linux-kernel - [tip:x86/fpu] x86/mpx: Trace #BR exceptions

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Message-ID: <tip-e7126cf5f10aef1555cb99eddb7efff41bdf9566@git.kernel.org>
Date:	Tue, 9 Jun 2015 05:33:00 -0700
From:	tip-bot for Dave Hansen <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	dave.hansen@...ux.intel.com, peterz@...radead.org, hpa@...or.com,
	akpm@...ux-foundation.org, mingo@...nel.org, dave@...1.net,
	linux-kernel@...r.kernel.org, tglx@...utronix.de,
	torvalds@...ux-foundation.org
Subject: [tip:x86/fpu] x86/mpx: Trace #BR exceptions

Commit-ID:  e7126cf5f10aef1555cb99eddb7efff41bdf9566
Gitweb:     http://git.kernel.org/tip/e7126cf5f10aef1555cb99eddb7efff41bdf9566
Author:     Dave Hansen <dave.hansen@...ux.intel.com>
AuthorDate: Sun, 7 Jun 2015 11:37:03 -0700
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Tue, 9 Jun 2015 12:24:31 +0200

x86/mpx: Trace #BR exceptions

This is the first in a series of MPX tracing patches.
I've found these extremely useful in the process of
debugging applications and the kernel code itself.

This exception hooks in to the bounds (#BR) exception
very early and allows capturing the key registers which
would influence how the exception is handled.

Note that bndcfgu/bndstatus are technically still
64-bit registers even in 32-bit mode.

Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Dave Hansen <dave@...1.net>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Link: http://lkml.kernel.org/r/20150607183703.5FE2619A@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/include/asm/trace/mpx.h | 50 ++++++++++++++++++++++++++++++++++++++++
 arch/x86/kernel/traps.c          |  2 ++
 arch/x86/mm/mpx.c                |  3 +++
 3 files changed, 55 insertions(+)

diff --git a/arch/x86/include/asm/trace/mpx.h b/arch/x86/include/asm/trace/mpx.h
new file mode 100644
index 0000000..5c03ec8
--- /dev/null
+++ b/arch/x86/include/asm/trace/mpx.h
@@ -0,0 +1,50 @@
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM mpx
+
+#if !defined(_TRACE_MPX_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_MPX_H
+
+#include <linux/tracepoint.h>
+
+#ifdef CONFIG_X86_INTEL_MPX
+
+TRACE_EVENT(bounds_exception_mpx,
+
+	TP_PROTO(const struct bndcsr *bndcsr),
+	TP_ARGS(bndcsr),
+
+	TP_STRUCT__entry(
+		__field(u64, bndcfgu)
+		__field(u64, bndstatus)
+	),
+
+	TP_fast_assign(
+		/* need to get rid of the 'const' on bndcsr */
+		__entry->bndcfgu   = (u64)bndcsr->bndcfgu;
+		__entry->bndstatus = (u64)bndcsr->bndstatus;
+	),
+
+	TP_printk("bndcfgu:0x%llx bndstatus:0x%llx",
+		__entry->bndcfgu,
+		__entry->bndstatus)
+);
+
+#else
+
+/*
+ * This gets used outside of MPX-specific code, so we need a stub.
+ */
+static inline void trace_bounds_exception_mpx(const struct bndcsr *bndcsr)
+{
+}
+
+#endif /* CONFIG_X86_INTEL_MPX */
+
+#undef TRACE_INCLUDE_PATH
+#define TRACE_INCLUDE_PATH asm/trace/
+#undef TRACE_INCLUDE_FILE
+#define TRACE_INCLUDE_FILE mpx
+#endif /* _TRACE_MPX_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index cffff66..36cb15b 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -60,6 +60,7 @@
 #include <asm/mach_traps.h>
 #include <asm/alternative.h>
 #include <asm/fpu/xstate.h>
+#include <asm/trace/mpx.h>
 #include <asm/mpx.h>
 
 #ifdef CONFIG_X86_64
@@ -399,6 +400,7 @@ dotraplinkage void do_bounds(struct pt_regs *regs, long error_code)
 	if (!bndcsr)
 		goto exit_trap;
 
+	trace_bounds_exception_mpx(bndcsr);
 	/*
 	 * The error code field of the BNDSTATUS register communicates status
 	 * information of a bound range exception #BR or operation involving
diff --git a/arch/x86/mm/mpx.c b/arch/x86/mm/mpx.c
index d6e02f3..1fef52c 100644
--- a/arch/x86/mm/mpx.c
+++ b/arch/x86/mm/mpx.c
@@ -17,6 +17,9 @@
 #include <asm/processor.h>
 #include <asm/fpu/internal.h>
 
+#define CREATE_TRACE_POINTS
+#include <asm/trace/mpx.h>
+
 static const char *mpx_mapping_name(struct vm_area_struct *vma)
 {
 	return "[mpx]";
--
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