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[PATCH] MIPS: Trap exception handling fixes

To: Ralf Baechle <ralf@linux-mips.org>
Subject: [PATCH] MIPS: Trap exception handling fixes
From: "Maciej W. Rozycki" <macro@codesourcery.com>
Date: Thu, 23 May 2013 16:31:23 +0100
Cc: <linux-mips@linux-mips.org>
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2a0b24f56c2492b932f1aed617ae80fb23500d21 broke Trap exception handling in 
the standard MIPS mode.  Additionally the microMIPS-mode trap code mask is 
wrong, as it's a 4-bit field.  Here's a fix.

Signed-off-by: Maciej W. Rozycki <macro@codesourcery.com>
---
Ralf, please apply.  Also the mention of: "A few NOP instructions are used 
to maintain the correct alignment[...]" in the commit referred makes me 
feel scared -- there is that .align pseudo-op, you know...  Maciej

linux-mips-do-tr.diff

 arch/mips/kernel/traps.c |   28 +++++++++++++++-------------
 1 files changed, 15 insertions(+), 13 deletions(-)

diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
index e3be670..a75ae40 100644
--- a/arch/mips/kernel/traps.c
+++ b/arch/mips/kernel/traps.c
@@ -897,22 +897,24 @@ out_sigsegv:
 
 asmlinkage void do_tr(struct pt_regs *regs)
 {
-       unsigned int opcode, tcode = 0;
+       u32 opcode, tcode = 0;
        u16 instr[2];
-       unsigned long epc = exception_epc(regs);
+       unsigned long epc = msk_isa16_mode(exception_epc(regs));
 
-       if ((__get_user(instr[0], (u16 __user *)msk_isa16_mode(epc))) ||
-               (__get_user(instr[1], (u16 __user *)msk_isa16_mode(epc + 2))))
+       if (get_isa16_mode(regs->cp0_epc)) {
+               if (__get_user(instr[0], (u16 __user *)(epc + 0)) ||
+                   __get_user(instr[1], (u16 __user *)(epc + 2)))
                        goto out_sigsegv;
-       opcode = (instr[0] << 16) | instr[1];
-
-       /* Immediate versions don't provide a code.  */
-       if (!(opcode & OPCODE)) {
-               if (get_isa16_mode(regs->cp0_epc))
-                       /* microMIPS */
-                       tcode = (opcode >> 12) & 0x1f;
-               else
-                       tcode = ((opcode >> 6) & ((1 << 10) - 1));
+               opcode = (instr[0] << 16) | instr[1];
+               /* Immediate versions don't provide a code.  */
+               if (!(opcode & OPCODE))
+                       tcode = (opcode >> 12) & ((1 << 4) - 1);
+       } else {
+               if (__get_user(opcode, (u32 __user *)epc))
+                       goto out_sigsegv;
+               /* Immediate versions don't provide a code.  */
+               if (!(opcode & OPCODE))
+                       tcode = (opcode >> 6) & ((1 << 10) - 1);
        }
 
        do_trap_or_bp(regs, tcode, "Trap");

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