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> I found better solution for system calls Yeah, I have seen that file. Thought last I checked, it crashes in certain conditions [1]; I didn't really go back t

> I found better solution for system calls Yeah, I have seen that file. Thought last I checked, it crashes in certain conditions [1]; I didn't really go back to it to fix it. > I actually planned to make my own ld-liblinux eventually Can you share this code? If not, could you document how exactly would you have done this? I lost all motivation once I realized that ld-linux and Glibc communicate with private APIs, but I'd love to actually work on it if it was possible to do this. > Do you think liblinux could have a future? Absolutely. The problem with Linux currently is that the loader rejects programs at the sign of slightest incompatibility before even trying to execute them, which means that there is nothing that the application code could do to work around said incompatibility. If we were able to get our code running (or, as I like to say it, make %RIP point inside the main function), we could then do whatever hacky-bullshit was required make the software work. All I need is to get our code executing, and from that point on, I'll handle system compatibility. [1]: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95411 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95411

matheusmoreira 6y ago
Not sure why the stack is unaligned there. The way I solved this in liblinux is to just pass the stack pointer to a C function and compute all the other pointers there. That way the compiler deals with the stack stuff. _start: xorq %rbp,%rbp /* user code should mark the deepest stack frame * by setting the frame pointer to zero */ movq %rsp,%rdi call liblinux_start movq %rax,%rdi movq $__NR_exit,%rax syscall static void *after(void *vector) { void **pointer = (void **) vector; while (*pointer++ != 0); return pointer; } int liblinux_start(void *stack_pointer) { long count; char *arguments; char *environment; struct auxiliary *values; count = *((long *) stack_pointer); arguments = ((char **) stack_pointer) + 1; environment = arguments + count + 1; values = after(environment); /* start is the main function */ return start(count, arguments, environment, values); } > Can you share this code? If not, could you document how exactly would you have done this? Unfortunately I didn't make it that far. I was planning to study how glibc and musl do it just like how I studied their system call implementations. If I start working on this again I'm gonna look this up. I'll need to learn this linking stuff in order to support the kernel vDSO anyway.

matheusmoreira 6y ago

Not sure why the stack is unaligned there. The way I solved this in liblinux is to just pass the stack pointer to a C function and compute all the other pointers there. That way the compiler deals with the stack stuff. _start: xorq %rbp,%rbp /* user code should mark the deepest stack frame * by setting the frame pointer to zero */ movq %rsp,%rdi call liblinux_start movq %rax,%rdi movq $__NR_exit,%rax syscall static void *after(void *vector) { void **pointer = (void **) vector; while (*pointer++ != 0); return pointer; } int liblinux_start(void *stack_pointer) { long count; char *arguments; char *environment; struct auxiliary *values; count = *((long *) stack_pointer); arguments = ((char **) stack_pointer) + 1; environment = arguments + count + 1; values = after(environment); /* start is the main function */ return start(count, arguments, environment, values); } > Can you share this code? If not, could you document how exactly would you have done this? Unfortunately I didn't make it that far. I was planning to study how glibc and musl do it just like how I studied their system call implementations. If I start working on this again I'm gonna look this up. I'll need to learn this linking stuff in order to support the kernel vDSO anyway.