linux/arch/x86/include/asm/unwind.h

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x86/unwind: Add new unwind interface and implementations The x86 stack dump code is a bit of a mess. dump_trace() uses callbacks, and each user of it seems to have slightly different requirements, so there are several slightly different callbacks floating around. Also there are some upcoming features which will need more changes to the stack dump code, including the printing of stack pt_regs, reliable stack detection for live patching, and a DWARF unwinder. Each of those features would at least need more callbacks and/or callback interfaces, resulting in a much bigger mess than what we have today. Before doing all that, we should try to clean things up and replace dump_trace() with something cleaner and more flexible. The new unwinder is a simple state machine which was heavily inspired by a suggestion from Andy Lutomirski: https://lkml.kernel.org/r/CALCETrUbNTqaM2LRyXGRx=kVLRPeY5A3Pc6k4TtQxF320rUT=w@mail.gmail.com It's also similar to the libunwind API: http://www.nongnu.org/libunwind/man/libunwind(3).html Some if its advantages: - Simplicity: no more callback sprawl and less code duplication. - Flexibility: it allows the caller to stop and inspect the stack state at each step in the unwinding process. - Modularity: the unwinder code, console stack dump code, and stack metadata analysis code are all better separated so that changing one of them shouldn't have much of an impact on any of the others. Two implementations are added which conform to the new unwind interface: - The frame pointer unwinder which is used for CONFIG_FRAME_POINTER=y. - The "guess" unwinder which is used for CONFIG_FRAME_POINTER=n. This isn't an "unwinder" per se. All it does is scan the stack for kernel text addresses. But with no frame pointers, guesses are better than nothing in most cases. Suggested-by: Andy Lutomirski <luto@amacapital.net> Signed-off-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: Byungchul Park <byungchul.park@lge.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Kees Cook <keescook@chromium.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Nilay Vaish <nilayvaish@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/6dc2f909c47533d213d0505f0a113e64585bec82.1474045023.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-09-16 19:18:12 +00:00
#ifndef _ASM_X86_UNWIND_H
#define _ASM_X86_UNWIND_H
#include <linux/sched.h>
#include <linux/ftrace.h>
#include <asm/ptrace.h>
#include <asm/stacktrace.h>
struct unwind_state {
struct stack_info stack_info;
unsigned long stack_mask;
struct task_struct *task;
int graph_idx;
stacktrace/x86: add function for detecting reliable stack traces 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>
2017-02-14 01:42:28 +00:00
bool error;
x86/unwind: Add new unwind interface and implementations The x86 stack dump code is a bit of a mess. dump_trace() uses callbacks, and each user of it seems to have slightly different requirements, so there are several slightly different callbacks floating around. Also there are some upcoming features which will need more changes to the stack dump code, including the printing of stack pt_regs, reliable stack detection for live patching, and a DWARF unwinder. Each of those features would at least need more callbacks and/or callback interfaces, resulting in a much bigger mess than what we have today. Before doing all that, we should try to clean things up and replace dump_trace() with something cleaner and more flexible. The new unwinder is a simple state machine which was heavily inspired by a suggestion from Andy Lutomirski: https://lkml.kernel.org/r/CALCETrUbNTqaM2LRyXGRx=kVLRPeY5A3Pc6k4TtQxF320rUT=w@mail.gmail.com It's also similar to the libunwind API: http://www.nongnu.org/libunwind/man/libunwind(3).html Some if its advantages: - Simplicity: no more callback sprawl and less code duplication. - Flexibility: it allows the caller to stop and inspect the stack state at each step in the unwinding process. - Modularity: the unwinder code, console stack dump code, and stack metadata analysis code are all better separated so that changing one of them shouldn't have much of an impact on any of the others. Two implementations are added which conform to the new unwind interface: - The frame pointer unwinder which is used for CONFIG_FRAME_POINTER=y. - The "guess" unwinder which is used for CONFIG_FRAME_POINTER=n. This isn't an "unwinder" per se. All it does is scan the stack for kernel text addresses. But with no frame pointers, guesses are better than nothing in most cases. Suggested-by: Andy Lutomirski <luto@amacapital.net> Signed-off-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: Byungchul Park <byungchul.park@lge.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Kees Cook <keescook@chromium.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Nilay Vaish <nilayvaish@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/6dc2f909c47533d213d0505f0a113e64585bec82.1474045023.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-09-16 19:18:12 +00:00
