From: Paul Burton Date: Fri, 2 Jun 2017 18:35:01 +0000 (-0700) Subject: MIPS: Fix bnezc/jialc return address calculation X-Git-Tag: v4.12-rc6~5^2~1 X-Git-Url: https://git.karo-electronics.de/?p=karo-tx-linux.git;a=commitdiff_plain;h=1a73d9310e093fc3adffba4d0a67b9fab2ee3f63 MIPS: Fix bnezc/jialc return address calculation The code handling the pop76 opcode (ie. bnezc & jialc instructions) in __compute_return_epc_for_insn() needs to set the value of $31 in the jialc case, which is encoded with rs = 0. However its check to differentiate bnezc (rs != 0) from jialc (rs = 0) was unfortunately backwards, meaning that if we emulate a bnezc instruction we clobber $31 & if we emulate a jialc instruction it actually behaves like a jic instruction. Fix this by inverting the check of rs to match the way the instructions are actually encoded. Signed-off-by: Paul Burton Fixes: 28d6f93d201d ("MIPS: Emulate the new MIPS R6 BNEZC and JIALC instructions") Cc: stable # v4.0+ Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/16178/ Signed-off-by: Ralf Baechle --- diff --git a/arch/mips/kernel/branch.c b/arch/mips/kernel/branch.c index b11facd11c9d..f702a459a830 100644 --- a/arch/mips/kernel/branch.c +++ b/arch/mips/kernel/branch.c @@ -804,8 +804,10 @@ int __compute_return_epc_for_insn(struct pt_regs *regs, break; } /* Compact branch: BNEZC || JIALC */ - if (insn.i_format.rs) + if (!insn.i_format.rs) { + /* JIALC: set $31/ra */ regs->regs[31] = epc + 4; + } regs->cp0_epc += 8; break; #endif