490 lines
12 KiB
C
490 lines
12 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Kernel unwinding support
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*
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* (c) 2002-2004 Randolph Chung <tausq@debian.org>
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*
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* Derived partially from the IA64 implementation. The PA-RISC
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* Runtime Architecture Document is also a useful reference to
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* understand what is happening here
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*/
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#include <linux/kernel.h>
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#include <linux/init.h>
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#include <linux/sched.h>
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#include <linux/slab.h>
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#include <linux/sort.h>
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#include <linux/sched/task_stack.h>
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#include <linux/uaccess.h>
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#include <asm/assembly.h>
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#include <asm/asm-offsets.h>
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#include <asm/ptrace.h>
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#include <asm/unwind.h>
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#include <asm/switch_to.h>
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#include <asm/sections.h>
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/* #define DEBUG 1 */
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#ifdef DEBUG
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#define dbg(x...) pr_debug(x)
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#else
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#define dbg(x...)
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#endif
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#define KERNEL_START (KERNEL_BINARY_TEXT_START)
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extern struct unwind_table_entry __start___unwind[];
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extern struct unwind_table_entry __stop___unwind[];
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static DEFINE_SPINLOCK(unwind_lock);
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/*
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* the kernel unwind block is not dynamically allocated so that
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* we can call unwind_init as early in the bootup process as
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* possible (before the slab allocator is initialized)
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*/
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static struct unwind_table kernel_unwind_table __ro_after_init;
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static LIST_HEAD(unwind_tables);
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static inline const struct unwind_table_entry *
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find_unwind_entry_in_table(const struct unwind_table *table, unsigned long addr)
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{
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const struct unwind_table_entry *e = NULL;
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unsigned long lo, hi, mid;
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lo = 0;
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hi = table->length - 1;
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while (lo <= hi) {
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mid = (hi - lo) / 2 + lo;
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e = &table->table[mid];
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if (addr < e->region_start)
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hi = mid - 1;
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else if (addr > e->region_end)
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lo = mid + 1;
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else
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return e;
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}
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return NULL;
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}
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static const struct unwind_table_entry *
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find_unwind_entry(unsigned long addr)
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{
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struct unwind_table *table;
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const struct unwind_table_entry *e = NULL;
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if (addr >= kernel_unwind_table.start &&
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addr <= kernel_unwind_table.end)
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e = find_unwind_entry_in_table(&kernel_unwind_table, addr);
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else {
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unsigned long flags;
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spin_lock_irqsave(&unwind_lock, flags);
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list_for_each_entry(table, &unwind_tables, list) {
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if (addr >= table->start &&
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addr <= table->end)
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e = find_unwind_entry_in_table(table, addr);
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if (e) {
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/* Move-to-front to exploit common traces */
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list_move(&table->list, &unwind_tables);
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break;
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}
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}
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spin_unlock_irqrestore(&unwind_lock, flags);
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}
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return e;
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}
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static void
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unwind_table_init(struct unwind_table *table, const char *name,
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unsigned long base_addr, unsigned long gp,
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void *table_start, void *table_end)
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{
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struct unwind_table_entry *start = table_start;
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struct unwind_table_entry *end =
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(struct unwind_table_entry *)table_end - 1;
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table->name = name;
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table->base_addr = base_addr;
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table->gp = gp;
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table->start = base_addr + start->region_start;
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table->end = base_addr + end->region_end;
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table->table = (struct unwind_table_entry *)table_start;
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table->length = end - start + 1;
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INIT_LIST_HEAD(&table->list);
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for (; start <= end; start++) {
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if (start < end &&
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start->region_end > (start+1)->region_start) {
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pr_warn("Out of order unwind entry! %px and %px\n",
