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-rw-r--r--arch/mips/kernel/unaligned.c51
1 files changed, 30 insertions, 21 deletions
diff --git a/arch/mips/kernel/unaligned.c b/arch/mips/kernel/unaligned.c
index 490cea5..5c62065 100644
--- a/arch/mips/kernel/unaligned.c
+++ b/arch/mips/kernel/unaligned.c
@@ -885,7 +885,7 @@ static void emulate_load_store_insn(struct pt_regs *regs,
{
union mips_instruction insn;
unsigned long value;
- unsigned int res;
+ unsigned int res, preempted;
unsigned long origpc;
unsigned long orig31;
void __user *fault_addr = NULL;
@@ -1226,27 +1226,36 @@ static void emulate_load_store_insn(struct pt_regs *regs,
if (!access_ok(VERIFY_READ, addr, sizeof(*fpr)))
goto sigbus;
- /*
- * Disable preemption to avoid a race between copying
- * state from userland, migrating to another CPU and
- * updating the hardware vector register below.
- */
- preempt_disable();
-
- res = __copy_from_user_inatomic(fpr, addr,
- sizeof(*fpr));
- if (res)
- goto fault;
-
- /*
- * Update the hardware register if it is in use by the
- * task in this quantum, in order to avoid having to
- * save & restore the whole vector context.
- */
- if (test_thread_flag(TIF_USEDMSA))
- write_msa_wr(wd, fpr, df);
+ do {
+ /*
+ * If we have live MSA context keep track of
+ * whether we get preempted in order to avoid
+ * the register context we load being clobbered
+ * by the live context as it's saved during
+ * preemption. If we don't have live context
+ * then it can't be saved to clobber the value
+ * we load.
+ */
+ preempted = test_thread_flag(TIF_USEDMSA);
+
+ res = __copy_from_user_inatomic(fpr, addr,
+ sizeof(*fpr));
+ if (res)
+ goto fault;
- preempt_enable();
+ /*
+ * Update the hardware register if it is in use
+ * by the task in this quantum, in order to
+ * avoid having to save & restore the whole
+ * vector context.
+ */
+ preempt_disable();
+ if (test_thread_flag(TIF_USEDMSA)) {
+ write_msa_wr(wd, fpr, df);
+ preempted = 0;
+ }
+ preempt_enable();
+ } while (preempted);
break;
case msa_st_op:
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