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From: Richard Henderson <richard.henderson@linaro.org>
To: qemu-devel@nongnu.org
Cc: alex.bennee@linaro.org
Subject: [PATCH v4 07/11] disas: Cleanup plugin_disas
Date: Mon, 21 Sep 2020 10:41:14 -0700
Message-ID: <20200921174118.39352-8-richard.henderson@linaro.org> (raw)
In-Reply-To: <20200921174118.39352-1-richard.henderson@linaro.org>

Do not retain a GString in thread-local storage.  Allocate a
new one and free it on every invocation.  Do not g_strdup the
result; return the buffer from the GString.  Do not use
warn_report.

Using cs_disasm allocated memory via the &insn parameter, but
that was never freed.  Use cs_disasm_iter so that we use the
memory that we've already allocated, and so that we only try
to disassemble one insn, as desired.  Do not allocate 1k to
hold the bytes for a single instruction.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 disas.c | 55 +++++++++++++++++++------------------------------------
 1 file changed, 19 insertions(+), 36 deletions(-)

diff --git a/disas.c b/disas.c
index bf19b1b0bf..d0ccd4b727 100644
--- a/disas.c
+++ b/disas.c
@@ -491,13 +491,12 @@ void target_disas(FILE *out, CPUState *cpu, target_ulong code,
     }
 }
 
-static __thread GString plugin_disas_output;
-
 static int plugin_printf(FILE *stream, const char *fmt, ...)
 {
-    va_list va;
-    GString *s = &plugin_disas_output;
+    /* We abuse the FILE parameter to pass a GString. */
+    GString *s = (GString *)stream;
     int initial_len = s->len;
+    va_list va;
 
     va_start(va, fmt);
     g_string_append_vprintf(s, fmt, va);
@@ -517,28 +516,20 @@ static void plugin_print_address(bfd_vma addr, struct disassemble_info *info)
 static
 bool cap_disas_plugin(disassemble_info *info, uint64_t pc, size_t size)
 {
-    uint8_t cap_buf[1024];
+    uint8_t cap_buf[64];
+    const uint8_t *cbuf = cap_buf;
     csh handle;
-    cs_insn *insn;
-    size_t csize = 0;
-    int count;
-    GString *s = &plugin_disas_output;
 
     if (cap_disas_start(info, &handle) != CS_ERR_OK) {
         return false;
     }
-    insn = cap_insn;
 
-    size_t tsize = MIN(sizeof(cap_buf) - csize, size);
-    const uint8_t *cbuf = cap_buf;
-    target_read_memory(pc, cap_buf, tsize, info);
+    assert(size < sizeof(cap_buf));
+    target_read_memory(pc, cap_buf, size, info);
 
-    count = cs_disasm(handle, cbuf, size, 0, 1, &insn);
-
-    if (count) {
-        g_string_printf(s, "%s %s", insn->mnemonic, insn->op_str);
-    } else {
-        g_string_printf(s, "cs_disasm failed");
+    if (cs_disasm_iter(handle, &cbuf, &size, &pc, cap_insn)) {
+        GString *s = (GString *)info->stream;
+        g_string_printf(s, "%s %s", cap_insn->mnemonic, cap_insn->op_str);
     }
 
     cs_close(&handle);
@@ -553,34 +544,26 @@ bool cap_disas_plugin(disassemble_info *info, uint64_t pc, size_t size)
  */
 char *plugin_disas(CPUState *cpu, uint64_t addr, size_t size)
 {
-    int count;
     CPUDebug s;
-    GString *ds = g_string_set_size(&plugin_disas_output, 0);
-
-    g_assert(ds == &plugin_disas_output);
+    GString *ds = g_string_new(NULL);
 
     initialize_debug_target(&s, cpu);
     s.info.fprintf_func = plugin_printf;
+    s.info.stream = (FILE *)ds;  /* abuse this slot */
     s.info.buffer_vma = addr;
     s.info.buffer_length = size;
     s.info.print_address_func = plugin_print_address;
 
     if (s.info.cap_arch >= 0 && cap_disas_plugin(&s.info, addr, size)) {
-        return g_strdup(ds->str);
+        ; /* done */
+    } else if (s.info.print_insn) {
+        s.info.print_insn(addr, &s.info);
+    } else {
+        ; /* cannot disassemble -- return empty string */
     }
 
-    if (s.info.print_insn == NULL) {
-        s.info.print_insn = print_insn_od_target;
-    }
-
-    count = s.info.print_insn(addr, &s.info);
-
-    /* The decoder probably read more than it needed it's not critical */
-    if (count < size) {
-        warn_report("%s: %zu bytes left over", __func__, size - count);
-    }
-
-    return g_strdup(ds->str);
+    /* Return the buffer, freeing the GString container.  */
+    return g_string_free(ds, false);
 }
 
 /* Disassemble this for me please... (debugging). */
-- 
2.25.1



  parent reply index

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-21 17:41 [PATCH v4 00/11] capstone + disassembler patches Richard Henderson
2020-09-21 17:41 ` [PATCH v4 01/11] capstone: Convert Makefile bits to meson bits Richard Henderson
2020-09-21 19:17   ` Alex Bennée
2020-09-21 17:41 ` [PATCH v4 02/11] capstone: Update to upstream "next" branch Richard Henderson
2020-09-21 19:18   ` Alex Bennée
2020-09-21 17:41 ` [PATCH v4 03/11] capstone: Require version 4.0 from a system library Richard Henderson
2020-09-21 19:19   ` Alex Bennée
2020-09-22 10:33   ` Philippe Mathieu-Daudé
2020-09-21 17:41 ` [PATCH v4 04/11] disas: Move host asm annotations to tb_gen_code Richard Henderson
2020-09-21 19:29   ` Alex Bennée
2020-09-21 19:53     ` Richard Henderson
2020-09-22  8:26       ` Philippe Mathieu-Daudé
2020-09-22  9:50         ` Alex Bennée
2020-09-21 17:41 ` [PATCH v4 05/11] disas: Clean up CPUDebug initialization Richard Henderson
2020-09-21 19:32   ` Alex Bennée
2020-09-21 17:41 ` [PATCH v4 06/11] disas: Use qemu/bswap.h for bfd endian loads Richard Henderson
2020-09-21 19:33   ` Alex Bennée
2020-09-21 17:41 ` Richard Henderson [this message]
2020-09-22 10:38   ` [PATCH v4 07/11] disas: Cleanup plugin_disas Alex Bennée
2020-09-21 17:41 ` [PATCH v4 08/11] disas: Configure capstone for aarch64 host without libvixl Richard Henderson
2020-09-22 10:48   ` Alex Bennée
2020-09-21 17:41 ` [PATCH v4 09/11] disas: Split out capstone code to disas/capstone.c Richard Henderson
2020-09-22 10:50   ` Alex Bennée
2020-09-21 17:41 ` [PATCH v4 10/11] disas: Enable capstone disassembly for s390x Richard Henderson
2020-09-22 10:58   ` Alex Bennée
2020-09-21 17:41 ` [PATCH v4 11/11] disas/capstone: Add skipdata hook " Richard Henderson
2020-09-22 10:59   ` Alex Bennée
2020-09-22  0:50 ` [PATCH v4 00/11] capstone + disassembler patches no-reply

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