#ifdef CONFIG_FRAME_POINTER
x86/unwind: Silence entry-related warnings A few people have reported unwinder warnings like the following: WARNING: kernel stack frame pointer at ffffc90000fe7ff0 in rsync:1157 has bad value (null) unwind stack type:0 next_sp: (null) mask:2 graph_idx:0 ffffc90000fe7f98: ffffc90000fe7ff0 (0xffffc90000fe7ff0) ffffc90000fe7fa0: ffffffffb7000f56 (trace_hardirqs_off_thunk+0x1a/0x1c) ffffc90000fe7fa8: 0000000000000246 (0x246) ffffc90000fe7fb0: 0000000000000000 ... ffffc90000fe7fc0: 00007ffe3af639bc (0x7ffe3af639bc) ffffc90000fe7fc8: 0000000000000006 (0x6) ffffc90000fe7fd0: 00007f80af433fc5 (0x7f80af433fc5) ffffc90000fe7fd8: 00007ffe3af638e0 (0x7ffe3af638e0) ffffc90000fe7fe0: 00007ffe3af638e0 (0x7ffe3af638e0) ffffc90000fe7fe8: 00007ffe3af63970 (0x7ffe3af63970) ffffc90000fe7ff0: 0000000000000000 ... ffffc90000fe7ff8: ffffffffb7b74b9a (entry_SYSCALL_64_after_swapgs+0x17/0x4f) This warning can happen when unwinding a code path where an interrupt occurred in x86 entry code before it set up the first stack frame. Silently ignore any warnings for this case. Reported-by: Daniel Borkmann <daniel@iogearbox.net> Reported-by: Dave Jones <davej@codemonkey.org.uk> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Acked-by: Thomas Gleixner <tglx@linutronix.de> 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> Fixes: c32c47c68a0a ("x86/unwind: Warn on bad frame pointer") Link: http://lkml.kernel.org/r/dbd6838826466a60dc23a52098185bc973ce2f1e.1492020577.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-04-12 18:47:12 +00:00
bool got_irq;
unsigned long *bp, *orig_sp;
x86/entry/unwind: Create stack frames for saved interrupt registers With frame pointers, when a task is interrupted, its stack is no longer completely reliable because the function could have been interrupted before it had a chance to save the previous frame pointer on the stack. So the caller of the interrupted function could get skipped by a stack trace. This is problematic for live patching, which needs to know whether a stack trace of a sleeping task can be relied upon. There's currently no way to detect if a sleeping task was interrupted by a page fault exception or preemption before it went to sleep. Another issue is that when dumping the stack of an interrupted task, the unwinder has no way of knowing where the saved pt_regs registers are, so it can't print them. This solves those issues by encoding the pt_regs pointer in the frame pointer on entry from an interrupt or an exception. This patch also updates the unwinder to be able to decode it, because otherwise the unwinder would be broken by this change. Note that this causes a change in the behavior of the unwinder: each instance of a pt_regs on the stack is now considered a "frame". So callers of unwind_get_return_address() will now get an occasional 'regs->ip' address that would have previously been skipped over. Suggested-by: Andy Lutomirski <luto@amacapital.net> Signed-off-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: http://lkml.kernel.org/r/8b9f84a21e39d249049e0547b559ff8da0df0988.1476973742.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-10-20 16:34:40 +00:00
struct pt_regs *regs;
unsigned long ip;
x86/unwind: Add new unwind interface and implementations The x86 stack dump code is a bit of a mess. dump_trace() uses callbacks, and each user of it seems to have slightly different requirements, so there are several slightly different callbacks floating around. Also there are some upcoming features which will need more changes to the stack dump code, including the printing of stack pt_regs, reliable stack detection for live patching, and a DWARF unwinder. Each of those features would at least need more callbacks and/or callback interfaces, resulting in a much bigger mess than what we have today. Before doing all that, we should try to clean things up and replace dump_trace() with something cleaner and more flexible. The new unwinder is a simple state machine which was heavily inspired by a suggestion from Andy Lutomirski: https://lkml.kernel.org/r/CALCETrUbNTqaM2LRyXGRx=kVLRPeY5A3Pc6k4TtQxF320rUT=w@mail.gmail.com It's also similar to the libunwind API: http://www.nongnu.org/libunwind/man/libunwind(3).html Some if its advantages: - Simplicity: no more callback sprawl and less code duplication. - Flexibility: it allows the caller to stop and inspect the stack state at each step in the unwinding process. - Modularity: the unwinder code, console stack dump code, and stack metadata analysis code are all better separated so that changing one of them shouldn't have much of an impact on any of the others. Two implementations are added which conform to the new unwind interface: - The frame pointer unwinder which is used for CONFIG_FRAME_POINTER=y. - The "guess" unwinder which is used for CONFIG_FRAME_POINTER=n. This isn't an "unwinder" per se. All it does is scan the stack for kernel text addresses. But with no frame pointers, guesses are better than nothing in most cases. Suggested-by: Andy Lutomirski <luto@amacapital.net> Signed-off-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: Byungchul Park <byungchul.park@lge.