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>

diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
index b6f23343a8db987b6a2c5a5896ea63d79f6aa360..a671d3358eb63d6cc1dfdf554bb912496342d710 100644 (file)
--- 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;