On 15/09/2020 01.02, Richard Henderson wrote:
> It is always possible to tell the length of an insn, even if the
> actual insn is unknown. Skip the correct number of bytes, so that
> we stay in sync with the instruction stream.
>
> Reviewed-by: Philippe Mathieu-Daudé <f4...@amsat.org>
> Signed-off-by: Richard Henderson <richard.hender...@linaro.org>
> ---
> disas/capstone.c | 42 +++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 41 insertions(+), 1 deletion(-)
>
> diff --git a/disas/capstone.c b/disas/capstone.c
> index b48f83958d..0a9ef9c892 100644
> --- a/disas/capstone.c
> +++ b/disas/capstone.c
> @@ -16,6 +16,39 @@
> */
> static __thread cs_insn *cap_insn;
>
> +/*
> + * The capstone library always skips 2 bytes for S390X.
> + * This is less than ideal, since we can tell from the first two bits
> + * the size of the insn and thus stay in sync with the insn stream.
> + */
> +static size_t CAPSTONE_API
> +cap_skipdata_s390x_cb(const uint8_t *code, size_t code_size,
> + size_t offset, void *user_data)
> +{
> + size_t ilen;
> +
> + /* See get_ilen() in target/s390x/internal.h. */
> + switch (code[offset] >> 6) {
> + case 0:
> + ilen = 2;
> + break;
> + case 1:
> + case 2:
> + ilen = 4;
> + break;
> + default:
> + ilen = 6;
> + break;
> + }
> +
> + return ilen;
> +}
> +
> +static const cs_opt_skipdata cap_skipdata_s390x = {
> + .mnemonic = ".byte",
> + .callback = cap_skipdata_s390x_cb
> +};
> +
> /*
> * Initialize the Capstone library.
> *
> @@ -42,13 +75,20 @@ static cs_err cap_disas_start(disassemble_info *info, csh
> *handle)
> /* "Disassemble" unknown insns as ".byte W,X,Y,Z". */
> cs_option(*handle, CS_OPT_SKIPDATA, CS_OPT_ON);
>
> - if (info->cap_arch == CS_ARCH_X86) {
> + switch (info->cap_arch) {
> + case CS_ARCH_SYSZ:
> + cs_option(*handle, CS_OPT_SKIPDATA_SETUP,
> + (uintptr_t)&cap_skipdata_s390x);
> + break;
> +
> + case 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);
> + break;
> }
>
> /* Allocate temp space for cs_disasm_iter. */
>
Acked-by: Thomas Huth <th...@redhat.com>
