From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754619Ab1DNXDV (ORCPT ); Thu, 14 Apr 2011 19:03:21 -0400 Received: from smtp-out.google.com ([74.125.121.67]:27960 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754588Ab1DNXDO (ORCPT ); Thu, 14 Apr 2011 19:03:14 -0400 From: Simon Glass To: linux-arm-kernel@lists.infradead.org Cc: Russell King , Tony Lindgren , Nicolas Pitre , Catalin Marinas , Joe Perches , Laurent Pinchart , Alexander Shishkin , Phil Carmody , Rabin Vincent , linux-kernel@vger.kernel.org, Omar Ramirez Luna , Stephen Boyd , Dave Martin , Simon Glass , Simon Glass Subject: [PATCH v4] ARM: Use generic BUG() handler Date: Thu, 14 Apr 2011 16:00:31 -0700 Message-Id: <1302822031-6752-1-git-send-email-sjg@chromium.org> X-Mailer: git-send-email 1.7.3.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Simon Glass ARM uses its own BUG() handler which makes its output slightly different from other archtectures. One of the problems is that the ARM implementation doesn't report the function with the BUG() in it, but always reports the PC being in __bug(). The generic implementation doesn't have this problem. Currently we get something like: kernel BUG at fs/proc/breakme.c:35! Unable to handle kernel NULL pointer dereference at virtual address 00000000 ... PC is at __bug+0x20/0x2c With this patch it displays: kernel BUG at fs/proc/breakme.c:35! Internal error: Oops - undefined instruction: 0 [#1] PREEMPT SMP ... PC is at write_breakme+0xd0/0x1b4 This implementation uses an undefined instruction to implement BUG, and sets up a bug table containing the relevant information. Many versions of gcc do not support %c properly for ARM (inserting a # when they shouldn't) so we work around this using distasteful macro magic. v1: Initial version to replace existing ARM BUG() implementation with something more similar to other architectures. v2: Add Thumb support, remove backtrace whitespace output changes. Change to use macros instead of requiring the asm %d flag to work (thanks to Dave Martin ) v3: Remove old BUG() implementation in favor of this one. Remove the Backtrace: message (will submit this separately). Use ARM_EXIT_KEEP() so that some architectures can dump exit text at link time thanks to Stephen Boyd (although since we always define GENERIC_BUG this might be academic.) Rebase to linux-2.6.git master. v4: Allow BUGS in modules (these were not reported correctly in v3) (thanks to Stephen Boyd for suggesting that.) Remove __bug() as this is no longer needed. Signed-off-by: Simon Glass --- arch/arm/Kconfig | 4 +++ arch/arm/include/asm/bug.h | 55 ++++++++++++++++++++++++++++++++++------ arch/arm/kernel/traps.c | 31 +++++++++++++++------- arch/arm/kernel/vmlinux.lds.S | 3 +- 4 files changed, 73 insertions(+), 20 deletions(-) diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 5b9f78b..7d7df40 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -207,6 +207,10 @@ config ARM_PATCH_PHYS_VIRT_16BIT def_bool y depends on ARM_PATCH_PHYS_VIRT && ARCH_MSM +config GENERIC_BUG + def_bool y + depends on BUG + source "init/Kconfig" source "kernel/Kconfig.freezer" diff --git a/arch/arm/include/asm/bug.h b/arch/arm/include/asm/bug.h index 4d88425..2914724 100644 --- a/arch/arm/include/asm/bug.h +++ b/arch/arm/include/asm/bug.h @@ -3,21 +3,58 @@ #ifdef CONFIG_BUG -#ifdef