GCC 4.9 sometimes fails to build with "m<>" constraint in
inline assembly.
CC lib/iov_iter.o
In file included from ./arch/powerpc/include/asm/cmpxchg.h:6:0,
from ./arch/powerpc/include/asm/atomic.h:11,
from ./include/linux/atomic.h:7,
from ./include/linux/crypto.h:15,
from ./include/crypto/hash.h:11,
from lib/iov_iter.c:2:
lib/iov_iter.c: In function 'iovec_from_user.part.30':
./arch/powerpc/include/asm/uaccess.h:287:2: error: 'asm' operand has impossible constraints
__asm__ __volatile__( \
^
./include/linux/compiler.h:78:42: note: in definition of macro 'unlikely'
# define unlikely(x) __builtin_expect(!!(x), 0)
^
./arch/powerpc/include/asm/uaccess.h:583:34: note: in expansion of macro 'unsafe_op_wrap'
#define unsafe_get_user(x, p, e) unsafe_op_wrap(__get_user_allowed(x, p), e)
^
./arch/powerpc/include/asm/uaccess.h:329:10: note: in expansion of macro '__get_user_asm'
case 4: __get_user_asm(x, (u32 __user *)ptr, retval, "lwz"); break; \
^
./arch/powerpc/include/asm/uaccess.h:363:3: note: in expansion of macro '__get_user_size_allowed'
__get_user_size_allowed(__gu_val, __gu_addr, __gu_size, __gu_err); \
^
./arch/powerpc/include/asm/uaccess.h:100:2: note: in expansion of macro '__get_user_nocheck'
__get_user_nocheck((x), (ptr), sizeof(*(ptr)), false)
^
./arch/powerpc/include/asm/uaccess.h:583:49: note: in expansion of macro '__get_user_allowed'
#define unsafe_get_user(x, p, e) unsafe_op_wrap(__get_user_allowed(x, p), e)
^
lib/iov_iter.c:1663:3: note: in expansion of macro 'unsafe_get_user'
unsafe_get_user(len, &uiov[i].iov_len, uaccess_end);
^
make[1]: *** [scripts/Makefile.build:283: lib/iov_iter.o] Error 1
Define a UPD_CONSTR macro that is "<>" by default and
only "" with GCC prior to GCC 5.
Fixes: fcf1f26895a4 ("powerpc/uaccess: Add pre-update addressing to __put_user_asm_goto()")
Fixes: 2f279eeb68b8 ("powerpc/uaccess: Add pre-update addressing to __get_user_asm() and __put_user_asm()")
Signed-off-by: Christophe Leroy <[email protected]>
Acked-by: Segher Boessenkool <[email protected]>
---
v2: Moved UPD_CONSTR to asm-const.h to avoid circular inclusion issues with patch 3.
---
arch/powerpc/include/asm/asm-const.h | 13 +++++++++++++
arch/powerpc/include/asm/uaccess.h | 4 ++--
2 files changed, 15 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/include/asm/asm-const.h b/arch/powerpc/include/asm/asm-const.h
index 082c1538c562..0ce2368bd20f 100644
--- a/arch/powerpc/include/asm/asm-const.h
+++ b/arch/powerpc/include/asm/asm-const.h
@@ -11,4 +11,17 @@
# define __ASM_CONST(x) x##UL
# define ASM_CONST(x) __ASM_CONST(x)
#endif
+
+/*
+ * Inline assembly memory constraint
+ *
+ * GCC 4.9 doesn't properly handle pre update memory constraint "m<>"
+ *
+ */
+#if defined(GCC_VERSION) && GCC_VERSION < 50000
+#define UPD_CONSTR ""
+#else
+#define UPD_CONSTR "<>"
+#endif
+
#endif /* _ASM_POWERPC_ASM_CONST_H */
diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h
index 604d705f1bb8..8f27ea48fadb 100644
--- a/arch/powerpc/include/asm/uaccess.h
+++ b/arch/powerpc/include/asm/uaccess.h
@@ -223,7 +223,7 @@ do { \
"1: " op "%U1%X1 %0,%1 # put_user\n" \
EX_TABLE(1b, %l2) \
: \
- : "r" (x), "m<>" (*addr) \
+ : "r" (x), "m"UPD_CONSTR (*addr) \
: \
: label)
@@ -294,7 +294,7 @@ extern long __get_user_bad(void);
".previous\n" \
EX_TABLE(1b, 3b) \
: "=r" (err), "=r" (x) \
- : "m<>" (*addr), "i" (-EFAULT), "0" (err))
+ : "m"UPD_CONSTR (*addr), "i" (-EFAULT), "0" (err))
#ifdef __powerpc64__
#define __get_user_asm2(x, addr, err) \
--
2.25.0
From: Mathieu Desnoyers <[email protected]>
The placeholder for instruction selection should use the second
argument's operand, which is %1, not %0. This could generate incorrect
assembly code if the memory addressing of operand %0 is a different
form from that of operand %1.
