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Commit 4cdf77a8 authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Ingo Molnar
Browse files

x86/kprobes: Fix build errors and blacklist context_track_user 



This essentially reverts commit:

  ecd50f71 ("kprobes, x86: Call exception_enter after kprobes handled")

since it causes build errors with CONFIG_CONTEXT_TRACKING and
that has been made from misunderstandings;
context_track_user_*() don't involve much in interrupt context,
it just returns if in_interrupt() is true.

Instead of changing the do_debug/int3(), this just adds
context_track_user_*() to kprobes blacklist, since those are
still can be called right before kprobes handles int3 and debug
exceptions, and probing those will cause an infinite loop.

Reported-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: default avatarMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Kees Cook <keescook@chromium.org>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Seiji Aguchi <seiji.aguchi@hds.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Kees Cook <keescook@chromium.org>
Link: http://lkml.kernel.org/r/20140614064711.7865.45957.stgit@kbuild-fedora.novalocal


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent ed9ea4ed

arch/x86/kernel/traps.c

+4 −3
Original line number Diff line number Diff line
@@ -343,6 +343,7 @@ dotraplinkage void notrace do_int3(struct pt_regs *regs, long error_code) 
	if (poke_int3_handler(regs))

		return;



	prev_state = exception_enter();

#ifdef CONFIG_KGDB_LOW_LEVEL_TRAP

	if (kgdb_ll_trap(DIE_INT3, "int3", regs, error_code, X86_TRAP_BP,

				SIGTRAP) == NOTIFY_STOP)
@@ -351,9 +352,8 @@ dotraplinkage void notrace do_int3(struct pt_regs *regs, long error_code) 


#ifdef CONFIG_KPROBES

	if (kprobe_int3_handler(regs))

		return;

		goto exit;

#endif

	prev_state = exception_enter();



	if (notify_die(DIE_INT3, "int3", regs, error_code, X86_TRAP_BP,

			SIGTRAP) == NOTIFY_STOP)
@@ -433,6 +433,8 @@ dotraplinkage void do_debug(struct pt_regs *regs, long error_code) 
	unsigned long dr6;

	int si_code;



	prev_state = exception_enter();



	get_debugreg(dr6, 6);



	/* Filter out all the reserved bits which are preset to 1 */
@@ -465,7 +467,6 @@ dotraplinkage void do_debug(struct pt_regs *regs, long error_code) 
	if (kprobe_debug_handler(regs))

		goto exit;

#endif

	prev_state = exception_enter();



	if (notify_die(DIE_DEBUG, "debug", regs, (long)&dr6, error_code,

							SIGTRAP) == NOTIFY_STOP)

kernel/context_tracking.c

+3 −0
Original line number Diff line number Diff line
@@ -19,6 +19,7 @@ 
#include <linux/sched.h>

#include <linux/hardirq.h>

#include <linux/export.h>

#include <linux/kprobes.h>



#define CREATE_TRACE_POINTS

#include <trace/events/context_tracking.h>
@@ -104,6 +105,7 @@ void context_tracking_user_enter(void) 
	}

	local_irq_restore(flags);

}

NOKPROBE_SYMBOL(context_tracking_user_enter);



#ifdef CONFIG_PREEMPT

/**
@@ -181,6 +183,7 @@ void context_tracking_user_exit(void) 
	}

	local_irq_restore(flags);

}

NOKPROBE_SYMBOL(context_tracking_user_exit);



/**

 * __context_tracking_task_switch - context switch the syscall callbacks