Re: [PATCH] mm/process_vm_access: move into ipc/
From: Hugh Dickins
Date: Mon May 26 2014 - 15:17:43 EST
On Sat, 24 May 2014, Konstantin Khlebnikov wrote:
> "CROSS_MEMORY_ATTACH" and mm/process_vm_access.c seems misnamed and misplaced.
> Actually it's a kind of IPC and it has no more relation to MM than sys_read().
> This patch moves code into ipc/ and config option into init/Kconfig.
>
> Signed-off-by: Konstantin Khlebnikov <koct9i@xxxxxxxxx>
I disagree, and SysV's ipc/ isn't where I would expect to find it.
How about we just leave it where it is in mm?
Hugh
> ---
> init/Kconfig | 10 +
> ipc/Makefile | 1
> ipc/process_vm_access.c | 383 +++++++++++++++++++++++++++++++++++++++++++++++
> mm/Kconfig | 10 -
> mm/Makefile | 4
> mm/process_vm_access.c | 383 -----------------------------------------------
> 6 files changed, 394 insertions(+), 397 deletions(-)
> create mode 100644 ipc/process_vm_access.c
> delete mode 100644 mm/process_vm_access.c
>
> diff --git a/init/Kconfig b/init/Kconfig
> index 9d3585b..d6ddb7a 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -261,6 +261,16 @@ config POSIX_MQUEUE_SYSCTL
> depends on SYSCTL
> default y
>
> +config CROSS_MEMORY_ATTACH
> + bool "Enable process_vm_readv/writev syscalls"
> + depends on MMU
> + default y
> + help
> + Enabling this option adds the system calls process_vm_readv and
> + process_vm_writev which allow a process with the correct privileges
> + to directly read from or write to to another process's address space.
> + See the man page for more details.
> +
> config FHANDLE
> bool "open by fhandle syscalls"
> select EXPORTFS
> diff --git a/ipc/Makefile b/ipc/Makefile
> index 9075e17..6982d3e 100644
> --- a/ipc/Makefile
> +++ b/ipc/Makefile
> @@ -9,4 +9,5 @@ obj_mq-$(CONFIG_COMPAT) += compat_mq.o
> obj-$(CONFIG_POSIX_MQUEUE) += mqueue.o msgutil.o $(obj_mq-y)
> obj-$(CONFIG_IPC_NS) += namespace.o
> obj-$(CONFIG_POSIX_MQUEUE_SYSCTL) += mq_sysctl.o
> +obj-$(CONFIG_CROSS_MEMORY_ATTACH) += process_vm_access.o
>
> diff --git a/ipc/process_vm_access.c b/ipc/process_vm_access.c
> new file mode 100644
> index 0000000..65aacea
> --- /dev/null
> +++ b/ipc/process_vm_access.c
> @@ -0,0 +1,383 @@
> +/*
> + * linux/ipc/process_vm_access.c
> + *
> + * Copyright (C) 2010-2011 Christopher Yeoh <cyeoh@xxxxxxxxxxx>, IBM Corp.
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * as published by the Free Software Foundation; either version
> + * 2 of the License, or (at your option) any later version.
