MIPS Kprobes: Refactor branch emulation

This patch refactors MIPS branch emulation code so as to allow skipping
delay slot instruction in case of branch likely instructions when branch is
not taken. This is useful for keeping the code common for use cases like
kprobes where one would like to handle the branch instructions keeping the
delay slot instuction also in picture for branch likely instructions. Also
allow emulation when instruction to be decoded is not at pt_regs->cp0_epc
as in case of kprobes where pt_regs->cp0_epc points to the breakpoint
instruction.

The patch also exports the function for modules.

Signed-off-by: Maneesh Soni <manesoni@cisco.com>
Signed-off-by: Victor Kamensky <kamensky@cisco.com>
Cc: David Daney <david.daney@cavium.com>
Cc: ananth@in.ibm.com
Cc: linux-kernel@vger.kernel.org
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/2913/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 5 insertions, 0 deletions

diff --git a/arch/mips/include/asm/branch.h b/arch/mips/include/asm/branch.h
index 37c6857c8d4a..888766ae1f85 100644
--- a/arch/mips/include/asm/branch.h
+++ b/arch/mips/include/asm/branch.h
@@ -9,6 +9,7 @@
 #define _ASM_BRANCH_H
 
 #include <asm/ptrace.h>
+#include <asm/inst.h>
 
 static inline int delay_slot(struct pt_regs *regs)
 {
@@ -23,7 +24,11 @@ static inline unsigned long exception_epc(struct pt_regs *regs)
         return regs->cp0_epc + 4;
 }
 
+#define BRANCH_LIKELY_TAKEN 0x0001
+
 extern int __compute_return_epc(struct pt_regs *regs);
+extern int __compute_return_epc_for_insn(struct pt_regs *regs,
+                                         union mips_instruction insn);
 
 static inline int compute_return_epc(struct pt_regs *regs)
 {