To add a system call that can be called in xv6’s shell, you should so something with the five files sysproc.c add the real implementation of your method here syscall.h define the position of the system call vector that connect to your implementation user.h define the function that can be called through the shell syscall.c … Read more
Extended-asm syntax requires writing %% to get a single % in the asm output. e.g. for x86: asm(“inc %eax”) // bad: undeclared clobber asm(“inc %%eax” ::: “eax”); // safe but still useless 😛 %r7 is treating r7 as an operand number. As commenters have pointed out, just omit the %s, because you don’t need them … Read more
I do not know an equivalent of VirtualQuery on Linux. But some other ways to do it which may or may not work are: you setup a signal handler trapping SIGBUS/SIGSEGV and go ahead with your read or write. If the memory is protected, your signal trapping code will be called. If not your signal … Read more
About read: read supports PerlIO layers. read works with any Perl file handle[1]. read buffers. read obtains data from the system in fixed sized blocks of 8 KiB[2]. read may block if less data than requested is available[3]. About sysread: sysread doesn’t support PerlIO layers (meaning it requires a raw a.k.a. binary handle). sysread only … Read more
os.system() does wait for its process to complete before returning. If you are seeing it not wait, the process you are launching is likely detaching itself to run in the background in which case the subprocess.Popen + wait example Dor gave won’t help. Side note: If all you want is subprocess.Popen + wait use subprocess.call: … Read more
You can use the wrap feature provided by ld. From man ld: –wrap symbol Use a wrapper function for symbol. Any undefined reference to symbol will be resolved to __wrap_symbol. Any undefined reference to __real_symbol will be resolved to symbol. So you just have to use the prefix __wrap_ for your wrapper function and __real_ … Read more
You can’t ret from start; it isn’t a function and there’s no return address on the stack. The stack pointer points at argc on process entry. As n.m. said in the comments, the issue is that you aren’t exiting the program, so execution runs off into garbage code and you get a segfault. What you … Read more
You first should understand what is the role of the linux kernel, and that applications interact with the kernel only thru system calls. In effect, an application runs on the “virtual machine” provided by the kernel: it is running in the user space and can only do (at the lowest machine level) the set of … Read more
More generic answer than what you asked. On Linux the man syscall (2) is a good start to find out how to make a system call in various architectures. Copied from that manpage: Architecture calling conventions Every architecture has its own way of invoking and passing arguments to the kernel. The details for various architectures … Read more