6a00ef4493
I tried different pieces of code which uses __builtin_frame_address(1)
(with both gcc version 7.5.0 and 10.3.0) to verify whether it works as
expected on riscv64. The result is negative.
What the compiler had generated is as below:
31 fp = (unsigned long)__builtin_frame_address(1);
0xffffffff80006024 <+200>: ld s1,0(s0)
It takes '0(s0)' as the address of frame 1 (caller), but the actual address
should be '-16(s0)'.
| ... | <-+
+-----------------+ |
| return address | |
| previous fp | |
| saved registers | |
| local variables | |
$fp --> | ... | |
+-----------------+ |
| return address | |
| previous fp --------+
| saved registers |
$sp --> | local variables |
+-----------------+
This leads the kernel can not dump the full stack trace on riscv.
[ 7.222126][ T1] Call Trace:
[ 7.222804][ T1] [<ffffffff80006058>] dump_backtrace+0x2c/0x3a
This problem is not exposed on most riscv builds just because the '0(s0)'
occasionally is the address frame 2 (caller's caller), if only ra and fp
are stored in frame 1 (caller).
| ... | <-+
+-----------------+ |
| return address | |
$fp --> | previous fp | |
+-----------------+ |
| return address | |
| previous fp --------+
| saved registers |
$sp --> | local variables |
+-----------------+
This could be a *bug* of gcc that should be fixed. But as noted in gcc
manual "Calling this function with a nonzero argument can have
unpredictable effects, including crashing the calling program.", let's
remove the '__builtin_frame_address(1)' in backtrace code.
With this fix now it can show full stack trace:
[ 10.444838][ T1] Call Trace:
[ 10.446199][ T1] [<ffffffff8000606c>] dump_backtrace+0x2c/0x3a
[ 10.447711][ T1] [<ffffffff800060ac>] show_stack+0x32/0x3e
[ 10.448710][ T1] [<ffffffff80a005c0>] dump_stack_lvl+0x58/0x7a
[ 10.449941][ T1] [<ffffffff80a005f6>] dump_stack+0x14/0x1c
[ 10.450929][ T1] [<ffffffff804c04ee>] ubsan_epilogue+0x10/0x5a
[ 10.451869][ T1] [<ffffffff804c092e>] __ubsan_handle_load_invalid_value+0x6c/0x78
[ 10.453049][ T1] [<ffffffff8018f834>] __pagevec_release+0x62/0x64
[ 10.455476][ T1] [<ffffffff80190830>] truncate_inode_pages_range+0x132/0x5be
[ 10.456798][ T1] [<ffffffff80190ce0>] truncate_inode_pages+0x24/0x30
[ 10.457853][ T1] [<ffffffff8045bb04>] kill_bdev+0x32/0x3c
...
Signed-off-by: Changbin Du <changbin.du@gmail.com>
Fixes: eac2f3059e ("riscv: stacktrace: fix the riscv stacktrace when CONFIG_FRAME_POINTER enabled")
Cc: stable@vger.kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
147 lines
3.3 KiB
C
147 lines
3.3 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Copyright (C) 2008 ARM Limited
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* Copyright (C) 2014 Regents of the University of California
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*/
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#include <linux/export.h>
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#include <linux/kallsyms.h>
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#include <linux/sched.h>
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#include <linux/sched/debug.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/ftrace.h>
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#include <asm/stacktrace.h>
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register unsigned long sp_in_global __asm__("sp");
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#ifdef CONFIG_FRAME_POINTER
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void notrace walk_stackframe(struct task_struct *task, struct pt_regs *regs,
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bool (*fn)(void *, unsigned long), void *arg)
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{
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unsigned long fp, sp, pc;
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int level = 0;
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if (regs) {
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fp = frame_pointer(regs);
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sp = user_stack_pointer(regs);
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pc = instruction_pointer(regs);
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} else if (task == NULL || task == current) {
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fp = (unsigned long)__builtin_frame_address(0);
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sp = sp_in_global;
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pc = (unsigned long)walk_stackframe;
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} else {
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/* task blocked in __switch_to */
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fp = task->thread.s[0];
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sp = task->thread.sp;
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pc = task->thread.ra;
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}
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for (;;) {
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unsigned long low, high;
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struct stackframe *frame;
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if (unlikely(!__kernel_text_address(pc) || (level++ >= 1 && !fn(arg, pc))))
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break;
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/* Validate frame pointer */
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low = sp + sizeof(struct stackframe);
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high = ALIGN(sp, THREAD_SIZE);
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if (unlikely(fp < low || fp > high || fp & 0x7))
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break;
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/* Unwind stack frame */
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frame = (struct stackframe *)fp - 1;
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sp = fp;
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if (regs && (regs->epc == pc) && (frame->fp & 0x7)) {
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fp = frame->ra;
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pc = regs->ra;
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} else {
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fp = frame->fp;
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pc = ftrace_graph_ret_addr(current, NULL, frame->ra,
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(unsigned long *)(fp - 8));
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}
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}
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}
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#else /* !CONFIG_FRAME_POINTER */
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void notrace walk_stackframe(struct task_struct *task,
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struct pt_regs *regs, bool (*fn)(void *, unsigned long), void *arg)
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{
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unsigned long sp, pc;
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unsigned long *ksp;
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if (regs) {
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sp = user_stack_pointer(regs);
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pc = instruction_pointer(regs);
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} else if (task == NULL || task == current) {
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sp = sp_in_global;
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pc = (unsigned long)walk_stackframe;
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} else {
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/* task blocked in __switch_to */
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sp = task->thread.sp;
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pc = task->thread.ra;
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}
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if (unlikely(sp & 0x7))
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return;
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ksp = (unsigned long *)sp;
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while (!kstack_end(ksp)) {
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if (__kernel_text_address(pc) && unlikely(!fn(arg, pc)))
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break;
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pc = (*ksp++) - 0x4;
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}
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}
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#endif /* CONFIG_FRAME_POINTER */
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static bool print_trace_address(void *arg, unsigned long pc)
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{
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const char *loglvl = arg;
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print_ip_sym(loglvl, pc);
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return true;
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}
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noinline void dump_backtrace(struct pt_regs *regs, struct task_struct *task,
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const char *loglvl)
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{
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walk_stackframe(task, regs, print_trace_address, (void *)loglvl);
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}
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void show_stack(struct task_struct *task, unsigned long *sp, const char *loglvl)
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{
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pr_cont("%sCall Trace:\n", loglvl);
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dump_backtrace(NULL, task, loglvl);
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}
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static bool save_wchan(void *arg, unsigned long pc)
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{
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if (!in_sched_functions(pc)) {
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unsigned long *p = arg;
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*p = pc;
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return false;
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}
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return true;
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}
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unsigned long __get_wchan(struct task_struct *task)
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{
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unsigned long pc = 0;
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if (!try_get_task_stack(task))
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return 0;
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walk_stackframe(task, NULL, save_wchan, &pc);
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put_task_stack(task);
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return pc;
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}
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noinline void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie,
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struct task_struct *task, struct pt_regs *regs)
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{
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walk_stackframe(task, regs, consume_entry, cookie);
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}
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