xtensa: save and restore scompare1 SR on kernel entry

Although scompare1 may be saved/restored by xchal_ncp_{load,store}
macros, explicit save/restore of registers manipulated by the kernel
itself is considered more correct.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Chris Zankel <chris@zankel.net>

3 files changed, 15 insertions, 1 deletions

diff --git a/arch/xtensa/include/asm/ptrace.h b/arch/xtensa/include/asm/ptrace.h
index da21c17f23aa..9fe249c8f90e 100644
--- a/arch/xtensa/include/asm/ptrace.h
+++ b/arch/xtensa/include/asm/ptrace.h
@@ -37,7 +37,7 @@ struct pt_regs {
         unsigned long windowstart;      /*  52 */
         unsigned long syscall;          /*  56 */
         unsigned long icountlevel;      /*  60 */
-        int reserved[1];                /*  64 */
+        unsigned long scompare1;        /*  64 */
 
         /* Additional configurable registers that are used by the compiler. */
         xtregs_opt_t xtregs_opt;
diff --git a/arch/xtensa/kernel/asm-offsets.c b/arch/xtensa/kernel/asm-offsets.c
index 7dc3f9157185..845475afc683 100644
--- a/arch/xtensa/kernel/asm-offsets.c
+++ b/arch/xtensa/kernel/asm-offsets.c
@@ -41,6 +41,7 @@ int main(void)
         DEFINE(PT_SAR, offsetof (struct pt_regs, sar));
         DEFINE(PT_ICOUNTLEVEL, offsetof (struct pt_regs, icountlevel));
         DEFINE(PT_SYSCALL, offsetof (struct pt_regs, syscall));
+        DEFINE(PT_SCOMPARE1, offsetof(struct pt_regs, scompare1));
         DEFINE(PT_AREG, offsetof (struct pt_regs, areg[0]));
         DEFINE(PT_AREG0, offsetof (struct pt_regs, areg[0]));
         DEFINE(PT_AREG1, offsetof (struct pt_regs, areg[1]));
diff --git a/arch/xtensa/kernel/entry.S b/arch/xtensa/kernel/entry.S
index 41ad9cfe9a2a..4c2f2706ad5b 100644
--- a/arch/xtensa/kernel/entry.S
+++ b/arch/xtensa/kernel/entry.S
@@ -372,6 +372,13 @@ common_exception:
         s32i    a2, a1, PT_LBEG
         s32i    a3, a1, PT_LEND
 
+        /* Save SCOMPARE1 */
+
+#if XCHAL_HAVE_S32C1I
+        rsr     a2, scompare1
+        s32i    a2, a1, PT_SCOMPARE1
+#endif
+
         /* Save optional registers. */
 
         save_xtregs_opt a1 a2 a4 a5 a6 a7 PT_XTREGS_OPT
@@ -433,6 +440,12 @@ common_exception_return:
 
         load_xtregs_opt a1 a2 a4 a5 a6 a7 PT_XTREGS_OPT
 
+        /* Restore SCOMPARE1 */
+
+#if XCHAL_HAVE_S32C1I
+        l32i    a2, a1, PT_SCOMPARE1
+        wsr     a2, scompare1
+#endif
         wsr     a3, ps          /* disable interrupts */
 
         _bbci.l a3, PS_UM_BIT, kernel_exception_exit