> + */
> +
> +#include <linux/mm.h>
> +#include <linux/uio.h>
> +#include <linux/sched.h>
> +#include <linux/highmem.h>
> +#include <linux/ptrace.h>
> +#include <linux/slab.h>
> +#include <linux/syscalls.h>
> +
> +#ifdef CONFIG_COMPAT
> +#include <linux/compat.h>
> +#endif
> +
> +/**
> + * process_vm_rw_pages - read/write pages from task specified
> + * @pages: array of pointers to pages we want to copy
> + * @start_offset: offset in page to start copying from/to
> + * @len: number of bytes to copy
> + * @iter: where to copy to/from locally
> + * @vm_write: 0 means copy from, 1 means copy to
> + * Returns 0 on success, error code otherwise
> + */
> +static int process_vm_rw_pages(struct page **pages,
> + unsigned offset,
> + size_t len,
> + struct iov_iter *iter,
> + int vm_write)
> +{
> + /* Do the copy for each page */
> + while (len && iov_iter_count(iter)) {
> + struct page *page = *pages++;
> + size_t copy = PAGE_SIZE - offset;
> + size_t copied;
> +
> + if (copy > len)
> + copy = len;
> +
> + if (vm_write) {
> + if (copy > iov_iter_count(iter))
> + copy = iov_iter_count(iter);
> + copied = iov_iter_copy_from_user(page, iter,
> + offset, copy);
> + iov_iter_advance(iter, copied);
> + set_page_dirty_lock(page);
> + } else {
> + copied = copy_page_to_iter(page, offset, copy, iter);
> + }
> + len -= copied;
> + if (copied < copy && iov_iter_count(iter))
> + return -EFAULT;
> + offset = 0;
> + }
> + return 0;
> +}
> +
> +/* Maximum number of pages kmalloc'd to hold struct page's during copy */
> +#define PVM_MAX_KMALLOC_PAGES (PAGE_SIZE * 2)
> +
> +/**
> + * process_vm_rw_single_vec - read/write pages from task specified
> + * @addr: start memory address of target process
> + * @len: size of area to copy to/from
> + * @iter: where to copy to/from locally
> + * @process_pages: struct pages area that can store at least
> + * nr_pages_to_copy struct page pointers
> + * @mm: mm for task
> + * @task: task to read/write from
> + * @vm_write: 0 means copy from, 1 means copy to
> + * Returns 0 on success or on failure error code
> + */
> +static int process_vm_rw_single_vec(unsigned long addr,
> + unsigned long len,
> + struct iov_iter *iter,
> + struct page **process_pages,
> + struct mm_struct *mm,
> + struct task_struct *task,
> + int vm_write)
> +{
> + unsigned long pa = addr & PAGE_MASK;
> + unsigned long start_offset = addr - pa;
> + unsigned long nr_pages;
> + ssize_t rc = 0;
> + unsigned long max_pages_per_loop = PVM_MAX_KMALLOC_PAGES
> + / sizeof(struct pages *);
> +
> + /* Work out address and page range required */
> + if (len == 0)
> + return 0;
> + nr_pages = (addr + len - 1) / PAGE_SIZE - addr / PAGE_SIZE + 1;
> +
> + while (!rc && nr_pages && iov_iter_count(iter)) {
> + int pages = min(nr_pages, max_pages_per_loop);
> + size_t bytes;
> +
> + /* Get the pages we're interested in */
> + down_read(&mm->mmap_sem);
> + pages = get_user_pages(task, mm, pa, pages,
> + vm_write, 0, process_pages, NULL);
> + up_read(&mm->mmap_sem);
> +
> + if (pages <= 0)
> + return -EFAULT;
> +
> + bytes = pages * PAGE_SIZE - start_offset;
> + if (bytes > len)
> + bytes = len;
> +
> + rc = process_vm_rw_pages(process_pages,
> + start_offset, bytes, iter,
> + vm_write);
> + len -= bytes;
> + start_offset = 0;
> + nr_pages -= pages;
> + pa += pages * PAGE_SIZE;
> + while (pages)
> + put_page(process_pages[--pages]);
> + }
> +
> + return rc;
> +}
> +
> +/* Maximum number of entries for process pages array
> + which lives on stack */
> +#define PVM_MAX_PP_ARRAY_COUNT 16
> +
> +/**
> + * process_vm_rw_core - core of reading/writing pages from task specified
> + * @pid: PID of process to read/write from/to
> + * @iter: where to copy to/from locally
> + * @rvec: iovec array specifying where to copy to/from in the other process
> + * @riovcnt: size of rvec array
> + * @flags: currently unused
> + * @vm_write: 0 if reading from other process, 1 if writing to other process
> + * Returns the number of bytes read/written or error code. May
> + * return less bytes than expected if an error occurs during the copying
> + * process.
