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    SubjectRe: Cross Memory Attach v3 (includes updated patch based on v4)
    On Thu, 21 Jul 2011 15:09:08 -0700
    Andrew Morton <akpm@linux-foundation.org> wrote:

    > On Tue, 19 Jul 2011 00:35:37 +0930
    > Christopher Yeoh <cyeoh@au1.ibm.com> wrote:
    >
    > > +
    > > +static ssize_t process_vm_rw(pid_t pid, const struct iovec *lvec,
    > > + unsigned long liovcnt,
    > > + const struct iovec *rvec,
    > > + unsigned long riovcnt,
    > > + unsigned long flags, int vm_write)
    > > +{
    > > + struct task_struct *task;
    > > + struct page **process_pages = NULL;
    > > + struct mm_struct *mm;
    > > + unsigned long i;
    > > + ssize_t rc;
    > > + ssize_t bytes_copied;
    > > + unsigned long nr_pages = 0;
    > > + unsigned long nr_pages_iov;
    > > + unsigned long iov_l_curr_idx = 0;
    > > + size_t iov_l_curr_offset = 0;
    > > + ssize_t iov_len;
    > > +
    > > + /*
    > > + * 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;
    > > +
    > > + /* 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);
    >
    > You might get some speed benefit by optimising for the small copies
    > here. Define a local on-stack array of N page*'s and point
    > process_pages at that if the number of pages is <= N. Saves a
    > malloc/free and is more cache-friendly. But only if the result is
    > measurable!

    I have done some benchmarking on this, and it gains about 5-7% on a
    microbenchmark with 4kb size copies and about a 1% gain with a more
    realistic (but modified for smaller copies) hpcc benchmark. The
    performance gain disappears into the noise by about 64kb sized copies.
    No measurable overhead for larger copies. So I think its worth including

    Included below is the patch (based on v4) - for ease of review the first diff
    is just against the latest version of CMA which has been posted here previously.
    The second is the entire CMA patch.

    Signed-off-by: Chris Yeoh <cyeoh@au1.ibm.com>
    ---
    process_vm_access.c | 25 +++++++++++++++++--------
    1 file changed, 17 insertions(+), 8 deletions(-)
    diff --git a/mm/process_vm_access.c b/mm/process_vm_access.c
    index 5ac8abc..e920aa3 100644
    --- a/mm/process_vm_access.c
    +++ b/mm/process_vm_access.c
    @@ -221,6 +221,10 @@ static int process_vm_rw_single_vec(unsigned long addr,
    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
    @@ -241,7 +245,8 @@ static ssize_t process_vm_rw_core(pid_t pid, const struct iovec *lvec,
    unsigned long flags, int vm_write)
    {
    struct task_struct *task;
    - struct page **process_pages = NULL;
    + 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;
    @@ -271,13 +276,16 @@ static ssize_t process_vm_rw_core(pid_t pid, const struct iovec *lvec,
    if (nr_pages == 0)
    return 0;

    - /* 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 (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;
    + if (!process_pages)
    + return -ENOMEM;
    + }

    /* Get process information */
    rcu_read_lock();
    @@ -331,7 +339,8 @@ put_task_struct:
    put_task_struct(task);

    free_proc_pages:
    - kfree(process_pages);
    + if (process_pages != pp_stack)
    + kfree(process_pages);
    return rc;
    }

