Re: [Qemu-devel] [PATCH 04/10] disas: Support the Capstone disassembler library

["Philippe Mathieu-Daudé" <f4bug@amsat.org>]

Hi Richard,

see inlined comments.

On 09/14/2017 03:35 PM, Richard Henderson wrote:
> If configured, prefer this over our rather dated copy of the
> GPLv2-only binutils.  This will be especially apparent with
> the proposed vector extensions to TCG, as disas/i386.c does
> not handle AVX.
> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>   include/disas/bfd.h      |  4 ++
>   include/disas/capstone.h | 38 +++++++++++++++++++
>   disas.c                  | 99 ++++++++++++++++++++++++++++++++++++++++++------
>   configure                | 17 +++++++++
>   4 files changed, 146 insertions(+), 12 deletions(-)
>   create mode 100644 include/disas/capstone.h
> 
> diff --git a/include/disas/bfd.h b/include/disas/bfd.h
> index b01e002b4c..0f4ecdeb88 100644
> --- a/include/disas/bfd.h
> +++ b/include/disas/bfd.h
> @@ -377,6 +377,10 @@ typedef struct disassemble_info {
>     /* Command line options specific to the target disassembler.  */
>     char * disassembler_options;
>   
> +  /* Options for Capstone disassembly.  */
> +  int cap_arch;
> +  int cap_mode;
> +
>   } disassemble_info;
>   
>   \f

> diff --git a/include/disas/capstone.h b/include/disas/capstone.h
> new file mode 100644
> index 0000000000..84e214956d
> --- /dev/null
> +++ b/include/disas/capstone.h
> @@ -0,0 +1,38 @@
> +#ifndef QEMU_CAPSTONE_H
> +#define QEMU_CAPSTONE_H 1
> +
> +#ifdef CONFIG_CAPSTONE
> +
> +#include <capstone.h>
> +
> +#else
> +
> +/* Just enough to allow backends to init without ifdefs.  */
> +
> +#define CS_ARCH_ARM     -1
> +#define CS_ARCH_ARM64   -1
> +#define CS_ARCH_MIPS    -1
> +#define CS_ARCH_X86     -1
> +#define CS_ARCH_PPC     -1
> +#define CS_ARCH_SPARC   -1
> +#define CS_ARCH_SYSZ    -1
> +
> +#define CS_MODE_LITTLE_ENDIAN    0
> +#define CS_MODE_BIG_ENDIAN       0
> +#define CS_MODE_ARM              0
> +#define CS_MODE_16               0
> +#define CS_MODE_32               0
> +#define CS_MODE_64               0
> +#define CS_MODE_THUMB            0
> +#define CS_MODE_MCLASS           0
> +#define CS_MODE_V8               0
> +#define CS_MODE_MICRO            0
> +#define CS_MODE_MIPS3            0
> +#define CS_MODE_MIPS32R6         0
> +#define CS_MODE_MIPSGP64         0
> +#define CS_MODE_V9               0
> +#define CS_MODE_MIPS32           0
> +#define CS_MODE_MIPS64           0
> +
> +#endif /* CONFIG_CAPSTONE */
> +#endif /* QEMU_CAPSTONE_H */
> diff --git a/disas.c b/disas.c
> index ad675dc361..76ea76b026 100644
> --- a/disas.c
> +++ b/disas.c
> @@ -6,6 +6,7 @@
>   
>   #include "cpu.h"
>   #include "disas/disas.h"
> +#include "disas/capstone.h"
>   
>   typedef struct CPUDebug {
>       struct disassemble_info info;
> @@ -171,6 +172,57 @@ static int print_insn_od_target(bfd_vma pc, disassemble_info *info)
>       return print_insn_objdump(pc, info, "OBJD-T");
>   }
>   
> +static bool cap_disas(disassemble_info *info, uint64_t pc, size_t size)

I'd rather use:

..,, target_ulong code, ...
> +{

uint64_t pc = (uint64_t)code;

> +    bool ret = false;

Isn't it cleaner to have a stubs/disas_capstone.c?

> +#ifdef CONFIG_CAPSTONE

this check here once:

     if (info->cap_arch < 0) {
         return false;
     }

> +    csh handle;

     cs_err err;

> +    cs_insn *insn;
> +    uint8_t *buf;
> +    const uint8_t *cbuf;
> +    uint64_t pc_start;
> +    cs_mode cap_mode = info->cap_mode;
> +
> +    cap_mode += (info->endian == BFD_ENDIAN_BIG ? CS_MODE_BIG_ENDIAN
> +                 : CS_MODE_LITTLE_ENDIAN);
> +

     assert(size); ?