> + */
> +static ssize_t process_vm_rw_core(pid_t pid, struct iov_iter *iter,
> + const struct iovec *rvec,
> + unsigned long riovcnt,
> + unsigned long flags, int vm_write)
> +{
> + struct task_struct *task;
> + struct page *pp_stack[PVM_MAX_PP_ARRAY_COUNT];
> + struct page **process_pages = pp_stack;
> + struct mm_struct *mm;
> + unsigned long i;
> + ssize_t rc = 0;
> + unsigned long nr_pages = 0;
> + unsigned long nr_pages_iov;
> + ssize_t iov_len;
> + size_t total_len = iov_iter_count(iter);
> +
> + /*
> + * Work out how many pages of struct pages we're going to need
> + * when eventually calling get_user_pages
> + */
> + for (i = 0; i < riovcnt; i++) {
> + iov_len = rvec[i].iov_len;
> + if (iov_len > 0) {
> + nr_pages_iov = ((unsigned long)rvec[i].iov_base
> + + iov_len)
> + / PAGE_SIZE - (unsigned long)rvec[i].iov_base
> + / PAGE_SIZE + 1;
> + nr_pages = max(nr_pages, nr_pages_iov);
> + }
> + }
> +
> + if (nr_pages == 0)
> + return 0;
> +
> + if (nr_pages > PVM_MAX_PP_ARRAY_COUNT) {
> + /* For reliability don't try to kmalloc more than
> + 2 pages worth */
> + process_pages = kmalloc(min_t(size_t, PVM_MAX_KMALLOC_PAGES,
> + sizeof(struct pages *)*nr_pages),
> + GFP_KERNEL);
> +
> + if (!process_pages)
> + return -ENOMEM;
> + }
> +
> + /* Get process information */
> + rcu_read_lock();
> + task = find_task_by_vpid(pid);
> + if (task)
> + get_task_struct(task);
> + rcu_read_unlock();
> + if (!task) {
> + rc = -ESRCH;
> + goto free_proc_pages;
> + }
> +
> + mm = mm_access(task, PTRACE_MODE_ATTACH);
> + if (!mm || IS_ERR(mm)) {
> + rc = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH;
> + /*
> + * Explicitly map EACCES to EPERM as EPERM is a more a
> + * appropriate error code for process_vw_readv/writev
> + */
> + if (rc == -EACCES)
> + rc = -EPERM;
> + goto put_task_struct;
> + }
> +
> + for (i = 0; i < riovcnt && iov_iter_count(iter) && !rc; i++)
> + rc = process_vm_rw_single_vec(
> + (unsigned long)rvec[i].iov_base, rvec[i].iov_len,
> + iter, process_pages, mm, task, vm_write);
> +
> + /* copied = space before - space after */
> + total_len -= iov_iter_count(iter);
> +
> + /* If we have managed to copy any data at all then
> + we return the number of bytes copied. Otherwise
> + we return the error code */
> + if (total_len)
> + rc = total_len;
> +
> + mmput(mm);
> +
> +put_task_struct:
> + put_task_struct(task);
> +
> +free_proc_pages:
> + if (process_pages != pp_stack)
> + kfree(process_pages);
> + return rc;
> +}
> +
> +/**
> + * process_vm_rw - check iovecs before calling core routine
> + * @pid: PID of process to read/write from/to
> + * @lvec: iovec array specifying where to copy to/from locally
> + * @liovcnt: size of lvec array
> + * @rvec: iovec array specifying where to copy to/from in the other process
> + * @riovcnt: size of rvec array
> + * @flags: currently unused
> + * @vm_write: 0 if reading from other process, 1 if writing to other process
> + * Returns the number of bytes read/written or error code. May
> + * return less bytes than expected if an error occurs during the copying
> + * process.
