x86_32 stat() is... bad
lunixbochs opened this issue · comments
./usercorn -prefix samples/linux-i686/ samples/linux-i686/bin/stat usercorn
Output:
File: 'usercorn'
Size: 1505252135 Blocks: 0 IO Block: 512 weird file
Device: 157a44c01000004h/96726563353001988d Inode: 0 Links: 0
Access: (0024/?----w-r--) Uid: ((*cpu.FileDesc)(nil)
invalid fetch: @0x885cb82, 0x1 = 0x0
----------------------------------------
Error: Fetch from non-executable memory (UC_ERR_FETCH_PROT)
Desired:
File: 'usercorn'
Size: 12965312 Blocks: 25323 IO Block: 1024 regular file
Device: 2ch/44d Inode: 21984 Links: 1
Access: (0755/-rwxr-xr-x) Uid: ( 1000/ vagrant) Gid: ( 1000/ vagrant)
Access: 2017-09-12 21:34:27.000000000 +0000
Modify: 2017-09-12 21:31:54.000000000 +0000
Change: 2017-09-12 21:31:54.000000000 +0000
Birth: -
http://man7.org/linux/man-pages/man2/stat.2.html
C library/kernel differences
Over time, increases in the size of the stat structure have led to
three successive versions of stat(): sys_stat() (slot __NR_oldstat),
sys_newstat() (slot __NR_stat), and sys_stat64() (slot __NR_stat64)
on 32-bit platforms such as i386. The first two versions were
already present in Linux 1.0 (albeit with different names); the last
was added in Linux 2.4. Similar remarks apply for fstat() and
lstat().
The kernel-internal versions of the stat structure dealt with by the
different versions are, respectively:
__old_kernel_stat
The original structure, with rather narrow fields, and no
padding.
stat Larger st_ino field and padding added to various parts of the
structure to allow for future expansion.
stat64 Even larger st_ino field, larger st_uid and st_gid fields to
accommodate the Linux-2.4 expansion of UIDs and GIDs to 32
bits, and various other enlarged fields and further padding in
the structure. (Various padding bytes were eventually
consumed in Linux 2.6, with the advent of 32-bit device IDs
and nanosecond components for the timestamp fields.)
fixed in 99aa070