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Diffstat (limited to 'arch/microblaze/kernel/unwind.c')
-rw-r--r-- | arch/microblaze/kernel/unwind.c | 318 |
1 files changed, 318 insertions, 0 deletions
diff --git a/arch/microblaze/kernel/unwind.c b/arch/microblaze/kernel/unwind.c new file mode 100644 index 00000000000..fefac5c3358 --- /dev/null +++ b/arch/microblaze/kernel/unwind.c @@ -0,0 +1,318 @@ +/* + * Backtrace support for Microblaze + * + * Copyright (C) 2010 Digital Design Corporation + * + * Based on arch/sh/kernel/cpu/sh5/unwind.c code which is: + * Copyright (C) 2004 Paul Mundt + * Copyright (C) 2004 Richard Curnow + * + * This file is subject to the terms and conditions of the GNU General Public + * License. See the file "COPYING" in the main directory of this archive + * for more details. + */ + +/* #define DEBUG 1 */ +#include <linux/kallsyms.h> +#include <linux/kernel.h> +#include <linux/sched.h> +#include <linux/stacktrace.h> +#include <linux/types.h> +#include <linux/errno.h> +#include <linux/module.h> +#include <linux/io.h> +#include <asm/sections.h> +#include <asm/exceptions.h> +#include <asm/unwind.h> + +struct stack_trace; + +/* + * On Microblaze, finding the previous stack frame is a little tricky. + * At this writing (3/2010), Microblaze does not support CONFIG_FRAME_POINTERS, + * and even if it did, gcc (4.1.2) does not store the frame pointer at + * a consistent offset within each frame. To determine frame size, it is + * necessary to search for the assembly instruction that creates or reclaims + * the frame and extract the size from it. + * + * Microblaze stores the stack pointer in r1, and creates a frame via + * + * addik r1, r1, -FRAME_SIZE + * + * The frame is reclaimed via + * + * addik r1, r1, FRAME_SIZE + * + * Frame creation occurs at or near the top of a function. + * Depending on the compiler, reclaim may occur at the end, or before + * a mid-function return. + * + * A stack frame is usually not created in a leaf function. + * + */ + +/** + * get_frame_size - Extract the stack adjustment from an + * "addik r1, r1, adjust" instruction + * @instr : Microblaze instruction + * + * Return - Number of stack bytes the instruction reserves or reclaims + */ +inline long get_frame_size(unsigned long instr) +{ + return abs((s16)(instr & 0xFFFF)); +} + +/** + * find_frame_creation - Search backward to find the instruction that creates + * the stack frame (hopefully, for the same function the + * initial PC is in). + * @pc : Program counter at which to begin the search + * + * Return - PC at which stack frame creation occurs + * NULL if this cannot be found, i.e. a leaf function + */ +static unsigned long *find_frame_creation(unsigned long *pc) +{ + int i; + + /* NOTE: Distance to search is arbitrary + * 250 works well for most things, + * 750 picks up things like tcp_recvmsg(), + * 1000 needed for fat_fill_super() + */ + for (i = 0; i < 1000; i++, pc--) { + unsigned long instr; + s16 frame_size; + + if (!kernel_text_address((unsigned long) pc)) + return NULL; + + instr = *pc; + + /* addik r1, r1, foo ? */ + if ((instr & 0xFFFF0000) != 0x30210000) + continue; /* No */ + + frame_size = get_frame_size(instr); + if ((frame_size < 8) || (frame_size & 3)) { + pr_debug(" Invalid frame size %d at 0x%p\n", + frame_size, pc); + return NULL; + } + + pr_debug(" Found frame creation at 0x%p, size %d\n", pc, + frame_size); + return pc; + } + + return NULL; +} + +/** + * lookup_prev_stack_frame - Find the stack frame of the previous function. + * @fp : Frame (stack) pointer for current function + * @pc : Program counter within current function + * @leaf_return : r15 value within current function. If the current function + * is a leaf, this is the caller's return address. + * @pprev_fp : On exit, set to frame (stack) pointer for previous function + * @pprev_pc : On exit, set to current function caller's return address + * + * Return - 0 on success, -EINVAL if the previous frame cannot be found + */ +static int lookup_prev_stack_frame(unsigned long fp, unsigned long pc, + unsigned long leaf_return, + unsigned long *pprev_fp, + unsigned long *pprev_pc) +{ + unsigned long *prologue = NULL; + + /* _switch_to is a special leaf function */ + if (pc != (unsigned long) &_switch_to) + prologue = find_frame_creation((unsigned long *)pc); + + if (prologue) { + long frame_size = get_frame_size(*prologue); + + *pprev_fp = fp + frame_size; + *pprev_pc = *(unsigned long *)fp; + } else { + if (!leaf_return) + return -EINVAL; + *pprev_pc = leaf_return; + *pprev_fp = fp; + } + + /* NOTE: don't check kernel_text_address here, to allow display + * of userland return address + */ + return (!