> + */
> +static ssize_t process_vm_rw(pid_t pid,
> + const struct iovec __user *lvec,
> + unsigned long liovcnt,
> + const struct iovec __user *rvec,
> + unsigned long riovcnt,
> + unsigned long flags, int vm_write)
> +{
> + struct iovec iovstack_l[UIO_FASTIOV];
> + struct iovec iovstack_r[UIO_FASTIOV];
> + struct iovec *iov_l = iovstack_l;
> + struct iovec *iov_r = iovstack_r;
> + struct iov_iter iter;
> + ssize_t rc;
> +
> + if (flags != 0)
> + return -EINVAL;
> +
> + /* Check iovecs */
> + if (vm_write)
> + rc = rw_copy_check_uvector(WRITE, lvec, liovcnt, UIO_FASTIOV,
> + iovstack_l, &iov_l);
> + else
> + rc = rw_copy_check_uvector(READ, lvec, liovcnt, UIO_FASTIOV,
> + iovstack_l, &iov_l);
> + if (rc <= 0)
> + goto free_iovecs;
> +
> + iov_iter_init(&iter, iov_l, liovcnt, rc, 0);
> +
> + rc = rw_copy_check_uvector(CHECK_IOVEC_ONLY, rvec, riovcnt, UIO_FASTIOV,
> + iovstack_r, &iov_r);
> + if (rc <= 0)
> + goto free_iovecs;
> +
> + rc = process_vm_rw_core(pid, &iter, iov_r, riovcnt, flags, vm_write);
> +
> +free_iovecs:
> + if (iov_r != iovstack_r)
> + kfree(iov_r);
> + if (iov_l != iovstack_l)
> + kfree(iov_l);
> +
> + return rc;
> +}
> +
> +SYSCALL_DEFINE6(process_vm_readv, pid_t, pid, const struct iovec __user *, lvec,
> + unsigned long, liovcnt, const struct iovec __user *, rvec,
> + unsigned long, riovcnt, unsigned long, flags)
> +{
> + return process_vm_rw(pid, lvec, liovcnt, rvec, riovcnt, flags, 0);
> +}
> +
> +SYSCALL_DEFINE6(process_vm_writev, pid_t, pid,
> + const struct iovec __user *, lvec,
> + unsigned long, liovcnt, const struct iovec __user *, rvec,
> + unsigned long, riovcnt, unsigned long, flags)
> +{
> + return process_vm_rw(pid, lvec, liovcnt, rvec, riovcnt, flags, 1);
> +}
> +
> +#ifdef CONFIG_COMPAT
> +
> +static ssize_t
> +compat_process_vm_rw(compat_pid_t pid,
> + const struct compat_iovec __user *lvec,
> + unsigned long liovcnt,
> + const struct compat_iovec __user *rvec,
> + unsigned long riovcnt,
> + unsigned long flags, int vm_write)
> +{
> + struct iovec iovstack_l[UIO_FASTIOV];
> + struct iovec iovstack_r[UIO_FASTIOV];
> + struct iovec *iov_l = iovstack_l;
> + struct iovec *iov_r = iovstack_r;
> + struct iov_iter iter;
> + ssize_t rc = -EFAULT;
> +
> + if (flags != 0)
> + return -EINVAL;
> +
> + if (vm_write)
> + rc = compat_rw_copy_check_uvector(WRITE, lvec, liovcnt,
> + UIO_FASTIOV, iovstack_l,
> + &iov_l);
> + else
> + rc = compat_rw_copy_check_uvector(READ, lvec, liovcnt,
> + UIO_FASTIOV, iovstack_l,
> + &iov_l);
> + if (rc <= 0)
> + goto free_iovecs;
> + iov_iter_init(&iter, iov_l, liovcnt, rc, 0);
> + rc = compat_rw_copy_check_uvector(CHECK_IOVEC_ONLY, rvec, riovcnt,
> + UIO_FASTIOV, iovstack_r,
> + &iov_r);
> + if (rc <= 0)
> + goto free_iovecs;
> +
> + rc = process_vm_rw_core(pid, &iter, iov_r, riovcnt, flags, vm_write);
> +
> +free_iovecs:
> + if (iov_r != iovstack_r)
> + kfree(iov_r);
> + if (iov_l != iovstack_l)
> + kfree(iov_l);
> + return rc;
> +}
> +
> +COMPAT_SYSCALL_DEFINE6(process_vm_readv, compat_pid_t, pid,
> + const struct compat_iovec __user *, lvec,
> + compat_ulong_t, liovcnt,
> + const struct compat_iovec __user *, rvec,
> + compat_ulong_t, riovcnt,
> + compat_ulong_t, flags)
> +{
> + return compat_process_vm_rw(pid, lvec, liovcnt, rvec,
> + riovcnt, flags, 0);
> +}
> +
> +COMPAT_SYSCALL_DEFINE6(process_vm_writev, compat_pid_t, pid,
> + const struct compat_iovec __user *, lvec,
> + compat_ulong_t, liovcnt,
> + const struct compat_iovec __user *, rvec,
> + compat_ulong_t, riovcnt,
> + compat_ulong_t, flags)
> +{
> + return compat_process_vm_rw(pid, lvec, liovcnt, rvec,
> + riovcnt, flags, 1);
> +}
> +
> +#endif
> diff --git a/mm/Kconfig b/mm/Kconfig
> index 1b5a95f..2ec35d7 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -430,16 +430,6 @@ choice
> benefit.
