/* * 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 #include #include #include #include #include #include #include #include #include #include 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 */ static 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); } }