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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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039a7a30ec
If a user task's stack is empty, or if it only has user regs, ORC
reports it as a reliable empty stack. But arch_stack_walk_reliable()
incorrectly treats it as unreliable.
That happens because the only success path for user tasks is inside the
loop, which only iterates on non-empty stacks. Generally, a user task
must end in a user regs frame, but an empty stack is an exception to
that rule.
Thanks to commit 71c9582528 ("x86/unwind/orc: Fix error handling in
__unwind_start()"), unwind_start() now sets state->error appropriately.
So now for both ORC and FP unwinders, unwind_done() and !unwind_error()
always means the end of the stack was successfully reached. So the
success path for kthreads is no longer needed -- it can also be used for
empty user tasks.
Reported-by: Wang ShaoBo <bobo.shaobowang@huawei.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Wang ShaoBo <bobo.shaobowang@huawei.com>
Link: https://lkml.kernel.org/r/f136a4e5f019219cbc4f4da33b30c2f44fa65b84.1594994374.git.jpoimboe@redhat.com
137 lines
3.1 KiB
C
137 lines
3.1 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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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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struct unwind_state state;
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unsigned long addr;
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if (regs && !consume_entry(cookie, regs->ip, false))
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return;
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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 || !consume_entry(cookie, addr, false))
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break;
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}
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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 arch_stack_walk_reliable(stack_trace_consume_fn consume_entry,
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void *cookie, 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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return 0;
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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 (!consume_entry(cookie, 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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return 0;
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}
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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 struct stack_frame_user __user *fp,
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struct stack_frame_user *frame)
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{
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int ret;
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if (__range_not_ok(fp, sizeof(*frame), TASK_SIZE))
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return 0;
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ret = 1;
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pagefault_disable();
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if (__get_user(frame->next_fp, &fp->next_fp) ||
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__get_user(frame->ret_addr, &fp->ret_addr))
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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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void arch_stack_walk_user(stack_trace_consume_fn consume_entry, void *cookie,
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const struct pt_regs *regs)
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{
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const void __user *fp = (const void __user *)regs->bp;
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if (!consume_entry(cookie, regs->ip, false))
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return;
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while (1) {
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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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break;
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if (!consume_entry(cookie, frame.ret_addr, false))
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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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