> +    if (cs_open(info->cap_arch, cap_mode, &handle) != CS_ERR_OK) {

     err = cs_open(info->cap_arch, cap_mode, &handle);
     if (err != CS_ERR_OK) {
         (*info->fprintf_func)(info->stream, "Capstone: %s\n",
                               cs_strerror(err));

> +        goto err0;
> +    }
> +
> +    /* ??? There probably ought to be a better place to put this.  */

looks fine.

> +    if (info->cap_arch == CS_ARCH_X86) {
> +        /* We don't care about errors (if for some reason the library
> +           is compiled without AT&T syntax); the user will just have
> +           to deal with the Intel syntax.  */
> +        cs_option(handle, CS_OPT_SYNTAX, CS_OPT_SYNTAX_ATT);
> +    }
> +
> +    insn = cs_malloc(handle);
> +    if (insn == NULL) {
> +        goto err1;
> +    }
> +
> +    cbuf = buf = g_malloc(size);

     if (buf == NULL) {
         goto err2;
     }

> +    info->read_memory_func(pc, buf, size, info);
> +
> +    pc_start = pc;
> +    while (cs_disasm_iter(handle, &cbuf, &size, &pc, insn)) {
> +        (*info->fprintf_func)(info->stream,
> +                              "0x%08" PRIx64 ":  %-12s %s\n",
> +                              pc_start, insn->mnemonic, insn->op_str);
> +        pc_start = pc;
> +    }
> +    ret = true;
> +

     cs_free(insn, 1);
err2:

> +    g_free(buf);
> + err1:
> +    cs_close(&handle);
> + err0:
> +#endif /* CONFIG_CAPSTONE */
> +    return ret;
> +}
> +
>   /* Disassemble this for me please... (debugging).  */
>   void target_disas(FILE *out, CPUState *cpu, target_ulong code,
>                     target_ulong size)
> @@ -188,6 +240,8 @@ void target_disas(FILE *out, CPUState *cpu, target_ulong code,
>       s.info.buffer_vma = code;
>       s.info.buffer_length = size;
>       s.info.print_address_func = generic_print_address;
> +    s.info.cap_arch = -1;
> +    s.info.cap_mode = 0;
>   
>   #ifdef TARGET_WORDS_BIGENDIAN
>       s.info.endian = BFD_ENDIAN_BIG;
> @@ -199,6 +253,10 @@ void target_disas(FILE *out, CPUState *cpu, target_ulong code,
>           cc->disas_set_info(cpu, &s.info);
>       }
>   
> +    if (s.info.cap_arch >= 0 && cap_disas(&s.info, code, size)) {
> +        return;
> +    }
> +
>       if (s.info.print_insn == NULL) {
>           s.info.print_insn = print_insn_od_target;
>       }
> @@ -206,18 +264,6 @@ void target_disas(FILE *out, CPUState *cpu, target_ulong code,
>       for (pc = code; size > 0; pc += count, size -= count) {
>   	fprintf(out, "0x" TARGET_FMT_lx ":  ", pc);
>   	count = s.info.print_insn(pc, &s.info);
> -#if 0
> -        {
> -            int i;
> -            uint8_t b;
> -            fprintf(out, " {");
> -            for(i = 0; i < count; i++) {
> -                target_read_memory(pc + i, &b, 1, &s.info);
> -                fprintf(out, " %02x", b);
> -            }
> -            fprintf(out, " }");
> -        }
> -#endif
>   	fprintf(out, "\n");
>   	if (count < 0)
>   	    break;
> @@ -245,6 +291,8 @@ void disas(FILE *out, void *code, unsigned long size)
>       s.info.buffer = code;
>       s.info.buffer_vma = (uintptr_t)code;
>       s.info.buffer_length = size;
> +    s.info.cap_arch = -1;
> +    s.info.cap_mode = 0;
>   
>   #ifdef HOST_WORDS_BIGENDIAN
>       s.info.endian = BFD_ENDIAN_BIG;
> @@ -256,21 +304,34 @@ void disas(FILE *out, void *code, unsigned long size)
>   #elif defined(__i386__)
>       s.info.mach = bfd_mach_i386_i386;
>       print_insn = print_insn_i386;
> +    s.info.cap_arch = CS_ARCH_X86;
> +    s.info.cap_mode = CS_MODE_32;
>   #elif defined(__x86_64__)
>       s.info.mach = bfd_mach_x86_64;
>       print_insn = print_insn_i386;
> +    s.info.cap_arch = CS_ARCH_X86;
> +    s.info.cap_mode = CS_MODE_64;
>   #elif defined(_ARCH_PPC)
>       s.info.disassembler_options = (char *)"any";
>       print_insn = print_insn_ppc;
> +    s.info.cap_arch = CS_ARCH_PPC;
> +# ifdef _ARCH_PPC64
> +    s.info.cap_mode = CS_MODE_64;
> +# endif
>   #elif defined(__aarch64__) && defined(CONFIG_ARM_A64_DIS)
>       print_insn = print_insn_arm_a64;
> +    s.info.cap_arch = CS_ARCH_ARM64;
>   #elif defined(__alpha__)
>       print_insn = print_insn_alpha;
>   #elif defined(__sparc__)
>       print_insn = print_insn_sparc;
>       s.info.mach = bfd_mach_sparc_v9b;
> +    s.info.cap_arch = CS_ARCH_SPARC;
> +    s.info.cap_mode = CS_MODE_V9;
>   #elif defined(__arm__)
>       print_insn = print_insn_arm;
> +    s.info.cap_arch = CS_ARCH_ARM;
> +    /* TCG only generates code for arm mode.  */
>   #elif defined(__MIPSEB__)
>       print_insn = print_insn_big_mips;
>   #elif defined(__MIPSEL__)
> @@ -279,9 +340,15 @@ void disas(FILE *out, void *code, unsigned long size)
>       print_insn = print_insn_m68k;
>   #elif defined(__s390__)
>       print_insn = print_insn_s390;
> +    s.info.cap_arch = CS_ARCH_SYSZ;
>   #elif defined(__hppa__)
>       print_insn = print_insn_hppa;
>   #endif
> +
> +    if (s.info.cap_arch >= 0 && cap_disas(&s.info, (uintptr_t)code, size)) {

