3.16.51-rc1 review patch. If anyone has any objections, please let me know.
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From: Matt Redfearn matt.redfearn@imgtec.com
commit 11887ed172a6960673f130dad8f8fb42778f64d7 upstream.
Commit 34c2f668d0f6b ("MIPS: microMIPS: Add unaligned access support.") added fairly broken support for handling 16bit microMIPS instructions in get_frame_info(). It adjusts the instruction pointer by 16bits in the case of a 16bit sp move instruction, but not any other 16bit instruction.
Commit b6c7a324df37 ("MIPS: Fix get_frame_info() handling of microMIPS function size") goes some way to fixing get_frame_info() to iterate over microMIPS instuctions, but the instruction pointer is still manipulated using a postincrement, and is of union mips_instruction type. Since the union is sized to the largest member (a word), but microMIPS instructions are a mix of halfword and word sizes, the function does not always iterate correctly, ending up misaligned with the instruction stream and interpreting it incorrectly.
Since the instruction modifying the stack pointer is usually the first in the function, that one is usually handled correctly. But the instruction which saves the return address to the sp is some variable number of instructions into the frame and is frequently missed due to not being on a word boundary, leading to incomplete walking of the stack.
Fix this by incrementing the instruction pointer based on the size of the previously decoded instruction (& remove the hack introduced by commit 34c2f668d0f6b ("MIPS: microMIPS: Add unaligned access support.") which adjusts the instruction pointer in the case of a 16bit sp move instruction, but not any other).
Fixes: 34c2f668d0f6b ("MIPS: microMIPS: Add unaligned access support.") Signed-off-by: Matt Redfearn matt.redfearn@imgtec.com Cc: Marcin Nowakowski marcin.nowakowski@imgtec.com Cc: James Hogan james.hogan@imgtec.com Cc: Ingo Molnar mingo@kernel.org Cc: Paul Burton paul.burton@imgtec.com Cc: linux-mips@linux-mips.org Cc: linux-kernel@vger.kernel.org Patchwork: https://patchwork.linux-mips.org/patch/16953/ Signed-off-by: Ralf Baechle ralf@linux-mips.org Signed-off-by: Ben Hutchings ben@decadent.org.uk --- arch/mips/kernel/process.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)
--- a/arch/mips/kernel/process.c +++ b/arch/mips/kernel/process.c @@ -375,6 +375,7 @@ static int get_frame_info(struct mips_fr bool is_mmips = IS_ENABLED(CONFIG_CPU_MICROMIPS); union mips_instruction insn, *ip, *ip_end; const unsigned int max_insns = 128; + unsigned int last_insn_size = 0; unsigned int i;
info->pc_offset = -1; @@ -386,15 +387,19 @@ static int get_frame_info(struct mips_fr
ip_end = (void *)ip + info->func_size;
- for (i = 0; i < max_insns && ip < ip_end; i++, ip++) { + for (i = 0; i < max_insns && ip < ip_end; i++) { + ip = (void *)ip + last_insn_size; if (is_mmips && mm_insn_16bit(ip->halfword[0])) { insn.halfword[0] = 0; insn.halfword[1] = ip->halfword[0]; + last_insn_size = 2; } else if (is_mmips) { insn.halfword[0] = ip->halfword[1]; insn.halfword[1] = ip->halfword[0]; + last_insn_size = 4; } else { insn.word = ip->word; + last_insn_size = 4; }
if (is_jump_ins(&insn)) @@ -416,8 +421,6 @@ static int get_frame_info(struct mips_fr tmp = (ip->halfword[0] >> 1); info->frame_size = -(signed short)(tmp & 0xf); } - ip = (void *) &ip->halfword[1]; - ip--; } else #endif info->frame_size = - ip->i_format.simmediate;