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Add preadv2/pwritev2 wrappers.

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They're in glibc, though not in musl.

Also add basic doc comments to the whole of <sys/uio.h>.

Bug: http://b/203002492
Test: treehugger
Change-Id: Ic607f7f349e5b7c9bf66c25b7bd68f827da530d6
This commit is contained in:
Elliott Hughes 2021-10-13 18:25:21 -07:00
parent ad60768bdf
commit cf59e19e22
7 changed files with 263 additions and 34 deletions
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1
libc/Android.bp
View file

@ -1121,6 +1121,7 @@ cc_library_static {
"bionic/posix_fallocate.cpp",
"bionic/posix_madvise.cpp",
"bionic/posix_timers.cpp",
"bionic/preadv_pwritev.cpp",
"bionic/ptrace.cpp",
"bionic/pty.cpp",
"bionic/raise.cpp",

11
libc/SYSCALLS.TXT
View file

@ -97,13 +97,14 @@ ssize_t pwrite64(int, void*, size_t, off64_t) lp32
ssize_t pwrite64|pwrite(int, void*, size_t, off_t) lp64
# On LP32, preadv/pwritev don't use off64_t --- they use pairs of 32-bit
# arguments to avoid problems on architectures like ARM where 64-bit arguments
# arguments to avoid problems on architectures like arm32 where 64-bit arguments
# must be in a register pair starting with an even-numbered register.
# See linux/fs/read_write.c and https://lwn.net/Articles/311630/.
ssize_t __preadv64:preadv(int, const struct iovec*, int, long, long) lp32
ssize_t preadv|preadv64(int, const struct iovec*, int, off_t) lp64
ssize_t __pwritev64:pwritev(int, const struct iovec*, int, long, long) lp32
ssize_t pwritev|pwritev64(int, const struct iovec*, int, off_t) lp64
# Note that there's an unused always-0 second long even on LP64!
ssize_t __preadv64:preadv(int, const struct iovec*, int, long, long) all
ssize_t __pwritev64:pwritev(int, const struct iovec*, int, long, long) all
ssize_t __preadv64v2:preadv2(int, const struct iovec*, int, long, long, int) all
ssize_t __pwritev64v2:pwritev2(int, const struct iovec*, int, long, long, int) all
int __close:close(int) all
pid_t __getpid:getpid() all

19
libc/bionic/legacy_32_bit_support.cpp
View file

@ -45,8 +45,6 @@
// System calls we need.
extern "C" int __llseek(int, unsigned long, unsigned long, off64_t*, int);
extern "C" int __preadv64(int, const struct iovec*, int, long, long);
extern "C" int __pwritev64(int, const struct iovec*, int, long, long);
// For lseek64 we need to use the llseek system call which splits the off64_t in two and
// returns the off64_t result via a pointer because 32-bit kernels can't return 64-bit results.
@ -70,23 +68,6 @@ ssize_t pwrite(int fd, const void* buf, size_t byte_count, off_t offset) {
return pwrite64(fd, buf, byte_count, static_cast<off64_t>(offset));
}
// On LP32, there is no off_t preadv/pwritev, and even the 64-bit preadv/pwritev
// don't use off64_t (see SYSCALLS.TXT for more). Here, this means that we need
// to implement all four functions because the two system calls don't match any
// of the userspace functions. Unlike llseek, the pair is split lo-hi, not hi-lo.
ssize_t preadv(int fd, const struct iovec* ios, int count, off_t offset) {
return preadv64(fd, ios, count, offset);
}
ssize_t preadv64(int fd, const struct iovec* ios, int count, off64_t offset) {
return __preadv64(fd, ios, count, offset, offset >> 32);
}
ssize_t pwritev(int fd, const struct iovec* ios, int count, off_t offset) {
return pwritev64(fd, ios, count, offset);
}
ssize_t pwritev64(int fd, const struct iovec* ios, int count, off64_t offset) {
return __pwritev64(fd, ios, count, offset, offset >> 32);
}
// There is no fallocate for 32-bit off_t, so we need to widen and call fallocate64.
int fallocate(int fd, int mode, off_t offset, off_t length) {
return fallocate64(fd, mode, static_cast<off64_t>(offset), static_cast<off64_t>(length));

