sh: unwinder: Use a special bug flag for unwinder traps.

This simplifies the unwinder trap handling, dropping the use of the
special trapa vector and simply piggybacking on top of the BUG support. A
new BUGFLAG_UNWINDER is added for flagging the unwinder fault, before
continuing on with regular BUG dispatch.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

4 files changed, 24 insertions, 35 deletions

diff --git a/arch/sh/include/asm/bug.h b/arch/sh/include/asm/bug.h
index b7d9822fd6c2..23c5504a3a01 100644
--- a/arch/sh/include/asm/bug.h
+++ b/arch/sh/include/asm/bug.h
@@ -1,8 +1,8 @@
 #ifndef __ASM_SH_BUG_H
 #define __ASM_SH_BUG_H
 
-#define TRAPA_UNWINDER_BUG_OPCODE 0xc33b /* trapa #0x3b */
 #define TRAPA_BUG_OPCODE        0xc33e  /* trapa #0x3e */
+#define BUGFLAG_UNWINDER        (1 << 1)
 
 #ifdef CONFIG_GENERIC_BUG
 #define HAVE_ARCH_BUG
@@ -73,15 +73,16 @@ do {							\
         unlikely(__ret_warn_on);                                \
 })
 
-#define UNWINDER_BUG()                                          \
+#define UNWINDER_BUG()                                  \
 do {                                                    \
         __asm__ __volatile__ (                          \
                 "1:\t.short %O0\n"                      \
-                _EMIT_BUG_ENTRY         \
+                _EMIT_BUG_ENTRY                         \
                  :                                      \
-                 : "n" (TRAPA_UNWINDER_BUG_OPCODE),     \
+                 : "n" (TRAPA_BUG_OPCODE),              \
                    "i" (__FILE__),                      \
-                   "i" (__LINE__), "i" (0),             \
+                   "i" (__LINE__),                      \
+                   "i" (BUGFLAG_UNWINDER),              \
                    "i" (sizeof(struct bug_entry)));     \
 } while (0)
 
diff --git a/arch/sh/kernel/debugtraps.S b/arch/sh/kernel/debugtraps.S
index cb00e4a82d4d..591741383ee6 100644
--- a/arch/sh/kernel/debugtraps.S
+++ b/arch/sh/kernel/debugtraps.S
@@ -21,10 +21,6 @@
 #define sh_bios_handler                 debug_trap_handler
 #endif
 
-#if !defined(CONFIG_DWARF_UNWINDER)
-#define unwinder_trap_handler           debug_trap_handler
-#endif
-
         .data
 
 ENTRY(debug_trap_table)
@@ -39,7 +35,7 @@ ENTRY(debug_trap_table)
         .long debug_trap_handler        /* 0x38 */
         .long debug_trap_handler        /* 0x39 */
         .long debug_trap_handler        /* 0x3a */
-        .long unwinder_trap_handler     /* 0x3b */
+        .long debug_trap_handler        /* 0x3b */
         .long breakpoint_trap_handler   /* 0x3c */
         .long singlestep_trap_handler   /* 0x3d */
         .long bug_trap_handler          /* 0x3e */
diff --git a/arch/sh/kernel/traps.c b/arch/sh/kernel/traps.c
index 881b9a32b7de..f69bd968fcca 100644
--- a/arch/sh/kernel/traps.c
+++ b/arch/sh/kernel/traps.c
@@ -5,18 +5,32 @@
 #include <linux/signal.h>
 #include <linux/sched.h>
 #include <linux/uaccess.h>
+#include <asm/unwinder.h>
 #include <asm/system.h>
 
 #ifdef CONFIG_BUG
 void handle_BUG(struct pt_regs *regs)
 {
+        const struct bug_entry *bug;
+        unsigned long bugaddr = regs->pc;
         enum bug_trap_type tt;
-        tt = report_bug(regs->pc, regs);
+
+        if (!is_valid_bugaddr(bugaddr))
+                goto invalid;
+
+        bug = find_bug(bugaddr);
+
+        /* Switch unwinders when unwind_stack() is called */
+        if (bug->flags & BUGFLAG_UNWINDER)
+                unwinder_faulted = 1;
+
+        tt = report_bug(bugaddr, regs);
         if (tt == BUG_TRAP_TYPE_WARN) {
-                regs->pc += instruction_size(regs->pc);
+                regs->pc += instruction_size(bugaddr);
                 return;
         }
 
+invalid:
         die("Kernel BUG", regs, TRAPA_BUG_OPCODE & 0xff);
 }
 
@@ -28,8 +42,7 @@ int is_valid_bugaddr(unsigned long addr)
                 return 0;
         if (probe_kernel_address((insn_size_t *)addr, opcode))
                 return 0;
-
-        if (opcode == TRAPA_BUG_OPCODE || opcode == TRAPA_UNWINDER_BUG_OPCODE)
+        if (opcode == TRAPA_BUG_OPCODE)
                 return 1;
 
         return 0;
diff --git a/arch/sh/kernel/unwinder.c b/arch/sh/kernel/unwinder.c
index e83861d9739c..468889d958f4 100644
--- a/arch/sh/kernel/unwinder.c
+++ b/arch/sh/kernel/unwinder.c
@@ -161,25 +161,4 @@ void unwind_stack(struct task_struct *task, struct pt_regs *regs,
 
         curr_unwinder->dump(task, regs, sp, ops, data);
 }
-
-/*
- * Trap handler for UWINDER_BUG() statements. We must switch to the
- * unwinder with the next highest rating.
- */
-BUILD_TRAP_HANDLER(unwinder)
-{
-        insn_size_t insn;
-        TRAP_HANDLER_DECL;
-
-        /* Rewind */
-        regs->pc -= instruction_size(ctrl_inw(regs->pc - 4));
-        insn = *(insn_size_t *)instruction_pointer(regs);
-
-        /* Switch unwinders when unwind_stack() is called */
-        unwinder_faulted = 1;
-
-#ifdef CONFIG_BUG
-        handle_BUG(regs);
-#endif
-}
 EXPORT_SYMBOL_GPL(unwind_stack);