    Signed-off-by: Chris Yeoh <cyeoh@au1.ibm.com>
    ---
    arch/powerpc/include/asm/systbl.h | 2
    arch/powerpc/include/asm/unistd.h | 4
    arch/x86/ia32/ia32entry.S | 2
    arch/x86/include/asm/unistd_32.h | 4
    arch/x86/include/asm/unistd_64.h | 4
    arch/x86/kernel/syscall_table_32.S | 2
    fs/aio.c | 4
    fs/compat.c | 7
    fs/read_write.c | 8
    include/linux/compat.h | 3
    include/linux/fs.h | 7
    include/linux/syscalls.h | 13
    kernel/sys_ni.c | 4
    mm/Makefile | 3
    mm/process_vm_access.c | 496 +++++++++++++++++++++++++++++++++++++
    security/keys/compat.c | 2
    security/keys/keyctl.c | 2
    17 files changed, 550 insertions(+), 17 deletions(-)
    diff --git a/arch/powerpc/include/asm/systbl.h b/arch/powerpc/include/asm/systbl.h
    index f6736b7..525db4b 100644
    --- a/arch/powerpc/include/asm/systbl.h
    +++ b/arch/powerpc/include/asm/systbl.h
    @@ -354,3 +354,5 @@ COMPAT_SYS_SPU(clock_adjtime)
    SYSCALL_SPU(syncfs)
    COMPAT_SYS_SPU(sendmmsg)
    SYSCALL_SPU(setns)
    +COMPAT_SYS(process_vm_readv)
    +COMPAT_SYS(process_vm_writev)
    diff --git a/arch/powerpc/include/asm/unistd.h b/arch/powerpc/include/asm/unistd.h
    index b8b3f59..d3d1b5e 100644
    --- a/arch/powerpc/include/asm/unistd.h
    +++ b/arch/powerpc/include/asm/unistd.h
    @@ -373,10 +373,12 @@
    #define __NR_syncfs 348
    #define __NR_sendmmsg 349
    #define __NR_setns 350
    +#define __NR_process_vm_readv 351
    +#define __NR_process_vm_writev 352

    #ifdef __KERNEL__

    -#define __NR_syscalls 351
    +#define __NR_syscalls 353

    #define __NR__exit __NR_exit
    #define NR_syscalls __NR_syscalls
    diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S
    index c1870dd..cde849f 100644
    --- a/arch/x86/ia32/ia32entry.S
    +++ b/arch/x86/ia32/ia32entry.S
    @@ -850,4 +850,6 @@ ia32_sys_call_table:
    .quad sys_syncfs
    .quad compat_sys_sendmmsg /* 345 */
    .quad sys_setns
    + .quad compat_sys_process_vm_readv
    + .quad compat_sys_process_vm_writev
    ia32_syscall_end:
    diff --git a/arch/x86/include/asm/unistd_32.h b/arch/x86/include/asm/unistd_32.h
    index 593485b..599c77d 100644
    --- a/arch/x86/include/asm/unistd_32.h
    +++ b/arch/x86/include/asm/unistd_32.h
    @@ -352,10 +352,12 @@
    #define __NR_syncfs 344
    #define __NR_sendmmsg 345
    #define __NR_setns 346
    +#define __NR_process_vm_readv 347
    +#define __NR_process_vm_writev 348

    #ifdef __KERNEL__

    -#define NR_syscalls 347
    +#define NR_syscalls 349

    #define __ARCH_WANT_IPC_PARSE_VERSION
    #define __ARCH_WANT_OLD_READDIR
    diff --git a/arch/x86/include/asm/unistd_64.h b/arch/x86/include/asm/unistd_64.h
    index 705bf13..1f1d1ef 100644
    --- a/arch/x86/include/asm/unistd_64.h
    +++ b/arch/x86/include/asm/unistd_64.h
    @@ -681,6 +681,10 @@ __SYSCALL(__NR_syncfs, sys_syncfs)
    __SYSCALL(__NR_sendmmsg, sys_sendmmsg)
    #define __NR_setns 308
    __SYSCALL(__NR_setns, sys_setns)
    +#define __NR_process_vm_readv 309
    +__SYSCALL(__NR_process_vm_readv, sys_process_vm_readv)
    +#define __NR_process_vm_writev 310
    +__SYSCALL(__NR_process_vm_writev, sys_process_vm_writev)