91
libc/bionic/preadv_pwritev.cpp Normal file
View file

@ -0,0 +1,91 @@
/*
* Copyright (C) 2008 The Android Open Source Project
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/uio.h>
// System calls we need.
extern "C" int __preadv64(int, const struct iovec*, int, long, long);
extern "C" int __preadv64v2(int, const struct iovec*, int, long, long, int);
extern "C" int __pwritev64(int, const struct iovec*, int, long, long);
extern "C" int __pwritev64v2(int, const struct iovec*, int, long, long, int);
// There is no 32-bit off_t preadv/pwritev (even on LP32).
// To avoid 32-bit ABI issues about which register pairs you're allowed
// to pass 64-bit values in, the kernel just takes two `long` arguments --
// which are int32_t for LP32, remember -- and stitches them together.
// It even does this for LP64, taking a second unused always-zero `long`.
// (The first long was int64_t, which is the same as off64_t.)
// The pair is split lo-hi (not hi-lo, as llseek is).
ssize_t preadv(int fd, const struct iovec* ios, int count, off_t offset) {
return preadv64(fd, ios, count, offset);
}
ssize_t preadv64(int fd, const struct iovec* ios, int count, off64_t offset) {
#if defined(__LP64__)
return __preadv64(fd, ios, count, offset, 0);
#else
return __preadv64(fd, ios, count, offset, offset >> 32);
#endif
}
ssize_t pwritev(int fd, const struct iovec* ios, int count, off_t offset) {
return pwritev64(fd, ios, count, offset);
}
ssize_t pwritev64(int fd, const struct iovec* ios, int count, off64_t offset) {
#if defined(__LP64__)
return __pwritev64(fd, ios, count, offset, 0);
#else
return __pwritev64(fd, ios, count, offset, offset >> 32);
#endif
}
ssize_t preadv2(int fd, const struct iovec* ios, int count, off_t offset, int flags) {
return preadv64v2(fd, ios, count, offset, flags);
}
ssize_t preadv64v2(int fd, const struct iovec* ios, int count, off64_t offset, int flags) {
#if defined(__LP64__)
return __preadv64v2(fd, ios, count, offset, 0, flags);
#else
return __preadv64v2(fd, ios, count, offset, offset >> 32, flags);
#endif
}
ssize_t pwritev2(int fd, const struct iovec* ios, int count, off_t offset, int flags) {
return pwritev64v2(fd, ios, count, offset, flags);
}
ssize_t pwritev64v2(int fd, const struct iovec* ios, int count, off64_t offset, int flags) {
#if defined(__LP64__)
return __pwritev64v2(fd, ios, count, offset, 0, flags);
#else
return __pwritev64v2(fd, ios, count, offset, offset >> 32, flags);
#endif
}

