5
int main(int argc, char *argv[])
{
return 0;
}
鉴于上述C程序，我使用clang test.c ; strace ./a.out得到以下输出。了解空c程序的输出
execve("./a.out", ["./a.out"], [/* 36 vars */]) = 0
brk(0) = 0x1a06000
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f785c40f000
access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=78590, ...}) = 0
mmap(NULL, 78590, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f785c3fb000
close(3) = 0
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
open("/lib/x86_64-linux-gnu/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\320\37\2\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=1840928, ...}) = 0
mmap(NULL, 3949248, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f785be2a000
mprotect(0x7f785bfe5000, 2093056, PROT_NONE) = 0
mmap(0x7f785c1e4000, 24576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1ba000) = 0x7f785c1e4000
mmap(0x7f785c1ea000, 17088, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7f785c1ea000
close(3) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f785c3fa000
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f785c3f8000
arch_prctl(ARCH_SET_FS, 0x7f785c3f8740) = 0
mprotect(0x7f785c1e4000, 16384, PROT_READ) = 0
mprotect(0x600000, 4096, PROT_READ) = 0
mprotect(0x7f785c411000, 4096, PROT_READ) = 0
munmap(0x7f785c3fb000, 78590) = 0
exit_group(0) = ?
+++ exited with 0 +++
东西我搞糊涂了：
- 什么用
0x7f785c40f000平均结尾行/怎么办？ - 为什么
3949248在mmap时libc.so是1840928大吗？ mprotect中使用的地址来自哪里？mmap使用的地址来自何时不是NULL？- 什么是
mmaparch_prctl之前分配的4k和8k内存？
很好的问题。以上应该几乎都是动态加载器的工作，它具有相当复杂的规范。将它与一个'-static'构建进行比较会很有趣，其中大部分内容不会发生，但其他内容（例如'uname'调用和一些'brk'调用，但不包含'mmap'）。 – PSkocik
@PSkocik是的，结果如此：http://paste.ubuntu.com/15001856/ – muru