    #ifndef __NO_STUBS
    #define __ARCH_WANT_OLD_READDIR
    diff --git a/arch/x86/kernel/syscall_table_32.S b/arch/x86/kernel/syscall_table_32.S
    index fbb0a04..ca0fe4d 100644
    --- a/arch/x86/kernel/syscall_table_32.S
    +++ b/arch/x86/kernel/syscall_table_32.S
    @@ -346,3 +346,5 @@ ENTRY(sys_call_table)
    .long sys_syncfs
    .long sys_sendmmsg /* 345 */
    .long sys_setns
    + .long sys_process_vm_readv
    + .long sys_process_vm_writev
    diff --git a/fs/aio.c b/fs/aio.c
    index e29ec48..632b235 100644
    --- a/fs/aio.c
    +++ b/fs/aio.c
    @@ -1387,13 +1387,13 @@ static ssize_t aio_setup_vectored_rw(int type, struct kiocb *kiocb, bool compat)
    ret = compat_rw_copy_check_uvector(type,
    (struct compat_iovec __user *)kiocb->ki_buf,
    kiocb->ki_nbytes, 1, &kiocb->ki_inline_vec,
    - &kiocb->ki_iovec);
    + &kiocb->ki_iovec, 1);
    else
    #endif
    ret = rw_copy_check_uvector(type,
    (struct iovec __user *)kiocb->ki_buf,
    kiocb->ki_nbytes, 1, &kiocb->ki_inline_vec,
    - &kiocb->ki_iovec);
    + &kiocb->ki_iovec, 1);
    if (ret < 0)
    goto out;

    diff --git a/fs/compat.c b/fs/compat.c
    index 0ea0083..ec53ccc 100644
    --- a/fs/compat.c
    +++ b/fs/compat.c
    @@ -550,7 +550,7 @@ out:
    ssize_t compat_rw_copy_check_uvector(int type,
    const struct compat_iovec __user *uvector, unsigned long nr_segs,
    unsigned long fast_segs, struct iovec *fast_pointer,
    - struct iovec **ret_pointer)
    + struct iovec **ret_pointer, int check_access)
    {
    compat_ssize_t tot_len;
    struct iovec *iov = *ret_pointer = fast_pointer;
    @@ -597,7 +597,8 @@ ssize_t compat_rw_copy_check_uvector(int type,
    }
    if (len < 0) /* size_t not fitting in compat_ssize_t .. */
    goto out;
    - if (!access_ok(vrfy_dir(type), compat_ptr(buf), len)) {
    + if (check_access &&
    + !access_ok(vrfy_dir(type), compat_ptr(buf), len)) {
    ret = -EFAULT;
    goto out;
    }
    @@ -1111,7 +1112,7 @@ static ssize_t compat_do_readv_writev(int type, struct file *file,
    goto out;

    tot_len = compat_rw_copy_check_uvector(type, uvector, nr_segs,
    - UIO_FASTIOV, iovstack, &iov);
    + UIO_FASTIOV, iovstack, &iov, 1);
    if (tot_len == 0) {
    ret = 0;
    goto out;
    diff --git a/fs/read_write.c b/fs/read_write.c
    index 5520f8a..b905826 100644
    --- a/fs/read_write.c
    +++ b/fs/read_write.c
    @@ -575,7 +575,8 @@ ssize_t do_loop_readv_writev(struct file *filp, struct iovec *iov,
    ssize_t rw_copy_check_uvector(int type, const struct iovec __user * uvector,
    unsigned long nr_segs, unsigned long fast_segs,
    struct iovec *fast_pointer,
    - struct iovec **ret_pointer)
    + struct iovec **ret_pointer,
    + int check_access)
    {
    unsigned long seg;
    ssize_t ret;
    @@ -631,7 +632,8 @@ ssize_t rw_copy_check_uvector(int type, const struct iovec __user * uvector,
    ret = -EINVAL;
    goto out;
    }
    - if (unlikely(!access_ok(vrfy_dir(type), buf, len))) {
    + if (check_access
    + && unlikely(!access_ok(vrfy_dir(type), buf, len))) {
    ret = -EFAULT;
    goto out;
    }
    @@ -663,7 +665,7 @@ static ssize_t do_readv_writev(int type, struct file *file,
    }