Fixes: 9bf2b5cdc5fe ("powerpc: Fixes for CONFIG_PTE_64BIT for SMP support")
Signed-off-by: Mathieu Desnoyers <[email protected]>
Cc: Christophe Leroy <[email protected]>
Cc: Kumar Gala <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: [email protected]
Cc: <[email protected]> # v2.6.28+
Acked-by: Segher Boessenkool <[email protected]>
[chleroy: revised commit log iaw segher's comment]
Signed-off-by: Christophe Leroy <[email protected]>
---
v2: Changed commit log.
---
arch/powerpc/include/asm/book3s/32/pgtable.h | 2 +-
arch/powerpc/include/asm/nohash/pgtable.h | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/include/asm/book3s/32/pgtable.h b/arch/powerpc/include/asm/book3s/32/pgtable.h
index 36443cda8dcf..34f5ca391f0c 100644
--- a/arch/powerpc/include/asm/book3s/32/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/32/pgtable.h
@@ -524,7 +524,7 @@ static inline void __set_pte_at(struct mm_struct *mm, unsigned long addr,
__asm__ __volatile__("\
stw%U0%X0 %2,%0\n\
eieio\n\
- stw%U0%X0 %L2,%1"
+ stw%U1%X1 %L2,%1"
: "=m" (*ptep), "=m" (*((unsigned char *)ptep+4))
: "r" (pte) : "memory");
diff --git a/arch/powerpc/include/asm/nohash/pgtable.h b/arch/powerpc/include/asm/nohash/pgtable.h
index 4b7c3472eab1..a00e4c1746d6 100644
--- a/arch/powerpc/include/asm/nohash/pgtable.h
+++ b/arch/powerpc/include/asm/nohash/pgtable.h
@@ -199,7 +199,7 @@ static inline void __set_pte_at(struct mm_struct *mm, unsigned long addr,
__asm__ __volatile__("\
stw%U0%X0 %2,%0\n\
eieio\n\
- stw%U0%X0 %L2,%1"
+ stw%U1%X1 %L2,%1"
: "=m" (*ptep), "=m" (*((unsigned char *)ptep+4))
: "r" (pte) : "memory");
return;
--
2.25.0
On Tue, 20 Oct 2020 07:40:07 +0000 (UTC), Christophe Leroy wrote:
> GCC 4.9 sometimes fails to build with "m<>" constraint in
> inline assembly.
>
> CC lib/iov_iter.o
> In file included from ./arch/powerpc/include/asm/cmpxchg.h:6:0,
> from ./arch/powerpc/include/asm/atomic.h:11,
> from ./include/linux/atomic.h:7,
> from ./include/linux/crypto.h:15,
> from ./include/crypto/hash.h:11,
> from lib/iov_iter.c:2:
> lib/iov_iter.c: In function 'iovec_from_user.part.30':
> ./arch/powerpc/include/asm/uaccess.h:287:2: error: 'asm' operand has impossible constraints
> __asm__ __volatile__( \
> ^
> ./include/linux/compiler.h:78:42: note: in definition of macro 'unlikely'
> # define unlikely(x) __builtin_expect(!!(x), 0)
> ^
> ./arch/powerpc/include/asm/uaccess.h:583:34: note: in expansion of macro 'unsafe_op_wrap'
> #define unsafe_get_user(x, p, e) unsafe_op_wrap(__get_user_allowed(x, p), e)
> ^
> ./arch/powerpc/include/asm/uaccess.h:329:10: note: in expansion of macro '__get_user_asm'
> case 4: __get_user_asm(x, (u32 __user *)ptr, retval, "lwz"); break; \
> ^
> ./arch/powerpc/include/asm/uaccess.h:363:3: note: in expansion of macro '__get_user_size_allowed'
> __get_user_size_allowed(__gu_val, __gu_addr, __gu_size, __gu_err); \
> ^
> ./arch/powerpc/include/asm/uaccess.h:100:2: note: in expansion of macro '__get_user_nocheck'
> __get_user_nocheck((x), (ptr), sizeof(*(ptr)), false)
> ^
> ./arch/powerpc/include/asm/uaccess.h:583:49: note: in expansion of macro '__get_user_allowed'
> #define unsafe_get_user(x, p, e) unsafe_op_wrap(__get_user_allowed(x, p), e)
> ^
> lib/iov_iter.c:1663:3: note: in expansion of macro 'unsafe_get_user'
> unsafe_get_user(len, &uiov[i].iov_len, uaccess_end);
> ^
> make[1]: *** [scripts/Makefile.build:283: lib/iov_iter.o] Error 1
>
> [...]
Patch 1 applied to powerpc/fixes.
[1/3] powerpc/uaccess: Don't use "m<>" constraint with GCC 4.9
https://git.kernel.org/powerpc/c/592bbe9c505d9a0ef69260f8c8263df47da2698e
cheers