linux/arch/x86/kernel/unwind_guess.c
Josh Poimboeuf 55f856e640 x86/unwind: Fix guess-unwinder regression
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>
2016-11-28 07:47:54 +01:00

68 lines
1.6 KiB
C

#include <linux/sched.h>
#include <linux/ftrace.h>
#include <asm/ptrace.h>
#include <asm/bitops.h>
#include <asm/stacktrace.h>
#include <asm/unwind.h>
unsigned long unwind_get_return_address(struct unwind_state *state)
{
unsigned long addr;
if (unwind_done(state))
return 0;
addr = READ_ONCE_NOCHECK(*state->sp);
return ftrace_graph_ret_addr(state->task, &state->graph_idx,
addr, state->sp);
}
EXPORT_SYMBOL_GPL(unwind_get_return_address);
bool unwind_next_frame(struct unwind_state *state)
{
struct stack_info *info = &state->stack_info;
if (unwind_done(state))
return false;
do {
for (state->sp++; state->sp < info->end; state->sp++) {
unsigned long addr = READ_ONCE_NOCHECK(*state->sp);
if (__kernel_text_address(addr))
return true;
}
state->sp = info->next_sp;
} while (!get_stack_info(state->sp, state->task, info,
&state->stack_mask));
return false;
}
EXPORT_SYMBOL_GPL(unwind_next_frame);
void __unwind_start(struct unwind_state *state, struct task_struct *task,
struct pt_regs *regs, unsigned long *first_frame)
{
memset(state, 0, sizeof(*state));
state->task = task;
state->sp = first_frame;
get_stack_info(first_frame, state->task, &state->stack_info,
&state->stack_mask);
/*
* The caller can provide the address of the first frame directly
* (first_frame) or indirectly (regs->sp) to indicate which stack frame
* to start unwinding at. Skip ahead until we reach it.
*/
if (!unwind_done(state) &&
(!on_stack(&state->stack_info, first_frame, sizeof(long)) ||
!__kernel_text_address(*first_frame)))
unwind_next_frame(state);
}
EXPORT_SYMBOL_GPL(__unwind_start);