127
libc/include/sys/uio.h
View file

@ -26,8 +26,12 @@
* SUCH DAMAGE.
*/
#ifndef _SYS_UIO_H_
#define _SYS_UIO_H_
#pragma once
/**
* @file sys/uio.h
* @brief Multi-buffer ("vector") I/O operations using `struct iovec`.
*/
#include <sys/cdefs.h>
#include <sys/types.h>
@ -35,21 +39,124 @@
__BEGIN_DECLS
/**
* [readv(2)](http://man7.org/linux/man-pages/man2/readv.2.html) reads
* from an fd into the `__count` buffers described by `__iov`.
*
* Returns the number of bytes read on success,
* and returns -1 and sets `errno` on failure.
*/
ssize_t readv(int __fd, const struct iovec* __iov, int __count);
/**
* [writev(2)](http://man7.org/linux/man-pages/man2/writev.2.html) writes
* to an fd from the `__count` buffers described by `__iov`.
*
* Returns the number of bytes written on success,
* and returns -1 and sets `errno` on failure.
*/
ssize_t writev(int __fd, const struct iovec* __iov, int __count);
#if defined(__USE_GNU)
ssize_t preadv(int __fd, const struct iovec* __iov, int __count, off_t __offset) __RENAME_IF_FILE_OFFSET64(preadv64) __INTRODUCED_IN(24);
ssize_t pwritev(int __fd, const struct iovec* __iov, int __count, off_t __offset) __RENAME_IF_FILE_OFFSET64(pwritev64) __INTRODUCED_IN(24);
ssize_t preadv64(int __fd, const struct iovec* __iov, int __count, off64_t __offset) __INTRODUCED_IN(24);
ssize_t pwritev64(int __fd, const struct iovec* __iov, int __count, off64_t __offset) __INTRODUCED_IN(24);
#endif
#if defined(__USE_GNU)
/**
* [preadv(2)](http://man7.org/linux/man-pages/man2/preadv.2.html) reads
* from an fd into the `__count` buffers described by `__iov`, starting at
* offset `__offset` into the file.
*
* Returns the number of bytes read on success,
* and returns -1 and sets `errno` on failure.
*
* Available since API level 24.
*/
ssize_t preadv(int __fd, const struct iovec* __iov, int __count, off_t __offset) __RENAME_IF_FILE_OFFSET64(preadv64) __INTRODUCED_IN(24);
/**
* [pwritev(2)](http://man7.org/linux/man-pages/man2/pwritev.2.html) writes
* to an fd from the `__count` buffers described by `__iov`, starting at offset
* `__offset` into the file.
*
* Returns the number of bytes written on success,
* and returns -1 and sets `errno` on failure.
*
* Available since API level 24.
*/
ssize_t pwritev(int __fd, const struct iovec* __iov, int __count, off_t __offset) __RENAME_IF_FILE_OFFSET64(pwritev64) __INTRODUCED_IN(24);
/**
* Like preadv() but with a 64-bit offset even in a 32-bit process.
*
* Available since API level 24.
*/
ssize_t preadv64(int __fd, const struct iovec* __iov, int __count, off64_t __offset) __INTRODUCED_IN(24);
/**
* Like pwritev() but with a 64-bit offset even in a 32-bit process.
*
* Available since API level 24.
*/
ssize_t pwritev64(int __fd, const struct iovec* __iov, int __count, off64_t __offset) __INTRODUCED_IN(24);
/**
* [preadv2(2)](http://man7.org/linux/man-pages/man2/preadv2.2.html) reads
* from an fd into the `__count` buffers described by `__iov`, starting at
* offset `__offset` into the file, with the given flags.
*
* Returns the number of bytes read on success,
* and returns -1 and sets `errno` on failure.
*
* Available since API level 33.
*/
ssize_t preadv2(int __fd, const struct iovec* __iov, int __count, off_t __offset, int __flags) __RENAME_IF_FILE_OFFSET64(preadv64v2) __INTRODUCED_IN(33);
/**
* [pwritev2(2)](http://man7.org/linux/man-pages/man2/pwritev2.2.html) writes
* to an fd from the `__count` buffers described by `__iov`, starting at offset
* `__offset` into the file, with the given flags.
*
* Returns the number of bytes written on success,
* and returns -1 and sets `errno` on failure.
*
* Available since API level 33.
*/
ssize_t pwritev2(int __fd, const struct iovec* __iov, int __count, off_t __offset, int __flags) __RENAME_IF_FILE_OFFSET64(pwritev64v2) __INTRODUCED_IN(33);
/**
* Like preadv2() but with a 64-bit offset even in a 32-bit process.
*
* Available since API level 33.
*/
ssize_t preadv64v2(int __fd, const struct iovec* __iov, int __count, off64_t __offset, int __flags) __INTRODUCED_IN(33);
/**
* Like pwritev2() but with a 64-bit offset even in a 32-bit process.
*
* Available since API level 33.
*/
ssize_t pwritev64v2(int __fd, const struct iovec* __iov, int __count, off64_t __offset, int __flags) __INTRODUCED_IN(33);
/**
* [process_vm_readv(2)](http://man7.org/linux/man-pages/man2/process_vm_readv.2.html)
* reads from the address space of another process.
*
* Returns the number of bytes read on success,
* and returns -1 and sets `errno` on failure.
*
* Available since API level 23.
*/
ssize_t process_vm_readv(pid_t __pid, const struct iovec* __local_iov, unsigned long __local_iov_count, const struct iovec* __remote_iov, unsigned long __remote_iov_count, unsigned long __flags) __INTRODUCED_IN(23);
/**
* [process_vm_writev(2)](http://man7.org/linux/man-pages/man2/process_vm_writev.2.html)
* writes to the address space of another process.
*
* Returns the number of bytes read on success,
* and returns -1 and sets `errno` on failure.
*
* Available since API level 23.
*/
ssize_t process_vm_writev(pid_t __pid, const struct iovec* __local_iov, unsigned long __local_iov_count, const struct iovec* __remote_iov, unsigned long __remote_iov_count, unsigned long __flags) __INTRODUCED_IN(23);
#endif
__END_DECLS
#endif

