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Commit e5779e8e authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Ingo Molnar
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perf/x86/hw_breakpoints: Disallow kernel breakpoints unless kprobe-safe 



Code on the kprobe blacklist doesn't want unexpected int3
exceptions. It probably doesn't want unexpected debug exceptions
either. Be safe: disallow breakpoints in nokprobes code.

On non-CONFIG_KPROBES kernels, there is no kprobe blacklist.  In
that case, disallow kernel breakpoints entirely.

It will be particularly important to keep hw breakpoints out of the
entry and NMI code once we move debug exceptions off the IST stack.

Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.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/e14b152af99640448d895e3c2a8c2d5ee19a1325.1438312874.git.luto@kernel.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent ae3f011f

arch/x86/kernel/hw_breakpoint.c

+15 −0
Original line number Diff line number Diff line
@@ -32,6 +32,7 @@ 
#include <linux/irqflags.h>

#include <linux/notifier.h>

#include <linux/kallsyms.h>

#include <linux/kprobes.h>

#include <linux/percpu.h>

#include <linux/kdebug.h>

#include <linux/kernel.h>
@@ -243,6 +244,20 @@ static int arch_build_bp_info(struct perf_event *bp) 
		info->type = X86_BREAKPOINT_RW;

		break;

	case HW_BREAKPOINT_X:

		/*

		 * We don't allow kernel breakpoints in places that are not

		 * acceptable for kprobes.  On non-kprobes kernels, we don't

		 * allow kernel breakpoints at all.

		 */

		if (bp->attr.bp_addr >= TASK_SIZE_MAX) {

#ifdef CONFIG_KPROBES

			if (within_kprobe_blacklist(bp->attr.bp_addr))

				return -EINVAL;

#else

			return -EINVAL;

#endif

		}



		info->type = X86_BREAKPOINT_EXECUTE;

		/*

		 * x86 inst breakpoints need to have a specific undefined len.

include/linux/kprobes.h

+2 −0
Original line number Diff line number Diff line
@@ -267,6 +267,8 @@ extern void show_registers(struct pt_regs *regs); 
extern void kprobes_inc_nmissed_count(struct kprobe *p);

extern bool arch_within_kprobe_blacklist(unsigned long addr);



extern bool within_kprobe_blacklist(unsigned long addr);



struct kprobe_insn_cache {

	struct mutex mutex;

	void *(*alloc)(void);	/* allocate insn page */

kernel/kprobes.c

+1 −1
Original line number Diff line number Diff line
@@ -1332,7 +1332,7 @@ bool __weak arch_within_kprobe_blacklist(unsigned long addr) 
	       addr < (unsigned long)__kprobes_text_end;

}



static bool within_kprobe_blacklist(unsigned long addr)

bool within_kprobe_blacklist(unsigned long addr)

{

	struct kprobe_blacklist_entry *ent;