for school work I have to add custom helloworld syscall to freebsd. I used following link as my guide: http://members.tripod.com/s_mathur/bsdhowto.html
OK!
In step two I got problem: root has not permission to run it so I used: "make sysent" instead. seems ok.
Step 4 says: 4. Modify the Makefile to include sys_hello.c,etc and recompile the kernel.!!!
Which makefile? and how to compile it and how call syscall hello?
tnx in advance
If sys_hello.c contains your syscall implementation - and it's in sys/kern/sys_hello.c - then add this file to conf/files. Search for eg. "kern_fork.c" there and add sys_hello.c in a similar way. Afterwards, rebuild and reinstall kernel and world (make buildkernel buildworld installkernel installworld); world rebuild is neccessary to get the userspace part into libc.so. As for calling - well, call it like you would call another syscall. You will need to add the syscall declaration somewhere.
Related
I am following a Linux System Programming Video Tutorial.
When I reached "how to add your own Linux System Call" section, the instructor shows that all System Call IDs (macros starting with __NR) are present in arch/x86/include/asm/unistd_32.h or unistd_64.h (depending on the target).
But in my source code(linux-5.0.1) I do not see those files, there's just one unistd.h which does not contain the system call IDs. Were these files moved elsewhere or does x86 not have its own system call table now.
Edit: I downloaded the latest kernel source code from kernel.org and I am trying to modify it. I cannot find unistd_32.h and unistd_64.h files at the aforementioned location. Do I need to do something first?
Arch Linux ships unistd_32.h and unistd_64.h in /usr/include/asm/. Just look at those headers unless you're modifying the kernel to add new system calls.
<asm/unistd.h> checks macros to figure out if its being included in 32 or 64-bit code (and checks for x32), and uses #include to pull in the right set of definitions for the target.
On my up-to-date x86-64 Arch system:
$ pacman -Fo /usr/include/asm/unistd*
usr/include/asm/unistd_32.h is owned by core/linux-api-headers 4.7-1
usr/include/asm/unistd_64.h is owned by core/linux-api-headers 4.7-1
usr/include/asm/unistd.h is owned by core/linux-api-headers 4.7-1
usr/include/asm/unistd_x32.h is owned by core/linux-api-headers 4.7-1
In the kernel source itself, starting with version 3.3, the unistd_32.h for use by user-space is built from other files.
https://github.com/torvalds/linux/search?q=unistd_32.h&unscoped_q=unistd_32.h finds this in arch/x86/entry/syscalls/Makefile
$(uapi)/unistd_32.h: $(syscall32) $(syshdr)
$(call if_changed,syshdr)
The syscall tables are defined in: arch/x86/entry/syscalls/syscall_32.tbl and .../syscall_64.tbl
https://github.com/torvalds/linux/tree/6f0d349d922ba44e4348a17a78ea51b7135965b1/arch/x86/entry/syscalls
The contents of syscall_32.tbl looks like:
# some comments
0 i386 restart_syscall sys_restart_syscall __ia32_sys_restart_syscall
1 i386 exit sys_exit __ia32_sys_exit
2 i386 fork sys_fork __ia32_sys_fork
3 i386 read sys_read __ia32_sys_read
...
I am trying to compile my led wrapper function program file with including linux/leds.h
using including kernel space header files
gcc -I /usr/src/linux-headers-3.13.0-44-generic/include/ example.c
by compiling it flooded the console with errors in many headers file those are depended on leds.h. Can any one please help me to compile this C file which is using kernel space header files in user space.
Thanks in advance. :)
This won't work.
First of all, don't use kernel-mode headers in user-mode programs, except for the (processed?) ones provided for userspace after kernel compilation. Kernel-mode headers depend on the kernel build system to work.
I tried this, just for curiosity, although I did already knew why it won't work (tl;dr, I use the Ubuntu-patched 3.13.0-24 kernel):
$ cd /usr/src/linux-headers-3.13.0-24/
$ echo '#include <linux/leds.h>' | gcc -E -x c -o - - -Iinclude
The preprocessor claims that <asm/linkage.h> is missing, and, correct me if I'm wrong, that header is generated by the kernel build system.
If you want, you can solve this by creating a kernel module that uses <linux/leds.h> et al, then export a userspace API through the module (usually done through /proc or /sys) and use that API to implement your usermode code's logic.
Hope this helps!
Thanks KemyLand, You were right that we can not use kernel space header file in user space. But your approach couldn't work for me. firstly it asked for asm/linkage.h, i included the path of it explicitly but again compilation terminated on another header file and i did same. But at last i blocked on some errors in headers files, which were not expected as i didn't make any changes in those files. but finally i got the solution. basically we have to do Interfacing functions between kernel space and the hardware device. I had to generate make file for it. obj-m :=file_name.o and compiled it by following command make -C /usr/src/linux-headers-3.13.0-44-generic/ -C /usr/include/ M=pwd modules it generated 4 files file_name.mod.o , file_name.o, file_name.ko, file_name.mod.c. and then loaded the module as root by insmod file_name.ko. for checking the loaded module type command lsmod. I can also execute it by typing command insmod ./file_name.o or can remove by rmmod file_name
Does Pintos have to be installed in a different way for the second Project (User Programs)? Whenever I try to run pintos -f -q on my installation, I get an error where Pintos doesn't recognize the arguments "-f".