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start, start+1);
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}
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start->region_start += base_addr;
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start->region_end += base_addr;
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}
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}
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static int cmp_unwind_table_entry(const void *a, const void *b)
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{
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return ((const struct unwind_table_entry *)a)->region_start
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- ((const struct unwind_table_entry *)b)->region_start;
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}
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static void
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unwind_table_sort(struct unwind_table_entry *start,
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struct unwind_table_entry *finish)
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{
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sort(start, finish - start, sizeof(struct unwind_table_entry),
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cmp_unwind_table_entry, NULL);
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}
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struct unwind_table *
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unwind_table_add(const char *name, unsigned long base_addr,
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unsigned long gp,
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void *start, void *end)
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{
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struct unwind_table *table;
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unsigned long flags;
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struct unwind_table_entry *s = (struct unwind_table_entry *)start;
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struct unwind_table_entry *e = (struct unwind_table_entry *)end;
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unwind_table_sort(s, e);
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table = kmalloc(sizeof(struct unwind_table), GFP_USER);
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if (table == NULL)
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return NULL;
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unwind_table_init(table, name, base_addr, gp, start, end);
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spin_lock_irqsave(&unwind_lock, flags);
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list_add_tail(&table->list, &unwind_tables);
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spin_unlock_irqrestore(&unwind_lock, flags);
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return table;
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}
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void unwind_table_remove(struct unwind_table *table)
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{
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unsigned long flags;
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spin_lock_irqsave(&unwind_lock, flags);
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list_del(&table->list);
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spin_unlock_irqrestore(&unwind_lock, flags);
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kfree(table);
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}
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/* Called from setup_arch to import the kernel unwind info */
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int __init unwind_init(void)
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{
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long start, stop;
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register unsigned long gp __asm__ ("r27");
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start = (long)&__start___unwind[0];
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stop = (long)&__stop___unwind[0];
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dbg("unwind_init: start = 0x%lx, end = 0x%lx, entries = %lu\n",
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start, stop,
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(stop - start) / sizeof(struct unwind_table_entry));
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unwind_table_init(&kernel_unwind_table, "kernel", KERNEL_START,
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gp,
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&__start___unwind[0], &__stop___unwind[0]);
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#if 0
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{
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int i;
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for (i = 0; i < 10; i++)
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{
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printk("region 0x%x-0x%x\n",
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__start___unwind[i].region_start,
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__start___unwind[i].region_end);
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}
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}
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#endif
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return 0;
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}
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static bool pc_is_kernel_fn(unsigned long pc, void *fn)
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{
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return (unsigned long)dereference_kernel_function_descriptor(fn) == pc;
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}
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static int unwind_special(struct unwind_frame_info *info, unsigned long pc, int frame_size)
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{
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/*
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* We have to use void * instead of a function pointer, because
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* function pointers aren't a pointer to the function on 64-bit.
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* Make them const so the compiler knows they live in .text
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* Note: We could use dereference_kernel_function_descriptor()
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* instead but we want to keep it simple here.
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*/
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extern void * const handle_interruption;
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extern void * const ret_from_kernel_thread;
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extern void * const syscall_exit;
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extern void * const intr_return;
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extern void * const _switch_to_ret;
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#ifdef CONFIG_IRQSTACKS
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extern void * const _call_on_stack;
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#endif /* CONFIG_IRQSTACKS */
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if (pc_is_kernel_fn(pc, handle_interruption)) {
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struct pt_regs *regs = (struct pt_regs *)(info->sp - frame_size - PT_SZ_ALGN);
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dbg("Unwinding through handle_interruption()\n");
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info->prev_sp = regs->gr[30];
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info->prev_ip = regs->iaoq[0];
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return 1;
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}
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if (pc_is_kernel_fn(pc, ret_from_kernel_thread) ||
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pc_is_kernel_fn(pc, syscall_exit)) {