    ret = rw_copy_check_uvector(type, uvector, nr_segs,
    - ARRAY_SIZE(iovstack), iovstack, &iov);
    + ARRAY_SIZE(iovstack), iovstack, &iov, 1);
    if (ret <= 0)
    goto out;

    diff --git a/include/linux/compat.h b/include/linux/compat.h
    index 846bb17..1cc917a 100644
    --- a/include/linux/compat.h
    +++ b/include/linux/compat.h
    @@ -557,7 +557,8 @@ extern ssize_t compat_rw_copy_check_uvector(int type,
    const struct compat_iovec __user *uvector,
    unsigned long nr_segs,
    unsigned long fast_segs, struct iovec *fast_pointer,
    - struct iovec **ret_pointer);
    + struct iovec **ret_pointer,
    + int check_access);

    extern void __user *compat_alloc_user_space(unsigned long len);

    diff --git a/include/linux/fs.h b/include/linux/fs.h
    index b5b9792..d97ffab 100644
    --- a/include/linux/fs.h
    +++ b/include/linux/fs.h
    @@ -1608,9 +1608,10 @@ struct inode_operations {
    struct seq_file;

    ssize_t rw_copy_check_uvector(int type, const struct iovec __user * uvector,
    - unsigned long nr_segs, unsigned long fast_segs,
    - struct iovec *fast_pointer,
    - struct iovec **ret_pointer);
    + unsigned long nr_segs, unsigned long fast_segs,
    + struct iovec *fast_pointer,
    + struct iovec **ret_pointer,
    + int check_access);

    extern ssize_t vfs_read(struct file *, char __user *, size_t, loff_t *);
    extern ssize_t vfs_write(struct file *, const char __user *, size_t, loff_t *);
    diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
    index 8c03b98..0dc0809 100644
    --- a/include/linux/syscalls.h
    +++ b/include/linux/syscalls.h
    @@ -847,4 +847,17 @@ asmlinkage long sys_open_by_handle_at(int mountdirfd,
    struct file_handle __user *handle,
    int flags);
    asmlinkage long sys_setns(int fd, int nstype);
    +asmlinkage long sys_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);
    +asmlinkage long sys_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);
    +
    #endif
    diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
    index 62cbc88..7a34e9f 100644
    --- a/kernel/sys_ni.c
    +++ b/kernel/sys_ni.c
    @@ -146,6 +146,10 @@ cond_syscall(sys_io_submit);
    cond_syscall(sys_io_cancel);
    cond_syscall(sys_io_getevents);
    cond_syscall(sys_syslog);
    +cond_syscall(sys_process_vm_readv);
    +cond_syscall(sys_process_vm_writev);
    +cond_syscall(compat_sys_process_vm_readv);
    +cond_syscall(compat_sys_process_vm_writev);

    /* arch-specific weak syscall entries */
    cond_syscall(sys_pciconfig_read);
    diff --git a/mm/Makefile b/mm/Makefile
    index 836e416..50ec00e 100644
    --- a/mm/Makefile
    +++ b/mm/Makefile
    @@ -5,7 +5,8 @@
    mmu-y := nommu.o
    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
    + vmalloc.o pagewalk.o pgtable-generic.o \
    + process_vm_access.o

