I'm trying to write to a character device in Android shell. But mksh responds with "Unknown error 517" for a whole range of operations. I've tried to use strace to track down the issue, but its not helpful. This also occurs for a whole range of device nodes in AOS 4.4, but not in 4.2.
This is what I do:
# chmod 666 /dev/smd0
Unable to open /dev/smd0: Unknown error 517
# cat /dev/smd0
tmp-mksh: cat: /dev/smd0: Unknown error 517
The device is there and I can both create it (mknod) and remove it, so it's not a permission problem as far as I can see.
# ls /dev/smd0
crw-rw---- 1 1000 1000 222, 0 Feb 13 2014 /dev/smd0
All I get in strace is:
ioctl(10</dev/tty>, SNDCTL_TMR_STOP or TCSETSW, {c_iflags=0x500, c_oflags=0x5, c_cflags=0xbf, c_lflags=0x8a3b, c_line=0, c_cc="\x03\x1c\x7f\x15\x04\x00\x01\x00\x11\x13\x1a\x00\x12\x0f\x17\x16\x00\x00\x00"}) = 0
ioctl(10</dev/tty>, TIOCSPGRP, [23069]) = 0
[pid 23069] open("/dev/smd0", O_RDONLY|O_LARGEFILE) = -1 EPROBE_DEFER (Unknown error 517)
[pid 23069] open("/dev/smd0", O_WRONLY|O_LARGEFILE) = -1 EPROBE_DEFER (Unknown error 517)
[pid 23069] write(2</dev/pts/5>, "Unable to open /dev/smd0: Unknown error 517\n", 44) = 44
Looking at the mksh sources in the shf.c file doesn't offer any insight either.
I also found the EPROBE_DEFER tag in the Linux Kernel sources, in the file: ../include/linux/errno.h:
#define EPROBE_DEFER 517 /* Driver requests probe retry */
Any ideas what could cause this problem?
This is simply because bionic’s error definitions do not know about errno #517 (yet). mksh just uses what the operating system(’s C library) — in this case, Android’s bionic — provides.
This part of shf.c generates the Unknown error: %d message when the underlying operating system(’s C library) doesn’t know about the error the underlying operating system(’s kernel) generates, which is here the case.