diff options
| -rw-r--r-- | arch/sh/include/asm/unwinder.h | 25 | ||||
| -rw-r--r-- | arch/sh/kernel/Makefile_32 | 4 | ||||
| -rw-r--r-- | arch/sh/kernel/Makefile_64 | 2 | ||||
| -rw-r--r-- | arch/sh/kernel/unwinder.c | 162 |
4 files changed, 190 insertions, 3 deletions
diff --git a/arch/sh/include/asm/unwinder.h b/arch/sh/include/asm/unwinder.h new file mode 100644 index 00000000000..3dc551453e2 --- /dev/null +++ b/arch/sh/include/asm/unwinder.h @@ -0,0 +1,25 @@ +#ifndef _LINUX_UNWINDER_H +#define _LINUX_UNWINDER_H + +#include <asm/stacktrace.h> + +struct unwinder { + const char *name; + struct list_head list; + int rating; + void (*dump)(struct task_struct *, struct pt_regs *, + unsigned long *, const struct stacktrace_ops *, void *); +}; + +extern int unwinder_init(void); +extern int unwinder_register(struct unwinder *); + +extern void unwind_stack(struct task_struct *, struct pt_regs *, + unsigned long *, const struct stacktrace_ops *, + void *); + +extern void stack_reader_dump(struct task_struct *, struct pt_regs *, + unsigned long *, const struct stacktrace_ops *, + void *); + +#endif /* _LINUX_UNWINDER_H */ diff --git a/arch/sh/kernel/Makefile_32 b/arch/sh/kernel/Makefile_32 index 6b32de701a7..37a3b7704fc 100644 --- a/arch/sh/kernel/Makefile_32 +++ b/arch/sh/kernel/Makefile_32 @@ -11,8 +11,8 @@ endif obj-y := debugtraps.o dumpstack.o idle.o io.o io_generic.o irq.o \ machvec.o process_32.o ptrace_32.o setup.o signal_32.o \ - sys_sh.o sys_sh32.o syscalls_32.o time.o topology.o \ - traps.o traps_32.o + sys_sh.o sys_sh32.o syscalls_32.o time.o topology.o \ + traps.o traps_32.o unwinder.o obj-y += cpu/ obj-$(CONFIG_VSYSCALL) += vsyscall/ diff --git a/arch/sh/kernel/Makefile_64 b/arch/sh/kernel/Makefile_64 index 67b9f6c6326..00b73e7598c 100644 --- a/arch/sh/kernel/Makefile_64 +++ b/arch/sh/kernel/Makefile_64 @@ -2,7 +2,7 @@ extra-y := head_64.o init_task.o vmlinux.lds obj-y := debugtraps.o idle.o io.o io_generic.o irq.o machvec.o process_64.o \ ptrace_64.o setup.o signal_64.o sys_sh.o sys_sh64.o \ - syscalls_64.o time.o topology.o traps.o traps_64.o + syscalls_64.o time.o topology.o traps.o traps_64.o unwinder.o obj-y += cpu/ obj-$(CONFIG_SMP) += smp.o diff --git a/arch/sh/kernel/unwinder.c b/arch/sh/kernel/unwinder.c new file mode 100644 index 00000000000..2b30fa28b44 --- /dev/null +++ b/arch/sh/kernel/unwinder.c @@ -0,0 +1,162 @@ +/* + * Copyright (C) 2009 Matt Fleming + * + * Based, in part, on kernel/time/clocksource.c. + * + * This file provides arbitration code for stack unwinders. + * + * Multiple stack unwinders can be available on a system, usually with + * the most accurate unwinder being the currently active one. + */ +#include <linux/errno.h> +#include <linux/list.h> +#include <linux/spinlock.h> +#include <asm/unwinder.h> +#include <asm/atomic.h> + +/* + * This is the most basic stack unwinder an architecture can + * provide. For architectures without reliable frame pointers, e.g. + * RISC CPUs, it can be implemented by looking through the stack for + * addresses that lie within the kernel text section. + * + * Other CPUs, e.g. x86, can use their frame pointer register to + * construct more accurate stack traces. + */ +static struct list_head unwinder_list; +static struct unwinder stack_reader = { + .name = "stack-reader", + .dump = stack_reader_dump, + .rating = 50, + .list = { + .next = &unwinder_list, + .prev = &unwinder_list, + }, +}; + +/* + * "curr_unwinder" points to the stack unwinder currently in use. This + * is the unwinder with the highest rating. + * + * "unwinder_list" is a linked-list of all available unwinders, sorted + * by rating. + * + * All modifications of "curr_unwinder" and "unwinder_list" must be + * performed whilst holding "unwinder_lock". + */ +static struct unwinder *curr_unwinder = &stack_reader; + +static struct list_head unwinder_list = { + .next = &stack_reader.list, + .prev = &stack_reader.list, +}; + +static DEFINE_SPINLOCK(unwinder_lock); + +static atomic_t unwinder_running = ATOMIC_INIT(0); + +/** + * select_unwinder - Select the best registered stack unwinder. + * + * Private function. Must hold unwinder_lock when called. + * + * Select the stack unwinder with the best rating. This is useful for + * setting up curr_unwinder. + */ +static struct unwinder *select_unwinder(void) +{ + struct unwinder *best; + + if (list_empty(&unwinder_list)) + return NULL; + + best = list_entry(unwinder_list.next, struct unwinder, list); + if (best == curr_unwinder) + return NULL; + + return best; +} + +/* + * Enqueue the stack unwinder sorted by rating. + */ +static int unwinder_enqueue(struct unwinder *ops) +{ + struct list_head *tmp, *entry = &unwinder_list; + + list_for_each(tmp, &unwinder_list) { + struct unwinder *o; + + o = list_entry(tmp, struct unwinder, list); + if (o == ops) + return -EBUSY; + /* Keep track of the place, where to insert */ + if (o->rating >= ops->rating) + entry = tmp; + } + list_add(&ops->list, entry); + + return 0; +} + +/** + * unwinder_register - Used to install new stack unwinder + * @u: unwinder to be registered + * + * Install the new stack unwinder on the unwinder list, which is sorted + * by rating. + * + * Returns -EBUSY if registration fails, zero otherwise. + */ +int unwinder_register(struct unwinder *u) +{ + unsigned long flags; + int ret; + + spin_lock_irqsave(&unwinder_lock, flags); + ret = unwinder_enqueue(u); + if (!ret) + curr_unwinder = select_unwinder(); + spin_unlock_irqrestore(&unwinder_lock, flags); + + return ret; +} + +/* + * Unwind the call stack and pass information to the stacktrace_ops + * functions. Also handle the case where we need to switch to a new + * stack dumper because the current one faulted unexpectedly. + */ +void unwind_stack(struct task_struct *task, struct pt_regs *regs, + unsigned long *sp, const struct stacktrace_ops *ops, + void *data) +{ + unsigned long flags; + + /* + * The problem with unwinders with high ratings is that they are + * inherently more complicated than the simple ones with lower + * ratings. We are therefore more likely to fault in the + * complicated ones, e.g. hitting BUG()s. If we fault in the + * code for the current stack unwinder we try to downgrade to + * one with a lower rating. + * + * Hopefully this will give us a semi-reliable stacktrace so we + * can diagnose why curr_unwinder->dump() faulted. + */ + if (atomic_inc_return(&unwinder_running) != 1) { + spin_lock_irqsave(&unwinder_lock, flags); + + if (!list_is_singular(&unwinder_list)) { + list_del(&curr_unwinder->list); + curr_unwinder = select_unwinder(); + } + + spin_unlock_irqrestore(&unwinder_lock, flags); + atomic_dec(&unwinder_running); + } + + curr_unwinder->dump(task, regs, sp, ops, data); + + atomic_dec(&unwinder_running); +} |