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.
Also remove the %Un placeholder because having %Un placeholders
for two operands which are based on the same local var (ptep) doesn't
make much sense. By the way, it doesn't change the current behaviour
because "<>" constraint is missing for the associated "=m".
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 comments and removed %U0]
Signed-off-by: Christophe Leroy <[email protected]>
---
v3: Remove %Un
v2: Changed commit log.
Signed-off-by: Christophe Leroy <[email protected]>
---
arch/powerpc/include/asm/book3s/32/pgtable.h | 4 ++--
arch/powerpc/include/asm/nohash/pgtable.h | 4 ++--
2 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/arch/powerpc/include/asm/book3s/32/pgtable.h b/arch/powerpc/include/asm/book3s/32/pgtable.h
index 36443cda8dcf..41d8bc6db303 100644
--- a/arch/powerpc/include/asm/book3s/32/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/32/pgtable.h
@@ -522,9 +522,9 @@ static inline void __set_pte_at(struct mm_struct *mm, unsigned long addr,
if (pte_val(*ptep) & _PAGE_HASHPTE)
flush_hash_entry(mm, ptep, addr);
__asm__ __volatile__("\
- stw%U0%X0 %2,%0\n\
+ stw%X0 %2,%0\n\
eieio\n\
- stw%U0%X0 %L2,%1"
+ stw%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 6277e7596ae5..ac75f4ab0dba 100644
--- a/arch/powerpc/include/asm/nohash/pgtable.h
+++ b/arch/powerpc/include/asm/nohash/pgtable.h
@@ -192,9 +192,9 @@ static inline void __set_pte_at(struct mm_struct *mm, unsigned long addr,
*/
if (IS_ENABLED(CONFIG_PPC32) && IS_ENABLED(CONFIG_PTE_64BIT) && !percpu) {
__asm__ __volatile__("\
- stw%U0%X0 %2,%0\n\
+ stw%X0 %2,%0\n\
eieio\n\
- stw%U0%X0 %L2,%1"
+ stw%X1 %L2,%1"
: "=m" (*ptep), "=m" (*((unsigned char *)ptep+4))
: "r" (pte) : "memory");
return;
--
2.25.0
In several places, inline assembly uses the "%Un" modifier
to enable the use of instruction with update form addressing,
but the associated "<>" constraint is missing.
As mentioned in previous patch, this fails with gcc 4.9, so
"<>" can't be used directly.
Use UPD_CONSTR macro everywhere %Un modifier is used.
Signed-off-by: Christophe Leroy <[email protected]>
Reviewed-by: Segher Boessenkool <[email protected]>
---
v3: __set_pte_at() not impacted anymore (%U0 removed in previous patch)
v2: Build failure (circular inclusion) fixed by change in patch 1
---
arch/powerpc/include/asm/atomic.h | 9 +++++----
arch/powerpc/include/asm/io.h | 4 ++--
arch/powerpc/kvm/powerpc.c | 4 ++--
3 files changed, 9 insertions(+), 8 deletions(-)
diff --git a/arch/powerpc/include/asm/atomic.h b/arch/powerpc/include/asm/atomic.h
index 8a55eb8cc97b..61c6e8b200e8 100644
--- a/arch/powerpc/include/asm/atomic.h
+++ b/arch/powerpc/include/asm/atomic.h
@@ -10,6 +10,7 @@
#include <linux/types.h>
#include <asm/cmpxchg.h>
#include <asm/barrier.h>
+#include <asm/asm-const.h>
/*
* Since *_return_relaxed and {cmp}xchg_relaxed are implemented with
