linux-kernel - [PATCH 3/4] NOMMU: Use copy_*_user_page() in access_process

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Message-ID: <20091222171736.11854.29270.stgit@warthog.procyon.org.uk>
Date:	Tue, 22 Dec 2009 17:17:36 +0000
From:	David Howells <dhowells@...hat.com>
To:	torvalds@...l.org, akpm@...ux-foundation.org
Cc:	linux-kernel@...r.kernel.org, uclinux-dev@...inux.org,
	Jie Zhang <jie.zhang@...log.com>,
	Mike Frysinger <vapier@...too.org>,
	David Howells <dhowells@...hat.com>,
	David McCullough <david_mccullough@...fee.com>,
	Paul Mundt <lethal@...ux-sh.org>,
	Greg Ungerer <gerg@...inux.org>
Subject: [PATCH 3/4] NOMMU: Use copy_*_user_page() in access_process_vm()

From: Jie Zhang <jie.zhang@...log.com>

The MMU code uses the copy_*_user_page() variants in access_process_vm()
rather than copy_*_user() as the former includes an icache flush.  This is
important when doing things like setting software breakpoints with gdb.
So switch the NOMMU code over to do the same.

This patch makes the reasonable assumption that copy_from_user_page() won't
fail - which is probably fine, as we've checked the VMA from which we're
copying is usable, and the copy is not allowed to cross VMAs.  The one case
where it might go wrong is if the VMA is a device rather than RAM, and that
device returns an error which - in which case rubbish will be returned rather
than EIO.

Signed-off-by: Jie Zhang <jie.zhang@...log.com>
Signed-off-by: Mike Frysinger <vapier@...too.org>
Signed-off-by: David Howells <dhowells@...hat.com>
Acked-by: David McCullough <david_mccullough@...fee.com>
Acked-by: Paul Mundt <lethal@...ux-sh.org>
Acked-by: Greg Ungerer <gerg@...inux.org>
---

 mm/nommu.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)


diff --git a/mm/nommu.c b/mm/nommu.c
index db52886..1e1ecb2 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -1896,9 +1896,11 @@ int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, in
 
 		/* only read or write mappings where it is permitted */
 		if (write && vma->vm_flags & VM_MAYWRITE)
-			len -= copy_to_user((void *) addr, buf, len);
+			copy_to_user_page(vma, NULL, addr,
+					 (void *) addr, buf, len);
 		else if (!write && vma->vm_flags & VM_MAYREAD)
-			len -= copy_from_user(buf, (void *) addr, len);
+			copy_from_user_page(vma, NULL, addr,
+					    buf, (void *) addr, len);
 		else
 			len = 0;
 	} else {

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