> endchoice
>
> -config CROSS_MEMORY_ATTACH
> - bool "Cross Memory Support"
> - depends on MMU
> - default y
> - help
> - Enabling this option adds the system calls process_vm_readv and
> - process_vm_writev which allow a process with the correct privileges
> - to directly read from or write to to another process's address space.
> - See the man page for more details.
> -
> #
> # UP and nommu archs use km based percpu allocator
> #
> diff --git a/mm/Makefile b/mm/Makefile
> index b484452..d624084 100644
> --- a/mm/Makefile
> +++ b/mm/Makefile
> @@ -7,10 +7,6 @@ mmu-$(CONFIG_MMU) := fremap.o highmem.o madvise.o memory.o mincore.o \
> mlock.o mmap.o mprotect.o mremap.o msync.o rmap.o \
> vmalloc.o pagewalk.o pgtable-generic.o
>
> -ifdef CONFIG_CROSS_MEMORY_ATTACH
> -mmu-$(CONFIG_MMU) += process_vm_access.o
> -endif
> -
> obj-y := filemap.o mempool.o oom_kill.o fadvise.o \
> maccess.o page_alloc.o page-writeback.o \
> readahead.o swap.o truncate.o vmscan.o shmem.o \
> diff --git a/mm/process_vm_access.c b/mm/process_vm_access.c
> deleted file mode 100644
> index 8505c92..0000000
> --- a/mm/process_vm_access.c
> +++ /dev/null
> @@ -1,383 +0,0 @@
> -/*
> - * linux/mm/process_vm_access.c
> - *
> - * Copyright (C) 2010-2011 Christopher Yeoh <cyeoh@xxxxxxxxxxx>, IBM Corp.
> - *
> - * This program is free software; you can redistribute it and/or
> - * modify it under the terms of the GNU General Public License
> - * as published by the Free Software Foundation; either version
> - * 2 of the License, or (at your option) any later version.
> - */
> -
> -#include <linux/mm.h>
> -#include <linux/uio.h>
> -#include <linux/sched.h>
> -#include <linux/highmem.h>
> -#include <linux/ptrace.h>
> -#include <linux/slab.h>
> -#include <linux/syscalls.h>
> -
> -#ifdef CONFIG_COMPAT
> -#include <linux/compat.h>
> -#endif
> -
> -/**
> - * process_vm_rw_pages - read/write pages from task specified
> - * @pages: array of pointers to pages we want to copy
> - * @start_offset: offset in page to start copying from/to
> - * @len: number of bytes to copy
> - * @iter: where to copy to/from locally
> - * @vm_write: 0 means copy from, 1 means copy to
> - * Returns 0 on success, error code otherwise
> - */
> -static int process_vm_rw_pages(struct page **pages,
> - unsigned offset,
> - size_t len,
> - struct iov_iter *iter,
> - int vm_write)
> -{
> - /* Do the copy for each page */
> - while (len && iov_iter_count(iter)) {
> - struct page *page = *pages++;
> - size_t copy = PAGE_SIZE - offset;
> - size_t copied;
> -
> - if (copy > len)
> - copy = len;
> -
> - if (vm_write) {
> - if (copy > iov_iter_count(iter))
> - copy = iov_iter_count(iter);
> - copied = iov_iter_copy_from_user(page, iter,
> - offset, copy);
> - iov_iter_advance(iter, copied);
> - set_page_dirty_lock(page);
> - } else {
