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Message-ID: <CAP-5=fWNy8CM8nKOAH=aXyNKg5h4U4vWfB92io_T5KpCsSgv9Q@mail.gmail.com>
Date: Fri, 24 Jan 2025 21:20:15 -0800
From: Ian Rogers <irogers@...gle.com>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>, Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>,
Adrian Hunter <adrian.hunter@...el.com>, Kan Liang <kan.liang@...ux.intel.com>,
Nathan Chancellor <nathan@...nel.org>, Nick Desaulniers <ndesaulniers@...gle.com>,
Bill Wendling <morbo@...gle.com>, Justin Stitt <justinstitt@...gle.com>,
Aditya Gupta <adityag@...ux.ibm.com>, "Steinar H. Gunderson" <sesse@...gle.com>,
Charlie Jenkins <charlie@...osinc.com>, Changbin Du <changbin.du@...wei.com>,
"Masami Hiramatsu (Google)" <mhiramat@...nel.org>, James Clark <james.clark@...aro.org>,
Kajol Jain <kjain@...ux.ibm.com>, Athira Rajeev <atrajeev@...ux.vnet.ibm.com>,
Li Huafei <lihuafei1@...wei.com>, Dmitry Vyukov <dvyukov@...gle.com>,
Andi Kleen <ak@...ux.intel.com>, Chaitanya S Prakash <chaitanyas.prakash@....com>,
linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
llvm@...ts.linux.dev, Song Liu <song@...nel.org>, bpf@...r.kernel.org
Subject: Re: [PATCH v3 06/18] perf capstone: Support for dlopen-ing libcapstone.so
On Fri, Jan 24, 2025 at 2:22 PM Namhyung Kim <namhyung@...nel.org> wrote:
>
> On Wed, Jan 22, 2025 at 09:42:56AM -0800, Ian Rogers wrote:
> > If perf wasn't built against libcapstone, no HAVE_LIBCAPSTONE_SUPPORT,
> > support dlopen-ing libcapstone.so and then calling the necessary
> > functions by looking them up using dlsym. Reverse engineer the types
> > in the API using pahole, adding only what's used in the perf code or
> > necessary for the sake of struct size and alignment.
> >
> > Signed-off-by: Ian Rogers <irogers@...gle.com>
> > ---
> > tools/perf/util/capstone.c | 287 ++++++++++++++++++++++++++++++++-----
> > 1 file changed, 248 insertions(+), 39 deletions(-)
> >
> > diff --git a/tools/perf/util/capstone.c b/tools/perf/util/capstone.c
> > index c9845e4d8781..8d65c7a55a8b 100644
> > --- a/tools/perf/util/capstone.c
> > +++ b/tools/perf/util/capstone.c
> > @@ -11,19 +11,249 @@
> > #include "print_insn.h"
> > #include "symbol.h"
> > #include "thread.h"
> > +#include <dlfcn.h>
> > #include <fcntl.h>
> > +#include <inttypes.h>
>
> These two can go under #else (!HAVE_LIBCAPSTONE_SUPPORT).
Ack.
> > #include <string.h>
> >
> > #ifdef HAVE_LIBCAPSTONE_SUPPORT
> > #include <capstone/capstone.h>
> > +#else
> > +typedef size_t csh;
> > +enum cs_arch {
> > + CS_ARCH_ARM = 0,
> > + CS_ARCH_ARM64 = 1,
> > + CS_ARCH_X86 = 3,
> > + CS_ARCH_SYSZ = 6,
> > +};
> > +enum cs_mode {
> > + CS_MODE_ARM = 0,
> > + CS_MODE_32 = 1 << 2,
> > + CS_MODE_64 = 1 << 3,
> > + CS_MODE_V8 = 1 << 6,
> > + CS_MODE_BIG_ENDIAN = 1 << 31,
> > +};
> > +enum cs_opt_type {
> > + CS_OPT_SYNTAX = 1,
> > + CS_OPT_DETAIL = 2,
> > +};
> > +enum cs_opt_value {
> > + CS_OPT_SYNTAX_ATT = 2,
> > + CS_OPT_ON = 3,
> > +};
> > +enum cs_err {
> > + CS_ERR_OK = 0,
> > + CS_ERR_HANDLE = 3,
> > +};
> > +enum x86_op_type {
> > + X86_OP_IMM = 2,
> > + X86_OP_MEM = 3,
> > +};
> > +enum x86_reg {
> > + X86_REG_RIP = 41,
> > +};
> > +typedef int32_t x86_avx_bcast;
> > +struct x86_op_mem {
> > + enum x86_reg segment;
