The ERETNC instruction, introduced in MIPS R5, is similar to the ERET
one, except it does not clear the LLB bit in the LLADDR register.
This feature is necessary to safely emulate R2 LL/SC instructions.
However, on context switches, we need to clear the LLAddr/LLB bit
in order to make sure that an SC instruction from the new thread
will never succeed if it happens to interrupt an LL operation on the
same address from the previous thread.
Signed-off-by: Markos Chandras <markos.chandras@xxxxxxxxxx>
---
arch/mips/include/asm/switch_to.h | 9 ++++++---
arch/mips/include/asm/thread_info.h | 2 +-
arch/mips/kernel/asm-offsets.c | 1 +
arch/mips/kernel/entry.S | 18 ++++++++++++++++++
arch/mips/kernel/traps.c | 2 ++
5 files changed, 28 insertions(+), 4 deletions(-)
diff --git a/arch/mips/include/asm/switch_to.h b/arch/mips/include/asm/switch_to.h
index b928b6f898cd..e92d6c4b5ed1 100644
--- a/arch/mips/include/asm/switch_to.h
+++ b/arch/mips/include/asm/switch_to.h
@@ -75,9 +75,12 @@ do { \
#endif
#define __clear_software_ll_bit() \
-do { \
- if (!__builtin_constant_p(cpu_has_llsc) || !cpu_has_llsc) \
- ll_bit = 0; \
+do { if (cpu_has_rw_llb) { \
+ write_c0_lladdr(0); \
+ } else { \
+ if (!__builtin_constant_p(cpu_has_llsc) || !cpu_has_llsc)\
+ ll_bit = 0; \
+ } \
} while (0)
#define switch_to(prev, next, last) \
diff --git a/arch/mips/include/asm/thread_info.h b/arch/mips/include/asm/thread_info.h
index 7de865805deb..ffdfb5b06e8b 100644
--- a/arch/mips/include/asm/thread_info.h
+++ b/arch/mips/include/asm/thread_info.h
@@ -28,7 +28,7 @@ struct thread_info {
unsigned long tp_value; /* thread pointer */
__u32 cpu; /* current CPU */
int preempt_count; /* 0 => preemptable, <0 => BUG */
-
+ int r2_emul_return; /* 1 => Returning from R2 emulator */
mm_segment_t addr_limit; /*
* thread address space limit:
* 0x7fffffff for user-thead
diff --git a/arch/mips/kernel/asm-offsets.c b/arch/mips/kernel/asm-offsets.c
index b1d84bd4efb3..7b6c11aa1cae 100644
--- a/arch/mips/kernel/asm-offsets.c
+++ b/arch/mips/kernel/asm-offsets.c
@@ -97,6 +97,7 @@ void output_thread_info_defines(void)
OFFSET(TI_TP_VALUE, thread_info, tp_value);
OFFSET(TI_CPU, thread_info, cpu);
OFFSET(TI_PRE_COUNT, thread_info, preempt_count);
+ OFFSET(TI_R2_EMUL_RET, thread_info, r2_emul_return);
OFFSET(TI_ADDR_LIMIT, thread_info, addr_limit);
OFFSET(TI_RESTART_BLOCK, thread_info, restart_block);
OFFSET(TI_REGS, thread_info, regs);
diff --git a/arch/mips/kernel/entry.S b/arch/mips/kernel/entry.S
index d5ab21c3fd12..af41ba6db960 100644
--- a/arch/mips/kernel/entry.S
+++ b/arch/mips/kernel/entry.S
@@ -46,6 +46,11 @@ resume_userspace:
local_irq_disable # make sure we dont miss an
# interrupt setting need_resched
# between sampling and return
+#ifdef CONFIG_MIPSR2_TO_R6_EMULATOR
+ lw k0, TI_R2_EMUL_RET($28)
+ bnez k0, restore_all_from_r2_emul
+#endif
+
LONG_L a2, TI_FLAGS($28) # current->work
andi t0, a2, _TIF_WORK_MASK # (ignoring syscall_trace)
bnez t0, work_pending
@@ -114,6 +119,19 @@ restore_partial: # restore partial frame
RESTORE_SP_AND_RET
.set at
+#ifdef CONFIG_MIPSR2_TO_R6_EMULATOR
+restore_all_from_r2_emul: # restore full frame
+ .set noat
+ sw zero, TI_R2_EMUL_RET($28) # reset it
+ RESTORE_TEMP
+ RESTORE_AT
+ RESTORE_STATIC
+ RESTORE_SOME
+ LONG_L sp, PT_R29(sp)
+ eretnc
+ .set at
+#endif
+
work_pending:
andi t0, a2, _TIF_NEED_RESCHED # a2 is preloaded with TI_FLAGS
beqz t0, work_notifysig
diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
index da0836574918..a0c4716c3c69 100644
--- a/arch/mips/kernel/traps.c
+++ b/arch/mips/kernel/traps.c
@@ -995,12 +995,14 @@ asmlinkage void do_ri(struct pt_regs *regs)
switch (status) {
case 0:
case SIGEMT:
+ task_thread_info(current)->r2_emul_return = 1;
return;
case SIGILL:
goto no_r2_instr;
default:
process_fpemu_return(status,
¤t->thread.cp0_baduaddr);
+ task_thread_info(current)->r2_emul_return = 1;
return;
}
}
--
2.2.0
