runtime/dyninst/copy.c - systemtap

Global variables defined

Functions defined

Macros defined

Source code

/* -*- linux-c -*-
* Copy from user space functions
* Copyright (C) 2012 Red Hat Inc.
*
* This file is part of systemtap, and is free software.  You can
* redistribute it and/or modify it under the terms of the GNU General
* Public License (GPL); either version 2, or (at your option) any
* later version.
*/

#ifndef _STAPDYN_COPY_C_
‌#define _STAPDYN_COPY_C_

#include <unistd.h>
#include <sys/syscall.h>
#include <sys/uio.h>

#include "stp_string.c"

‌static int _stp_mem_fd = -1;

‌static inline __must_check ssize_t __self_readv(const struct iovec *lvec,
                        unsigned long liovcnt,
                        const struct iovec *rvec,
                        unsigned long riovcnt)
{
#if !__GLIBC_PREREQ(2, 15)
#ifdef __NR_process_vm_readv
‌#define process_vm_readv(...) \
    syscall(__NR_process_vm_readv, __VA_ARGS__)
#else
#define process_vm_readv(...) \
    ({ (void)lvec; (void)liovcnt; \
     (void)rvec; (void)riovcnt; \
     errno = ENOSYS; -1 })
#endif
#endif
    return process_vm_readv(getpid(), lvec, liovcnt, rvec, riovcnt, 0UL);
}

‌static inline __must_check ssize_t __self_writev(const struct iovec *lvec,
                         unsigned long liovcnt,
                         const struct iovec *rvec,
                         unsigned long riovcnt)
{
#if !__GLIBC_PREREQ(2, 15)
#ifdef __NR_process_vm_writev
‌#define process_vm_writev(...) \
    syscall(__NR_process_vm_writev, __VA_ARGS__)
#else
#define process_vm_writev(...) \
    ({ (void)lvec; (void)liovcnt; \
     (void)rvec; (void)riovcnt; \
     errno = ENOSYS; -1 })
#endif
#endif
    return process_vm_writev(getpid(), lvec, liovcnt, rvec, riovcnt, 0UL);
}

‌static int _stp_copy_init(void)
{
    /* Try a no-op process_vm_readv/writev to make sure they're available,
     * esp. not ENOSYS, then we don't need to bother /proc/self/mem.  */
    if ((__self_readv(NULL, 0, NULL, 0) == 0) &&
            (__self_writev(NULL, 0, NULL, 0) == 0))
        return 0;

    _stp_mem_fd = open("/proc/self/mem", O_RDWR /*| O_LARGEFILE*/);
    if (_stp_mem_fd < 0)
        return -errno;
    fcntl(_stp_mem_fd, F_SETFD, FD_CLOEXEC);
    return 0;
}

‌static void _stp_copy_destroy(void)
{
    if (_stp_mem_fd >= 0) {
        close (_stp_mem_fd);
        _stp_mem_fd = -1;
    }
}

‌static inline __must_check long __copy_from_user(void *to,
        const void __user * from, unsigned long n)
{
    int rc = 0;

    if (_stp_mem_fd >= 0) {
        /* pread is like lseek+read, without racing other threads. */
        if (pread(_stp_mem_fd, to, n, (off_t)(uintptr_t)from) != n)
            rc = -EFAULT;
    } else {
        struct iovec lvec = { .iov_base = to, .iov_len = n };
        struct iovec rvec = { .iov_base = (void *)from, .iov_len = n };
        if (__self_readv(&lvec, 1, &rvec, 1) != n)
            rc = -EFAULT;
    }

    return rc;
}

‌static inline __must_check long __copy_to_user(void *to, const void *from,
                           unsigned long n)
{
    int rc = 0;

    if (_stp_mem_fd >= 0) {
        /* pwrite is like lseek+write, without racing other threads. */
        /* NB: some kernels will refuse to write /proc/self/mem  */
        if (pwrite(_stp_mem_fd, from, n, (off_t)(uintptr_t)to) != n)
            rc = -EFAULT;
    } else {
        struct iovec lvec = { .iov_base = (void *)from, .iov_len = n };
        struct iovec rvec = { .iov_base = to, .iov_len = n };
        if (__self_writev(&lvec, 1, &rvec, 1) != n)
            rc = -EFAULT;
    }

    return rc;
}

static long
‌_stp_strncpy_from_user(char *dst, const char *src, long count)
{
    if (count <= 0)
        return -EINVAL;

    /* Reads are batched on aligned 4k boundaries, approximately
     * page size, to reduce the number of pread syscalls.  It will
     * likely read past the terminating '\0', but shouldn't fault.
     * NB: We shouldn't try to read the entire 'count' at once, in
     * case some small string is already near the end of its page.
     */
    long i = 0;
    while (i < count) {
        long n = 0x1000 - ((long)(src + i) & 0xFFF);
        n = min(n, count - i);
        if (__copy_from_user(dst + i, src + i, n))
            return -EFAULT;

        char *dst0 = memchr(dst + i, 0, n);
        if (dst0 != NULL)
            return (dst0 - dst);

        i += n;
    }

    dst[i - 1] = 0;
    return i - 1;
}

‌static unsigned long _stp_copy_from_user(char *dst, const char *src, unsigned long count)
{
    if (count && __copy_from_user(dst, src, count) == 0)
        return 0;
    return count;
}

#endif /* _STAPDYN_COPY_C_ */