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From: Jiri Olsa <jolsa@kernel.org>
To: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: lkml <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@kernel.org>,
	Namhyung Kim <namhyung@kernel.org>,
	David Ahern <dsahern@gmail.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Milind Chabbi <chabbi.milind@gmail.com>,
	Oleg Nesterov <oleg@redhat.com>,
	Frederic Weisbecker <frederic@kernel.org>
Subject: [PATCH 5/5] perf/hw_breakpoint: Add fallback code for ptrace_set_breakpoint_addr
Date: Thu,  9 Aug 2018 14:03:05 +0200	[thread overview]
Message-ID: <20180809120305.20693-6-jolsa@kernel.org> (raw)
In-Reply-To: <20180809120305.20693-1-jolsa@kernel.org>

Restoring the breakpoint after unsuccesfull address change,
so following user code no longer produces disabled breakpoint.

  ptrace(PTRACE_POKEUSER, child, offsetof(struct user, u_debugreg[0]), addr_1)
  ptrace(PTRACE_POKEUSER, child, offsetof(struct user, u_debugreg[7]), dr7)
  ptrace(PTRACE_POKEUSER, child, offsetof(struct user, u_debugreg[0]), -1)

The first 2 ptrace calls set breakpoint on addr_1. The 3rd ptrace
call tries to set it to bogus address (-1). This would normaly
end up with disabled breakpoint. This patch adds the code that
restores the breakpoint to its original state.

Link: http://lkml.kernel.org/n/tip-h9ut835vl297roen0v163zg6@git.kernel.org
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 arch/x86/kernel/ptrace.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index e2ee403865eb..22c06d0a38d1 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -693,9 +693,14 @@ static int ptrace_set_breakpoint_addr(struct task_struct *tsk, int nr,
 			t->ptrace_bps[nr] = bp;
 	} else {
 		struct perf_event_attr attr = bp->attr;
+		bool disabled = attr.disabled;
 
 		attr.bp_addr = addr;
 		err = modify_user_hw_breakpoint(bp, &attr);
+		if (err && !disabled) {
+			bp->attr.disabled = false;
+			WARN_ON(modify_user_hw_breakpoint(bp, &bp->attr));
+		}
 	}
 
 	return err;
-- 
2.17.1


  parent reply	other threads:[~2018-08-09 12:03 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-09 12:03 [PATCHv2 0/5] perf/hw_breakpoint: Fix breakpoint modify Jiri Olsa
2018-08-09 12:03 ` [PATCH 1/5] perf tests: Add breakpoint modify tests Jiri Olsa
2018-08-09 12:03 ` [PATCH 2/5] perf/hw_breakpoint: Modify breakpoint even if the new attr has disabled set Jiri Olsa
2018-08-09 12:03 ` [PATCH 3/5] perf/hw_breakpoint: Remove superfluous bp->attr.disabled = 0 Jiri Olsa
2018-08-09 13:59   ` Oleg Nesterov
2018-08-09 12:03 ` [PATCH 4/5] perf/hw_breakpoint: Set breakpoint as disabled in modify_user_hw_breakpoint error path Jiri Olsa
2018-08-09 14:17   ` Oleg Nesterov
2018-08-09 16:30     ` Jiri Olsa
2018-08-28 14:29       ` Arnaldo Carvalho de Melo
2018-08-28 14:38         ` Jiri Olsa
2018-08-28 14:39           ` Arnaldo Carvalho de Melo
2018-08-09 12:03 ` Jiri Olsa [this message]
2018-08-28 14:25 ` [PATCHv2 0/5] perf/hw_breakpoint: Fix breakpoint modify Arnaldo Carvalho de Melo

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