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From:   Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>
Date:   Fri, 26 Jul 2019 16:38:06 -0300
To:     Adrian Hunter <adrian.hunter@intel.com>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Numfor Mbiziwo-Tiapo <nums@google.com>
Cc:     peterz@infradead.org, mingo@redhat.com,
        alexander.shishkin@linux.intel.com, jolsa@redhat.com,
        namhyung@kernel.org, songliubraving@fb.com, mbd@fb.com,
        linux-kernel@vger.kernel.org, irogers@google.com,
        eranian@google.com
Subject: Re: [PATCH 3/3] Fix insn.c misaligned address error
Message-ID: <20190726193806.GB24867@kernel.org>
References: <20190724184512.162887-1-nums@google.com>
 <20190724184512.162887-4-nums@google.com>
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Em Wed, Jul 24, 2019 at 11:45:12AM -0700, Numfor Mbiziwo-Tiapo escreveu:
> The ubsan (undefined behavior sanitizer) version of perf throws an
> error on the 'x86 instruction decoder - new instructions' function
> of perf test.
> 
> To reproduce this run:
> make -C tools/perf USE_CLANG=1 EXTRA_CFLAGS="-fsanitize=undefined"
> 
> then run: tools/perf/perf test 62 -v
> 
> The error occurs in the __get_next macro (line 34) where an int is
> read from a potentially unaligned address. Using memcpy instead of
> assignment from an unaligned pointer.

Since this came from the kernel, don't we have to fix it there as well?
Masami, Adrian?

[acme@quaco perf]$ find . -name insn.c
./arch/x86/lib/insn.c
./arch/arm/kernel/insn.c
./arch/arm64/kernel/insn.c
./tools/objtool/arch/x86/lib/insn.c
./tools/perf/util/intel-pt-decoder/insn.c
[acme@quaco perf]$ diff -u ./tools/perf/util/intel-pt-decoder/insn.c ./arch/x86/lib/insn.c
--- ./tools/perf/util/intel-pt-decoder/insn.c	2019-07-06 16:59:05.734265998 -0300
+++ ./arch/x86/lib/insn.c	2019-07-06 16:59:01.369202998 -0300
@@ -10,8 +10,8 @@
 #else
 #include <string.h>
 #endif
-#include "inat.h"
-#include "insn.h"
+#include <asm/inat.h>
+#include <asm/insn.h>

 /* Verify next sizeof(t) bytes can be on the same instruction */
 #define validate_next(t, insn, n)	\
[acme@quaco perf]$


- Arnaldo
 
> Signed-off-by: Numfor Mbiziwo-Tiapo <nums@google.com>
> ---
>  tools/perf/util/intel-pt-decoder/insn.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/perf/util/intel-pt-decoder/insn.c b/tools/perf/util/intel-pt-decoder/insn.c
> index ca983e2bea8b..de1944c60aa9 100644
> --- a/tools/perf/util/intel-pt-decoder/insn.c
> +++ b/tools/perf/util/intel-pt-decoder/insn.c
> @@ -31,7 +31,8 @@
>  	((insn)->next_byte + sizeof(t) + n <= (insn)->end_kaddr)
>  
>  #define __get_next(t, insn)	\
> -	({ t r = *(t*)insn->next_byte; insn->next_byte += sizeof(t); r; })
> +	({ t r; memcpy(&r, insn->next_byte, sizeof(t)); \
> +		insn->next_byte += sizeof(t); r; })
>  
>  #define __peek_nbyte_next(t, insn, n)	\
>  	({ t r = *(t*)((insn)->next_byte + n); r; })
> -- 
> 2.22.0.657.g960e92d24f-goog

-- 

- Arnaldo