@@ -26,14 +27,14 @@ static __inline__ int atomic_read(const atomic_t *v)
{
int t;
- __asm__ __volatile__("lwz%U1%X1 %0,%1" : "=r"(t) : "m"(v->counter));
+ __asm__ __volatile__("lwz%U1%X1 %0,%1" : "=r"(t) : "m"UPD_CONSTR(v->counter));
return t;
}
static __inline__ void atomic_set(atomic_t *v, int i)
{
- __asm__ __volatile__("stw%U0%X0 %1,%0" : "=m"(v->counter) : "r"(i));
+ __asm__ __volatile__("stw%U0%X0 %1,%0" : "=m"UPD_CONSTR(v->counter) : "r"(i));
}
#define ATOMIC_OP(op, asm_op) \
@@ -316,14 +317,14 @@ static __inline__ s64 atomic64_read(const atomic64_t *v)
{
s64 t;
- __asm__ __volatile__("ld%U1%X1 %0,%1" : "=r"(t) : "m"(v->counter));
+ __asm__ __volatile__("ld%U1%X1 %0,%1" : "=r"(t) : "m"UPD_CONSTR(v->counter));
return t;
}
static __inline__ void atomic64_set(atomic64_t *v, s64 i)
{
- __asm__ __volatile__("std%U0%X0 %1,%0" : "=m"(v->counter) : "r"(i));
+ __asm__ __volatile__("std%U0%X0 %1,%0" : "=m"UPD_CONSTR(v->counter) : "r"(i));
}
#define ATOMIC64_OP(op, asm_op) \
diff --git a/arch/powerpc/include/asm/io.h b/arch/powerpc/include/asm/io.h
index 58635960403c..87964dfb838e 100644
--- a/arch/powerpc/include/asm/io.h
+++ b/arch/powerpc/include/asm/io.h
@@ -122,7 +122,7 @@ static inline u##size name(const volatile u##size __iomem *addr) \
{ \
u##size ret; \
__asm__ __volatile__("sync;"#insn"%U1%X1 %0,%1;twi 0,%0,0;isync"\
- : "=r" (ret) : "m" (*addr) : "memory"); \
+ : "=r" (ret) : "m"UPD_CONSTR (*addr) : "memory"); \
return ret; \
}
@@ -130,7 +130,7 @@ static inline u##size name(const volatile u##size __iomem *addr) \
static inline void name(volatile u##size __iomem *addr, u##size val) \
{ \
__asm__ __volatile__("sync;"#insn"%U0%X0 %1,%0" \
- : "=m" (*addr) : "r" (val) : "memory"); \
+ : "=m"UPD_CONSTR (*addr) : "r" (val) : "memory"); \
mmiowb_set_pending(); \
}
diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 13999123b735..cf52d26f49cd 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -1087,7 +1087,7 @@ static inline u64 sp_to_dp(u32 fprs)
preempt_disable();
enable_kernel_fp();
- asm ("lfs%U1%X1 0,%1; stfd%U0%X0 0,%0" : "=m" (fprd) : "m" (fprs)
+ asm ("lfs%U1%X1 0,%1; stfd%U0%X0 0,%0" : "=m"UPD_CONSTR (fprd) : "m"UPD_CONSTR (fprs)
: "fr0");
preempt_enable();
return fprd;
@@ -1099,7 +1099,7 @@ static inline u32 dp_to_sp(u64 fprd)
preempt_disable();
enable_kernel_fp();
- asm ("lfd%U1%X1 0,%1; stfs%U0%X0 0,%0" : "=m" (fprs) : "m" (fprd)
+ asm ("lfd%U1%X1 0,%1; stfs%U0%X0 0,%0" : "=m"UPD_CONSTR (fprs) : "m"UPD_CONSTR (fprd)
: "fr0");
preempt_enable();
return fprs;
--
2.25.0
On Thu, 22 Oct 2020 09:29:19 +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
>
> [...]
Patches 2-3 applied to powerpc/next.
[2/3] powerpc: Fix incorrect stw{, ux, u, x} instructions in __set_pte_at
https://git.kernel.org/powerpc/c/d85be8a49e733dcd23674aa6202870d54bf5600d
[3/3] powerpc: Fix update form addressing in inline assembly
https://git.kernel.org/powerpc/c/ff57698a9610fcf7d9c4469bf68c881eff22e2f8
cheers