> > + enum x86_reg base;
> > + enum x86_reg index;
> > + int scale;
> > + int64_t disp;
> > +};
> > +
> > +struct cs_x86_op {
> > + enum x86_op_type type;
> > + union {
> > + enum x86_reg reg;
> > + int64_t imm;
> > + struct x86_op_mem mem;
> > + };
> > + uint8_t size;
> > + uint8_t access;
> > + x86_avx_bcast avx_bcast;
> > + bool avx_zero_opmask;
> > +};
> > +struct cs_x86_encoding {
> > + uint8_t modrm_offset;
> > + uint8_t disp_offset;
> > + uint8_t disp_size;
> > + uint8_t imm_offset;
> > + uint8_t imm_size;
> > +};
> > +typedef int32_t x86_xop_cc;
> > +typedef int32_t x86_sse_cc;
> > +typedef int32_t x86_avx_cc;
> > +typedef int32_t x86_avx_rm;
> > +struct cs_x86 {
> > + uint8_t prefix[4];
> > + uint8_t opcode[4];
> > + uint8_t rex;
> > + uint8_t addr_size;
> > + uint8_t modrm;
> > + uint8_t sib;
> > + int64_t disp;
> > + enum x86_reg sib_index;
> > + int8_t sib_scale;
> > + enum x86_reg sib_base;
> > + x86_xop_cc xop_cc;
> > + x86_sse_cc sse_cc;
> > + x86_avx_cc avx_cc;
> > + bool avx_sae;
> > + x86_avx_rm avx_rm;
> > + union {
> > + uint64_t eflags;
> > + uint64_t fpu_flags;
> > + };
> > + uint8_t op_count;
> > + struct cs_x86_op operands[8];
> > + struct cs_x86_encoding encoding;
> > +};
> > +struct cs_detail {
> > + uint16_t regs_read[12];
> > + uint8_t regs_read_count;
> > + uint16_t regs_write[20];
> > + uint8_t regs_write_count;
> > + uint8_t groups[8];
> > + uint8_t groups_count;
> > +
> > + union {
> > + struct cs_x86 x86;
> > + };
> > +};
>
> As discussed, let's remove the detail part.
I kind of feel there should be a #warning in that case. I'd rather
leave it as is and not have a build warning.
> > +struct cs_insn {
> > + unsigned int id;
> > + uint64_t address;
> > + uint16_t size;
> > + uint8_t bytes[16];
> > + char mnemonic[32];
> > + char op_str[160];
> > + struct cs_detail *detail;
> > +};
> > +#endif
> > +
> > +#ifndef HAVE_LIBCAPSTONE_SUPPORT
> > +static void *perf_cs_dll_handle(void)
> > +{
> > + static bool dll_handle_init;
> > + static void *dll_handle;
> > +
> > + if (!dll_handle_init) {
> > + dll_handle_init = true;
> > + dll_handle = dlopen("libcapstone.so", RTLD_LAZY);
> > + if (!dll_handle)
> > + pr_debug("dlopen failed for libcapstone.so\n");
> > + }
> > + return dll_handle;
> > +}
> > +#endif
> > +
> > +static enum cs_err perf_cs_open(enum cs_arch arch, enum cs_mode mode, csh *handle)
> > +{
> > +#ifdef HAVE_LIBCAPSTONE_SUPPORT
> > + return cs_open(arch, mode, handle);
> > +#else
> > + static bool fn_init;
> > + static enum cs_err (*fn)(enum cs_arch arch, enum cs_mode mode, csh *handle);
> > +
> > + if (!fn_init) {
> > + fn = dlsym(perf_cs_dll_handle(), "cs_open");
> > + if (!fn)
> > + pr_debug("dlsym failed for cs_open\n");
> > + fn_init = true;
> > + }
> > + if (!fn)
> > + return CS_ERR_HANDLE;
> > + return fn(arch, mode, handle);
> > +#endif
> > +}
>
> I think it's better to organize the code with less #ifdef's.
I think this reduces readability - 100s of lines where it isn't clear
there is something conditional going on, or losing the fact a function
is a shim. More details in:
https://lore.kernel.org/lkml/CAP-5=fV0w9tLFr7xYHFUH=UUq+tr+o5EYUik0d74rMWa9=Qi+A@mail.gmail.com/
Thanks,
Ian
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