sh: BUG() handling through trapa vector.

Previously we haven't been doing anything with verbose BUG() reporting,
and we've been relying on the oops path for handling BUG()'s, which is
rather sub-optimal.

This switches BUG handling to use a fixed trapa vector (#0x3e) where we
construct a small bug frame post trapa instruction to get the context
right. This also makes it trivial to wire up a DIE_BUG for the atomic
die chain, which we couldn't really do before.

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

diff --git a/arch/sh/kernel/process.c b/arch/sh/kernel/process.c
index f3e2631be14456033c845eb28f0760ef8a875cea..7347f6afa030c9db5a35e5e1805c04e5004f3d02 100644 (file)
--- a/arch/sh/kernel/process.c
+++ b/arch/sh/kernel/process.c
@@ -498,6 +498,16 @@ asmlinkage void break_point_trap_software(unsigned long r4, unsigned long r5,
 {
        struct pt_regs *regs = RELOC_HIDE(&__regs, 0);
 
+       /* Rewind */
        regs->pc -= 2;
+
+#ifdef CONFIG_BUG
+       if (__kernel_text_address(instruction_pointer(regs))) {
+               u16 insn = *(u16 *)instruction_pointer(regs);
+               if (insn == TRAPA_BUG_OPCODE)
+                       handle_BUG(regs);
+       }
+#endif
+
        force_sig(SIGTRAP, current);
 }

diff --git a/arch/sh/kernel/traps.c b/arch/sh/kernel/traps.c
index 3762d9dc20466a026720b1e2821e3c7a4aef8db8..ec110157992df81c91d8b38eddc3e5f4634894b4 100644 (file)
--- a/arch/sh/kernel/traps.c
+++ b/arch/sh/kernel/traps.c
@@ -19,6 +19,7 @@
 #include <linux/kallsyms.h>
 #include <linux/io.h>
 #include <linux/debug_locks.h>
+#include <linux/limits.h>
 #include <asm/system.h>
 #include <asm/uaccess.h>
 
@@ -129,6 +130,40 @@ static int die_if_no_fixup(const char * str, struct pt_regs * regs, long err)
        return -EFAULT;
 }
 
+#ifdef CONFIG_BUG
+#ifdef CONFIG_DEBUG_BUGVERBOSE
+static inline void do_bug_verbose(struct pt_regs *regs)
+{
+       struct bug_frame f;
+       long len;
+
+       if (__copy_from_user(&f, (const void __user *)regs->pc,
+                            sizeof(struct bug_frame)))
+               return;
+
+       len = __strnlen_user(f.file, PATH_MAX) - 1;
+       if (unlikely(len < 0 || len >= PATH_MAX))
+               f.file = "<bad filename>";
+       len = __strnlen_user(f.func, PATH_MAX) - 1;
+       if (unlikely(len < 0 || len >= PATH_MAX))
+               f.func = "<bad function>";
+
+       printk(KERN_ALERT "kernel BUG in %s() at %s:%d!\n",
+              f.func, f.file, f.line);
+}
+#else
+static inline void do_bug_verbose(struct pt_regs *regs)
+{
+}
+#endif /* CONFIG_DEBUG_BUGVERBOSE */
+#endif /* CONFIG_BUG */
+
+void handle_BUG(struct pt_regs *regs)
+{
+       do_bug_verbose(regs);
+       die("Kernel BUG", regs, TRAPA_BUG_OPCODE & 0xff);
+}
+
 /*
  * handle an instruction that does an unaligned memory access by emulating the
  * desired behaviour

diff --git a/include/asm-sh/bug.h b/include/asm-sh/bug.h
index 1b4fc52a59e86beb62adf210158260c453a01ab5..2f89dd06d0cdbb140adf5d518e895af28a971e7f 100644 (file)
--- a/include/asm-sh/bug.h
+++ b/include/asm-sh/bug.h
@@ -1,19 +1,54 @@
 #ifndef __ASM_SH_BUG_H
 #define __ASM_SH_BUG_H
 
-
 #ifdef CONFIG_BUG
-/*
- * Tell the user there is some problem.
- */
-#define BUG() do { \
-       printk("kernel BUG at %s:%d!\n", __FILE__, __LINE__); \
-       *(volatile int *)0 = 0; \
+
+struct bug_frame {
+       unsigned short  opcode;
+       unsigned short  line;
+       const char      *file;
+       const char      *func;
+};
+
+struct pt_regs;
+
+extern void handle_BUG(struct pt_regs *);
+
+#define TRAPA_BUG_OPCODE       0xc33e  /* trapa #0x3e */
+
+#ifdef CONFIG_DEBUG_BUGVERBOSE
+
+#define BUG()                                          \
+do {                                                   \
+       __asm__ __volatile__ (                          \
+               ".align 2\n\t"                          \
+               ".short %O0\n\t"                        \
+               ".short %O1\n\t"                        \
+               ".long  %O2\n\t"                        \
+               ".long  %O3\n\t"                        \
+               :                                       \
+               : "n" (TRAPA_BUG_OPCODE),               \
+                 "i" (__LINE__), "X" (__FILE__),       \
+                 "X" (__FUNCTION__));                  \
+} while (0)
+
+#else
+
+#define BUG()                                  \
+do {                                           \
+       __asm__ __volatile__ (                  \
+               ".align 2\n\t"                  \
+               ".short %O0\n\t"                \
+               :                               \
+               : "n" (TRAPA_BUG_OPCODE));      \
 } while (0)
 
+#endif /* CONFIG_DEBUG_BUGVERBOSE */
+
 #define HAVE_ARCH_BUG
-#endif
+
+#endif /* CONFIG_BUG */
 
 #include <asm-generic/bug.h>
 
-#endif
+#endif /* __ASM_SH_BUG_H */