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