Store values always in little endian as the trace defines it.

Author: Rot127

contrib/plugins/bap-tracing/trace_meta.c

@@ -191,3 +191,25 @@ void write_meta(WLOCKED FILE *file, char **plugin_argv, size_t plugin_argc) {
   g_free(host);
   g_free(arg_bin_path);
 }
+
+/// Copies src to dst. dst will always be in little endian byte order.
+void memcpy_le(uint8_t *dst, uint8_t *src, size_t len, bool big_endian) {
+  if (!big_endian) {
+    memcpy(dst, src, len);
+    return;
+  }
+  for (size_t k = 0; k < len; ++k) {
+    dst[k] = src[len - 1 - k];
+  }
+}
+
+void swap_to_le(uint8_t *buf, size_t len, bool big_endian) {
+  if (!big_endian || len == 1) {
+    return;
+  }
+  for (size_t k = 0; k < len / 2; ++k) {
+    uint8_t tmp = buf[k];
+    buf[k] = buf[len - 1 - k];
+    buf[len - 1 - k] = tmp;
+  }
+}

contrib/plugins/bap-tracing/trace_meta.h

@@ -5,6 +5,8 @@
 #define BAP_TRACE_META_H
 
 #include <err.h>
+#include <stdbool.h>
+#include <stdint.h>
 #include <stdio.h>
 
 /**
@@ -34,5 +36,7 @@
 void write_meta(WLOCKED FILE *file, char **plugin_argv, size_t plugin_argc);
 char *get_argv_val(char **argv, int argc, const char *key);
 void file_exists_exit(const char *file);
+void memcpy_le(uint8_t *dst, uint8_t *src, size_t len, bool big_endian);
+void swap_to_le(uint8_t *buf, size_t len, bool big_endian);
 
 #endif

contrib/plugins/bap-tracing/tracing.c

@@ -9,6 +9,7 @@
 #include "frame_buffer.h"
 #include "qemu-plugin.h"
 #include "trace_consts.h"
+#include "trace_meta.h"
 #include "tracing.h"
 
 static TraceState state = {0};
@@ -52,6 +53,7 @@ static void add_post_reg_state(VCPU *vcpu, unsigned int vcpu_index,
         &g_array_index(current_regs, qemu_plugin_reg_descriptor, i);
     int s = qemu_plugin_read_register(reg->handle, rdata);
     assert(s == prev_reg->content->len);
+    swap_to_le(rdata->data, s, state.is_big_endian);
     if (!memcmp(rdata->data, prev_reg->content->data, s)) {
       // No change
       // Flush byte array
@@ -79,7 +81,7 @@ static void add_pre_reg_state(VCPU *vcpu, unsigned int vcpu_index,
     Register *prev_reg = g_ptr_array_index(vcpu->registers, i);
     g_assert(!strcmp(prev_reg->name, reg->name) &&
              prev_reg->handle == reg->handle);
-    memcpy(prev_reg->content->data, rdata->data, prev_reg->content->len);
+    memcpy_le(prev_reg->content->data, rdata->data, prev_reg->content->len, state.is_big_endian);
     frame_buffer_append_reg_info(fbuf, reg->name, rdata, s, OperandRead);
     // Flush byte array
     g_byte_array_set_size(rdata, 0);
@@ -338,6 +340,14 @@ QEMU_PLUGIN_EXPORT int qemu_plugin_install(qemu_plugin_id_t id,
     qemu_plugin_outs("Pass it with 'out=<output_file>'.\n\n");
     exit(1);
   }
+  char *endianess = get_argv_val(argv, argc, "endianess");
+  if (!endianess || (strcmp(endianess, "b") && strcmp(endianess, "l"))) {
+    qemu_plugin_outs("'endianess' argument is missing or is not 'b' or 'l'.\n");
+    qemu_plugin_outs("This is required until QEMU plugins get a richer API.\n");
+    qemu_plugin_outs("Pass it with 'endianess=[b/l]'.\n\n");
+    exit(1);
+  }
+  state.is_big_endian = endianess[0] == 'b';
 
   state.target_name = g_strdup(info->target_name);
   state.frame_buffer = g_ptr_array_new();

contrib/plugins/bap-tracing/tracing.h

@@ -171,6 +171,7 @@ typedef struct {
   GPtrArray /*<const char *>*/ *vcpu_modes; ///< Indexed by vcpu id.
 
   const char *target_name;
+  bool is_big_endian;
 } TraceState;
 
 VCPU *vcpu_new(void);