8
libc/libc.map.txt
View file

@ -1565,6 +1565,14 @@ LIBC_S { # introduced=S
process_madvise;
} LIBC_R;
LIBC_T { # introduced=Tiramisu
global:
preadv2;
preadv64v2;
pwritev2;
pwritev64v2;
} LIBC_S;
LIBC_PRIVATE {
global:
__accept4; # arm x86

40
tests/sys_uio_test.cpp
View file

@ -16,7 +16,11 @@
#include <gtest/gtest.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/uio.h>
#include <unistd.h>
#include <android-base/file.h>
@ -68,6 +72,42 @@ TEST(sys_uio, preadv64_pwritev64) {
TestPreadVPwriteV(preadv64, pwritev64);
}
template <typename ReadFn, typename WriteFn>
void TestPreadV2PwriteV2(ReadFn read_fn, WriteFn write_fn) {
TemporaryFile tf;
char buf[] = "world";
iovec ios[] = {{buf, 5}};
ASSERT_EQ(5, write_fn(tf.fd, ios, 1, 5, 0)) << strerror(errno);
ASSERT_EQ(0, lseek(tf.fd, 0, SEEK_CUR));
strcpy(buf, "hello");
ASSERT_EQ(5, write_fn(tf.fd, ios, 1, 0, 0)) << strerror(errno);
ASSERT_EQ(0, lseek(tf.fd, 0, SEEK_CUR));
ASSERT_EQ(5, read_fn(tf.fd, ios, 1, 5, 0)) << strerror(errno);
ASSERT_STREQ("world", buf);
ASSERT_EQ(5, read_fn(tf.fd, ios, 1, 0, 0)) << strerror(errno);
ASSERT_STREQ("hello", buf);
}
TEST(sys_uio, preadv2_pwritev2) {
#if defined(__BIONIC__)
TestPreadV2PwriteV2(preadv2, pwritev2);
#else
GTEST_SKIP() << "preadv2/pwritev2 not available";
#endif
}
TEST(sys_uio, preadv64v2_pwritev64v2) {
#if defined(__BIONIC__)
TestPreadV2PwriteV2(preadv64v2, pwritev64v2);
#else
GTEST_SKIP() << "preadv2/pwritev2 not available";
#endif
}
TEST(sys_uio, process_vm_readv) {
ASSERT_EQ(0, process_vm_readv(0, nullptr, 0, nullptr, 0, 0));