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info->prev_sp = info->prev_ip = 0;
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return 1;
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}
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if (pc_is_kernel_fn(pc, intr_return)) {
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struct pt_regs *regs;
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dbg("Found intr_return()\n");
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regs = (struct pt_regs *)(info->sp - PT_SZ_ALGN);
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info->prev_sp = regs->gr[30];
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info->prev_ip = regs->iaoq[0];
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info->rp = regs->gr[2];
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return 1;
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}
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if (pc_is_kernel_fn(pc, _switch_to) ||
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pc_is_kernel_fn(pc, _switch_to_ret)) {
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info->prev_sp = info->sp - CALLEE_SAVE_FRAME_SIZE;
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info->prev_ip = *(unsigned long *)(info->prev_sp - RP_OFFSET);
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return 1;
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}
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#ifdef CONFIG_IRQSTACKS
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if (pc_is_kernel_fn(pc, _call_on_stack)) {
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info->prev_sp = *(unsigned long *)(info->sp - FRAME_SIZE - REG_SZ);
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info->prev_ip = *(unsigned long *)(info->sp - FRAME_SIZE - RP_OFFSET);
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return 1;
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}
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#endif
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return 0;
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}
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static void unwind_frame_regs(struct unwind_frame_info *info)
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{
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const struct unwind_table_entry *e;
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unsigned long npc;
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unsigned int insn;
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long frame_size = 0;
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int looking_for_rp, rpoffset = 0;
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e = find_unwind_entry(info->ip);
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if (e == NULL) {
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unsigned long sp;
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dbg("Cannot find unwind entry for %pS; forced unwinding\n",
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(void *) info->ip);
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/* Since we are doing the unwinding blind, we don't know if
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we are adjusting the stack correctly or extracting the rp
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correctly. The rp is checked to see if it belongs to the
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kernel text section, if not we assume we don't have a
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correct stack frame and we continue to unwind the stack.
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This is not quite correct, and will fail for loadable
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modules. */
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sp = info->sp & ~63;
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do {
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unsigned long tmp;
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info->prev_sp = sp - 64;
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info->prev_ip = 0;
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/* Check if stack is inside kernel stack area */
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if ((info->prev_sp - (unsigned long) task_stack_page(info->t))
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>= THREAD_SIZE) {
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info->prev_sp = 0;
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break;
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}
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if (copy_from_kernel_nofault(&tmp,
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(void *)info->prev_sp - RP_OFFSET, sizeof(tmp)))
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break;
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info->prev_ip = tmp;
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sp = info->prev_sp;
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} while (!kernel_text_address(info->prev_ip));
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info->rp = 0;
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dbg("analyzing func @ %lx with no unwind info, setting "
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"prev_sp=%lx prev_ip=%lx\n", info->ip,
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info->prev_sp, info->prev_ip);
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} else {
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dbg("e->start = 0x%x, e->end = 0x%x, Save_SP = %d, "
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"Save_RP = %d, Millicode = %d size = %u\n",
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e->region_start, e->region_end, e->Save_SP, e->Save_RP,
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e->Millicode, e->Total_frame_size);
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looking_for_rp = e->Save_RP;
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for (npc = e->region_start;
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(frame_size < (e->Total_frame_size << 3) ||
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looking_for_rp) &&
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npc < info->ip;
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npc += 4) {
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insn = *(unsigned int *)npc;
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if ((insn & 0xffffc001) == 0x37de0000 ||
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(insn & 0xffe00001) == 0x6fc00000) {
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/* ldo X(sp), sp, or stwm X,D(sp) */
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frame_size += (insn & 0x3fff) >> 1;
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dbg("analyzing func @ %lx, insn=%08x @ "
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"%lx, frame_size = %ld\n", info->ip,
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insn, npc, frame_size);
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} else if ((insn & 0xffe00009) == 0x73c00008) {
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/* std,ma X,D(sp) */
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frame_size += ((insn >> 4) & 0x3ff) << 3;
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dbg("analyzing func @ %lx, insn=%08x @ "
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"%lx, frame_size = %ld\n", info->ip,
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insn, npc, frame_size);
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} else if (insn == 0x6bc23fd9) {
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/* stw rp,-20(sp) */
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rpoffset = 20;
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looking_for_rp = 0;
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dbg("analyzing func @ %lx, insn=stw rp,"
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"-20(sp) @ %lx\n", info->ip, npc);
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} else if (insn == 0x0fc212c1) {
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/* std rp,-16(sr0,sp) */
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rpoffset = 16;