> - copied = copy_page_to_iter(page, offset, copy, iter);
> - }
> - len -= copied;
> - if (copied < copy && iov_iter_count(iter))
> - return -EFAULT;
> - offset = 0;
> - }
> - return 0;
> -}
> -
> -/* Maximum number of pages kmalloc'd to hold struct page's during copy */
> -#define PVM_MAX_KMALLOC_PAGES (PAGE_SIZE * 2)
> -
> -/**
> - * process_vm_rw_single_vec - read/write pages from task specified
> - * @addr: start memory address of target process
> - * @len: size of area to copy to/from
> - * @iter: where to copy to/from locally
> - * @process_pages: struct pages area that can store at least
> - * nr_pages_to_copy struct page pointers
> - * @mm: mm for task
> - * @task: task to read/write from
> - * @vm_write: 0 means copy from, 1 means copy to
> - * Returns 0 on success or on failure error code
> - */
> -static int process_vm_rw_single_vec(unsigned long addr,
> - unsigned long len,
> - struct iov_iter *iter,
> - struct page **process_pages,
> - struct mm_struct *mm,
> - struct task_struct *task,
> - int vm_write)
> -{
> - unsigned long pa = addr & PAGE_MASK;
> - unsigned long start_offset = addr - pa;
> - unsigned long nr_pages;
> - ssize_t rc = 0;
> - unsigned long max_pages_per_loop = PVM_MAX_KMALLOC_PAGES
> - / sizeof(struct pages *);
> -
> - /* Work out address and page range required */
> - if (len == 0)
> - return 0;
> - nr_pages = (addr + len - 1) / PAGE_SIZE - addr / PAGE_SIZE + 1;
> -
> - while (!rc && nr_pages && iov_iter_count(iter)) {
> - int pages = min(nr_pages, max_pages_per_loop);
> - size_t bytes;
> -
> - /* Get the pages we're interested in */
> - down_read(&mm->mmap_sem);
> - pages = get_user_pages(task, mm, pa, pages,
> - vm_write, 0, process_pages, NULL);
> - up_read(&mm->mmap_sem);
> -
> - if (pages <= 0)
> - return -EFAULT;
> -
> - bytes = pages * PAGE_SIZE - start_offset;
> - if (bytes > len)
> - bytes = len;
> -
> - rc = process_vm_rw_pages(process_pages,
> - start_offset, bytes, iter,
> - vm_write);
> - len -= bytes;
> - start_offset = 0;
> - nr_pages -= pages;
> - pa += pages * PAGE_SIZE;
> - while (pages)
> - put_page(process_pages[--pages]);
> - }
> -
> - return rc;
> -}
> -
> -/* Maximum number of entries for process pages array
> - which lives on stack */
> -#define PVM_MAX_PP_ARRAY_COUNT 16
> -
> -/**
> - * process_vm_rw_core - core of reading/writing pages from task specified
> - * @pid: PID of process to read/write from/to
> - * @iter: where to copy to/from locally
> - * @rvec: iovec array specifying where to copy to/from in the other process
> - * @riovcnt: size of rvec array
> - * @flags: currently unused
> - * @vm_write: 0 if reading from other process, 1 if writing to other process
> - * Returns the number of bytes read/written or error code. May
> - * return less bytes than expected if an error occurs during the copying
> - * process.