    obj-y := filemap.o mempool.o oom_kill.o fadvise.o \
    maccess.o page_alloc.o page-writeback.o \
    diff --git a/mm/process_vm_access.c b/mm/process_vm_access.c
    new file mode 100644
    index 0000000..e920aa3
    --- /dev/null
    +++ b/mm/process_vm_access.c
    @@ -0,0 +1,496 @@
    +/*
    + * linux/mm/process_vm_access.c
    + *
    + * Copyright (C) 2010-2011 Christopher Yeoh <cyeoh@au1.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
    + * @task: task to read/write from
    + * @mm: mm for task
    + * @process_pages: struct pages area that can store at least
    + * nr_pages_to_copy struct page pointers
    + * @pa: address of page in task to start copying from/to
    + * @start_offset: offset in page to start copying from/to
    + * @len: number of bytes to copy
    + * @lvec: iovec array specifying where to copy to/from
    + * @lvec_cnt: number of elements in iovec array
    + * @lvec_current: index in iovec array we are up to
    + * @lvec_offset: offset in bytes from current iovec iov_base we are up to
    + * @vm_write: 0 means copy from, 1 means copy to
    + * @nr_pages_to_copy: number of pages to copy
    + * @bytes_copied: returns number of bytes successfully copied
    + * Returns 0 on success, error code otherwise
    + */
    +static int process_vm_rw_pages(struct task_struct *task,
    + struct mm_struct *mm,
    + struct page **process_pages,
    + unsigned long pa,
    + unsigned long start_offset,
    + unsigned long len,
    + const struct iovec *lvec,
    + unsigned long lvec_cnt,
    + unsigned long *lvec_current,
    + size_t *lvec_offset,
    + int vm_write,
    + unsigned int nr_pages_to_copy,
    + ssize_t *bytes_copied)
    +{
    + int pages_pinned;
    + void *target_kaddr;
    + int pgs_copied = 0;
    + int j;
    + int ret;
    + ssize_t bytes_to_copy;
    + ssize_t rc = 0;
    +
    + *bytes_copied = 0;
    +
    + /* Get the pages we're interested in */
    + down_read(&mm->mmap_sem);
    + pages_pinned = get_user_pages(task, mm, pa,
    + nr_pages_to_copy,
    + vm_write, 0, process_pages, NULL);
    + up_read(&mm->mmap_sem);
    +
    + if (pages_pinned != nr_pages_to_copy) {
    + rc = -EFAULT;
    + goto end;
    + }
    +
    + /* Do the copy for each page */
    + for (pgs_copied = 0;
    + (pgs_copied < nr_pages_to_copy) && (*lvec_current < lvec_cnt);
    + pgs_copied++) {
    + /* Make sure we have a non zero length iovec */
    + while (*lvec_current < lvec_cnt
    + && lvec[*lvec_current].iov_len == 0)
    + (*lvec_current)++;
    + if (*lvec_current == lvec_cnt)
    + break;
    +
    + /*
    + * Will copy smallest of:
    + * - bytes remaining in page
    + * - bytes remaining in destination iovec
    + */
    + bytes_to_copy = min_t(ssize_t, PAGE_SIZE - start_offset,
    + len - *bytes_copied);
    + bytes_to_copy = min_t(ssize_t, bytes_to_copy,
    + lvec[*lvec_current].iov_len
    + - *lvec_offset);
    +
    + target_kaddr = kmap(process_pages[pgs_copied]) + start_offset;
    +
    + if (vm_write)
    + ret = copy_from_user(target_kaddr,
    + lvec[*lvec_current].iov_base
    + + *lvec_offset,
    + bytes_to_copy);
    + else
    + ret = copy_to_user(lvec[*lvec_current].iov_base
    + + *lvec_offset,
    + target_kaddr, bytes_to_copy);
    + kunmap(process_pages[pgs_copied]);
    + if (ret) {
    + *bytes_copied += bytes_to_copy - ret;
    + pgs_copied++;
    + rc = -EFAULT;
    + goto end;
    + }
    + *bytes_copied += bytes_to_copy;
    + *lvec_offset += bytes_to_copy;
    + if (*lvec_offset == lvec[*lvec_current].iov_len) {
    + /*