(target_ulong)(uintptr_t)code, ?

> +        return;
> +    }
> +
>       if (print_insn == NULL) {
>           print_insn = print_insn_od_host;
>       }
> @@ -357,6 +424,14 @@ void monitor_disas(Monitor *mon, CPUState *cpu,
>           cc->disas_set_info(cpu, &s.info);
>       }
>   
> +    /* ??? Capstone requires that we copy the data into a host-addressable
> +       buffer first and has no call-back to read more.  Therefore we need
> +       an estimate of buffer size.  This will work for most RISC, but we'll
> +       need to figure out something else for variable-length ISAs.  */
> +    if (s.info.cap_arch >= 0 && cap_disas(&s.info, pc, 4 * nb_insn)) {

.., MIN(16 * nb_insn, TARGET_PAGE_SIZE))) ?

> +        return;
> +    }
> +
>       if (!s.info.print_insn) {
>           monitor_printf(mon, "0x" TARGET_FMT_lx
>                          ": Asm output not supported on this arch\n", pc);
> diff --git a/configure b/configure
> index fd7e3a5e81..a55a8eda8a 100755
> --- a/configure
> +++ b/configure
> @@ -366,6 +366,7 @@ opengl_dmabuf="no"
>   cpuid_h="no"
>   avx2_opt="no"
>   zlib="yes"
> +capstone=""
>   lzo=""
>   snappy=""
>   bzip2=""
> @@ -4381,6 +4382,18 @@ EOF
>   fi
>   
>   ##########################################
> +# capstone
> +
> +if test "$capstone" != no; then
> +  capstone=no
> +  if $pkg_config capstone; then
> +    capstone=yes
> +    QEMU_CFLAGS="$QEMU_CFLAGS $($pkg_config --cflags capstone)"
> +    LDFLAGS="$LDFLAGS $($pkg_config --libs capstone)"
> +  fi
> +fi
> +
> +##########################################
>   # check if we have fdatasync
>   
>   fdatasync=no
> @@ -5402,6 +5415,7 @@ echo "jemalloc support  $jemalloc"
>   echo "avx2 optimization $avx2_opt"
>   echo "replication support $replication"
>   echo "VxHS block device $vxhs"
> +echo "capstone          $capstone"
>   
>   if test "$sdl_too_old" = "yes"; then
>   echo "-> Your SDL version is too old - please upgrade to have SDL support"
> @@ -6050,6 +6064,9 @@ fi
>   if test "$ivshmem" = "yes" ; then
>     echo "CONFIG_IVSHMEM=y" >> $config_host_mak
>   fi
> +if test "$capstone" = "yes" ; then
> +  echo "CONFIG_CAPSTONE=y" >> $config_host_mak
> +fi
>   
>   # Hold two types of flag:
>   #   CONFIG_THREAD_SETNAME_BYTHREAD  - we've got a way of setting the name on
>