disas: Split out capstone code to disas/capstone.c

There is nothing target-specific about this code, so it
can be added to common_ss.  This also requires that the
base capstone dependency be added to common_ss, so that
we get the correct include paths added to CFLAGS.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

2 files changed, 287 insertions, 0 deletions

diff --git a/disas/capstone.c b/disas/capstone.c
new file mode 100644
index 0000000..b48f839
--- /dev/null
+++ b/disas/capstone.c
@@ -0,0 +1,286 @@
+/*
+ * Interface to the capstone disassembler.
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/bswap.h"
+#include "disas/dis-asm.h"
+#include "disas/capstone.h"
+
+
+/*
+ * Temporary storage for the capstone library.  This will be alloced via
+ * malloc with a size private to the library; thus there's no reason not
+ * to share this across calls and across host vs target disassembly.
+ */
+static __thread cs_insn *cap_insn;
+
+/*
+ * 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
+ * parameters via cs_option(CS_OPT_MODE, new_mode), but we cannot change
+ * CS_ARCH_* in this way.  Thus we would need to be able to close and
+ * re-open the target handle with a different arch for the target in order
+ * to handle AArch64 vs AArch32 mode switching.
+ */
+static cs_err cap_disas_start(disassemble_info *info, csh *handle)
+{
+    cs_mode cap_mode = info->cap_mode;
+    cs_err err;
+
+    cap_mode += (info->endian == BFD_ENDIAN_BIG ? CS_MODE_BIG_ENDIAN
+                 : CS_MODE_LITTLE_ENDIAN);
+
+    err = cs_open(info->cap_arch, cap_mode, handle);
+    if (err != CS_ERR_OK) {
+        return err;
+    }
+
+    /* "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) {
+        /*
+         * 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);
+    }
+
+    /* Allocate temp space for cs_disasm_iter.  */
+    if (cap_insn == NULL) {
+        cap_insn = cs_malloc(*handle);
+        if (cap_insn == NULL) {
+            cs_close(handle);
+            return CS_ERR_MEM;
+        }
+    }
+    return CS_ERR_OK;
+}
+
+static void cap_dump_insn_units(disassemble_info *info, cs_insn *insn,
+                                int i, int n)
+{
+    fprintf_function print = info->fprintf_func;
+    FILE *stream = info->stream;
+
+    switch (info->cap_insn_unit) {
+    case 4:
+        if (info->endian == BFD_ENDIAN_BIG) {
+            for (; i < n; i += 4) {
+                print(stream, " %08x", ldl_be_p(insn->bytes + i));
+
+            }
+        } else {
+            for (; i < n; i += 4) {
+                print(stream, " %08x", ldl_le_p(insn->bytes + i));
+            }
+        }
+        break;
+
+    case 2:
+        if (info->endian == BFD_ENDIAN_BIG) {
+            for (; i < n; i += 2) {
+                print(stream, " %04x", lduw_be_p(insn->bytes + i));
+            }
+        } else {
+            for (; i < n; i += 2) {
+                print(stream, " %04x", lduw_le_p(insn->bytes + i));
+            }
+        }
+        break;
+
+    default:
+        for (; i < n; i++) {
+            print(stream, " %02x", insn->bytes[i]);
+        }
+        break;
+    }
+}
+
+static void cap_dump_insn(disassemble_info *info, cs_insn *insn)
+{
+    fprintf_function print = info->fprintf_func;
+    FILE *stream = info->stream;
+    int i, n, split;
+
+    print(stream, "0x%08" PRIx64 ": ", insn->address);
+
+    n = insn->size;
+    split = info->cap_insn_split;
+
+    /* Dump the first SPLIT bytes of the instruction.  */
+    cap_dump_insn_units(info, insn, 0, MIN(n, split));
+
+    /* Add padding up to SPLIT so that mnemonics line up.  */
+    if (n < split) {
+        int width = (split - n) / info->cap_insn_unit;
+        width *= (2 * info->cap_insn_unit + 1);
+        print(stream, "%*s", width, "");
+    }
+
+    /* Print the actual instruction.  */
+    print(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) {
+        print(stream, "0x%08" PRIx64 ": ", insn->address + i);
+        cap_dump_insn_units(info, insn, i, MIN(n, i + split));
+        print(stream, "\n");
+    }
+}
+
+/* Disassemble SIZE bytes at PC for the target.  */
+bool cap_disas_target(disassemble_info *info, uint64_t pc, size_t size)
+{
+    uint8_t cap_buf[1024];
+    csh handle;
+    cs_insn *insn;
+    size_t csize = 0;
+
+    if (cap_disas_start(info, &handle) != CS_ERR_OK) {
+        return false;
+    }
+    insn = cap_insn;
+
+    while (1) {
+        size_t tsize = MIN(sizeof(cap_buf) - csize, size);
+        const uint8_t *cbuf = cap_buf;