CONFIG_DEBUG_BUGVERBOSE -extern void __bug(const char *file, int line) __attribute__((noreturn)); - -/* give file/line information */ -#define BUG() __bug(__FILE__, __LINE__) +/* + * Use a suitable undefined instruction to use for ARM/Thumb2 bug handling. + * We need to be careful not to conflict with those used by other modules and + * the register_undef_hook() system. + */ +#ifdef CONFIG_THUMB2_KERNEL +#define BUG_INSTR_VALUE 0xde02 +#define BUG_INSTR_TYPE ".hword " #else +#define BUG_INSTR_VALUE 0xe7f001f2 +#define BUG_INSTR_TYPE ".word " +#endif -/* this just causes an oops */ -#define BUG() do { *(int *)0 = 0; } while (1) -#endif +#define BUG() _BUG(__FILE__, __LINE__, BUG_INSTR_VALUE) +#define _BUG(file, line, value) __BUG(file, line, value) + +#ifdef CONFIG_DEBUG_BUGVERBOSE + +/* + * The extra indirection is to ensure that the __FILE__ string comes through + * OK. Many version of gcc do not support the asm %c parameter which would be + * preferable to this unpleasantness. We use mergeable string sections to + * avoid multiple copies of the string appearing in the kernel image. + */ + +#define __BUG(__file, __line, __value) \ +do { \ + BUILD_BUG_ON(sizeof(struct bug_entry) != 12); \ + asm volatile("1:\t" BUG_INSTR_TYPE #__value "\n" \ + ".pushsection .rodata.str, \"aMS\", 1\n" \ + "2:\t.asciz " #__file "\n" \ + ".popsection\n" \ + ".pushsection __bug_table,\"a\"\n" \ + "3:\t.word 1b, 2b\n" \ + "\t.hword " #__line ", 0\n" \ + ".popsection"); \ + unreachable(); \ +} while (0) + +#else /* not CONFIG_DEBUG_BUGVERBOSE */ + +#define __BUG(__file, __line, __value) \ +do { \ + asm volatile(BUG_INSTR_TYPE #__value); \ + unreachable(); \ +} while (0) +#endif /* CONFIG_DEBUG_BUGVERBOSE */ #define HAVE_ARCH_BUG -#endif +#endif /* CONFIG_BUG */ #include diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c index f0000e1..400df50 100644 --- a/arch/arm/kernel/traps.c +++ b/arch/arm/kernel/traps.c @@ -21,6 +21,7 @@ #include #include #include +#include #include #include #include @@ -271,6 +272,8 @@ void die(const char *str, struct pt_regs *regs, int err) spin_lock_irq(&die_lock); console_verbose(); bust_spinlocks(1); + if (!user_mode(regs)) + report_bug(regs->ARM_pc, regs); ret = __die(str, err, thread, regs); if (regs && kexec_should_crash(thread->task)) @@ -302,6 +305,24 @@ void arm_notify_die(const char *str, struct pt_regs *regs, } } +#ifdef CONFIG_GENERIC_BUG + +int is_valid_bugaddr(unsigned long pc) +{ +#ifdef CONFIG_THUMB2_KERNEL + unsigned short bkpt; +#else + unsigned long bkpt; +#endif + + if (probe_kernel_address((unsigned *)pc, bkpt)) + return 0; + + return bkpt == BUG_INSTR_VALUE; +} + +#endif + static LIST_HEAD(undef_hook); static DEFINE_SPINLOCK(undef_lock); @@ -693,16 +714,6 @@ baddataabort(int code, unsigned long instr, struct pt_regs *regs) arm_notify_die("unknown data abort code", regs, &info, instr, 0); } -void __attribute__((noreturn)) __bug(const char *file, int line) -{ - printk(KERN_CRIT"kernel BUG at %s:%d!