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Date: Mon, 26 May 2014 23:59:06 +0400
From: Konstantin Khlebnikov <koct9i@...il.com>
To: Hugh Dickins <hughd@...gle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
"linux-mm@...ck.org" <linux-mm@...ck.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH] mm/process_vm_access: move into ipc/
On Mon, May 26, 2014 at 11:16 PM, Hugh Dickins <hughd@...gle.com> wrote:
> 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@...il.com>
>
> 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?
Ok, how about moving only config option? It adds couple syscalls and
nothing more.
I don't think it should be in "Processor type and features".
All other options related to non-standard syscalls are in "General
setup' init/Kconfig.
>
> 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@....ibm.com>, 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@....ibm.com>, 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
>>
>> --
>> To unsubscribe, send a message with 'unsubscribe linux-mm' in
>> the body to majordomo@...ck.org. For more info on Linux MM,
>> see: http://www.linux-mm.org/ .
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>>
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