> - */
> -static ssize_t process_vm_rw_core(pid_t pid, struct iov_iter *iter,
> - const struct iovec *rvec,
> - unsigned long riovcnt,
> - unsigned long flags, int vm_write)
> -{
> - struct task_struct *task;
> - struct page *pp_stack[PVM_MAX_PP_ARRAY_COUNT];
> - struct page **process_pages = pp_stack;
> - struct mm_struct *mm;
> - unsigned long i;
> - ssize_t rc = 0;
> - unsigned long nr_pages = 0;
> - unsigned long nr_pages_iov;
> - ssize_t iov_len;
> - size_t total_len = iov_iter_count(iter);
> -
> - /*
> - * Work out how many pages of struct pages we're going to need
> - * when eventually calling get_user_pages
> - */
> - for (i = 0; i < riovcnt; i++) {
> - iov_len = rvec[i].iov_len;
> - if (iov_len > 0) {
> - nr_pages_iov = ((unsigned long)rvec[i].iov_base
> - + iov_len)
> - / PAGE_SIZE - (unsigned long)rvec[i].iov_base
> - / PAGE_SIZE + 1;
> - nr_pages = max(nr_pages, nr_pages_iov);
> - }
> - }
> -
> - if (nr_pages == 0)
> - return 0;
> -
> - if (nr_pages > PVM_MAX_PP_ARRAY_COUNT) {
> - /* For reliability don't try to kmalloc more than
> - 2 pages worth */
> - process_pages = kmalloc(min_t(size_t, PVM_MAX_KMALLOC_PAGES,
> - sizeof(struct pages *)*nr_pages),
> - GFP_KERNEL);
> -
> - if (!process_pages)
> - return -ENOMEM;
> - }
> -
> - /* Get process information */
> - rcu_read_lock();
> - task = find_task_by_vpid(pid);
> - if (task)
> - get_task_struct(task);
> - rcu_read_unlock();
> - if (!task) {
> - rc = -ESRCH;
> - goto free_proc_pages;
> - }
> -
> - mm = mm_access(task, PTRACE_MODE_ATTACH);
> - if (!mm || IS_ERR(mm)) {
> - rc = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH;
> - /*
> - * Explicitly map EACCES to EPERM as EPERM is a more a
> - * appropriate error code for process_vw_readv/writev
> - */
> - if (rc == -EACCES)
> - rc = -EPERM;
> - goto put_task_struct;
> - }
> -
> - for (i = 0; i < riovcnt && iov_iter_count(iter) && !rc; i++)
> - rc = process_vm_rw_single_vec(
> - (unsigned long)rvec[i].iov_base, rvec[i].iov_len,
> - iter, process_pages, mm, task, vm_write);
> -
> - /* copied = space before - space after */
> - total_len -= iov_iter_count(iter);
> -
> - /* If we have managed to copy any data at all then
> - we return the number of bytes copied. Otherwise
> - we return the error code */
> - if (total_len)
> - rc = total_len;
> -
> - mmput(mm);
> -
> -put_task_struct:
> - put_task_struct(task);
> -
> -free_proc_pages:
> - if (process_pages != pp_stack)
> - kfree(process_pages);
> - return rc;
> -}
> -
> -/**
> - * process_vm_rw - check iovecs before calling core routine
> - * @pid: PID of process to read/write from/to
> - * @lvec: iovec array specifying where to copy to/from locally
> - * @liovcnt: size of lvec array
> - * @rvec: iovec array specifying where to copy to/from in the other process
> - * @riovcnt: size of rvec array
> - * @flags: currently unused
> - * @vm_write: 0 if reading from other process, 1 if writing to other process
> - * Returns the number of bytes read/written or error code. May
> - * return less bytes than expected if an error occurs during the copying
> - * process.
> - */
> -static ssize_t process_vm_rw(pid_t pid,
> - const struct iovec __user *lvec,
> - unsigned long liovcnt,
> - const struct iovec __user *rvec,
> - unsigned long riovcnt,
> - unsigned long flags, int vm_write)
> -{
> - struct iovec iovstack_l[UIO_FASTIOV];
> - struct iovec iovstack_r[UIO_FASTIOV];
> - struct iovec *iov_l = iovstack_l;
> - struct iovec *iov_r = iovstack_r;
