I forgot everything about the low-level x86_64 code, but...
On 03/11, Jiri Olsa wrote:
>
> #ifdef CONFIG_X86_64
> +
> +asm (
> + ".pushsection .rodata\n"
> + ".global uretprobe_syscall_entry\n"
> + "uretprobe_syscall_entry:\n"
> + "push %rax\n"
> + "mov $462, %rax\n"
> + "syscall\n"
Hmm... I think you need to save/restore more registers clobbered by
syscall/entry_SYSCALL_64 ?
> +SYSCALL_DEFINE1(uprobe, unsigned long, cmd)
> +{
> + struct pt_regs *regs = task_pt_regs(current);
> + unsigned long ax, err;
> +
> + /*
> + * We get invoked from the trampoline that pushed rax
> + * value on stack, read and restore the value.
> + */
> + err = copy_from_user((void*) &ax, (void *) regs->sp, sizeof(ax));
> + WARN_ON_ONCE(err);
> +
> + regs->ax = ax;
probably not strictly needed, we are going to return ax...
> + regs->orig_ax = ax;
This doesn't look right. I think you need
regs->orig_ax = -1;
Say, to avoid the "Did we come from a system call" checks in
arch_do_signal_or_restart() or handle_signal().
Oleg.
