[patch 14/22] x86: be careful about tailcall breakage for sys_opentoo

Greg KH
2006-04-21T04:48:04Z

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From: Linus Torvalds <torvalds@osdl.org>

x86: be careful about tailcall breakage for sys_open[at] too

Came up through a quick grep for other cases similar to the ftruncate()
one in commit 0a489cb3b6a7b277030cdbc97c2c65905db94536.

Also, add a comment, so that people who read the code understand why we
do what looks like a no-op.

(Again, this won't actually matter to any sane user, since libc will
save and restore the register gcc stomps on, but it's still wrong to
stomp on it)

Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
fs/open.c | 16 ++++++++++++++--
1 file changed, 14 insertions(+), 2 deletions(-)

--- linux-2.6.16.9.orig/fs/open.c
+++ linux-2.6.16.9/fs/open.c
@@ -331,6 +331,7 @@ out:
asmlinkage long sys_ftruncate(unsigned int fd, unsigned long length)
{
long ret = do_sys_ftruncate(fd, length, 1);
+ /* avoid REGPARM breakage on x86: */
prevent_tail_call(ret);
return ret;
}
@@ -345,6 +346,7 @@ asmlinkage long sys_truncate64(const cha
asmlinkage long sys_ftruncate64(unsigned int fd, loff_t length)
{
long ret = do_sys_ftruncate(fd, length, 0);
+ /* avoid REGPARM breakage on x86: */
prevent_tail_call(ret);
return ret;
}
@@ -1087,20 +1089,30 @@ long do_sys_open(int dfd, const char __u

asmlinkage long sys_open(const char __user *filename, int flags, int mode)
{
+ long ret;
+
if (force_o_largefile())
flags |= O_LARGEFILE;

- return do_sys_open(AT_FDCWD, filename, flags, mode);
+ ret = do_sys_open(AT_FDCWD, filename, flags, mode);
+ /* avoid REGPARM breakage on x86: */
+ prevent_tail_call(ret);
+ return ret;
}
EXPORT_SYMBOL_GPL(sys_open);

asmlinkage long sys_openat(int dfd, const char __user *filename, int flags,
int mode)
{
+ long ret;
+
if (force_o_largefile())
flags |= O_LARGEFILE;

- return do_sys_open(dfd, filename, flags, mode);
+ ret = do_sys_open(dfd, filename, flags, mode);
+ /* avoid REGPARM breakage on x86: */
+ prevent_tail_call(ret);
+ return ret;
}
EXPORT_SYMBOL_GPL(sys_openat);

--