背景：
euler2403 docker buildx 不可用
结论：
x86默认4K对齐，LA默认16K对齐。
main.c:
int main() {}
cmd:
gcc main.c -o main_sepol -lsepol
dl_main -> dl_map_objects: 根据文件名映射动态对象。
_dl_map_object_deps：加载已映射对象的依赖对象。
#0 _dl_map_segments (loader=0x0, has_holes=false, maplength=16408, nloadcmds=4, loadcmds=0x7fffffffd860, type=2, header=0x7fffffffde38, fd=3, l=0x7ffff7ffe2d0) at ./dl-map-segments.h:83
#1 _dl_map_object_from_fd (name=0x7fffffffe7da "./main_sepol", origname=0x0, fd=3, fbp=0x7fffffffde30, realname=0x7ffff7ffe2c0 "./main_sepol", loader=0x0, l_type=0, mode=536870912,
stack_endp=0x7fffffffde20, nsid=0) at dl-load.c:1260
#2 0x00007ffff7fd49fb in _dl_map_object (loader=0x0, name=0x7fffffffe7da "./main_sepol", type=0, trace_mode=0, mode=536870912, nsid=0) at dl-load.c:2254
#3 0x00007ffff7feaa59 in dl_main (phdr=<optimized out>, phnum=<optimized out>, user_entry=<optimized out>, auxv=<optimized out>) at rtld.c:1590
#4 0x00007ffff7fe82f3 in _dl_sysdep_start (start_argptr=start_argptr@entry=0x7fffffffe5d0, dl_main=dl_main@entry=0x7ffff7fe9b10 <dl_main>) at ../sysdeps/unix/sysv/linux/dl-sysdep.c:140
#5 0x00007ffff7fe9914 in _dl_start_final (arg=0x7fffffffe5d0) at rtld.c:497
#6 _dl_start (arg=0x7fffffffe5d0) at rtld.c:582#7 0x00007ffff7fe88c8 in _start ()
#0 _dl_map_segments (loader=0x7ffff7ffe2d0, has_holes=false, maplength=761480, nloadcmds=4, loadcmds=0x7fffffffd250, type=3, header=0x7fffffffd7b8, fd=3, l=0x7ffff7fc50c0)
at ./dl-map-segments.h:83
#1 _dl_map_object_from_fd (name=0x4004b0 "libsepol.so.2", origname=0x0, fd=3, fbp=0x7fffffffd7b0, realname=0x7ffff7fc50a0 "/usr/lib64/libsepol.so.2", loader=0x7ffff7ffe2d0, l_type=1, mode=0,
stack_endp=0x7fffffffd7a0, nsid=0) at dl-load.c:1260
#2 0x00007ffff7fd49fb in _dl_map_object (loader=0x7ffff7ffe2d0, name=0x4004b0 "libsepol.so.2", type=1, trace_mode=0, mode=0, nsid=0) at dl-load.c:2254
#3 0x00007ffff7fcf2a5 in openaux (a=a@entry=0x7fffffffddb0) at dl-deps.c:64
#4 0x00007ffff7fce0e1 in __GI__dl_catch_exception (exception=exception@entry=0x7fffffffdd90, operate=operate@entry=0x7ffff7fcf270 <openaux>, args=args@entry=0x7fffffffddb0) at dl-catch.c:237
#5 0x00007ffff7fcf6f2 in _dl_map_object_deps (map=map@entry=0x7ffff7ffe2d0, preloads=preloads@entry=0x0, npreloads=npreloads@entry=0, trace_mode=<optimized out>, open_mode=open_mode@entry=0)
at dl-deps.c:232
#6 0x00007ffff7feb342 in dl_main (phdr=<optimized out>, phnum=<optimized out>, user_entry=<optimized out>, auxv=<optimized out>) at rtld.c:1973
#7 0x00007ffff7fe82f3 in _dl_sysdep_start (start_argptr=start_argptr@entry=0x7fffffffe5d0, dl_main=dl_main@entry=0x7ffff7fe9b10 <dl_main>) at ../sysdeps/unix/sysv/linux/dl-sysdep.c:140
#8 0x00007ffff7fe9914 in _dl_start_final (arg=0x7fffffffe5d0) at rtld.c:497
#9 _dl_start (arg=0x7fffffffe5d0) at rtld.c:582#10 0x00007ffff7fe88c8 in _start ()
该参数的作用就是从加载文件中获取PT_LOAD部分内容，后续传递给加载器，以进行具体的映射。
struct loadcmd
{
ElfW(Addr) mapstart, mapend, dataend, allocend, mapalign;
ElfW(Off) mapoff;
int prot; // 权限域
};
重点的，mapalign, 4K很常见，但是LA目前主要还是16K。
PT_LOAD 是一种程序头类型，指该segment是可加载的。相关的内容会从文件加载到内存中。
p *loadcmds$5 = {mapstart = 0, mapend = 1859584, dataend = 1855719, allocend = 1855719, mapalign = 4096, mapoff = 0, prot = 5}
(gdb) set loadcmds.mapalign = 0x4000
(gdb) p *loadcmds$14 = {mapstart = 0, mapend = 1859584, dataend = 1855719, allocend = 1855719, mapalign = 16384, mapoff = 0, prot = 5}
或者修改mapend进行验证，亦可说明是页对齐导致的mmap分配错误。
同时，也可借助readelf工具查看libsepol,.so的对齐情况：
Program Headers:
Type Offset VirtAddr PhysAddr
FileSiz MemSiz Flags Align
LOAD 0x0000000000000000 0x0000000000000000 0x0000000000000000
0x0000000000007650 0x0000000000007650 R 0x1000
LOAD 0x0000000000008000 0x0000000000008000 0x0000000000008000
0x0000000000083ce9 0x0000000000083ce9 R E 0x1000
LOAD 0x000000000008c000 0x000000000008c000 0x000000000008c000
0x00000000000297e8 0x00000000000297e8 R 0x1000
LOAD 0x00000000000b5ff0 0x00000000000b6ff0 0x00000000000b6ff0 0x0000000000001140 0x0000000000002e98 RW 0x1000
./qemu-x86_64 -L /usr/x86_64-linux-gnu/ -g 1234 ~/main_sepol
qemu-user 需要使能gdb调试: --enable-debug
./gdb/gdb ~/main_sepol // 这里的gdb是交叉构建出来的，configure使能target=x86_64-linux-gnu即可
target remote localhost:1234