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0c414367c0
save_stack_trace_reliable now returns "non reliable" when there are kernel pt_regs on stack. This means an interrupt or exception happened somewhere down the route. It is a problem for the frame pointer unwinder, because the frame might not have been set up yet when the irq happened, so the unwinder might fail to unwind from the interrupted function. With ORC, this is not a problem, as ORC has out-of-band data. We can find ORC data even for the IP in the interrupted function and always unwind one level up reliably. So lift the check to apply only when CONFIG_FRAME_POINTER=y is enabled. Signed-off-by: Jiri Slaby <jslaby@suse.cz> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: https://lkml.kernel.org/lkml/20180518064713.26440-4-jslaby@suse.cz Signed-off-by: Ingo Molnar <mingo@kernel.org>
230 lines
5.2 KiB
C
230 lines
5.2 KiB
C
/*
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* Stack trace management functions
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*
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* Copyright (C) 2006-2009 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
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*/
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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/export.h>
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#include <linux/uaccess.h>
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#include <asm/stacktrace.h>
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#include <asm/unwind.h>
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static int save_stack_address(struct stack_trace *trace, unsigned long addr,
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bool nosched)
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{
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if (nosched && in_sched_functions(addr))
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return 0;
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if (trace->skip > 0) {
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trace->skip--;
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return 0;
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}
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if (trace->nr_entries >= trace->max_entries)
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return -1;
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trace->entries[trace->nr_entries++] = addr;
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return 0;
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}
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static void noinline __save_stack_trace(struct stack_trace *trace,
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struct task_struct *task, struct pt_regs *regs,
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bool nosched)
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{
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struct unwind_state state;
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unsigned long addr;
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if (regs)
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save_stack_address(trace, regs->ip, nosched);
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for (unwind_start(&state, task, regs, NULL); !unwind_done(&state);
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unwind_next_frame(&state)) {
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addr = unwind_get_return_address(&state);
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if (!addr || save_stack_address(trace, addr, nosched))
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break;
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}
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if (trace->nr_entries < trace->max_entries)
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trace->entries[trace->nr_entries++] = ULONG_MAX;
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}
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/*
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* Save stack-backtrace addresses into a stack_trace buffer.
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*/
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void save_stack_trace(struct stack_trace *trace)
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{
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trace->skip++;
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__save_stack_trace(trace, current, NULL, false);
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}
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EXPORT_SYMBOL_GPL(save_stack_trace);
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void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
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{
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__save_stack_trace(trace, current, regs, false);
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}
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void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
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{
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if (!try_get_task_stack(tsk))
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return;
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if (tsk == current)
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trace->skip++;
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__save_stack_trace(trace, tsk, NULL, true);
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put_task_stack(tsk);
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}
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EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
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#ifdef CONFIG_HAVE_RELIABLE_STACKTRACE
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static int __always_inline
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__save_stack_trace_reliable(struct stack_trace *trace,
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struct task_struct *task)
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{
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struct unwind_state state;
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struct pt_regs *regs;
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unsigned long addr;
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for (unwind_start(&state, task, NULL, NULL);
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!unwind_done(&state) && !unwind_error(&state);
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unwind_next_frame(&state)) {
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regs = unwind_get_entry_regs(&state, NULL);
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if (regs) {
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/* Success path for user tasks */
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if (user_mode(regs))
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goto success;
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/*
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* Kernel mode registers on the stack indicate an
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* in-kernel interrupt or exception (e.g., preemption
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* or a page fault), which can make frame pointers
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* unreliable.
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*/
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if (IS_ENABLED(CONFIG_FRAME_POINTER))
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return -EINVAL;
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}
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addr = unwind_get_return_address(&state);
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/*
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* A NULL or invalid return address probably means there's some
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* generated code which __kernel_text_address() doesn't know
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* about.
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*/
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if (!addr)
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return -EINVAL;
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if (save_stack_address(trace, addr, false))
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return -EINVAL;
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}
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/* Check for stack corruption */
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if (unwind_error(&state))
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return -EINVAL;
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/* Success path for non-user tasks, i.e. kthreads and idle tasks */
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if (!(task->flags & (PF_KTHREAD | PF_IDLE)))
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return -EINVAL;
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success:
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if (trace->nr_entries < trace->max_entries)
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trace->entries[trace->nr_entries++] = ULONG_MAX;
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return 0;
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}
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/*
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* This function returns an error if it detects any unreliable features of the
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* stack. Otherwise it guarantees that the stack trace is reliable.
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*
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* If the task is not 'current', the caller *must* ensure the task is inactive.
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*/
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int save_stack_trace_tsk_reliable(struct task_struct *tsk,
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struct stack_trace *trace)
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{
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int ret;
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/*
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* If the task doesn't have a stack (e.g., a zombie), the stack is
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* "reliably" empty.
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*/
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if (!try_get_task_stack(tsk))
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return 0;
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ret = __save_stack_trace_reliable(trace, tsk);
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put_task_stack(tsk);
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return ret;
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}
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#endif /* CONFIG_HAVE_RELIABLE_STACKTRACE */
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/* Userspace stacktrace - based on kernel/trace/trace_sysprof.c */
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struct stack_frame_user {
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const void __user *next_fp;
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unsigned long ret_addr;
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};
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static int
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copy_stack_frame(const void __user *fp, struct stack_frame_user *frame)
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{
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int ret;
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if (!access_ok(VERIFY_READ, fp, sizeof(*frame)))
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return 0;
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ret = 1;
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pagefault_disable();
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if (__copy_from_user_inatomic(frame, fp, sizeof(*frame)))
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ret = 0;
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pagefault_enable();
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return ret;
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}
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static inline void __save_stack_trace_user(struct stack_trace *trace)
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{
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const struct pt_regs *regs = task_pt_regs(current);
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const void __user *fp = (const void __user *)regs->bp;
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if (trace->nr_entries < trace->max_entries)
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trace->entries[trace->nr_entries++] = regs->ip;
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while (trace->nr_entries < trace->max_entries) {
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struct stack_frame_user frame;
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frame.next_fp = NULL;
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frame.ret_addr = 0;
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if (!copy_stack_frame(fp, &frame))
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break;
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if ((unsigned long)fp < regs->sp)
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break;
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if (frame.ret_addr) {
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trace->entries[trace->nr_entries++] =
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frame.ret_addr;
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}
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if (fp == frame.next_fp)
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break;
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fp = frame.next_fp;
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}
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}
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void save_stack_trace_user(struct stack_trace *trace)
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{
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/*
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* Trace user stack if we are not a kernel thread
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*/
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if (current->mm) {
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__save_stack_trace_user(trace);
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}
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if (trace->nr_entries < trace->max_entries)
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trace->entries[trace->nr_entries++] = ULONG_MAX;
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}
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