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Kees Cook <keescook@chromium.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Nilay Vaish <nilayvaish@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/6dc2f909c47533d213d0505f0a113e64585bec82.1474045023.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-09-16 19:18:12 +00:00
#else
unsigned long *sp;
#endif
};
void __unwind_start(struct unwind_state *state, struct task_struct *task,
struct pt_regs *regs, unsigned long *first_frame);
bool unwind_next_frame(struct unwind_state *state);
unsigned long unwind_get_return_address(struct unwind_state *state);
x86/unwind: Add new unwind interface and implementations The x86 stack dump code is a bit of a mess. dump_trace() uses callbacks, and each user of it seems to have slightly different requirements, so there are several slightly different callbacks floating around. Also there are some upcoming features which will need more changes to the stack dump code, including the printing of stack pt_regs, reliable stack detection for live patching, and a DWARF unwinder. Each of those features would at least need more callbacks and/or callback interfaces, resulting in a much bigger mess than what we have today. Before doing all that, we should try to clean things up and replace dump_trace() with something cleaner and more flexible. The new unwinder is a simple state machine which was heavily inspired by a suggestion from Andy Lutomirski: https://lkml.kernel.org/r/CALCETrUbNTqaM2LRyXGRx=kVLRPeY5A3Pc6k4TtQxF320rUT=w@mail.gmail.com It's also similar to the libunwind API: http://www.nongnu.org/libunwind/man/libunwind(3).html Some if its advantages: - Simplicity: no more callback sprawl and less code duplication. - Flexibility: it allows the caller to stop and inspect the stack state at each step in the unwinding process. - Modularity: the unwinder code, console stack dump code, and stack metadata analysis code are all better separated so that changing one of them shouldn't have much of an impact on any of the others. Two implementations are added which conform to the new unwind interface: - The frame pointer unwinder which is used for CONFIG_FRAME_POINTER=y. - The "guess" unwinder which is used for CONFIG_FRAME_POINTER=n. This isn't an "unwinder" per se. All it does is scan the stack for kernel text addresses. But with no frame pointers, guesses are better than nothing in most cases. Suggested-by: Andy Lutomirski <luto@amacapital.net> Signed-off-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: Byungchul Park <byungchul.park@lge.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Kees Cook <keescook@chromium.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Nilay Vaish <nilayvaish@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/6dc2f909c47533d213d0505f0a113e64585bec82.1474045023.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-09-16 19:18:12 +00:00
static inline bool unwind_done(struct unwind_state *state)
{
return state->stack_info.type == STACK_TYPE_UNKNOWN;
}
static inline
void unwind_start(struct unwind_state *state, struct task_struct *task,
struct pt_regs *regs, unsigned long *first_frame)
{
first_frame = first_frame ? : get_stack_pointer(task, regs);
__unwind_start(state, task, regs, first_frame);
}
stacktrace/x86: add function for detecting reliable stack traces 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>
2017-02-14 01:42:28 +00:00
static inline bool unwind_error(struct unwind_state *state)
{
return state->error;
}
x86/unwind: Add new unwind interface and implementations The x86 stack dump code is a bit of a mess. dump_trace() uses callbacks, and each user of it seems to have slightly different requirements, so there are several slightly different callbacks floating around. Also there are some upcoming features which will need more changes to the stack dump code, including the printing of stack pt_regs, reliable stack detection for live patching, and a DWARF unwinder. Each of those features would at least need more callbacks and/or callback interfaces, resulting in a much bigger mess than what we have today. Before doing all that, we should try to clean things up and replace dump_trace() with something cleaner and more flexible. The new unwinder is a simple state machine which was heavily inspired by a suggestion from Andy Lutomirski: https://lkml.kernel.org/r/CALCETrUbNTqaM2LRyXGRx=kVLRPeY5A3Pc6k4TtQxF320rUT=w@mail.gmail.com It's also similar to the libunwind API: http://www.nongnu.org/libunwind/man/libunwind(3).html Some if its advantages: - Simplicity: no more callback sprawl and less code duplication. - Flexibility: it allows the caller to stop and inspect the stack state at each step in the unwinding process. - Modularity: the unwinder code, console stack dump code, and stack metadata analysis code are all better separated so that changing one of them shouldn't have much of an impact on any of the others. Two implementations are added which conform to the new unwind interface: - The frame pointer unwinder which is used for CONFIG_FRAME_POINTER=y. - The "guess" unwinder which is used for CONFIG_FRAME_POINTER=n. This isn't an "unwinder" per se. All it does is scan the stack for kernel text addresses. But with no frame pointers, guesses are better than nothing in most cases. Suggested-by: Andy Lutomirski <luto@amacapital.net> Signed-off-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: Byungchul Park <byungchul.park@lge.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Kees Cook <keescook@chromium.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Nilay Vaish <nilayvaish@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/6dc2f909c47533d213d0505f0a113e64585bec82.1474045023.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-09-16 19:18:12 +00:00
#ifdef CONFIG_FRAME_POINTER
static inline
unsigned long *unwind_get_return_address_ptr(struct unwind_state *state)
{
if (unwind_done(state))
return NULL;
x86/entry/unwind: Create stack frames for saved interrupt registers With frame pointers, when a task is interrupted, its stack is no longer completely reliable because the function could have been interrupted before it had a chance to save the previous frame pointer on the stack. So the caller of the interrupted function could get skipped by a stack trace. This is problematic for live patching, which needs to know whether a stack trace of a sleeping task can be relied upon. There's currently no way to detect if a sleeping task was interrupted by a page fault exception or preemption before it went to sleep. Another issue is that when dumping the stack of an interrupted task, the unwinder has no way of knowing where the saved pt_regs registers are, so it can't print them. This solves those issues by encoding the pt_regs pointer in the frame pointer on entry from an interrupt or an exception. This patch also updates the unwinder to be able to decode it, because otherwise the unwinder would be broken by this change. Note that this causes a change in the behavior of the unwinder: each instance of a pt_regs on the stack is now considered a "frame". So callers of unwind_get_return_address() will now get an occasional 'regs->ip' address that would have previously been skipped over. Suggested-by: Andy Lutomirski <luto@amacapital.net> Signed-off-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: http://lkml.kernel.org/r/8b9f84a21e39d249049e0547b559ff8da0df0988.1476973742.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-10-20 16:34:40 +00:00
return state->regs ? &state->regs->ip : state->bp + 1;
}
static inline struct pt_regs *unwind_get_entry_regs(struct unwind_state *state)
{
if (unwind_done(state))
return NULL;
return state->regs;
x86/unwind: Add new unwind interface and implementations The x86 stack dump code is a bit of a mess. dump_trace() uses callbacks, and each user of it seems to have slightly different requirements, so there are several slightly different callbacks floating around. Also there are some upcoming features which will need more changes to the stack dump code, including the printing of stack pt_regs, reliable stack detection for live patching, and a DWARF unwinder. Each of those features would at least need more callbacks and/or callback interfaces, resulting in a much bigger mess than what we have today. Before doing all that, we should try to clean things up and replace dump_trace() with something cleaner and more flexible. The new unwinder is a simple state machine which was heavily inspired by a suggestion from Andy Lutomirski: https://lkml.kernel.org/r/CALCETrUbNTqaM2LRyXGRx=kVLRPeY5A3Pc6k4TtQxF320rUT=w@mail.gmail.com It's also similar to the libunwind API: http://www.nongnu.org/libunwind/man/libunwind(3).html Some if its advantages: - Simplicity: no more callback sprawl and less code duplication. - Flexibility: it allows the caller to stop and inspect the stack state at each step in the unwinding process. - Modularity: the unwinder code, console stack dump code, and stack metadata analysis code are all better separated so that changing one of them shouldn't have much of an impact on any of the others. Two implementations are added which conform to the new unwind interface: - The frame pointer unwinder which is used for CONFIG_FRAME_POINTER=y. - The "guess" unwinder which is used for CONFIG_FRAME_POINTER=n. This isn't an "unwinder" per se. All it does is scan the stack for kernel text addresses. But with no frame pointers, guesses are better than nothing in most cases. Suggested-by: Andy Lutomirski <luto@amacapital.net> Signed-off-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: Byungchul Park <byungchul.park@lge.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Kees Cook <keescook@chromium.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Nilay Vaish <nilayvaish@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/6dc2f909c47533d213d0505f0a113e64585bec82.1474045023.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-09-16 19:18:12 +00:00
