@ if it was interrupted in a critical region. Here we
@ perform a quick test inline since it should be false
@ 99.9999% of the time. The rest is done out of line.
- cmp r2, #TASK_SIZE
+ cmp r4, #TASK_SIZE
- blhs kuser_cmpxchg_fixup
+ blhs kuser_cmpxchg64_fixup
#endif
#endif
.endm
__kuser_helper_start:
/*
- * Reference prototype:
- *
- * void __kernel_memory_barrier(void)
- *
- * Input:
- *
- * lr = return address
- *
- * Output:
- *
- * none
- *
- * Clobbered:
- *
- * none
- *
- * Definition and user space usage example:
- *
- * typedef void (__kernel_dmb_t)(void);
- * #define __kernel_dmb (*(__kernel_dmb_t *)0xffff0fa0)
- *
- * Apply any needed memory barrier to preserve consistency with data modified
- * manually and __kuser_cmpxchg usage.
- *
- * This could be used as follows:
- *
- * #define __kernel_dmb() \
- * asm volatile ( "mov r0, #0xffff0fff; mov lr, pc; sub pc, r0, #95" \
- * : : : "r0", "lr","cc" )
+ * Due to the length of some sequences, __kuser_cmpxchg64 spans 2 regular
+ * kuser "slots", therefore 0xffff0f80 is not used as a valid entry point.
*/
- __kuser_memory_barrier: @ 0xffff0fa0
+ __kuser_cmpxchg64: @ 0xffff0f60
+
+ #if defined(CONFIG_NEEDS_SYSCALL_FOR_CMPXCHG)
+
+ /*
+ * Poor you. No fast solution possible...
+ * The kernel itself must perform the operation.
+ * A special ghost syscall is used for that (see traps.c).
+ */
+ stmfd sp!, {r7, lr}
+ ldr r7, 1f @ it's 20 bits
+ swi __ARM_NR_cmpxchg64
+ ldmfd sp!, {r7, pc}
+ 1: .word __ARM_NR_cmpxchg64
+
+ #elif defined(CONFIG_CPU_32v6K)
+
+ stmfd sp!, {r4, r5, r6, r7}
+ ldrd r4, r5, [r0] @ load old val
+ ldrd r6, r7, [r1] @ load new val
+ smp_dmb arm
+ 1: ldrexd r0, r1, [r2] @ load current val
+ eors r3, r0, r4 @ compare with oldval (1)
+ eoreqs r3, r1, r5 @ compare with oldval (2)
+ strexdeq r3, r6, r7, [r2] @ store newval if eq
+ teqeq r3, #1 @ success?
+ beq 1b @ if no then retry
smp_dmb arm
- @ r2 = address of interrupted insn (must be preserved).
+ rsbs r0, r3, #0 @ set returned val and C flag
+ ldmfd sp!, {r4, r5, r6, r7}
+ bx lr
+
+ #elif !defined(CONFIG_SMP)
+
+ #ifdef CONFIG_MMU
+
+ /*
+ * The only thing that can break atomicity in this cmpxchg64
+ * implementation is either an IRQ or a data abort exception
+ * causing another process/thread to be scheduled in the middle of
+ * the critical sequence. The same strategy as for cmpxchg is used.
+ */
+ stmfd sp!, {r4, r5, r6, lr}
+ ldmia r0, {r4, r5} @ load old val
+ ldmia r1, {r6, lr} @ load new val
+ 1: ldmia r2, {r0, r1} @ load current val
+ eors r3, r0, r4 @ compare with oldval (1)
+ eoreqs r3, r1, r5 @ compare with oldval (2)
+ 2: stmeqia r2, {r6, lr} @ store newval if eq
+ rsbs r0, r3, #0 @ set return val and C flag
+ ldmfd sp!, {r4, r5, r6, pc}
+
+ .text
+ kuser_cmpxchg64_fixup:
+ @ Called from kuser_cmpxchg_fixup.
- @ If r2 >= 1b and r2 <= 2b then saved pc_usr is set to 1b.
++ @ r4 = address of interrupted insn (must be preserved).
+ @ sp = saved regs. r7 and r8 are clobbered.
+ @ 1b = first critical insn, 2b = last critical insn.
- subs r8, r2, r7
++ @ If r4 >= 1b and r4 <= 2b then saved pc_usr is set to 1b.
+ mov r7, #0xffff0fff
+ sub r7, r7, #(0xffff0fff - (0xffff0f60 + (1b - __kuser_cmpxchg64)))
++ subs r8, r4, r7
+ rsbcss r8, r8, #(2b - 1b)
+ strcs r7, [sp, #S_PC]
+ #if __LINUX_ARM_ARCH__ < 6
+ bcc kuser_cmpxchg32_fixup
+ #endif
+ mov pc, lr
+ .previous
+
+ #else
+ #warning "NPTL on non MMU needs fixing"
+ mov r0, #-1
+ adds r0, r0, #0
usr_ret lr
+ #endif
+
+ #else
+ #error "incoherent kernel configuration"
+ #endif
+
+ /* pad to next slot */
+ .rept (16 - (. - __kuser_cmpxchg64)/4)
+ .word 0
+ .endr
.align 5
usr_ret lr
.text
- kuser_cmpxchg_fixup:
+ kuser_cmpxchg32_fixup:
@ Called from kuser_cmpxchg_check macro.
- @ r2 = address of interrupted insn (must be preserved).
+ @ r4 = address of interrupted insn (must be preserved).
@ sp = saved regs. r7 and r8 are clobbered.
@ 1b = first critical insn, 2b = last critical insn.
- @ If r2 >= 1b and r2 <= 2b then saved pc_usr is set to 1b.
+ @ If r4 >= 1b and r4 <= 2b then saved pc_usr is set to 1b.
mov r7, #0xffff0fff
sub r7, r7, #(0xffff0fff - (0xffff0fc0 + (1b - __kuser_cmpxchg)))
- subs r8, r2, r7
+ subs r8, r4, r7
rsbcss r8, r8, #(2b - 1b)
strcs r7, [sp, #S_PC]
mov pc, lr