From 45f62159f3aafe27e2df45a3ec83b32ca7304410 Mon Sep 17 00:00:00 2001 From: Paul Mackerras Date: Fri, 1 Sep 2017 09:51:23 +1000 Subject: [PATCH] powerpc: Wrap register number correctly for string load/store instructions Michael Ellerman reported that emulate_loadstore() was trying to access element 32 of regs->gpr[], which doesn't exist, when emulating a string store instruction. This is because the string load and store instructions (lswi, lswx, stswi and stswx) are defined to wrap around from register 31 to register 0 if the number of bytes being loaded or stored is sufficiently large. This wrapping was not implemented in the emulation code. To fix it, we mask the register number after incrementing it. Reported-by: Michael Ellerman Fixes: c9f6f4ed95d4 ("powerpc: Implement emulation of string loads and stores") Signed-off-by: Paul Mackerras Signed-off-by: Michael Ellerman --- arch/powerpc/lib/sstep.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c index f168ea006242..06dd61d8d48b 100644 --- a/arch/powerpc/lib/sstep.c +++ b/arch/powerpc/lib/sstep.c @@ -2865,7 +2865,8 @@ int emulate_loadstore(struct pt_regs *regs, struct instruction_op *op) v32 = byterev_4(v32); regs->gpr[rd] = v32; ea += 4; - ++rd; + /* reg number wraps from 31 to 0 for lsw[ix] */ + rd = (rd + 1) & 0x1f; } break; @@ -2934,7 +2935,8 @@ int emulate_loadstore(struct pt_regs *regs, struct instruction_op *op) if (err) break; ea += 4; - ++rd; + /* reg number wraps from 31 to 0 for stsw[ix] */ + rd = (rd + 1) & 0x1f; } break; -- 2.20.1