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looking_for_rp = 0;
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dbg("analyzing func @ %lx, insn=std rp,"
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"-16(sp) @ %lx\n", info->ip, npc);
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}
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}
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if (frame_size > e->Total_frame_size << 3)
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frame_size = e->Total_frame_size << 3;
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if (!unwind_special(info, e->region_start, frame_size)) {
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info->prev_sp = info->sp - frame_size;
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if (e->Millicode)
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info->rp = info->r31;
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else if (rpoffset)
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info->rp = *(unsigned long *)(info->prev_sp - rpoffset);
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info->prev_ip = info->rp;
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info->rp = 0;
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}
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dbg("analyzing func @ %lx, setting prev_sp=%lx "
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"prev_ip=%lx npc=%lx\n", info->ip, info->prev_sp,
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info->prev_ip, npc);
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}
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}
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void unwind_frame_init(struct unwind_frame_info *info, struct task_struct *t,
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struct pt_regs *regs)
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{
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memset(info, 0, sizeof(struct unwind_frame_info));
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info->t = t;
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info->sp = regs->gr[30];
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info->ip = regs->iaoq[0];
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info->rp = regs->gr[2];
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info->r31 = regs->gr[31];
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dbg("(%d) Start unwind from sp=%08lx ip=%08lx\n",
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t ? (int)t->pid : -1, info->sp, info->ip);
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}
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void unwind_frame_init_from_blocked_task(struct unwind_frame_info *info, struct task_struct *t)
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{
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struct pt_regs *r = &t->thread.regs;
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struct pt_regs *r2;
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r2 = kmalloc(sizeof(struct pt_regs), GFP_ATOMIC);
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if (!r2)
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return;
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*r2 = *r;
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r2->gr[30] = r->ksp;
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r2->iaoq[0] = r->kpc;
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unwind_frame_init(info, t, r2);
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kfree(r2);
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}
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#define get_parisc_stackpointer() ({ \
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unsigned long sp; \
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__asm__("copy %%r30, %0" : "=r"(sp)); \
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(sp); \
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})
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void unwind_frame_init_task(struct unwind_frame_info *info,
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struct task_struct *task, struct pt_regs *regs)
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{
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task = task ? task : current;
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if (task == current) {
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struct pt_regs r;
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if (!regs) {
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memset(&r, 0, sizeof(r));
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r.iaoq[0] = _THIS_IP_;
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r.gr[2] = _RET_IP_;
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r.gr[30] = get_parisc_stackpointer();
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regs = &r;
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}
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unwind_frame_init(info, task, regs);
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} else {
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unwind_frame_init_from_blocked_task(info, task);
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}
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}
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int unwind_once(struct unwind_frame_info *next_frame)
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{
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unwind_frame_regs(next_frame);
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if (next_frame->prev_sp == 0 ||
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next_frame->prev_ip == 0)
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return -1;
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next_frame->sp = next_frame->prev_sp;
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next_frame->ip = next_frame->prev_ip;
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next_frame->prev_sp = 0;
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next_frame->prev_ip = 0;
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dbg("(%d) Continue unwind to sp=%08lx ip=%08lx\n",
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next_frame->t ? (int)next_frame->t->pid : -1,
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next_frame->sp, next_frame->ip);
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return 0;
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}
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int unwind_to_user(struct unwind_frame_info *info)
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{
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int ret;
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do {
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ret = unwind_once(info);
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} while (!ret && !(info->ip & 3));
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return ret;
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}
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unsigned long return_address(unsigned int level)
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{
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struct unwind_frame_info info;
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/* initialize unwind info */
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unwind_frame_init_task(&info, current, NULL);
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/* unwind stack */
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level += 2;
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do {
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if (unwind_once(&info) < 0 || info.ip == 0)
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return 0;
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if (!kernel_text_address(info.ip))
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return 0;
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} while (info.ip && level--);
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return info.ip;
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}
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