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// SPDX-License-Identifier: Apache-2.0
/*
* Create/Print backtraces, check stack usage etc.
*
* Copyright 2013-2019 IBM Corp.
*/
#include <skiboot.h>
#include <processor.h>
#include <cpu.h>
#include <stack.h>
#include <mem_region.h>
#include <unistd.h>
#include <lock.h>
#define STACK_BUF_ENTRIES 60
static struct bt_entry bt_buf[STACK_BUF_ENTRIES];
/* Dumps backtrace to buffer */
void __nomcount backtrace_create(struct bt_entry *entries,
unsigned int max_ents,
struct bt_metadata *metadata)
{
unsigned long *fp = __builtin_frame_address(0);
unsigned long top_adj = top_of_ram;
struct stack_frame *eframe = (struct stack_frame *)fp;
/* Assume one stack for early backtraces */
if (top_of_ram == SKIBOOT_BASE + SKIBOOT_SIZE)
top_adj = top_of_ram + STACK_SIZE;
metadata->ents = 0;
while (max_ents) {
fp = (unsigned long *)fp[0];
if (!fp || (unsigned long)fp > top_adj)
break;
eframe = (struct stack_frame *)fp;
entries->sp = (unsigned long)fp;
entries->pc = fp[2];
entries++;
metadata->ents++;
max_ents--;
}
metadata->r1_caller = eframe->gpr[1];
if (fp)
metadata->token = eframe->gpr[0];
else
metadata->token = -1UL;
metadata->pir = mfspr(SPR_PIR);
}
void backtrace_print(struct bt_entry *entries, struct bt_metadata *metadata,
char *out_buf, unsigned int *len, bool symbols)
{
static char bt_text_buf[4096];
int i, l = 0, max;
char *buf = out_buf;
unsigned long bottom, top, normal_top, tbot, ttop;
char mark;
if (!out_buf) {
buf = bt_text_buf;
max = sizeof(bt_text_buf) - 16;
} else
max = *len - 1;
bottom = cpu_stack_bottom(metadata->pir);
normal_top = cpu_stack_top(metadata->pir);
top = cpu_emergency_stack_top(metadata->pir);
tbot = SKIBOOT_BASE;
ttop = (unsigned long)&_etext;
l += snprintf(buf, max, "CPU %04lx Backtrace:\n", metadata->pir);
for (i = 0; i < metadata->ents && l < max; i++) {
if (entries->sp < bottom || entries->sp > top)
mark = '!';
else if (entries->sp > normal_top)
mark = 'E';
else if (entries->pc < tbot || entries->pc > ttop)
mark = '*';
else
mark = ' ';
l += snprintf(buf + l, max - l,
" S: %016lx R: %016lx %c ",
entries->sp, entries->pc, mark);
if (symbols)
l += snprintf_symbol(buf + l, max - l, entries->pc);
l += snprintf(buf + l, max - l, "\n");
entries++;
}
if (metadata->token <= OPAL_LAST)
l += snprintf(buf + l, max - l,
" --- OPAL call token: 0x%lx caller R1: 0x%016lx ---\n",
metadata->token, metadata->r1_caller);
else if (metadata->token == -1UL)
l += snprintf(buf + l, max - l, " --- OPAL boot ---\n");
if (!out_buf)
write(stdout->fd, bt_text_buf, l);
buf[l++] = 0;
if (len)
*len = l;
}
/*
* To ensure that we always get backtrace output we bypass the usual console
* locking paths. The downside is that when multiple threads need to print
* a backtrace they garble each other. To prevent this we use a seperate
* lock to serialise printing of the dumps.
*/
static struct lock bt_lock = LOCK_UNLOCKED;
void backtrace(void)
{
struct bt_metadata metadata;
lock(&bt_lock);
backtrace_create(bt_buf, STACK_BUF_ENTRIES, &metadata);
backtrace_print(bt_buf, &metadata, NULL, NULL, true);
unlock(&bt_lock);
}
void __nomcount __stack_chk_fail(void);
void __nomcount __stack_chk_fail(void)
{
static bool failed_once;
if (failed_once)
return;
failed_once = true;
prlog(PR_EMERG, "Stack corruption detected !\n");
abort();
}
#ifdef STACK_CHECK_ENABLED
static int64_t lowest_stack_mark = LONG_MAX;
static struct lock stack_check_lock = LOCK_UNLOCKED;
void __nomcount __mcount_stack_check(uint64_t sp, uint64_t lr);
void __nomcount __mcount_stack_check(uint64_t sp, uint64_t lr)
{
struct cpu_thread *c = this_cpu();
uint64_t base = (uint64_t)c;
uint64_t bot = base + sizeof(struct cpu_thread);
int64_t mark = sp - bot;
uint64_t top = base + NORMAL_STACK_SIZE;
/*
* Don't check the emergency stack just yet.
*/
if (c->in_opal_call > 1)
return;
/*
* Don't re-enter on this CPU or don't enter at all if somebody
* has spotted an overflow
*/
if (c->in_mcount)
return;
c->in_mcount = true;
/* Capture lowest stack for this thread */
if (mark < c->stack_bot_mark) {
lock(&stack_check_lock);
c->stack_bot_mark = mark;
c->stack_bot_pc = lr;
c->stack_bot_tok = c->current_token;
backtrace_create(c->stack_bot_bt, CPU_BACKTRACE_SIZE,
&c->stack_bot_bt_metadata);
unlock(&stack_check_lock);
}
/* Stack is within bounds ? check for warning and bail */
if (sp >= (bot + STACK_SAFETY_GAP) && sp < top) {
if (mark < STACK_WARNING_GAP) {
prlog(PR_EMERG, "CPU %04x Stack usage danger !"
" pc=%08llx sp=%08llx (gap=%lld) token=%lld\n",
c->pir, lr, sp, mark, c->current_token);
backtrace();
}
c->in_mcount = false;
return;
}
prlog(PR_EMERG, "CPU %04x Stack overflow detected !"
" pc=%08llx sp=%08llx (gap=%lld) token=%lld\n",
c->pir, lr, sp, mark, c->current_token);
abort();
}
void check_stacks(void)
{
struct cpu_thread *c, *lowest = NULL;
/* We should never call that from mcount */
assert(!this_cpu()->in_mcount);
/* Mark ourselves "in_mcount" to avoid deadlock on stack
* check lock
*/
this_cpu()->in_mcount = true;
for_each_cpu(c) {
if (!c->stack_bot_mark ||
c->stack_bot_mark >= lowest_stack_mark)
continue;
lock(&stack_check_lock);
if (c->stack_bot_mark < lowest_stack_mark) {
lowest = c;
lowest_stack_mark = c->stack_bot_mark;
}
unlock(&stack_check_lock);
}
if (lowest) {
lock(&stack_check_lock);
prlog(PR_NOTICE, "CPU %04x lowest stack mark %lld bytes left"
" pc=%08llx token=%lld\n",
lowest->pir, lowest->stack_bot_mark, lowest->stack_bot_pc,
lowest->stack_bot_tok);
backtrace_print(lowest->stack_bot_bt,
&lowest->stack_bot_bt_metadata,
NULL, NULL, true);
unlock(&stack_check_lock);
}
this_cpu()->in_mcount = false;
}
#endif /* STACK_CHECK_ENABLED */
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