Back to tcg accelerator.
PiLo hda1
Loading..........
Kernel command line: -f -q
Kernel PANIC at ../../threads/init.c:264 in parse_options(): unknown option `-f' (use -h for help)
Call stack: 0xc00283de.
The `backtrace' program can make call stacks useful.
Read "Backtraces" in the "Debugging Tools" chapter
of the Pintos documentation for more information.
This is where all the arguments are handled by Pintos:
http://www.cse.iitd.ernet.in/~sbansal/csl373/pintos/doc/pintos_html/init_8c-source.html
I can't find the definition of FILESYS anywhere either. Can someone please help me out here?
In utils/pintos change line number 259 to /home/<your home username>/<pintos dir>/src/userprog/build/kernel.bin
In utils/Pintos.pm change line number 362 to /home/<your home username>/<pintos dir>/src/userprog/build/loader.bin
Run make in userprog, utils again.
Had the same problem
You need to point the Kernel and Loader to the Kernel and Loader in userprog/build instead of threads/build as done while installing pintos
I am running red had linux 7.3 (old, I know), and for the past few months I've been learning assembly programming, writing small programs and compiling with nasm. For months, things have been going fine, and now for some unknown reason, I cannot execute any programs that I compile.
nasm file.s //used to work just fine, then I'd execute ./file
now, when I run ./file, first I get "permission denied", which never used to happen before. then, once i chmod +777 file, I get "cannot execute binary file".
I have NO IDEA why this is happening, but it is extremely frustrating since NOTHING I compile will run anymore.
Logging in as root doesn't change anything.
All suggestions are welcome, THANK YOU!!
nasm does not produce an executable, but just an object file (like gcc -c would). You still need to run the linker on it.
N.B.: “0777 is almost always wrong.”
Run the file command on your binaries and make sure they're identified correctly as executables.
Also try the ldd command. It will very likely fail for the exact same reason, but it's worth a shot.
This can happen if the file system you operate on is mounted with the noexec option. You could check that by doing mount | grep noexec and see if your current working directory suffers from that.
"Cannot execute binary file" is the strerror(3) message for the error code ENOEXEC. That has a very specific meaning: (quoting the manpage for execve(2))
[ENOEXEC] The new process file has the appropriate access
permission, but has an unrecognized format
(e.g., an invalid magic number in its header).
So what that means is, your nasm invocation is not producing an executable, but rather something else. As John Kugelman suggests, the file command will tell you what it is (user502515 is very likely to be right that it's an unlinked object file, but I have never used nasm myself so I don't know).
BTW, you'll do yourself a favor if you learn GAS/"AT&T" assembly syntax now, rather than when you need to rewrite your assembly code for an architecture that doesn't do Intel bizarro-world syntax. And I do hope you're using assembly only for inner-loop subroutines that actually need to be hand-optimized.
This just happened to me. After running
file <executable name>
it output <file name> ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.15, not stripped
And the problem was that I was trying to run a 64 bit app on a 32 bit machine!
You may try looking into /var/log for some change in the system from this start to happen.
These are the steps I am doing to compile the linux source on my machine :
1. Copy the config file from /boot to /usr/src/kernels/2.6.29.4-167.fc11.i586/ directory
2. make oldconfig
3. make
Step 3 fails with the following error :
make[1]: *** No rule to make target `missing-syscalls'. Stop.
Compiling on a x86 box.
Any suggestions ?
Please feel free to close this question if it does not belong here.
As archaic as it may sound it appears that currently in order to get kernel source on a system you have to manually select the source you want. One supposes that people don't build kernels as often as they used to and of course you may want to develop a kernel that does not match the version that you are running..
So for example I wanted to install VBox on my CentOS 6.2 box and while most kernel modules can be compiled without complete sources this update failed.
So I found this wiki page:
http://wiki.centos.org/HowTos/I_need_the_Kernel_Source
It doesn't list 6.2 and the naming conventions have changed on the final directory name so to get the 6.2 kernel source you go to http://vault.centos.org/6.2/updates/Source/ and select the version you want. If you want source for a different version go to http://vault.centos.org/ and navigate from there.
The docs recommend against doing an rpm-build on the kernel sources.
Make a new config file. Maybe the old one isn't working?
I have not been able to answer why this error happens :
Step 3 fails with the following error : make[1]: *** No rule to make target `missing-syscalls'. Stop.
But I was able to compile the vanilla version fine, without the above error.
I asked the same question on serverfault as well, which has a more detailed explanation of the steps taken : https://serverfault.com/questions/61354/missing-syscalls-error-during-kernel-compilation
since kernel 3.x.x this message appears if trying to build external modules having only single Makefile prepared.
Instead, according to this manual,
splitting into Kbuild (where all the source files are listed, example):
obj-m := module_source.c
and simple Makefile (having only default make directive, example):
default:
$(MAKE) -C $(KDIR) M=$$PWD
will solve the problem.
just in case, external module build directive would be following:
make -C <kernel source path> -M=<module source folder>
example: make -C . -M=extra/