> - struct iov_iter iter;
> - ssize_t rc;
> -
> - if (flags != 0)
> - return -EINVAL;
> -
> - /* Check iovecs */
> - if (vm_write)
> - rc = rw_copy_check_uvector(WRITE, lvec, liovcnt, UIO_FASTIOV,
> - iovstack_l, &iov_l);
> - else
> - rc = rw_copy_check_uvector(READ, lvec, liovcnt, UIO_FASTIOV,
> - iovstack_l, &iov_l);
> - if (rc <= 0)
> - goto free_iovecs;
> -
> - iov_iter_init(&iter, iov_l, liovcnt, rc, 0);
> -
> - rc = rw_copy_check_uvector(CHECK_IOVEC_ONLY, rvec, riovcnt, UIO_FASTIOV,
> - iovstack_r, &iov_r);
> - if (rc <= 0)
> - goto free_iovecs;
> -
> - rc = process_vm_rw_core(pid, &iter, iov_r, riovcnt, flags, vm_write);
> -
> -free_iovecs:
> - if (iov_r != iovstack_r)
> - kfree(iov_r);
> - if (iov_l != iovstack_l)
> - kfree(iov_l);
> -
> - return rc;
> -}
> -
> -SYSCALL_DEFINE6(process_vm_readv, pid_t, pid, const struct iovec __user *, lvec,
> - unsigned long, liovcnt, const struct iovec __user *, rvec,
> - unsigned long, riovcnt, unsigned long, flags)
> -{
> - return process_vm_rw(pid, lvec, liovcnt, rvec, riovcnt, flags, 0);
> -}
> -
> -SYSCALL_DEFINE6(process_vm_writev, pid_t, pid,
> - const struct iovec __user *, lvec,
> - unsigned long, liovcnt, const struct iovec __user *, rvec,
> - unsigned long, riovcnt, unsigned long, flags)
> -{
> - return process_vm_rw(pid, lvec, liovcnt, rvec, riovcnt, flags, 1);
> -}
> -
> -#ifdef CONFIG_COMPAT
> -
> -static ssize_t
> -compat_process_vm_rw(compat_pid_t pid,
> - const struct compat_iovec __user *lvec,
> - unsigned long liovcnt,
> - const struct compat_iovec __user *rvec,
> - unsigned long riovcnt,
> - unsigned long flags, int vm_write)
> -{
> - struct iovec iovstack_l[UIO_FASTIOV];
> - struct iovec iovstack_r[UIO_FASTIOV];
> - struct iovec *iov_l = iovstack_l;
> - struct iovec *iov_r = iovstack_r;
> - struct iov_iter iter;
> - ssize_t rc = -EFAULT;
> -
> - if (flags != 0)
> - return -EINVAL;
> -
> - if (vm_write)
> - rc = compat_rw_copy_check_uvector(WRITE, lvec, liovcnt,
> - UIO_FASTIOV, iovstack_l,
> - &iov_l);
> - else
> - rc = compat_rw_copy_check_uvector(READ, lvec, liovcnt,
> - UIO_FASTIOV, iovstack_l,
> - &iov_l);
> - if (rc <= 0)
> - goto free_iovecs;
> - iov_iter_init(&iter, iov_l, liovcnt, rc, 0);
> - rc = compat_rw_copy_check_uvector(CHECK_IOVEC_ONLY, rvec, riovcnt,
> - UIO_FASTIOV, iovstack_r,
> - &iov_r);
> - if (rc <= 0)
> - goto free_iovecs;
> -
> - rc = process_vm_rw_core(pid, &iter, iov_r, riovcnt, flags, vm_write);
> -
> -free_iovecs:
> - if (iov_r != iovstack_r)
> - kfree(iov_r);
> - if (iov_l != iovstack_l)
> - kfree(iov_l);
> - return rc;
> -}
> -
> -COMPAT_SYSCALL_DEFINE6(process_vm_readv, compat_pid_t, pid,
> - const struct compat_iovec __user *, lvec,
> - compat_ulong_t, liovcnt,
> - const struct compat_iovec __user *, rvec,
> - compat_ulong_t, riovcnt,
> - compat_ulong_t, flags)
> -{
> - return compat_process_vm_rw(pid, lvec, liovcnt, rvec,
> - riovcnt, flags, 0);
> -}
> -
> -COMPAT_SYSCALL_DEFINE6(process_vm_writev, compat_pid_t, pid,
> - const struct compat_iovec __user *, lvec,
> - compat_ulong_t, liovcnt,
> - const struct compat_iovec __user *, rvec,
> - compat_ulong_t, riovcnt,
> - compat_ulong_t, flags)
> -{
> - return compat_process_vm_rw(pid, lvec, liovcnt, rvec,
> - riovcnt, flags, 1);
> -}
> -
> -#endif
>
> --
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> see: http://www.linux-mm.org/ .
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>
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