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[Qemu-devel] [RFC PATCH 4/4] disas: allow capstone to defer to a fallbac
From: |
Alex Bennée |
Subject: |
[Qemu-devel] [RFC PATCH 4/4] disas: allow capstone to defer to a fallback function on failure |
Date: |
Wed, 8 Aug 2018 13:39:34 +0100 |
We can abuse the CS_OPT_SKIPDATA by providing a call back when
capstone can't disassemble something. The passing of the string to the
dump function is a little clunky but works.
Signed-off-by: Alex Bennée <address@hidden>
---
disas.c | 30 +++++++++++++++++++++++++++++-
include/disas/bfd.h | 11 ++++++++++-
target/arm/cpu.c | 4 ++++
3 files changed, 43 insertions(+), 2 deletions(-)
diff --git a/disas.c b/disas.c
index 5325b7e6be..dfd2c251c5 100644
--- a/disas.c
+++ b/disas.c
@@ -178,6 +178,20 @@ static int print_insn_od_target(bfd_vma pc,
disassemble_info *info)
to share this across calls and across host vs target disassembly. */
static __thread cs_insn *cap_insn;
+
+/* Handle fall-back dissasembly. We don't print here but we do set
+ * cap_fallback_str for cap_dump_insn to used*/
+static size_t cap_disas_fallback(const uint8_t *code, size_t code_size,
+ size_t offset, void *user_data)
+{
+ disassemble_info *info = (disassemble_info *) user_data;
+ info->cap_fallback_str = g_malloc0(256);
+ size_t skip = info->capstone_fallback_func(code + offset,
+ info->cap_fallback_str, 256);
+ return skip;
+}
+
+
/* Initialize the Capstone library. */
/* ??? It would be nice to cache this. We would need one handle for the
host and one for the target. For most targets we can reset specific
@@ -206,6 +220,14 @@ static cs_err cap_disas_start(disassemble_info *info, csh
*handle)
cs_option(*handle, CS_OPT_SYNTAX, CS_OPT_SYNTAX_ATT);
}
+ if (info->capstone_fallback_func) {
+ cs_opt_skipdata skipdata = {
+ .callback = cap_disas_fallback,
+ .user_data = info,
+ };
+ cs_option(*handle, CS_OPT_SKIPDATA_SETUP, (size_t) &skipdata);
+ }
+
/* "Disassemble" unknown insns as ".byte W,X,Y,Z". */
cs_option(*handle, CS_OPT_SKIPDATA, CS_OPT_ON);
@@ -281,7 +303,13 @@ static void cap_dump_insn(disassemble_info *info, cs_insn
*insn)
}
/* Print the actual instruction. */
- print(info->stream, " %-8s %s\n", insn->mnemonic, insn->op_str);
+ if (info->cap_fallback_str) {
+ print(info->stream, " %s\n", info->cap_fallback_str);
+ g_free(info->cap_fallback_str);
+ info->cap_fallback_str = NULL;
+ } else {
+ print(info->stream, " %-8s %s\n", insn->mnemonic, insn->op_str);
+ }
/* Dump any remaining part of the insn on subsequent lines. */
for (i = split; i < n; i += split) {
diff --git a/include/disas/bfd.h b/include/disas/bfd.h
index 1f69a6e9d3..9d99bfef48 100644
--- a/include/disas/bfd.h
+++ b/include/disas/bfd.h
@@ -377,6 +377,12 @@ typedef struct disassemble_info {
int cap_insn_unit;
int cap_insn_split;
+ /* Fallback function to disassemble things capstone can't. */
+ size_t (*capstone_fallback_func)
+ (const uint8_t *insn, char *ptr, size_t n);
+
+ char *cap_fallback_str;
+
} disassemble_info;
@@ -491,7 +497,10 @@ int generic_symbol_at_address(bfd_vma, struct
disassemble_info *);
(INFO).bytes_per_chunk = 0, \
(INFO).display_endian = BFD_ENDIAN_UNKNOWN, \
(INFO).disassembler_options = NULL, \
- (INFO).insn_info_valid = 0
+ (INFO).insn_info_valid = 0, \
+ (INFO).capstone_fallback_func = NULL, \
+ (INFO).cap_fallback_str = NULL
+
#ifndef ATTRIBUTE_UNUSED
#define ATTRIBUTE_UNUSED __attribute__((unused))
diff --git a/target/arm/cpu.c b/target/arm/cpu.c
index 64a8005a4b..cfefbfb0b9 100644
--- a/target/arm/cpu.c
+++ b/target/arm/cpu.c
@@ -519,6 +519,10 @@ static void arm_disas_set_info(CPUState *cpu,
disassemble_info *info)
info->cap_arch = CS_ARCH_ARM64;
info->cap_insn_unit = 4;
info->cap_insn_split = 4;
+
+#if defined(TARGET_AARCH64)
+ info->capstone_fallback_func = do_aarch64_fallback_disassembly;
+#endif
} else {
int cap_mode;
if (env->thumb) {
--
2.17.1