Hi,
Going on Richard's advice, I've tried to write an alpha futex
implementation based on the powerpc futex.h.
I've gotten this far.. :\
#define __futex_atomic_op(insn, ret, oldval, uaddr, oparg) \
__asm__ __volatile( \
"1: ldl_l %0,%2\n" \
insn \
/* something needs to happen here
* to save result of insn across
* stl_c? */
" stl_c %1,%2\n" \
" beq %1,2f\n" \
" mb\n" \
/* something needs to happen here
* for the ret */
" .subsection 2\n" \
"2: br 1b\n" \
" .previous\n" \
: "=&r" (oldval), "=&r" (ret) \
: "b" (uaddr) \
: "memory")
Could someone take a look and help finish it?
For futex_atomic_cmpxchg_inatomic, I think Ivan's DRM_CAS
implementation can be used with only trivial changes. See
http://cgit.freedesktop.org/mesa/drm/commit/?id=6feac49398d0f037103a4ae3d5a512badeed61fb
Please CC me on responses, as I'm not subscribed to linux-kernel@.
Thanks,
Matt Turner
Hi!
30-rc1 doesn't compile on alpha:
net/socket.c: In function 'sock_alloc':
net/socket.c:496: error: implicit declaration of function 'percpu_add'
net/socket.c:496: error: 'sockets_in_use' undeclared (first use in this function)
net/socket.c:496: error: (Each undeclared identifier is reported only once
net/socket.c:496: error: for each function it appears in.)
net/socket.c: In function 'sock_release':
net/socket.c:538: error: implicit declaration of function 'percpu_sub'
net/socket.c:538: error: 'sockets_in_use' undeclared (first use in this function)
I vaguely remember seeing discussion about this on lkml, but I
can't find it right now.
gcc is 4.3.3. Distro is Gentoo, machine is a UP1500 (Nautilus).
Regards,
Tobias
--
Save a tree - disband an ISO working group today.
Matt Turner wrote:
> Hi,
>
> Going on Richard's advice, I've tried to write an alpha futex
> implementation based on the powerpc futex.h.
>
> I've gotten this far.. :\
>
#define __futex_atomic_op(insn, ret, oldval, uaddr, oparg) \
__asm__ __volatile( \
__ASM_MB \
"1: ldl_l %0,0(%3)\n" \
insn \
"2: stl_c %1,0(%3)\n" \
" beq %1,4f\n" \
" mov $31,%1\n" \
"3: .subsection 2\n" \
"4: br 1b\n" \
" .previous\n" \
".section __ex_table,\"a\"\n" \
" .long 1b-.\n" \
" lda %0,3b-1b(%2)\n" \
" .long 2b-.\n" \
" lda %0,3b-2b(%2)\n" \
" .previous\n" \
: "=&r" (oldval), "=&r"(ret) \
: "r" (uaddr), "r"(oparg) \
: "memory")
switch (op) {
case FUTEX_OP_SET:
__futex_atomic_op("mov %0,%1", ret, oldval, uaddr, oparg);
break;
case FUTEX_OP_ADD:
__futex_atomic_op("addl %0,%4,%1\n", ret, oldval, uaddr, oparg);
break;
case FUTEX_OP_OR:
__futex_atomic_op("or %0,%4,%1\n", ret, oldval, uaddr, oparg);
break;
case FUTEX_OP_ANDN:
__futex_atomic_op("andnot %0,%4,%1\n", ret, oldval, uaddr, oparg);
break;
case FUTEX_OP_XOR:
__futex_atomic_op("xor %0,%4,%1\n", ret, oldval, uaddr, oparg);
break;
default:
ret = -ENOSYS;
}
Also, there's a bug in the powerpc implementation. It appears that
oparg is clobbered, and if stwcx fails the operation will be repeated
with incorrect inputs.
r~
Richard Henderson <[email protected]> writes:
> switch (op) {
> case FUTEX_OP_SET:
> __futex_atomic_op("mov %0,%1", ret, oldval, uaddr, oparg);
That should probably be "mov %4,%1\n"?
Andreas.
--
Andreas Schwab, [email protected]
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5
"And now for something completely different."
Andreas Schwab wrote:
> Richard Henderson <[email protected]> writes:
>
>> switch (op) {
>> case FUTEX_OP_SET:
>> __futex_atomic_op("mov %0,%1", ret, oldval, uaddr, oparg);
>
> That should probably be "mov %4,%1\n"?
You're right.
r~
> Also, there's a bug in the powerpc implementation. It appears that
> oparg is clobbered, and if stwcx fails the operation will be
> repeated with incorrect inputs.
If either the lwarx or the stwcx. faults, the routine returns -EFAULT
and doesn't retry (label "3" is the end of the asm).
If the stwcx. fails because the CPU lost the reservation, %1 isn't
clobbered as far as I see?
Segher
> If either the lwarx or the stwcx. faults, the routine returns -EFAULT
> and doesn't retry (label "3" is the end of the asm).
>
> If the stwcx. fails because the CPU lost the reservation, %1 isn't
> clobbered as far as I see?
Oh, "insn" writes to %1, never mind.