    + * Need to copy remaining part of page into the
    + * next iovec if there are any bytes left in page
    + */
    + (*lvec_current)++;
    + *lvec_offset = 0;
    + start_offset = (start_offset + bytes_to_copy)
    + % PAGE_SIZE;
    + if (start_offset)
    + pgs_copied--;
    + } else {
    + start_offset = 0;
    + }
    + }
    +
    +end:
    + if (vm_write) {
    + for (j = 0; j < pages_pinned; j++) {
    + if (j < pgs_copied)
    + set_page_dirty_lock(process_pages[j]);
    + put_page(process_pages[j]);
    + }
    + } else {
    + for (j = 0; j < pages_pinned; j++)
    + put_page(process_pages[j]);
    + }
    +
    + return rc;
    +}
    +
    +/* 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
    + * @lvec: iovec array specifying where to copy to/from locally
    + * @lvec_cnt: number of elements in iovec array
    + * @lvec_current: index in iovec array we are up to
    + * @lvec_offset: offset in bytes from current iovec iov_base we are up to
    + * @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
    + * @bytes_copied: returns number of bytes successfully copied
    + * Returns 0 on success or on failure error code
    + */
    +static int process_vm_rw_single_vec(unsigned long addr,
    + unsigned long len,
    + const struct iovec *lvec,
    + unsigned long lvec_cnt,
    + unsigned long *lvec_current,
    + size_t *lvec_offset,
    + struct page **process_pages,
    + struct mm_struct *mm,
    + struct task_struct *task,
    + int vm_write,
    + ssize_t *bytes_copied)
    +{
    + unsigned long pa = addr & PAGE_MASK;
    + unsigned long start_offset = addr - pa;
    + unsigned long nr_pages;
    + ssize_t bytes_copied_loop;
    + ssize_t rc = 0;
    + unsigned long nr_pages_copied = 0;
    + unsigned long nr_pages_to_copy;
    + unsigned long max_pages_per_loop = PVM_MAX_KMALLOC_PAGES
    + / sizeof(struct pages *);
    +
    + *bytes_copied = 0;
    +
    + /* Work out address and page range required */
    + if (len == 0)
    + return 0;
    + nr_pages = (addr + len - 1) / PAGE_SIZE - addr / PAGE_SIZE + 1;
    +
    + while ((nr_pages_copied < nr_pages) && (*lvec_current < lvec_cnt)) {
    + nr_pages_to_copy = min(nr_pages - nr_pages_copied,
    + max_pages_per_loop);
    +
    + rc = process_vm_rw_pages(task, mm, process_pages, pa,
    + start_offset, len,
    + lvec, lvec_cnt,
    + lvec_current, lvec_offset,
    + vm_write, nr_pages_to_copy,
    + &bytes_copied_loop);
    + start_offset = 0;
    + *bytes_copied += bytes_copied_loop;
    +
    + if (rc < 0) {
    + return rc;
    + } else {
    + len -= bytes_copied_loop;
    + nr_pages_copied += nr_pages_to_copy;
    + pa += nr_pages_to_copy * PAGE_SIZE;
    + }
    + }
    +
    + 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
    + * @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_core(pid_t pid, const struct iovec *lvec,
    + unsigned long liovcnt,
    + 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;
    + ssize_t bytes_copied_loop;
    + ssize_t bytes_copied = 0;
    + unsigned long nr_pages = 0;
    + unsigned long nr_pages_iov;
    + unsigned long iov_l_curr_idx = 0;
    + size_t iov_l_curr_offset = 0;
    + ssize_t iov_len;
    +
    + /*
    + * 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;
    + }
    +
    + task_lock(task);
    + if (__ptrace_may_access(task, PTRACE_MODE_ATTACH)) {
    + task_unlock(task);
    + rc = -EPERM;
    + goto put_task_struct;
    + }
    + mm = task->mm;
    +
    + if (!mm || (task->flags & PF_KTHREAD)) {
    + task_unlock(task);
    + rc = -EINVAL;
    + goto put_task_struct;
    + }
