[PATCH] mm/process_vm_access: move into ipc/

[PATCH] mm/process_vm_access: move into ipc/

[Konstantin Khlebnikov]

"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@gmail.com>
---
 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@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
+ * @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@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
- * @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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Re: [PATCH] mm/process_vm_access: move into ipc/

[Hugh Dickins]

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@gmail.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?

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@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
> + * @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@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
> - * @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@kvack.org.  For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
> 

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Re: [PATCH] mm/process_vm_access: move into ipc/

[Al Viro]

On Mon, May 26, 2014 at 12:16:20PM -0700, Hugh Dickins 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@gmail.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?

Anything playing with get_user_pages(tsk, ...) with tsk != current is very
much a part of VM guts.

While we are at it, do_generic_file_read() *is* in mm/filemap.c.  And signals
and pipes are also "a kind of IPC", so the rationale is really weak.

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Re: [PATCH] mm/process_vm_access: move into ipc/

[Konstantin Khlebnikov]

On Mon, May 26, 2014 at 11:16 PM, Hugh Dickins <hughd@google.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@gmail.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@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
>> + * @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@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
>> - * @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@kvack.org.  For more info on Linux MM,
>> see: http://www.linux-mm.org/ .
>> Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
>>

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Re: [PATCH] mm/process_vm_access: move into ipc/

[Hugh Dickins]

On Mon, 26 May 2014, Konstantin Khlebnikov wrote:
> On Mon, May 26, 2014 at 11:16 PM, Hugh Dickins <hughd@google.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@gmail.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.

That sounds reasonable to me.  I see you also snuck in a change
to the prompt string: which indeed seems an improvement, but you
ought to mention it in the comment, rather than hiding it in the move.

(I sometimes wonder if its help text ought to say "This CMA has
absolutely nothing to do with the Contiguous Memory Allocator";
but adding that might increase the confusion rather than reduce it,)

Hugh

> 
> >> 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.
> >> +
> >> 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
> >>  #

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Re: [PATCH] mm/process_vm_access: move into ipc/

[Davidlohr Bueso]

On Mon, 2014-05-26 at 12:16 -0700, Hugh Dickins 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@gmail.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?

Agreed, the ipc directory is only for sysv and posix IPC, mm is much
more suitable.

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