Hi Benjamin,
After merging the aio tree, today's linux-next build (powerpc
ppc44x_defconfig) failed like this:
fs/built-in.o: In function `aio_thread_op_foo_at':
aio.c:(.text+0x4dab4): undefined reference to `__get_user_bad'
aio.c:(.text+0x4daec): undefined reference to `__get_user_bad'
Caused by commit
150a0b4905f1 ("aio: add support for async openat()")
despite commit
d2f7a973e11e ("aio: don't use __get_user() for 64 bit values")
This is due to a bug in the powerpc __get_user_check() macro (the return
value is defined to be "unsigned long" which is only 32 bits on a 32
bit platform).
I applied the patch below which seems to help (Michael, what do you
think?), but given Al's and Christoph's reactions, I am inclined to
remove the aio tree from tomorrow and maybe it can be revisited after
the merge window.
From: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
Date: Tue, 15 Mar 2016 16:36:06 +1100
Subject: [PATCH] powerpc: fix get_user for 64 bit typs on 32 bit platforms
solution borrowed from the x86 uaccess.h
Signed-off-by: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
---
arch/powerpc/include/asm/uaccess.h | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h
index b7c20f0b8fbe..52262b2f37fc 100644
--- a/arch/powerpc/include/asm/uaccess.h
+++ b/arch/powerpc/include/asm/uaccess.h
@@ -261,10 +261,13 @@ do { \
} \
} while (0)
+#define __inttype(x) \
+ __typeof__(__builtin_choose_expr(sizeof(x) > sizeof(0UL), 0ULL, 0UL))
+
#define __get_user_nocheck(x, ptr, size) \
({ \
long __gu_err; \
- unsigned long __gu_val; \
+ __inttype(*(ptr)) __gu_val; \
__typeof__(*(ptr)) __user *__gu_addr = (ptr); \
__chk_user_ptr(ptr); \
if (!is_kernel_addr((unsigned long)__gu_addr)) \
@@ -277,7 +280,7 @@ do { \
#define __get_user_check(x, ptr, size) \
({ \
long __gu_err = -EFAULT; \
- unsigned long __gu_val = 0; \
+ __inttype(*(ptr)) __gu_val = 0; \
__typeof__(*(ptr)) __user *__gu_addr = (ptr); \
might_fault(); \
if (access_ok(VERIFY_READ, __gu_addr, (size))) \
@@ -289,7 +292,7 @@ do { \
#define __get_user_nosleep(x, ptr, size) \
({ \
long __gu_err; \
- unsigned long __gu_val; \
+ __inttype(*(ptr)) __gu_val; \
__typeof__(*(ptr)) __user *__gu_addr = (ptr); \
__chk_user_ptr(ptr); \
__get_user_size(__gu_val, __gu_addr, (size), __gu_err); \
--
2.7.0
--
Cheers,
Stephen Rothwell
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