On Tue, Jan 14, 2025 at 11:58:03AM +0100, Oleg Nesterov wrote: > On 01/14, Jiri Olsa wrote: > > > > --- a/arch/x86/kernel/uprobes.c > > +++ b/arch/x86/kernel/uprobes.c > > @@ -315,14 +315,25 @@ asm ( > > ".global uretprobe_trampoline_entry\n" > > "uretprobe_trampoline_entry:\n" > > "pushq %rax\n" > > + "pushq %rbx\n" > > "pushq %rcx\n" > > "pushq %r11\n" > > + "movq $1, %rbx\n" > > "movq $" __stringify(__NR_uretprobe) ", %rax\n" > > "syscall\n" > > ".global uretprobe_syscall_check\n" > > "uretprobe_syscall_check:\n" > > + "or %rbx,%rbx\n" > > + "jz uretprobe_syscall_return\n" > > "popq %r11\n" > > "popq %rcx\n" > > + "popq %rbx\n" > > + "popq %rax\n" > > + "int3\n" > > + "uretprobe_syscall_return:\n" > > + "popq %r11\n" > > + "popq %rcx\n" > > + "popq %rbx\n" > > But why do we need to abuse %rbx? Can't uretprobe_trampoline_entry do > > syscall > > // int3_section, in case sys_uretprobe() doesn't work > popq %r11 > popq %rcx > popq %rax > int3 > > uretprobe_syscall_return: > popq %r11 > popq %rcx > popq %rbx > retq > > and change sys_uretprobe() to do > > - regs->ip = ip; > + regs->ip = ip + sizeof(int3_section); nice idea, I wonder we get the trampoline size under one xol slot with that thanks, jirka
