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55f856e640
My attempt at fixing some KASAN false positive warnings was rather brain
dead, and it broke the guess unwinder. With frame pointers disabled,
/proc/<pid>/stack is broken:
# cat /proc/1/stack
[<ffffffffffffffff>] 0xffffffffffffffff
Restore the code flow to more closely resemble its previous state, while
still using READ_ONCE_NOCHECK() macros to silence KASAN false positives.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: c2d75e03d6 ("x86/unwind: Prevent KASAN false positive warnings in guess unwinder")
Link: http://lkml.kernel.org/r/b824f92c2c22eca5ec95ac56bd2a7c84cf0b9df9.1480309971.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
68 lines
1.6 KiB
C
68 lines
1.6 KiB
C
#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/bitops.h>
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#include <asm/stacktrace.h>
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#include <asm/unwind.h>
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unsigned long unwind_get_return_address(struct unwind_state *state)
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{
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unsigned long addr;
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if (unwind_done(state))
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return 0;
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addr = READ_ONCE_NOCHECK(*state->sp);
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return ftrace_graph_ret_addr(state->task, &state->graph_idx,
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addr, state->sp);
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}
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EXPORT_SYMBOL_GPL(unwind_get_return_address);
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bool unwind_next_frame(struct unwind_state *state)
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{
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struct stack_info *info = &state->stack_info;
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if (unwind_done(state))
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return false;
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do {
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for (state->sp++; state->sp < info->end; state->sp++) {
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unsigned long addr = READ_ONCE_NOCHECK(*state->sp);
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if (__kernel_text_address(addr))
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return true;
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}
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state->sp = info->next_sp;
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} while (!get_stack_info(state->sp, state->task, info,
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&state->stack_mask));
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return false;
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}
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EXPORT_SYMBOL_GPL(unwind_next_frame);
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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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memset(state, 0, sizeof(*state));
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state->task = task;
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state->sp = first_frame;
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get_stack_info(first_frame, state->task, &state->stack_info,
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&state->stack_mask);
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/*
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* The caller can provide the address of the first frame directly
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* (first_frame) or indirectly (regs->sp) to indicate which stack frame
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* to start unwinding at. Skip ahead until we reach it.
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*/
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if (!unwind_done(state) &&
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(!on_stack(&state->stack_info, first_frame, sizeof(long)) ||
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!__kernel_text_address(*first_frame)))
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unwind_next_frame(state);
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}
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EXPORT_SYMBOL_GPL(__unwind_start);
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