When the immediate encoded in the instruction is accessed, it is sign
extended due to being a signed value being assigned to a signed integer.
The ISA specifies that this operation is an unsigned operation.
The sign extension leads us to incorrectly decode:
801e9c8e: cbf1 sw ra,68(sp)
As having an immediate of 1073741809.
Since the instruction format does not specify signed/unsigned, and this
is currently the only location to use this instuction format, change it
to an unsigned immediate.
Fixes: bb9bc4689b9c ("MIPS: Calculate microMIPS ra properly when unwinding the stack")
Suggested-by: Paul Burton <paul.burton@xxxxxxxxxx>
Signed-off-by: Matt Redfearn <matt.redfearn@xxxxxxxxxx>
Reviewed-by: James Hogan <james.hogan@xxxxxxxxxx>
---
Changes in v3: None
Changes in v2: None
arch/mips/include/uapi/asm/inst.h | 2 +-
arch/mips/kernel/process.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/mips/include/uapi/asm/inst.h b/arch/mips/include/uapi/asm/inst.h
index d61897535926..6abea5183d7c 100644
--- a/arch/mips/include/uapi/asm/inst.h
+++ b/arch/mips/include/uapi/asm/inst.h
@@ -981,7 +981,7 @@ struct mm16_r3_format { /* Load from global pointer format */
struct mm16_r5_format { /* Load/store from stack pointer format */
__BITFIELD_FIELD(unsigned int opcode : 6,
__BITFIELD_FIELD(unsigned int rt : 5,
- __BITFIELD_FIELD(signed int simmediate : 5,
+ __BITFIELD_FIELD(unsigned int imm : 5,
__BITFIELD_FIELD(unsigned int : 16, /* Ignored */
;))))
};
diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c
index 288a79bd0e72..6fa726b0be01 100644
--- a/arch/mips/kernel/process.c
+++ b/arch/mips/kernel/process.c
@@ -214,7 +214,7 @@ static inline int is_ra_save_ins(union mips_instruction *ip, int *poff)
if (ip->mm16_r5_format.rt != 31)
return 0;
- *poff = ip->mm16_r5_format.simmediate;
+ *poff = ip->mm16_r5_format.imm;
*poff = (*poff << 2) / sizeof(ulong);
return 1;
--
2.7.4