    +
    + atomic_inc(&mm->mm_users);
    + task_unlock(task);
    +
    + for (i = 0; i < riovcnt && iov_l_curr_idx < liovcnt; i++) {
    + rc = process_vm_rw_single_vec(
    + (unsigned long)rvec[i].iov_base, rvec[i].iov_len,
    + lvec, liovcnt, &iov_l_curr_idx, &iov_l_curr_offset,
    + process_pages, mm, task, vm_write, &bytes_copied_loop);
    + bytes_copied += bytes_copied_loop;
    + if (rc != 0) {
    + /* 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 (bytes_copied)
    + rc = bytes_copied;
    + goto put_mm;
    + }
    + }
    +
    + rc = bytes_copied;
    +put_mm:
    + 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;
    + 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, 1);
    + else
    + rc = rw_copy_check_uvector(READ, lvec, liovcnt, UIO_FASTIOV,
    + iovstack_l, &iov_l, 1);
    + if (rc <= 0)
    + goto free_iovecs;
    +
    + rc = rw_copy_check_uvector(READ, rvec, riovcnt, UIO_FASTIOV,
    + iovstack_r, &iov_r, 0);
    + if (rc <= 0)
    + goto free_iovecs;
    +
    + rc = process_vm_rw_core(pid, iov_l, liovcnt, 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
    +
    +asmlinkage 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;
    + ssize_t rc = -EFAULT;
    +
    + if (flags != 0)
    + return -EINVAL;
    +
    + if (!access_ok(VERIFY_READ, lvec, liovcnt * sizeof(*lvec)))
    + goto out;
    +
    + if (!access_ok(VERIFY_READ, rvec, riovcnt * sizeof(*rvec)))
    + goto out;
    +
    + if (vm_write)
    + rc = compat_rw_copy_check_uvector(WRITE, lvec, liovcnt,
    + UIO_FASTIOV, iovstack_l,
    + &iov_l, 1);
    + else
    + rc = compat_rw_copy_check_uvector(READ, lvec, liovcnt,
    + UIO_FASTIOV, iovstack_l,
    + &iov_l, 1);
    + if (rc <= 0)
    + goto free_iovecs;
    + rc = compat_rw_copy_check_uvector(READ, rvec, riovcnt,
    + UIO_FASTIOV, iovstack_r,
    + &iov_r, 0);
    + if (rc <= 0)
    + goto free_iovecs;
    +
    + rc = process_vm_rw_core(pid, iov_l, liovcnt, iov_r, riovcnt, flags,
    + vm_write);
    +
    +free_iovecs:
    + if (iov_r != iovstack_r)
    + kfree(iov_r);
    + if (iov_l != iovstack_l)
    + kfree(iov_l);
    +
    +out:
    + return rc;
    +}
    +
    +asmlinkage ssize_t
    +compat_sys_process_vm_readv(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)
    +{
    + return compat_process_vm_rw(pid, lvec, liovcnt, rvec,
    + riovcnt, flags, 0);
    +}
    +
    +asmlinkage ssize_t
    +compat_sys_process_vm_writev(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)
    +{
    + return compat_process_vm_rw(pid, lvec, liovcnt, rvec,
    + riovcnt, flags, 1);
    +}
    +
    +#endif
    diff --git a/security/keys/compat.c b/security/keys/compat.c
    index 338b510..4c48e13 100644
    --- a/security/keys/compat.c
    +++ b/security/keys/compat.c
    @@ -38,7 +38,7 @@ long compat_keyctl_instantiate_key_iov(

    ret = compat_rw_copy_check_uvector(WRITE, _payload_iov, ioc,
    ARRAY_SIZE(iovstack),
    - iovstack, &iov);
    + iovstack, &iov, 1);
    if (ret < 0)
    return ret;
    if (ret == 0)
    diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
    index eca5191..0b3f5d7 100644
    --- a/security/keys/keyctl.c
    +++ b/security/keys/keyctl.c
    @@ -1065,7 +1065,7 @@ long keyctl_instantiate_key_iov(key_serial_t id,
    goto no_payload;

    ret = rw_copy_check_uvector(WRITE, _payload_iov, ioc,
    - ARRAY_SIZE(iovstack), iovstack, &iov);
    + ARRAY_SIZE(iovstack), iovstack, &iov, 1);
    if (ret < 0)
    return ret;
    if (ret == 0)


    --
    cyeoh@au.ibm.com


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