*pprev_pc || (*pprev_pc & 3)) ? -EINVAL : 0; +} + +static void microblaze_unwind_inner(struct task_struct *task, + unsigned long pc, unsigned long fp, + unsigned long leaf_return, + struct stack_trace *trace); + +/** + * unwind_trap - Unwind through a system trap, that stored previous state + * on the stack. + */ +#ifdef CONFIG_MMU +static inline void unwind_trap(struct task_struct *task, unsigned long pc, + unsigned long fp, struct stack_trace *trace) +{ + /* To be implemented */ +} +#else +static inline void unwind_trap(struct task_struct *task, unsigned long pc, + unsigned long fp, struct stack_trace *trace) +{ + const struct pt_regs *regs = (const struct pt_regs *) fp; + microblaze_unwind_inner(task, regs->pc, regs->r1, regs->r15, trace); +} +#endif + +/** + * microblaze_unwind_inner - Unwind the stack from the specified point + * @task : Task whose stack we are to unwind (may be NULL) + * @pc : Program counter from which we start unwinding + * @fp : Frame (stack) pointer from which we start unwinding + * @leaf_return : Value of r15 at pc. If the function is a leaf, this is + * the caller's return address. + * @trace : Where to store stack backtrace (PC values). + * NULL == print backtrace to kernel log + */ +void microblaze_unwind_inner(struct task_struct *task, + unsigned long pc, unsigned long fp, + unsigned long leaf_return, + struct stack_trace *trace) +{ + int ofs = 0; + + pr_debug(" Unwinding with PC=%p, FP=%p\n", (void *)pc, (void *)fp); + if (!pc || !fp || (pc & 3) || (fp & 3)) { + pr_debug(" Invalid state for unwind, aborting\n"); + return; + } + for (; pc != 0;) { + unsigned long next_fp, next_pc = 0; + unsigned long return_to = pc + 2 * sizeof(unsigned long); + const struct trap_handler_info *handler = + µblaze_trap_handlers; + + /* Is previous function the HW exception handler? */ + if ((return_to >= (unsigned long)&_hw_exception_handler) + &&(return_to < (unsigned long)&ex_handler_unhandled)) { + /* + * HW exception handler doesn't save all registers, + * so we open-code a special case of unwind_trap() + */ +#ifndef CONFIG_MMU + const struct pt_regs *regs = + (const struct pt_regs *) fp; +#endif + pr_info("HW EXCEPTION\n"); +#ifndef CONFIG_MMU + microblaze_unwind_inner(task, regs->r17 - 4, + fp + EX_HANDLER_STACK_SIZ, + regs->r15, trace); +#endif + return; + } + + /* Is previous function a trap handler? */ + for (; handler->start_addr; ++handler) { + if ((return_to >= handler->start_addr) + && (return_to <= handler->end_addr)) { + if (!trace) + pr_info("%s\n", handler->trap_name); + unwind_trap(task, pc, fp, trace); + return; + } + } + pc -= ofs; + + if (trace) { +#ifdef CONFIG_STACKTRACE + if (trace->skip > 0) + trace->skip--; + else + trace->entries[trace->nr_entries++] = pc; + + if (trace->nr_entries >= trace->max_entries) + break; +#endif + } else { + /* Have we reached userland? */ + if (unlikely(pc == task_pt_regs(task)->pc)) { + pr_info("[<%p>] PID %lu [%s]\n", + (void *) pc, + (unsigned long) task->pid, + task->comm); + break; + } else + print_ip_sym(pc); + } + + /* Stop when we reach anything not part of the kernel */ + if (!kernel_text_address(pc)) + break; + + if (lookup_prev_stack_frame(fp, pc, leaf_return, &next_fp, + &next_pc) == 0) { + ofs = sizeof(unsigned long); + pc = next_pc & ~3; + fp = next_fp; + leaf_return = 0; + } else { + pr_debug(" Failed to find previous stack frame\n"); + break; + } + + pr_debug(" Next PC=%p, next FP=%p\n", + (void *)next_pc, (void *)next_fp); + } +} + +/** + * microblaze_unwind - Stack unwinder for Microblaze (external entry point) + * @task : Task whose stack we are to unwind (NULL == current) + * @trace : Where to store stack backtrace (PC values). + * NULL == print backtrace to kernel log + */ +void microblaze_unwind(struct task_struct *task, struct stack_trace *trace) +{ + if (task) { + if (task == current) { + const struct pt_regs *regs = task_pt_regs(task); + microblaze_unwind_inner(task, regs->pc, regs->r1, + regs->r15, trace); + } else { + struct thread_info *thread_info = + (struct thread_info *)(task->stack); + const struct cpu_context *cpu_context = + &thread_info->cpu_context; + + microblaze_unwind_inner(task, + (unsigned long) &_switch_to, + cpu_context->r1, + cpu_context->r15, trace); + } + } else { + unsigned long pc, fp; + + __asm__ __volatile__ ("or %0, r1, r0" : "=r" (fp)); + + __asm__ __volatile__ ( + "brlid %0, 0f;" + "nop;" + "0:" + : "=r" (pc) + ); + + /* Since we are not a leaf function, use leaf_return = 0 */ + microblaze_unwind_inner(current, pc, fp, 0, trace); + } +} + |