linux-kernel - [PATCH 06/17] x86, mpx: trace attempts to find bounds tables

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Message-Id: <20150326183341.A0AA7CBF@viggo.jf.intel.com>
Date:	Thu, 26 Mar 2015 11:33:41 -0700
From:	Dave Hansen <dave@...1.net>
To:	linux-kernel@...r.kernel.org
Cc:	x86@...nel.org, tglx@...utronix.de, Dave Hansen <dave@...1.net>,
	dave.hansen@...ux.intel.com
Subject: [PATCH 06/17] x86, mpx: trace attempts to find bounds tables


From: Dave Hansen <dave.hansen@...ux.intel.com>

This event traces any time we go looking to unmap a bounds table
for a given virtual address range.  This is useful to ensure
that the kernel actually "tried" to free a bounds table versus
times it succeeded.

It might try and fail if it realized that a table was shared
with an adjacent VMA which is not being unmapped.


Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
---

 b/arch/x86/include/asm/trace/mpx.h |   22 ++++++++++++++++++++++
 b/arch/x86/mm/mpx.c                |    1 +
 2 files changed, 23 insertions(+)

diff -puN arch/x86/include/asm/trace/mpx.h~mpx-trace_unmap_search arch/x86/include/asm/trace/mpx.h
--- a/arch/x86/include/asm/trace/mpx.h~mpx-trace_unmap_search	2015-03-26 11:27:06.684292099 -0700
+++ b/arch/x86/include/asm/trace/mpx.h	2015-03-26 11:27:06.689292324 -0700
@@ -75,6 +75,28 @@ TRACE_EVENT(mpx_unmap_zap,
 	)
 );
 
+TRACE_EVENT(mpx_unmap_search,
+
+	TP_PROTO(unsigned long start,
+		 unsigned long end),
+	TP_ARGS(start, end),
+
+	TP_STRUCT__entry(
+		__field(unsigned long, start)
+		__field(unsigned long, end)
+	),
+
+	TP_fast_assign(
+		__entry->start = start;
+		__entry->end   = end;
+	),
+
+	TP_printk("0x%p -> 0x%p",
+		(void *)__entry->start,
+		(void *)__entry->end
+	)
+);
+
 #else
 
 /*
diff -puN arch/x86/mm/mpx.c~mpx-trace_unmap_search arch/x86/mm/mpx.c
--- a/arch/x86/mm/mpx.c~mpx-trace_unmap_search	2015-03-26 11:27:06.686292189 -0700
+++ b/arch/x86/mm/mpx.c	2015-03-26 11:27:06.689292324 -0700
@@ -843,6 +843,7 @@ static int mpx_unmap_tables(struct mm_st
 	long __user *bd_entry, *bde_start, *bde_end;
 	unsigned long bt_addr;
 
+	trace_mpx_unmap_search(start, end);
 	/*
 	 * "Edge" bounds tables are those which are being used by the region
 	 * (start -> end), but that may be shared with adjacent areas.  If they
_
--
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