+
+        info->read_memory_func(pc + csize, cap_buf + csize, tsize, info);
+        csize += tsize;
+        size -= tsize;
+
+        while (cs_disasm_iter(handle, &cbuf, &csize, &pc, insn)) {
+            cap_dump_insn(info, insn);
+        }
+
+        /* If the target memory is not consumed, go back for more... */
+        if (size != 0) {
+            /*
+             * ... taking care to move any remaining fractional insn
+             * to the beginning of the buffer.
+             */
+            if (csize != 0) {
+                memmove(cap_buf, cbuf, csize);
+            }
+            continue;
+        }
+
+        /*
+         * Since the target memory is consumed, we should not have
+         * a remaining fractional insn.
+         */
+        if (csize != 0) {
+            info->fprintf_func(info->stream,
+                "Disassembler disagrees with translator "
+                "over instruction decoding\n"
+                "Please report this to qemu-devel@nongnu.org\n");
+        }
+        break;
+    }
+
+    cs_close(&handle);
+    return true;
+}
+
+/* Disassemble SIZE bytes at CODE for the host.  */
+bool cap_disas_host(disassemble_info *info, void *code, size_t size)
+{
+    csh handle;
+    const uint8_t *cbuf;
+    cs_insn *insn;
+    uint64_t pc;
+
+    if (cap_disas_start(info, &handle) != CS_ERR_OK) {
+        return false;
+    }
+    insn = cap_insn;
+
+    cbuf = code;
+    pc = (uintptr_t)code;
+
+    while (cs_disasm_iter(handle, &cbuf, &size, &pc, insn)) {
+        cap_dump_insn(info, insn);
+    }
+    if (size != 0) {
+        info->fprintf_func(info->stream,
+            "Disassembler disagrees with TCG over instruction encoding\n"
+            "Please report this to qemu-devel@nongnu.org\n");
+    }
+
+    cs_close(&handle);
+    return true;
+}
+
+/* Disassemble COUNT insns at PC for the target.  */
+bool cap_disas_monitor(disassemble_info *info, uint64_t pc, int count)
+{
+    uint8_t cap_buf[32];
+    csh handle;
+    cs_insn *insn;
+    size_t csize = 0;
+
+    if (cap_disas_start(info, &handle) != CS_ERR_OK) {
+        return false;
+    }
+    insn = cap_insn;
+
+    while (1) {
+        /*
+         * We want to read memory for one insn, but generically we do not
+         * know how much memory that is.  We have a small buffer which is
+         * known to be sufficient for all supported targets.  Try to not
+         * read beyond the page, Just In Case.  For even more simplicity,
+         * ignore the actual target page size and use a 1k boundary.  If
+         * that turns out to be insufficient, we'll come back around the
+         * loop and read more.
+         */
+        uint64_t epc = QEMU_ALIGN_UP(pc + csize + 1, 1024);
+        size_t tsize = MIN(sizeof(cap_buf) - csize, epc - pc);
+        const uint8_t *cbuf = cap_buf;
+
+        /* Make certain that we can make progress.  */
+        assert(tsize != 0);
+        info->read_memory_func(pc, cap_buf + csize, tsize, info);
+        csize += tsize;
+
+        if (cs_disasm_iter(handle, &cbuf, &csize, &pc, insn)) {
+            cap_dump_insn(info, insn);
+            if (--count <= 0) {
+                break;
+            }
+        }
+        memmove(cap_buf, cbuf, csize);
+    }
+
+    cs_close(&handle);
+    return true;
+}
+
+/* Disassemble a single instruction directly into plugin output */
+bool cap_disas_plugin(disassemble_info *info, uint64_t pc, size_t size)
+{
+    uint8_t cap_buf[32];
+    const uint8_t *cbuf = cap_buf;
+    csh handle;
+
+    if (cap_disas_start(info, &handle) != CS_ERR_OK) {
+        return false;
+    }
+
+    assert(size < sizeof(cap_buf));
+    info->read_memory_func(pc, cap_buf, size, info);
+
+    if (cs_disasm_iter(handle, &cbuf, &size, &pc, cap_insn)) {
+        info->fprintf_func(info->stream, "%s %s",
+                           cap_insn->mnemonic, cap_insn->op_str);
+    }
+
+    cs_close(&handle);
+    return true;
+}
diff --git a/disas/meson.build b/disas/meson.build
index bde8280..09a8527 100644
--- a/disas/meson.build
+++ b/disas/meson.build
@@ -21,5 +21,6 @@ common_ss.add(when: 'CONFIG_S390_DIS', if_true: files('s390.c'))
 common_ss.add(when: 'CONFIG_SH4_DIS', if_true: files('sh4.c'))
 common_ss.add(when: 'CONFIG_SPARC_DIS', if_true: files('sparc.c'))
 common_ss.add(when: 'CONFIG_XTENSA_DIS', if_true: files('xtensa.c'))
+common_ss.add(when: capstone, if_true: files('capstone.c'))
 
 specific_ss.add(when: 'CONFIG_TCG_INTERPRETER', if_true: files('tci.c'))