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x86/mpx: Trace #BR exceptions

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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@linux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dave Hansen <dave@sr71.net>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20150607183703.5FE2619A@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Dave Hansen 2015-06-07 11:37:03 -07:00 committed by Ingo Molnar
parent 8c3641e957
commit e7126cf5f1
3 changed files with 55 additions and 0 deletions
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50
arch/x86/include/asm/trace/mpx.h Normal file
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@ -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>

2
arch/x86/kernel/traps.c
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@ -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

3
arch/x86/mm/mpx.c
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@ -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]";