On Tue, Mar 19, 2024 at 09:25:57AM -0700, Andrii Nakryiko wrote: > On Tue, Mar 19, 2024 at 4:08 AM Jiri Olsa <olsajiri@xxxxxxxxx> wrote: > > > > On Tue, Mar 19, 2024 at 11:25:24AM +0100, Oleg Nesterov wrote: > > > Obviously not for inclusion yet ;) untested, lacks the comments, and I am not > > > sure it makes sense. > > > > > > But I am wondering if this change can speedup uretprobes a bit more. Any chance > > > you can test it? > > > > > > With 1/3 sys_uretprobe() changes regs->r11/cx, this is correct but implies iret. > > > See the /* SYSRET requires RCX == RIP and R11 == EFLAGS */ code in do_syscall_64(). > > > > nice idea, looks like sysexit should be faster > > > > > > > > With this patch uretprobe_syscall_entry restores rcx/r11 itself and does retq, > > > sys_uretprobe() needs to hijack regs->ip after uprobe_handle_trampoline() to > > > make it possible. > > > > > > Comments? > > > > > > Oleg. > > > --- > > > > > > diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c > > > index 069371e86180..b99f1d80a8c8 100644 > > > --- a/arch/x86/kernel/uprobes.c > > > +++ b/arch/x86/kernel/uprobes.c > > > @@ -319,6 +319,9 @@ asm ( > > > "pushq %r11\n" > > > "movq $462, %rax\n" > > > "syscall\n" > > > + "popq %r11\n" > > > + "popq %rcx\n" > > > + "retq\n" > > > > using rax space on stack for return pointer, cool :) > > > > I'll run the test with this change > > > > I can do some benchmarking on my side as well, given I have everything that'd be great, thanks > set up for this anyways. Thanks for the help with speeding all this > up! > > BTW, Jiri, what are you plans regarding sys_uprobe (entry probe > optimization through syscall), while we are on the topic? I plan to work on that after this one is sorted out jirka