\n", file, line); - *(int *)0 = 0; - - /* Avoid "noreturn function does return" */ - for (;;); -} -EXPORT_SYMBOL(__bug); - void __readwrite_bug(const char *fn) { printk("%s called, but not implemented\n", fn); diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S index b4348e6..81d4efe 100644 --- a/arch/arm/kernel/vmlinux.lds.S +++ b/arch/arm/kernel/vmlinux.lds.S @@ -21,7 +21,8 @@ #define ARM_CPU_KEEP(x) #endif -#if defined(CONFIG_SMP_ON_UP) && !defined(CONFIG_DEBUG_SPINLOCK) +#if (defined(CONFIG_SMP_ON_UP) && !defined(CONFIG_DEBUG_SPINLOCK)) || \ + defined(CONFIG_GENERIC_BUG) #define ARM_EXIT_KEEP(x) x #else #define ARM_EXIT_KEEP(x) -- 1.7.3.1 From mboxrd@z Thu Jan 1 00:00:00 1970 From: sjg@chromium.org (Simon Glass) Date: Thu, 14 Apr 2011 16:00:31 -0700 Subject: [PATCH v4] ARM: Use generic BUG() handler Message-ID: <1302822031-6752-1-git-send-email-sjg@chromium.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org From: Simon Glass ARM uses its own BUG() handler which makes its output slightly different from other archtectures. One of the problems is that the ARM implementation doesn't report the function with the BUG() in it, but always reports the PC being in __bug(). The generic implementation doesn't have this problem. Currently we get something like: kernel BUG at fs/proc/breakme.c:35! Unable to handle kernel NULL pointer dereference at virtual address 00000000 ... PC is at __bug+0x20/0x2c With this patch it displays: kernel BUG at fs/proc/breakme.c:35! Internal error: Oops - undefined instruction: 0 [#1] PREEMPT SMP ... PC is at write_breakme+0xd0/0x1b4 This implementation uses an undefined instruction to implement BUG, and sets up a bug table containing the relevant information. Many versions of gcc do not support %c properly for ARM (inserting a # when they shouldn't) so we work around this using distasteful macro magic. v1: Initial version to replace existing ARM BUG() implementation with something more similar to other architectures. v2: Add Thumb support, remove backtrace whitespace output changes. Change to use macros instead of requiring the asm %d flag to work (thanks to Dave Martin ) v3: Remove old BUG() implementation in favor of this one. Remove the Backtrace: message (will submit this separately). Use ARM_EXIT_KEEP() so that some architectures can dump exit text at link time thanks to Stephen Boyd (although since we always define GENERIC_BUG this might be academic.) Rebase to linux-2.6.git master. v4: Allow BUGS in modules (these were not reported correctly in v3) (thanks to Stephen Boyd for suggesting that.) Remove __bug() as this is no longer needed. Signed-off-by: Simon Glass --- arch/arm/Kconfig | 4 +++ arch/arm/include/asm/bug.h | 55 ++++++++++++++++++++++++++++++++++------ arch/arm/kernel/traps.c | 31 +++++++++++++++------- arch/arm/kernel/vmlinux.lds.S | 3 +- 4 files changed, 73 insertions(+), 20 deletions(-) diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 5b9f78b..7d7df40 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -207,6 +207,10 @@ config ARM_PATCH_PHYS_VIRT_16BIT def_bool y depends on ARM_PATCH_PHYS_VIRT && ARCH_MSM +config GENERIC_BUG + def_bool y + depends on BUG + source "init/Kconfig" source "kernel/Kconfig.freezer" diff --git a/arch/arm/include/asm/bug.h b/arch/arm/include/asm/bug.h index 4d88425..2914724 100644 --- a/arch/arm/include/asm/bug.h +++ b/arch/arm/include/asm/bug.h @@ -3,21 +3,58 @@ #ifdef CONFIG_BUG -#ifdef CONFIG_DEBUG_BUGVERBOSE -extern void __bug(const char *file, int line) __attribute__((noreturn)); - -/* give file/line information */ -#define BUG() __bug(__FILE__, __LINE__) +/* + * Use a suitable undefined instruction to use for ARM/Thumb2 bug handling. + * We need to be careful not