root@RT-AC86U:/# strace df ..
execve("/bin/df", ["df", ".."], [/* 16 vars */]) = 0
brk(NULL) = 0xab54a000
uname({sysname="Linux", nodename="RT-AC86U", ...}) = 0
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
mmap2(NULL, 12288, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xf77c2000
access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=6840, ...}) = 0
mmap2(NULL, 6840, PROT_READ, MAP_PRIVATE, 3, 0) = 0xf77c0000
close(3) = 0
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
open("/lib/arm-linux-gnueabihf/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\1\1\1\3\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0\331e\1\0004\0\0\0"..., 512) = 512
lseek(3, 900076, SEEK_SET) = 900076
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 2920) = 2920
lseek(3, 896524, SEEK_SET) = 896524
read(3, "A4\0\0\0aeabi\0\1*\0\0\0\0057-A\0\6\n\7A\10\1\t\2\n\3\f"..., 53) = 53
fstat64(3, {st_mode=S_IFREG|0755, st_size=902996, ...}) = 0
mmap2(NULL, 972128, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xf76b0000
mprotect(0xf7789000, 61440, PROT_NONE) = 0
mmap2(0xf7798000, 12288, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0xd8000) = 0xf7798000
mmap2(0xf779b000, 9568, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0xf779b000
close(3) = 0
set_tls(0xf77c47e0, 0xf77c4eb8, 0xf77c6050, 0xf77c47e0, 0xf77c6050) = 0
mprotect(0xf7798000, 8192, PROT_READ) = 0
mprotect(0xaae97000, 4096, PROT_READ) = 0
mprotect(0xf77c5000, 4096, PROT_READ) = 0
munmap(0xf77c0000, 6840) = 0
brk(NULL) = 0xab54a000
brk(0xab56b000) = 0xab56b000
open("..", O_RDONLY|O_NOCTTY|O_LARGEFILE) = 3
fstat64(3, {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
close(3) = 0
open("/proc/self/mountinfo", O_RDONLY|O_LARGEFILE) = 3
fstat64(3, {st_mode=S_IFREG|0444, st_size=0, ...}) = 0
read(3, "25 23 0:6 / /dev rw,relatime - d"..., 1024) = 216
read(3, "", 1024) = 0
_llseek(3, 0, [216], SEEK_CUR) = 0
close(3) = 0
getcwd("/", 4096) = 2
open(".", O_RDONLY|O_LARGEFILE) = 3
fcntl64(3, F_GETFD) = 0
fcntl64(3, F_SETFD, FD_CLOEXEC) = 0
chdir("..") = 0
stat64("..", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
getcwd("/", 4096) = 2
fchdir(3) = 0
close(3) = 0
uname({sysname="Linux", nodename="RT-AC86U", ...}) = 0
statfs64("/", 88, 0xff87de30) = 0
fstat64(1, {st_mode=S_IFCHR|0622, st_rdev=makedev(136, 0), ...}) = 0
write(1, "Filesystem 1K-blocks Us"..., 61Filesystem 1K-blocks Used Available Use% Mounted on
) = 61
write(1, "- 961271120 4397083"..., 52- 961271120 439708376 472709960 49% /
) = 52
close(1) = 0
close(2) = 0
exit_group(0) = ?
+++ exited with 0 +++
root@RT-AC86U:/# cat /proc/self/mountinfo
25 23 0:6 / /dev rw,relatime - devtmpfs devtmpfs rw,mode=0755
26 25 0:11 / /dev/pts rw,relatime - devpts devpts rw,mode=600
27 23 0:4 / /proc rw,relatime - proc proc rw
28 23 0:14 / /sys rw,relatime - sysfs sysfs rw
root@RT-AC86U:/#