}
#else /* !CONFIG_FRAME_POINTER */
static inline
unsigned long *unwind_get_return_address_ptr(struct unwind_state *state)
{
return NULL;
}
x86/entry/unwind: Create stack frames for saved interrupt registers With frame pointers, when a task is interrupted, its stack is no longer completely reliable because the function could have been interrupted before it had a chance to save the previous frame pointer on the stack. So the caller of the interrupted function could get skipped by a stack trace. This is problematic for live patching, which needs to know whether a stack trace of a sleeping task can be relied upon. There's currently no way to detect if a sleeping task was interrupted by a page fault exception or preemption before it went to sleep. Another issue is that when dumping the stack of an interrupted task, the unwinder has no way of knowing where the saved pt_regs registers are, so it can't print them. This solves those issues by encoding the pt_regs pointer in the frame pointer on entry from an interrupt or an exception. This patch also updates the unwinder to be able to decode it, because otherwise the unwinder would be broken by this change. Note that this causes a change in the behavior of the unwinder: each instance of a pt_regs on the stack is now considered a "frame". So callers of unwind_get_return_address() will now get an occasional 'regs->ip' address that would have previously been skipped over. Suggested-by: Andy Lutomirski <luto@amacapital.net> Signed-off-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: http://lkml.kernel.org/r/8b9f84a21e39d249049e0547b559ff8da0df0988.1476973742.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-10-20 16:34:40 +00:00
static inline struct pt_regs *unwind_get_entry_regs(struct unwind_state *state)
{
return NULL;
}
x86/unwind: Add new unwind interface and implementations The x86 stack dump code is a bit of a mess. dump_trace() uses callbacks, and each user of it seems to have slightly different requirements, so there are several slightly different callbacks floating around. Also there are some upcoming features which will need more changes to the stack dump code, including the printing of stack pt_regs, reliable stack detection for live patching, and a DWARF unwinder. Each of those features would at least need more callbacks and/or callback interfaces, resulting in a much bigger mess than what we have today. Before doing all that, we should try to clean things up and replace dump_trace() with something cleaner and more flexible. The new unwinder is a simple state machine which was heavily inspired by a suggestion from Andy Lutomirski: https://lkml.kernel.org/r/CALCETrUbNTqaM2LRyXGRx=kVLRPeY5A3Pc6k4TtQxF320rUT=w@mail.gmail.com It's also similar to the libunwind API: http://www.nongnu.org/libunwind/man/libunwind(3).html Some if its advantages: - Simplicity: no more callback sprawl and less code duplication. - Flexibility: it allows the caller to stop and inspect the stack state at each step in the unwinding process. - Modularity: the unwinder code, console stack dump code, and stack metadata analysis code are all better separated so that changing one of them shouldn't have much of an impact on any of the others. Two implementations are added which conform to the new unwind interface: - The frame pointer unwinder which is used for CONFIG_FRAME_POINTER=y. - The "guess" unwinder which is used for CONFIG_FRAME_POINTER=n. This isn't an "unwinder" per se. All it does is scan the stack for kernel text addresses. But with no frame pointers, guesses are better than nothing in most cases. Suggested-by: Andy Lutomirski <luto@amacapital.net> Signed-off-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: Byungchul Park <byungchul.park@lge.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Kees Cook <keescook@chromium.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Nilay Vaish <nilayvaish@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/6dc2f909c47533d213d0505f0a113e64585bec82.1474045023.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-09-16 19:18:12 +00:00
#endif /* CONFIG_FRAME_POINTER */
#endif /* _ASM_X86_UNWIND_H */