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authorPaul Burton <paul.burton@imgtec.com>2017-06-02 11:35:01 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-06-26 07:13:11 +0200
commitc24159adf2226709053c48b3d536e756bf033e31 (patch)
treed716d6a8f83a85f9aa4c2ca040b0b61764312785
parent94695386c79caccd82bf4048da642e6c9643fb92 (diff)
MIPS: Fix bnezc/jialc return address calculation
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>
-rw-r--r--arch/mips/kernel/branch.c4
1 files changed, 3 insertions, 1 deletions
diff --git a/arch/mips/kernel/branch.c b/arch/mips/kernel/branch.c
index d8f9b357b222..e9fed8ca9b42 100644
--- a/arch/mips/kernel/branch.c
+++ b/arch/mips/kernel/branch.c
@@ -816,8 +816,10 @@ 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