to conflict with those used by other modules and + * the register_undef_hook() system. + */ +#ifdef CONFIG_THUMB2_KERNEL +#define BUG_INSTR_VALUE 0xde02 +#define BUG_INSTR_TYPE ".hword " #else +#define BUG_INSTR_VALUE 0xe7f001f2 +#define BUG_INSTR_TYPE ".word " +#endif -/* this just causes an oops */ -#define BUG() do { *(int *)0 = 0; } while (1) -#endif +#define BUG() _BUG(__FILE__, __LINE__, BUG_INSTR_VALUE) +#define _BUG(file, line, value) __BUG(file, line, value) + +#ifdef CONFIG_DEBUG_BUGVERBOSE + +/* + * The extra indirection is to ensure that the __FILE__ string comes through + * OK. Many version of gcc do not support the asm %c parameter which would be + * preferable to this unpleasantness. We use mergeable string sections to + * avoid multiple copies of the string appearing in the kernel image. + */ + +#define __BUG(__file, __line, __value) \ +do { \ + BUILD_BUG_ON(sizeof(struct bug_entry) != 12); \ + asm volatile("1:\t" BUG_INSTR_TYPE #__value "\n" \ + ".pushsection .rodata.str, \"aMS\", 1\n" \ + "2:\t.asciz " #__file "\n" \ + ".popsection\n" \ + ".pushsection __bug_table,\"a\"\n" \ + "3:\t.word 1b, 2b\n" \ + "\t.hword " #__line ", 0\n" \ + ".popsection"); \ + unreachable(); \ +} while (0) + +#else /* not CONFIG_DEBUG_BUGVERBOSE */ + +#define __BUG(__file, __line, __value) \ +do { \ + asm volatile(BUG_INSTR_TYPE #__value); \ + unreachable(); \ +} while (0) +#endif /* CONFIG_DEBUG_BUGVERBOSE */ #define HAVE_ARCH_BUG -#endif +#endif /* CONFIG_BUG */ #include diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c index f0000e1..400df50 100644 --- a/arch/arm/kernel/traps.c +++ b/arch/arm/kernel/traps.c @@ -21,6 +21,7 @@ #include #include #include +#include #include #include #include @@ -271,6 +272,8 @@ void die(const char *str, struct pt_regs *regs, int err) spin_lock_irq(&die_lock); console_verbose(); bust_spinlocks(1); + if (!user_mode(regs)) + report_bug(regs->ARM_pc, regs); ret = __die(str, err, thread, regs); if (regs && kexec_should_crash(thread->task)) @@ -302,6 +305,24 @@ void arm_notify_die(const char *str, struct pt_regs *regs, } } +#ifdef CONFIG_GENERIC_BUG + +int is_valid_bugaddr(unsigned long pc) +{ +#ifdef CONFIG_THUMB2_KERNEL + unsigned short bkpt; +#else + unsigned long bkpt; +#endif + + if (probe_kernel_address((unsigned *)pc, bkpt)) + return 0; + + return bkpt == BUG_INSTR_VALUE; +} + +#endif + static LIST_HEAD(undef_hook); static DEFINE_SPINLOCK(undef_lock); @@ -693,16 +714,6 @@ baddataabort(int code, unsigned long instr, struct pt_regs *regs) arm_notify_die("unknown data abort code", regs, &info, instr, 0); } -void __attribute__((noreturn)) __bug(const char *file, int line) -{ - printk(KERN_CRIT"kernel BUG at %s:%d!\n", file, line); - *(int *)0 = 0; - - /* Avoid "noreturn function does return" */ - for (;;); -} -EXPORT_SYMBOL(__bug); - void __readwrite_bug(const char *fn) { printk("%s called, but not implemented\n", fn); diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S index b4348e6..81d4efe 100644 --- a/arch/arm/kernel/vmlinux.lds.S +++ b/arch/arm/kernel/vmlinux.lds.S @@ -21,7 +21,8 @@ #define ARM_CPU_KEEP(x) #endif -#if defined(CONFIG_SMP_ON_UP) && !defined(CONFIG_DEBUG_SPINLOCK) +#if (defined(CONFIG_SMP_ON_UP) && !defined(CONFIG_DEBUG_SPINLOCK)) || \ + defined(CONFIG_GENERIC_BUG) #define ARM_EXIT_KEEP(x) x #else #define ARM_EXIT_KEEP(x) -- 1.7.3.1