MIPS: BREAK instruction interpretation corrections

Add the missing microMIPS BREAK16 instruction code interpretation and
reshape code removing instruction fetching duplication and the separate
call to `do_trap_or_bp' in the MIPS16 path.

Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/9696/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 18 insertions, 18 deletions

diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
index b6f23343a8db..a671d3358eb6 100644
--- a/arch/mips/kernel/traps.c
+++ b/arch/mips/kernel/traps.c
@@ -901,10 +901,9 @@ void do_trap_or_bp(struct pt_regs *regs, unsigned int code,
 
 asmlinkage void do_bp(struct pt_regs *regs)
 {
+        unsigned long epc = msk_isa16_mode(exception_epc(regs));
         unsigned int opcode, bcode;
         enum ctx_state prev_state;
-        unsigned long epc;
-        u16 instr[2];
         mm_segment_t seg;
 
         seg = get_fs();
@@ -913,26 +912,28 @@ asmlinkage void do_bp(struct pt_regs *regs)
 
         prev_state = exception_enter();
         if (get_isa16_mode(regs->cp0_epc)) {
-                /* Calculate EPC. */
-                epc = exception_epc(regs);
-                if (cpu_has_mmips) {
-                        if ((__get_user(instr[0], (u16 __user *)msk_isa16_mode(epc)) ||
-                            (__get_user(instr[1], (u16 __user *)msk_isa16_mode(epc + 2)))))
-                                goto out_sigsegv;
-                        opcode = (instr[0] << 16) | instr[1];
-                } else {
+                u16 instr[2];
+
+                if (__get_user(instr[0], (u16 __user *)epc))
+                        goto out_sigsegv;
+
+                if (!cpu_has_mmips) {
                         /* MIPS16e mode */
-                        if (__get_user(instr[0],
-                                       (u16 __user *)msk_isa16_mode(epc)))
-                                goto out_sigsegv;
                         bcode = (instr[0] >> 5) & 0x3f;
-                        do_trap_or_bp(regs, bcode, "Break");
-                        goto out;
+                } else if (mm_insn_16bit(instr[0])) {
+                        /* 16-bit microMIPS BREAK */
+                        bcode = instr[0] & 0xf;
+                } else {
+                        /* 32-bit microMIPS BREAK */
+                        if (__get_user(instr[1], (u16 __user *)(epc + 2)))
+                                goto out_sigsegv;
+                        opcode = (instr[0] << 16) | instr[1];
+                        bcode = (opcode >> 6) & ((1 << 20) - 1);
                 }
         } else {
-                if (__get_user(opcode,
-                               (unsigned int __user *) exception_epc(regs)))
+                if (__get_user(opcode, (unsigned int __user *)epc))
                         goto out_sigsegv;
+                bcode = (opcode >> 6) & ((1 << 20) - 1);
         }
 
         /*
@@ -941,7 +942,6 @@ asmlinkage void do_bp(struct pt_regs *regs)
          * Gas is bug-compatible, but not always, grrr...
          * We handle both cases with a simple heuristics.  --macro
          */
-        bcode = ((opcode >> 6) & ((1 << 20) - 1));
         if (bcode >= (1 << 10))
                 bcode >>= 10;