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Commit dc34d312 authored by Paul Mundt's avatar Paul Mundt
Browse files

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: default avatarPaul Mundt <lethal@linux-sh.org>
parent 1b73e6ae

arch/sh/kernel/process.c

+10 −0
Original line number Diff line number Diff line
@@ -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);

}

arch/sh/kernel/traps.c

+35 −0
Original line number Diff line number Diff line
@@ -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

include/asm-sh/bug.h

+44 −9
Original line number Diff line number Diff line 
#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 */