Segher
Hi,
Attached is a patch to (almost) add native futex support to Alpha.
It doesn't compile...
CC kernel/futex.o
kernel/futex.c: In function 'do_futex':
/usr/src/linux-radeon/glisse-drm/arch/alpha/include/asm/futex.h:47:
error: invalid 'asm': operand number out of range
{standard input}: Assembler messages:
{standard input}:3722: Error: bad expression
{standard input}:3722: Error: syntax error
I can't make much sense out of that.
I changed the %4's to %3 as we don't have a %4.
Please review.
Matt Turner
On Tue, Apr 14, 2009 at 06:38:52PM -0400, Matt Turner wrote:
> CC kernel/futex.o
> kernel/futex.c: In function 'do_futex':
> /usr/src/linux-radeon/glisse-drm/arch/alpha/include/asm/futex.h:47:
> error: invalid 'asm': operand number out of range
> {standard input}: Assembler messages:
> {standard input}:3722: Error: bad expression
> {standard input}:3722: Error: syntax error
>
> I can't make much sense out of that.
>
> I changed the %4's to %3 as we don't have a %4.
Other operands are messed up too.
Here is compile-tested variant.
Ivan.
---
arch/alpha/include/asm/barrier.h | 2 +
arch/alpha/include/asm/futex.h | 118 ++++++++++++++++++++++++++++++++++++-
2 files changed, 116 insertions(+), 4 deletions(-)
diff --git a/arch/alpha/include/asm/barrier.h b/arch/alpha/include/asm/barrier.h
index ac78eba..ce8860a 100644
--- a/arch/alpha/include/asm/barrier.h
+++ b/arch/alpha/include/asm/barrier.h
@@ -16,11 +16,13 @@ __asm__ __volatile__("wmb": : :"memory")
__asm__ __volatile__("mb": : :"memory")
#ifdef CONFIG_SMP
+#define __ASM_SMP_MB "\tmb\n"
#define smp_mb() mb()
#define smp_rmb() rmb()
#define smp_wmb() wmb()
#define smp_read_barrier_depends() read_barrier_depends()
#else
+#define __ASM_SMP_MB
#define smp_mb() barrier()
#define smp_rmb() barrier()
#define smp_wmb() barrier()
diff --git a/arch/alpha/include/asm/futex.h b/arch/alpha/include/asm/futex.h
index 6a332a9..f18ea4e 100644
--- a/arch/alpha/include/asm/futex.h
+++ b/arch/alpha/include/asm/futex.h
@@ -1,6 +1,116 @@
-#ifndef _ASM_FUTEX_H
-#define _ASM_FUTEX_H
+#ifndef _ASM_ALPHA_FUTEX_H
+#define _ASM_ALPHA_FUTEX_H
-#include <asm-generic/futex.h>
+#ifdef __KERNEL__
-#endif
+#include <linux/futex.h>
+#include <linux/uaccess.h>
+#include <asm/errno.h>
+#include <asm/barrier.h>
+
+#define __futex_atomic_op(insn, ret, oldval, uaddr, oparg) \
+ __asm__ __volatile__( \
+ __ASM_SMP_MB \
+ "1: ldl_l %0,0(%2)\n" \
+ insn \
+ "2: stl_c %1,0(%2)\n" \
+ " beq %1,4f\n" \
+ " mov $31,%1\n" \
+ "3: .subsection 2\n" \
+ "4: br 1b\n" \
+ " .previous\n" \
+ " .section __ex_table,\"a\"\n" \
+ " .long 1b-.\n" \
+ " lda $31,3b-1b(%1)\n" \
+ " .long 2b-.\n" \
+ " lda $31,3b-2b(%1)\n" \
+ " .previous\n" \
+ : "=&r" (oldval), "=&r"(ret) \
+ : "r" (uaddr), "r"(oparg) \
+ : "memory")
+
+static inline int futex_atomic_op_inuser (int encoded_op, int __user *uaddr)
+{
+ int op = (encoded_op >> 28) & 7;
+ int cmp = (encoded_op >> 24) & 15;
+ int oparg = (encoded_op << 8) >> 20;
+ int cmparg = (encoded_op << 20) >> 20;
+ int oldval = 0, ret;
+ if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
+ oparg = 1 << oparg;
+
+ if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int)))
+ return -EFAULT;
+
+ pagefault_disable();
+
+ switch (op) {
+ case FUTEX_OP_SET:
+ __futex_atomic_op("mov %3,%1\n", ret, oldval, uaddr, oparg);
+ break;
+ case FUTEX_OP_ADD:
+ __futex_atomic_op("addl %0,%3,%1\n", ret, oldval, uaddr, oparg);
+ break;
+ case FUTEX_OP_OR:
+ __futex_atomic_op("or %0,%3,%1\n", ret, oldval, uaddr, oparg);
+ break;
+ case FUTEX_OP_ANDN:
+ __futex_atomic_op("andnot %0,%3,%1\n", ret, oldval, uaddr, oparg);
+ break;
+ case FUTEX_OP_XOR:
+ __futex_atomic_op("xor %0,%3,%1\n", ret, oldval, uaddr, oparg);
+ break;
+ default:
+ ret = -ENOSYS;
+ }
+
+ pagefault_enable();
+
+ if (!ret) {
+ switch (cmp) {
+ case FUTEX_OP_CMP_EQ: ret = (oldval == cmparg); break;
+ case FUTEX_OP_CMP_NE: ret = (oldval != cmparg); break;
+ case FUTEX_OP_CMP_LT: ret = (oldval < cmparg); break;
+ case FUTEX_OP_CMP_GE: ret = (oldval >= cmparg); break;
+ case FUTEX_OP_CMP_LE: ret = (oldval <= cmparg); break;
+ case FUTEX_OP_CMP_GT: ret = (oldval > cmparg); break;
+ default: ret = -ENOSYS;
+ }
+ }
+ return ret;
+}
+
+static inline int
+futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval, int newval)
+{
+ int prev, cmp;
+
+ if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int)))
+ return -EFAULT;
+
+ __asm__ __volatile__ (
+ __ASM_SMP_MB \
+ "1: ldl_l %0,0(%2)\n"
+ " cmpeq %0,%3,%1\n"
+ " beq %1,3f\n"
+ " mov %4,%1\n"
+ "2: stl_c %1,0(%2)\n"
+ " beq %1,4f\n"
+ "3: .subsection 2\n"
+ "4: br 1b\n"
+ " .previous"
+ " .section __ex_table,\"a\"\n"
+ " .long 1b-.\n"
+ " lda $31,3b-1b(%0)\n"
+ " .long 2b-.\n"
+ " lda $31,3b-2b(%0)\n"
+ " .previous\n"
+ : "=&r"(prev), "=&r"(cmp)
+ : "r"(uaddr), "r"((long)oldval), "r"(newval)
+ : "memory");
+
+ return prev;
+}
+
+#endif /* __KERNEL__ */
+#endif /* _ASM_ALPHA_FUTEX_H */
On Wed, Apr 15, 2009 at 08:55:52PM -0400, Matt Turner wrote:
> I tested the patch, unfortunately it causes the kernel to panic on start up.
Ah, I see.
Exception fixups for sections other than .text (like one in
futex_init()) break the natural ordering of fixup entries,
so sorting is required.
Without that the result of the exception table search depends
on phase of the moon.
Ivan.
diff --git a/arch/alpha/include/asm/uaccess.h b/arch/alpha/include/asm/uaccess.h
index 163f305..b49ec2f 100644
--- a/arch/alpha/include/asm/uaccess.h
+++ b/arch/alpha/include/asm/uaccess.h
@@ -507,5 +507,7 @@ struct exception_table_entry
(pc) + (_fixup)->fixup.bits.nextinsn; \
})
+#define ARCH_HAS_SORT_EXTABLE
+#define ARCH_HAS_SEARCH_EXTABLE
#endif /* __ALPHA_UACCESS_H */
diff --git a/arch/alpha/mm/extable.c b/arch/alpha/mm/extable.c
index dc7aeda..62dc379 100644
--- a/arch/alpha/mm/extable.c
+++ b/arch/alpha/mm/extable.c
@@ -3,11 +3,49 @@
*/
#include <linux/module.h>
+#include <linux/sort.h>
#include <asm/uaccess.h>
+static inline unsigned long ex_to_addr(const struct exception_table_entry *x)
+{
+ return (unsigned long)&x->insn + x->insn;
+}
+
+static void swap_ex(void *a, void *b, int size)
+{
+ struct exception_table_entry *ex_a = a, *ex_b = b;
+ unsigned long addr_a = ex_to_addr(ex_a), addr_b = ex_to_addr(ex_b);
+ unsigned int t = ex_a->fixup.unit;
+
+ ex_a->fixup.unit = ex_b->fixup.unit;
+ ex_b->fixup.unit = t;
+ ex_a->insn = (int)(addr_b - (unsigned long)&ex_a->insn);
+ ex_b->insn = (int)(addr_a - (unsigned long)&ex_b->insn);
+}
+
+/*
+ * The exception table needs to be sorted so that the binary
+ * search that we use to find entries in it works properly.
+ * This is used both for the kernel exception table and for
+ * the exception tables of modules that get loaded.
+ */
+static int cmp_ex(const void *a, const void *b)
+{
+ const struct exception_table_entry *x = a, *y = b;
+
+ /* avoid overflow */
+ if (ex_to_addr(x) > ex_to_addr(y))
+ return 1;
+ if (ex_to_addr(x) < ex_to_addr(y))
+ return -1;
+ return 0;
+}
+
void sort_extable(struct exception_table_entry *start,
struct exception_table_entry *finish)
{
+ sort(start, finish - start, sizeof(struct exception_table_entry),
+ cmp_ex, swap_ex);
}
const struct exception_table_entry *
@@ -20,7 +58,7 @@ search_extable(const struct exception_table_entry *first,
unsigned long mid_value;
mid = (last - first) / 2 + first;
- mid_value = (unsigned long)&mid->insn + mid->insn;
+ mid_value = ex_to_addr(mid);
if (mid_value == value)
return mid;
else if (mid_value < value)