4.9-stable review patch. If anyone has any objections, please let me know.
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[ Upstream commit cea8cd498f4f1c30ea27e3664b3c671e495c4fce ]
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@imgtec.com Signed-off-by: Matt Redfearn matt.redfearn@imgtec.com Reviewed-by: James Hogan james.hogan@imgtec.com Cc: Marcin Nowakowski marcin.nowakowski@imgtec.com Cc: Miodrag Dinic miodrag.dinic@imgtec.com Cc: Ingo Molnar mingo@kernel.org Cc: David Daney david.daney@cavium.com Cc: linux-mips@linux-mips.org Cc: linux-kernel@vger.kernel.org Patchwork: https://patchwork.linux-mips.org/patch/16957/ Signed-off-by: Ralf Baechle ralf@linux-mips.org Signed-off-by: Sasha Levin sashal@kernel.org --- 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 77429d1622b3..711d9b8465b8 100644 --- a/arch/mips/include/uapi/asm/inst.h +++ b/arch/mips/include/uapi/asm/inst.h @@ -964,7 +964,7 @@ 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 ba315e523b33..0211dc737a21 100644 --- a/arch/mips/kernel/process.c +++ b/arch/mips/kernel/process.c @@ -212,7 +212,7 @@ 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;