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af085d9084
For live patching and possibly other use cases, a stack trace is only useful if it can be assured that it's completely reliable. Add a new save_stack_trace_tsk_reliable() function to achieve that. Note that if the target task isn't the current task, and the target task is allowed to run, then it could be writing the stack while the unwinder is reading it, resulting in possible corruption. So the caller of save_stack_trace_tsk_reliable() must ensure that the task is either 'current' or inactive. save_stack_trace_tsk_reliable() relies on the x86 unwinder's detection of pt_regs on the stack. If the pt_regs are not user-mode registers from a syscall, then they indicate an in-kernel interrupt or exception (e.g. preemption or a page fault), in which case the stack is considered unreliable due to the nature of frame pointers. It also relies on the x86 unwinder's detection of other issues, such as: - corrupted stack data - stack grows the wrong way - stack walk doesn't reach the bottom - user didn't provide a large enough entries array Such issues are reported by checking unwind_error() and !unwind_done(). Also add CONFIG_HAVE_RELIABLE_STACKTRACE so arch-independent code can determine at build time whether the function is implemented. Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Reviewed-by: Miroslav Benes <mbenes@suse.cz> Acked-by: Ingo Molnar <mingo@kernel.org> # for the x86 changes Signed-off-by: Jiri Kosina <jkosina@suse.cz>
84 lines
1.8 KiB
C
84 lines
1.8 KiB
C
#ifndef _ASM_X86_UNWIND_H
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#define _ASM_X86_UNWIND_H
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#include <linux/sched.h>
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#include <linux/ftrace.h>
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#include <asm/ptrace.h>
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#include <asm/stacktrace.h>
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struct unwind_state {
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struct stack_info stack_info;
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unsigned long stack_mask;
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struct task_struct *task;
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int graph_idx;
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bool error;
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#ifdef CONFIG_FRAME_POINTER
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unsigned long *bp, *orig_sp;
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struct pt_regs *regs;
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#else
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unsigned long *sp;
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#endif
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};
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void __unwind_start(struct unwind_state *state, struct task_struct *task,
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struct pt_regs *regs, unsigned long *first_frame);
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bool unwind_next_frame(struct unwind_state *state);
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unsigned long unwind_get_return_address(struct unwind_state *state);
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static inline bool unwind_done(struct unwind_state *state)
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{
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return state->stack_info.type == STACK_TYPE_UNKNOWN;
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}
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static inline
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void unwind_start(struct unwind_state *state, struct task_struct *task,
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struct pt_regs *regs, unsigned long *first_frame)
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{
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first_frame = first_frame ? : get_stack_pointer(task, regs);
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__unwind_start(state, task, regs, first_frame);
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}
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static inline bool unwind_error(struct unwind_state *state)
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{
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return state->error;
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}
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#ifdef CONFIG_FRAME_POINTER
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static inline
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unsigned long *unwind_get_return_address_ptr(struct unwind_state *state)
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{
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if (unwind_done(state))
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return NULL;
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return state->regs ? &state->regs->ip : state->bp + 1;
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}
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static inline struct pt_regs *unwind_get_entry_regs(struct unwind_state *state)
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{
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if (unwind_done(state))
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return NULL;
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return state->regs;
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}
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#else /* !CONFIG_FRAME_POINTER */
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static inline
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unsigned long *unwind_get_return_address_ptr(struct unwind_state *state)
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{
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return NULL;
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}
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static inline struct pt_regs *unwind_get_entry_regs(struct unwind_state *state)
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{
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return NULL;
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}
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#endif /* CONFIG_FRAME_POINTER */
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#endif /* _ASM_X86_UNWIND_H */
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