perf/x86/hw_breakpoints: Disallow kernel breakpoints unless kprobe-safe (e5779e8e) · Commits · 戴 / test

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:

Andy Lutomirski <luto@kernel.org> Signed-off-by:

Peter 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:

Ingo Molnar <mingo@kernel.org>

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;

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