Re: [PATCH 1/2] perf, capstone: Support 32bit code under 64bit OS

[Adrian Hunter <adrian.hunter@intel.com>]

On 28/02/24 01:48, Andi Kleen wrote:
> Use the DSO to resolve whether an IP is 32bit or 64bit and use that to
> configure capstone to the correct mode. This allows to correctly
> disassemble 32bit code under a 64bit OS.
> 
> % cat > loop.c
> volatile int var;
> int main(void)
> {
> 	int i;
> 	for (i = 0; i < 100000; i++)
> 		var++;
> }
> % gcc -m32 -o loop loop.c
> % perf record -e cycles:u ./loop
> % perf script -F +disasm
>             loop   82665 1833176.618023:          1 cycles:u:          f7eed500 _start+0x0 (/usr/lib/ld-linux.so.2)             movl %esp, %eax
>             loop   82665 1833176.618029:          1 cycles:u:          f7eed500 _start+0x0 (/usr/lib/ld-linux.so.2)             movl %esp, %eax
>             loop   82665 1833176.618031:          7 cycles:u:          f7eed500 _start+0x0 (/usr/lib/ld-linux.so.2)             movl %esp, %eax
>             loop   82665 1833176.618034:         91 cycles:u:          f7eed500 _start+0x0 (/usr/lib/ld-linux.so.2)             movl %esp, %eax
>             loop   82665 1833176.618036:       1242 cycles:u:          f7eed500 _start+0x0 (/usr/lib/ld-linux.so.2)             movl %esp, %eax
> 
> Signed-off-by: Andi Kleen <ak@linux.intel.com>
> ---
>  tools/perf/util/print_insn.c | 20 +++++++++++++++++---
>  1 file changed, 17 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/perf/util/print_insn.c b/tools/perf/util/print_insn.c
> index 459e0e93d7b1..bd7a95e64ce5 100644
> --- a/tools/perf/util/print_insn.c
> +++ b/tools/perf/util/print_insn.c
> @@ -12,6 +12,8 @@
>  #include "machine.h"
>  #include "thread.h"
>  #include "print_insn.h"
> +#include "map.h"
> +#include "dso.h"
>  
>  size_t sample__fprintf_insn_raw(struct perf_sample *sample, FILE *fp)
>  {
> @@ -28,12 +30,12 @@ size_t sample__fprintf_insn_raw(struct perf_sample *sample, FILE *fp)
>  #ifdef HAVE_LIBCAPSTONE_SUPPORT
>  #include <capstone/capstone.h>
>  
> -static int capstone_init(struct machine *machine, csh *cs_handle)
> +static int capstone_init(struct machine *machine, csh *cs_handle, bool is64)
>  {
>  	cs_arch arch;
>  	cs_mode mode;
>  
> -	if (machine__is(machine, "x86_64")) {
> +	if (machine__is(machine, "x86_64") && is64) {
>  		arch = CS_ARCH_X86;
>  		mode = CS_MODE_64;
>  	} else if (machine__normalized_is(machine, "x86")) {
> @@ -101,9 +103,21 @@ size_t sample__fprintf_insn_asm(struct perf_sample *sample, struct thread *threa
>  	size_t count;
>  	size_t printed = 0;
>  	int ret;
> +	struct addr_location al;
> +	bool is64bit = machine__is(machine, "x86_64");
> +	struct dso *dso;
> +
> +	addr_location__init(&al);
> +	if (thread__find_map(thread, sample->cpumode, sample->ip, &al) &&
> +		(dso = map__dso(al.map)) != NULL &&
> +		(dso->data.status != DSO_DATA_STATUS_ERROR)) {
> +		map__load(al.map);
> +		is64bit = dso->is_64_bit;
> +	}
> +	addr_location__exit(&al);

Maybe 'al' could be passed down through perf_sample__fprintf_insn()

>  
>  	/* TODO: Try to initiate capstone only once but need a proper place. */
> -	ret = capstone_init(machine, &cs_handle);
> +	ret = capstone_init(machine, &cs_handle, is64bit);
>  	if (ret < 0) {
>  		/* fallback */
>  		return sample__fprintf_insn_raw(sample, fp);