user: 请从给定的汇编指令推导出C源代码:

```asm
<linuxtrack_get_prefix>:
  endbr64
  push   %r15
  lea    D35(%rip),%rdi
  push   %r14
  push   %r13
  push   %r12
  push   %rbp
  push   %rbx
  sub    $0x8,%rsp
  call   <getenv@plt>
  mov    %rax,%r15
  test   %rax,%rax
  je     L99
  lea    D67(%rip),%rdx
  lea    D8(%rip),%rsi
  mov    %rax,%rdi
  call   <construct_name@plt>
  lea    D33(%rip),%rsi
  mov    %rax,%rdi
  mov    %rax,%r12
  call   <fopen@plt>
  mov    %r12,%rdi
  mov    %rax,%rbp
  test   %rax,%rax
  je     L85
  call   <free@plt>
  mov    $0x1000,%edi
  lea    D39(%rip),%rbx
  lea    D43(%rip),%r15
  call   <malloc@plt>
  mov    $0x1000,%edi
  mov    %rax,%r12
  call   <malloc@plt>
  mov    $0x1000,%edi
  mov    %rax,%r14
  call   <malloc@plt>
  mov    %rax,%r13
  jmp    L21
  nopl   (%rax)
L24:
  mov    %rbp,%rdx
  mov    $0xfff,%esi
  mov    %r12,%rdi
  call   <fgets@plt>
  test   %rax,%rax
  jne    L69
L21:
  mov    %rbp,%rdi
  call   <feof@plt>
  test   %eax,%eax
  je     L24
  xor    %r15d,%r15d
L83:
  mov    %rbp,%rdi
  call   <fclose@plt>
  mov    %r12,%rdi
  call   <free@plt>
  mov    %r14,%rdi
  call   <free@plt>
  mov    %r13,%rdi
  call   <free@plt>
L93:
  add    $0x8,%rsp
  mov    %r15,%rax
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
  cs nopw 0x0(%rax,%rax,1)
L69:
  mov    %r14,%rcx
  mov    %r13,%rdx
  mov    %rbx,%rsi
  mov    %r12,%rdi
  call   <sscanf@plt>
  cmp    $0x2,%eax
  jne    L21
  mov    %r15,%rsi
  mov    %r13,%rdi
  call   <strcasecmp@plt>
  test   %rax,%rax
  jne    L21
  mov    %r14,%rdi
  call   <strdup@plt>
  mov    %rax,%r15
  jmp    L83
  nopl   0x0(%rax,%rax,1)
L99:
  lea    D13(%rip),%rdi
  call   <linuxtrack_log@plt>
  jmp    L93
L85:
  call   <free@plt>
  xor    %r15d,%r15d
  jmp    L93
```

tool_calls: name: retrieve_data
arguments: data_label: D35
type: string
name: retrieve_data
arguments: data_label: D67
type: string
name: retrieve_data
arguments: data_label: D8
type: string
name: retrieve_data
arguments: data_label: D33
type: string
name: retrieve_data
arguments: data_label: D39
type: string
name: retrieve_data
arguments: data_label: D43
type: string
name: retrieve_data
arguments: data_label: D13
type: string

tool: D35: HOME

tool: 

tool: D8: /.config/linuxtrack/linuxtrack1.conf

tool: D33: r

tool: D39: %s = "%[^"
]

tool: D43: prefix

tool: D13: Please set HOME variable!


assistant: ```c
char *linuxtrack_get_prefix() {
  char *prefix = NULL;
  char *home = getenv("HOME");
  char *cfg = (char *)"/.config/linuxtrack/linuxtrack1.conf";
  char *fname;
  FILE *f;
  char *line;
  char *val, *key;
  if (home == NULL) {
    linuxtrack_log("Please set HOME variable!\n");
    return NULL;
  }
  fname = construct_name(home, cfg, "");
  if ((f = fopen(fname, "r")) == NULL) {
    free(fname);
    return NULL;
  }
  free(fname);
  line = (char *)malloc(4096);
  val = (char *)malloc(4096);
  key = (char *)malloc(4096);
  while (!feof(f)) {
    if (fgets(line, 4095, f) != NULL) {
      if ((sscanf(line, "%s = \"%[^\"\n]", key, val) == 2) && strcasecmp(key, "prefix") == 0) {
        prefix = strdup(val);
        break;
      }
    }
  }
  fclose(f);
  free(line);
  free(val);
  free(key);
  return prefix;
}
```