Messages in this thread | | | Date | Sat, 30 May 2015 08:55:11 +0900 | From | Masami Hiramatsu <> | Subject | Re: Re: [RFC PATCH v2 09/15] perf probe: Support $params without debuginfo |
| |
On 2015/05/29 15:30, He Kuang wrote: > hi, Alexei > > On 2015/5/29 2:10, Alexei Starovoitov wrote: >> On 5/28/15 6:01 AM, He Kuang wrote: >>>> I don't think you can break it down in two steps like this. >>>>> There is no such thing as 'calling regs'. x86_32 with ax,dx,cx >>>>> are not 'calling regs'. 64-bit values will be passed in a pair. >>>>> Only 'pt_regs + arch + func_proto + asmlinkage' makes sense >>>> >from the user point of view. >>>>> Adding 'asmlinkage' attr is also trivial. >>>>> 'func(long, char) asmlinkage' is easy to parse and the user >>> I think at this early stage, we could make our bpf variable >>> prologue work with debuginfo while keeping bpf 'SEC' syntax >>> consistent with original perf probe. After all, we can use >>> pt_regs directly or relay to perf-probe cache by Masami to deal >>> with non-debug cases. >> >> so you're saying you don't want to support non-debug case for now? >> Sure, as long as section name parser will be able to support >> 'func(long, char) asmlinkage' syntax in the future without breaking >> compatibility. I'm mostly interested in cases when debug info >> is not available at all. So perf-probe cache is of no use to me. >> >> > > Yes, that syntax do deal with the situation which current 'perf > probe' syntax not covered, so not only bpf prologue would benifit > from that, maybe we could try to let perf probe involve that.
Hmm, then how about below syntax?
perf probe x86_acpi_enter_sleep_state $regparams:asmlinkage(char)
So, regparams has following synopsis.
$regparams[:[asmlinkage|0-6]([u8|u16|u32|u64|ptr][,...])]
Note that asmlinkage is a synonym of 0, and default depends on arch :) Some architecture ignores this part, e.g. x86_64 always uses regs. And it is automatically expanded to argX="%reg or $stackX".
e.g. $regparams is expanded to arg1=%di arg2=%si arg3=%dx arg4=%cx arg5=%r8 arg6=%r9 (on x86_64) arg1=%ax arg2=%dx arg3=%cx arg4=$stack1 arg5=$stack2 arg6=$stack3 (on i386)
$regparams:0 is expanded to arg1=%di arg2=%si arg3=%dx arg4=%cx arg5=%r8 arg6=%r9 (on x86_64) arg1=$stack1 arg2=$stack2 arg3=$stack3 arg4=$stack4 arg5=$stack5 arg6=$stack6 (on i386)
$regparams:3(char,long) is expanded to arg1=%di:s8 arg2=%si:s64 (on x86_64) arg1=%ax:s8 arg2=%dx:s64 (on i386)
How is this?
Thank you,
-- Masami HIRAMATSU Linux Technology Research Center, System Productivity Research Dept. Center for Technology Innovation - Systems Engineering Hitachi, Ltd., Research & Development Group E-mail: masami.hiramatsu.pt@hitachi.com
| |