[PATCH 4.4 074/113] ARC: use correct offset in pt_regs for saving/restoring user mode r25

Greg Kroah-Hartman
2016-09-05T16:54:24Z

From: Liav Rehana <liavr@mellanox.com>

commit 86147e3cfa5e118b61e78f4f0bf29e920dcbd477 upstream.

User mode callee regs are explicitly collected before signal delivery or
breakpoint trap. r25 is special for kernel as it serves as task pointer,
so user mode value is clobbered very early. It is saved in pt_regs where
generally only scratch (aka caller saved) regs are saved.

The code to access the corresponding pt_regs location had a subtle bug as
it was using load/store with scaling of offset, whereas the offset was already
byte wise correct. So fix this by replacing LD.AS with a standard LD

Signed-off-by: Liav Rehana <liavr@mellanox.com>
Reviewed-by: Alexey Brodkin <abrodkin@synopsys.com>
[vgupta: rewrote title and commit log]
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/arc/include/asm/entry.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/arc/include/asm/entry.h
+++ b/arch/arc/include/asm/entry.h
@@ -142,7 +142,7 @@

#ifdef CONFIG_ARC_CURR_IN_REG
; Retrieve orig r25 and save it with rest of callee_regs
- ld.as r12, [r12, PT_user_r25]
+ ld r12, [r12, PT_user_r25]
PUSH r12
#else
PUSH r25
@@ -198,7 +198,7 @@

; SP is back to start of pt_regs
#ifdef CONFIG_ARC_CURR_IN_REG
- st.as r12, [sp, PT_user_r25]
+ st r12, [sp, PT_user_r25]
#endif
.endm