[Qemu-devel] [PATCH 3/3] capstone: Enable disassembly for s390x

[Richard Henderson <richard.henderson@linaro.org>]

Enable s390x, aka SYSZ, in the git submodule build.
Set the capstone parameters for both s390x host and guest.
Install a skipdata hook to keep capstone in sync with the
instruction stream for unknown opcodes.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 Makefile           |  1 +
 disas.c            | 40 ++++++++++++++++++++++++++++++++++++++++
 target/s390x/cpu.c |  4 ++++
 3 files changed, 45 insertions(+)

diff --git a/Makefile b/Makefile
index 155f066a20..a37e872825 100644
--- a/Makefile
+++ b/Makefile
@@ -477,6 +477,7 @@ CAP_CFLAGS += -DCAPSTONE_USE_SYS_DYN_MEM
 CAP_CFLAGS += -DCAPSTONE_HAS_ARM
 CAP_CFLAGS += -DCAPSTONE_HAS_ARM64
 CAP_CFLAGS += -DCAPSTONE_HAS_POWERPC
+CAP_CFLAGS += -DCAPSTONE_HAS_SYSZ
 CAP_CFLAGS += -DCAPSTONE_HAS_X86
 
 subdir-capstone: .git-submodule-status
diff --git a/disas.c b/disas.c
index 41ad0102e2..c1ecd2d769 100644
--- a/disas.c
+++ b/disas.c
@@ -179,6 +179,39 @@ 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;
 
+/*
+ * 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.  */
 /* ??? 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
@@ -209,6 +242,10 @@ 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_SYSZ) {
+        cs_option(*handle, CS_OPT_SKIPDATA_SETUP,
+                  (uintptr_t)&cap_skipdata_s390x);
+    }
 
     /* Allocate temp space for cs_disasm_iter.  */
     if (cap_insn == NULL) {
@@ -551,6 +588,9 @@ 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;
+    s.info.cap_insn_unit = 2;
+    s.info.cap_insn_split = 6;
 #elif defined(__hppa__)
     print_insn = print_insn_hppa;
 #endif
diff --git a/target/s390x/cpu.c b/target/s390x/cpu.c
index b1df63d82c..553571d86b 100644
--- a/target/s390x/cpu.c
+++ b/target/s390x/cpu.c
@@ -41,6 +41,7 @@
 #include "sysemu/sysemu.h"
 #endif
 #include "fpu/softfloat.h"
+#include "disas/capstone.h"
 
 #define CR0_RESET       0xE0UL
 #define CR14_RESET      0xC2000000UL;
@@ -175,6 +176,9 @@ static void s390_cpu_disas_set_info(CPUState *cpu, disassemble_info *info)
 {
     info->mach = bfd_mach_s390_64;
     info->print_insn = print_insn_s390;
+    info->cap_arch = CS_ARCH_SYSZ;
+    info->cap_insn_unit = 2;
+    info->cap_insn_split = 6;
 }
 
 static void s390_cpu_realizefn(DeviceState *dev, Error **errp)
-- 
2.17.1