powerpc/32: Avoid miscompilation w/GCC 4.6.3 - don't inline copy_to/from_user()
Larry Finger reported that his Powerbook G4 was no longer booting with v4.12-rc,
userspace was up but giving weird errors such as:
udevd[64]: starting version 175
udevd[64]: Unable to receive ctrl message: Bad address.
modprobe: chdir(4.12-rc1): No such file or directory
He bisected the problem to commit 3448890c32c3 ("powerpc: get rid of zeroing,
switch to RAW_COPY_USER").
Al identified that the problem is actually a miscompilation by GCC 4.6.3, which
is exposed by the above commit.
Al also pointed out that inlining copy_to/from_user() is probably of little or
no benefit, which is correct. Using Anton's copy_to_user benchmark, with a
pathological single byte copy, we see a small increase in performance
by *removing* inlining:
Before (inlined):
# time ./copy_to_user -w -l 1 -i 10000000 ( x 3 )
real 0m22.063s
real 0m22.059s
real 0m22.076s
After:
# time ./copy_to_user -w -l 1 -i 10000000 ( x 3 )
real 0m21.325s
real 0m21.299s
real 0m21.364s
So as a small performance improvement and to avoid the miscompilation, drop
inlining copy_to/from_user() on 32-bit.
Fixes: 3448890c32c3 ("powerpc: get rid of zeroing, switch to RAW_COPY_USER")
Reported-by: Larry Finger <Larry.Finger@lwfinger.net>
Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h
index 5c0d8a8..41e88d3 100644
--- a/arch/powerpc/include/asm/uaccess.h
+++ b/arch/powerpc/include/asm/uaccess.h
@@ -267,13 +267,7 @@
extern unsigned long __copy_tofrom_user(void __user *to,
const void __user *from, unsigned long size);
-#ifndef __powerpc64__
-
-#define INLINE_COPY_FROM_USER
-#define INLINE_COPY_TO_USER
-
-#else /* __powerpc64__ */
-
+#ifdef __powerpc64__
static inline unsigned long
raw_copy_in_user(void __user *to, const void __user *from, unsigned long n)
{