From mboxrd@z Thu Jan 1 00:00:00 1970 From: sjg@chromium.org (Simon Glass) Date: Tue, 29 Mar 2011 12:02:19 -0700 Subject: [PATCH] ARM: Use generic BUG() handler In-Reply-To: <1300307259-834-1-git-send-email-sjg@chromium.org> References: <1300307259-834-1-git-send-email-sjg@chromium.org> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi, does anyone have any more comments on this? Has anyone tried it apart from anish kumar? Thanks, Simon On Wed, Mar 16, 2011 at 1:27 PM, Simon Glass wrote: > 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 version of gcc do not > support %c properly for ARM (inserting a # when they shouldn't) so we work > around this using distasteful macro magic. > > Also the backtrace the message now appears even when CONFIG_ARM_UNWIND is > defined. > > You can fall back to the previous BUG implementation by making GENERIC_BUG > default to n in arch/arm/Kconfig. > > Change-Id: I07d77c832e816f5ad2390e25f466ddf750adecf4 > > Signed-off-by: Simon Glass > --- > ?arch/arm/Kconfig ? ? ? ? ? ? ?| ? ?4 +++ > ?arch/arm/include/asm/bug.h ? ?| ? 57 +++++++++++++++++++++++++++++++++++++++++ > ?arch/arm/kernel/traps.c ? ? ? | ? 24 +++++++++++++++++ > ?arch/arm/kernel/vmlinux.lds.S | ? 12 ++++++++ > ?4 files changed, 97 insertions(+), 0 deletions(-) > > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig > index 166efa2..7c8f11c 100644 > --- a/arch/arm/Kconfig > +++ b/arch/arm/Kconfig > @@ -191,6 +191,10 @@ config VECTORS_BASE > ? ? ? ?help > ? ? ? ? ?The base address of exception vectors. > > +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..3f8a798 100644 > --- a/arch/arm/include/asm/bug.h > +++ b/arch/arm/include/asm/bug.h > @@ -3,6 +3,61 @@ > > > ?#ifdef CONFIG_BUG > + > +#ifdef CONFIG_GENERIC_BUG > + > +/* > + * 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 > + > + > +#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 */ > + > + > +#else ?/* not CONFIG_GENERIC_BUG */ > + > ?#ifdef CONFIG_DEBUG_BUGVERBOSE > ?extern void __bug(const char *file, int line) __attribute__((noreturn)); > > @@ -16,6 +71,8 @@ extern void __bug(const char *file, int line) __attribute__((noreturn)); > > ?#endif > > +#endif ?/* CONFIG_GENERIC_BUG */ > + > ?#define HAVE_ARCH_BUG > ?#endif > > diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c > index ee57640..1199cfe 100644 > --- a/arch/arm/kernel/traps.c > +++ b/arch/arm/kernel/traps.c > @@ -21,6 +21,7 @@ > ?#include > ?#include > ?#include > +#include > ?#include > ?#include > > @@ -163,6 +164,7 @@ static void dump_instr(const char *lvl, struct pt_regs *regs) > ?#ifdef CONFIG_ARM_UNWIND > ?static inline void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk) > ?{ > + ? ? ? printk("Backtrace: "); > ? ? ? ?unwind_backtrace(regs, tsk); > ?} > ?#else > @@ -271,6 +273,8 @@ 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 +306,26 @@ 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 (pc < PAGE_OFFSET) > + ? ? ? ? ? ? ? return 0; > + ? ? ? 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); > > diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S > index 6146279..4f22346 100644 > --- a/arch/arm/kernel/vmlinux.lds.S > +++ b/arch/arm/kernel/vmlinux.lds.S > @@ -80,6 +80,18 @@ SECTIONS > > ? ? ? ?PERCPU(PAGE_SIZE) > > + ? ? ? /* > + ? ? ? * .exit.text is discarded at runtime, not link time, to deal with > + ? ? ? * ?references from bug_table > + ? ? ? */ > + ? ? ? .exit.text : AT(ADDR(.exit.text)) { > + ? ? ? ? ? ? ? EXIT_TEXT > + ? ? ? } > + > + ? ? ? .exit.data : AT(ADDR(.exit.data)) { > + ? ? ? ? ? ? ? EXIT_DATA > + ? ? ? } > + > ?#ifndef CONFIG_XIP_KERNEL > ? ? ? ?. = ALIGN(PAGE_SIZE); > ? ? ? ?__init_end = .; > -- > 1.7.3.1 > >