| Message ID | 1311926200-24806-1-git-send-email-sjg@chromium.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 07/29/2011 12:56 AM, Simon Glass wrote: > From: Simon Glass <sjg@google.com> > > 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 <dave.martin@linaro.org>) > > 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 <sboyd@codeaurora.org> (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 <sboyd@codeaurora.org> for suggesting that.) > Remove __bug() as this is no longer needed. > > v5: Add %progbits as the section flags. Tested-by: Stephen Boyd <sboyd@codeaurora.org> > Signed-off-by: Simon Glass <sjg@chromium.org> > --- > Can you update the patch in the patch tracker? It would be great to see this in the next merge window.
OK, yes will do, thanks. -Simon On Tue, Aug 9, 2011 at 3:15 PM, Stephen Boyd <sboyd@codeaurora.org> wrote: > On 07/29/2011 12:56 AM, Simon Glass wrote: >> From: Simon Glass <sjg@google.com> >> >> 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 <dave.martin@linaro.org>) >> >> 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 <sboyd@codeaurora.org> (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 <sboyd@codeaurora.org> for suggesting that.) >> Remove __bug() as this is no longer needed. >> >> v5: Add %progbits as the section flags. > > Tested-by: Stephen Boyd <sboyd@codeaurora.org> > >> Signed-off-by: Simon Glass <sjg@chromium.org> >> --- >> > > Can you update the patch in the patch tracker? It would be great to see > this in the next merge window. > > -- > Sent by an employee of the Qualcomm Innovation Center, Inc. > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum. > >
> On Tue, Aug 9, 2011 at 3:15 PM, Stephen Boyd <sboyd@codeaurora.org> wrote: >> On 07/29/2011 12:56 AM, Simon Glass wrote: >>> From: Simon Glass <sjg@google.com> >>> >>> 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 <dave.martin@linaro.org>) >>> >>> 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 <sboyd@codeaurora.org> (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 <sboyd@codeaurora.org> for suggesting that.) >>> Remove __bug() as this is no longer needed. >>> >>> v5: Add %progbits as the section flags. >> >> Tested-by: Stephen Boyd <sboyd@codeaurora.org> >> >>> Signed-off-by: Simon Glass <sjg@chromium.org> >>> --- >>> >> >> Can you update the patch in the patch tracker? It would be great to see >> this in the next merge window. Hi, I have done this against 3.1-rc2 and it is here: http://www.arm.linux.org.uk/developer/patches/viewpatch.php?id=7017/1 Please let me know if there are any problems. Regards, Simon >> >> -- >> Sent by an employee of the Qualcomm Innovation Center, Inc. >> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum. >> >> >
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 09ebf0b..4570473 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -216,6 +216,10 @@ config ARM_PATCH_PHYS_VIRT_16BIT to allow physical memory down to a theoretical minimum of 64K boundaries. +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..9abe7a0 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\", %progbits, 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 <asm-generic/bug.h> diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c index bc9f9da..7496924 100644 --- a/arch/arm/kernel/traps.c +++ b/arch/arm/kernel/traps.c @@ -21,6 +21,7 @@ #include <linux/kdebug.h> #include <linux/module.h> #include <linux/kexec.h> +#include <linux/bug.h> #include <linux/delay.h> #include <linux/init.h> #include <linux/sched.h> @@ -270,6 +271,8 @@ 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)) @@ -301,6 +304,24 @@ 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); @@ -706,16 +727,6 @@ 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 bf977f8..7b2541e 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)