From 97efebf1bc30a80122af3295ebdb726dbc040ca6 Mon Sep 17 00:00:00 2001 From: Dave Hansen Date: Sun, 7 Jun 2015 11:37:03 -0700 Subject: [PATCH] x86/mpx: Trace entry to bounds exception paths There are two basic things that can happen as the result of a bounds exception (#BR): 1. We allocate a new bounds table 2. We pass up a bounds exception to userspace. This patch adds a trace point for the case where we are passing the exception up to userspace with a signal. We are also explicit that we're printing out the inverse of the 'upper' that we encounter. If you want to filter, for instance, you need to ~ the value first. The reason we do this is because of how 'upper' is stored in the bounds table. If a pointer's range is: 0x1000 -> 0x2000 it is stored in the bounds table as (32-bits here for brevity): lower: 0x00001000 upper: 0xffffdfff That is so that an all 0's entry: lower: 0x00000000 upper: 0x00000000 corresponds to the "init" bounds which store a *range* of: 0x00000000 -> 0xffffffff That is, by far, the common case, and that lets us use the zero page, or deduplicate the memory, etc... The 'upper' stored in the table is gibberish to print by itself, so we print ~upper to get the *actual*, logical, human-readable value printed out. Signed-off-by: Dave Hansen Reviewed-by: Thomas Gleixner Cc: Andrew Morton Cc: Dave Hansen Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/20150607183703.027BB9B0@viggo.jf.intel.com Signed-off-by: Ingo Molnar --- arch/x86/include/asm/trace/mpx.h | 34 ++++++++++++++++++++++++++++++++ arch/x86/mm/mpx.c | 1 + 2 files changed, 35 insertions(+) diff --git a/arch/x86/include/asm/trace/mpx.h b/arch/x86/include/asm/trace/mpx.h index 5c03ec8a90d6..5c3af06a2ae1 100644 --- a/arch/x86/include/asm/trace/mpx.h +++ b/arch/x86/include/asm/trace/mpx.h @@ -8,6 +8,40 @@ #ifdef CONFIG_X86_INTEL_MPX +TRACE_EVENT(mpx_bounds_register_exception, + + TP_PROTO(void *addr_referenced, + const struct bndreg *bndreg), + TP_ARGS(addr_referenced, bndreg), + + TP_STRUCT__entry( + __field(void *, addr_referenced) + __field(u64, lower_bound) + __field(u64, upper_bound) + ), + + TP_fast_assign( + __entry->addr_referenced = addr_referenced; + __entry->lower_bound = bndreg->lower_bound; + __entry->upper_bound = bndreg->upper_bound; + ), + /* + * Note that we are printing out the '~' of the upper + * bounds register here. It is actually stored in its + * one's complement form so that its 'init' state + * corresponds to all 0's. But, that looks like + * gibberish when printed out, so print out the 1's + * complement instead of the actual value here. Note + * though that you still need to specify filters for the + * actual value, not the displayed one. + */ + TP_printk("address referenced: 0x%p bounds: lower: 0x%llx ~upper: 0x%llx", + __entry->addr_referenced, + __entry->lower_bound, + ~__entry->upper_bound + ) +); + TRACE_EVENT(bounds_exception_mpx, TP_PROTO(const struct bndcsr *bndcsr), diff --git a/arch/x86/mm/mpx.c b/arch/x86/mm/mpx.c index 1fef52c17fc8..75e5d7043f65 100644 --- a/arch/x86/mm/mpx.c +++ b/arch/x86/mm/mpx.c @@ -335,6 +335,7 @@ siginfo_t *mpx_generate_siginfo(struct pt_regs *regs) err = -EINVAL; goto err_out; } + trace_mpx_bounds_register_exception(info->si_addr, bndreg); return info; err_out: /* info might be NULL, but kfree() handles that */ -- 2.20.1