| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.9 55/60] MIPS: Fix bnezc/jialc return address calculation | Date | Mon, 19 Jun 2017 23:17:49 +0800 |
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4.9-stable review patch. If anyone has any objections, please let me know.
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From: Paul Burton <paul.burton@imgtec.com>
commit 1a73d9310e093fc3adffba4d0a67b9fab2ee3f63 upstream.
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 <paul.burton@imgtec.com> Fixes: 28d6f93d201d ("MIPS: Emulate the new MIPS R6 BNEZC and JIALC instructions") Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/16178/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- arch/mips/kernel/branch.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
--- a/arch/mips/kernel/branch.c +++ b/arch/mips/kernel/branch.c @@ -804,8 +804,10 @@ int __compute_return_epc_for_insn(struct 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
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