explicit_bzero(void* _Nonnull 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 47bdd7271..e601ea022 100644
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--- a/libc/include/string.h
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+++ b/libc/include/string.h
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@@ -64,6 +64,8 @@ void* _Nonnull memmove(void* _Nonnull __dst, const void* _Nonnull __src, size_t
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*/
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void* _Nonnull memset(void* _Nonnull __dst, int __ch, size_t __n);
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+void* _Nonnull explicit_bzero(void* _Nonnull s, size_t n);
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+
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/**
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* [memset_explicit(3)](http://man7.org/linux/man-pages/man3/memset_explicit.3.html)
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* writes the bottom 8 bits of the given int to the next `n` bytes of `dst`,
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diff --git a/libc/libc.map.txt b/libc/libc.map.txt
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index f5340c172..9a0e7fb99 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=33
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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 8e6f87da8..26dc01863 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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@@ -57,10 +57,6 @@ 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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-#if !defined(ANDROID_HOST_MUSL)
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-#define explicit_bzero(p, s) memset(p, 0, s)
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-#endif
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-
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#if defined(ANDROID_HOST_MUSL)
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#define __LIBC_HIDDEN__ __attribute__((visibility("hidden")))
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#endif
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