On Wed, 25 Apr 2018 21:16:06 +0900 Masami Hiramatsu mhiramat@kernel.org wrote:
Hi,
This is the 7th version of the fetch-arg improvement series. This includes variable changes on fetcharg framework like,
- Add fetcharg testcases (syntax, argN, symbol, string and array) and probepoint testcase.
- Rewrite fetcharg framework with fetch_insn, switch-case based instead of function pointer.
- Add "symbol" type support, which shows symbol+offset instead of address value.
- Add "$argN" fetcharg, which fetches function parameters. (currently only for x86-64)
- Add array type support (including string arrary :) ) , which enables to get fixed length array from probe-events.
- Add array type support for perf-probe, so that user can dump partial array entries.
V6 is here: https://lkml.org/lkml/2018/3/17/75
Changes from the v6 are here: [6/16] - Fix to return an error if failed to fetch string and fill zero-length data_loc in error case. [11/16] - Update document for restructured text. [15/16] - Fix README test. [16/16] - Add type-casting description (and note) to documentation.
And rebased on the latest Steve's ftrace/core branch.
Hi Masami,
I skimmed through the patches and it they appear fine. I've applied them and started playing a little.
I've been thinking my function based events, and thought instead I would make them part of the kprobe infrastructure. Just have a slightly different format, and instead of being p: or r: be f: And keep the format I was suggesting.
What do you think?
Also, when looking at the kprobe code, I was looking at this function:
/* Ftrace callback handler for kprobes -- called under preepmt disabed */ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip, struct ftrace_ops *ops, struct pt_regs *regs) { struct kprobe *p; struct kprobe_ctlblk *kcb;
/* Preempt is disabled by ftrace */ p = get_kprobe((kprobe_opcode_t *)ip); if (unlikely(!p) || kprobe_disabled(p)) return;
kcb = get_kprobe_ctlblk(); if (kprobe_running()) { kprobes_inc_nmissed_count(p); } else { unsigned long orig_ip = regs->ip; /* Kprobe handler expects regs->ip = ip + 1 as breakpoint hit */ regs->ip = ip + sizeof(kprobe_opcode_t);
/* To emulate trap based kprobes, preempt_disable here */ preempt_disable(); __this_cpu_write(current_kprobe, p); kcb->kprobe_status = KPROBE_HIT_ACTIVE; if (!p->pre_handler || !p->pre_handler(p, regs)) { __skip_singlestep(p, regs, kcb, orig_ip); preempt_enable_no_resched();
This preemption disabling and enabling looks rather strange. Looking at git blame, it appears this was added for jprobes. Can we remove it now that jprobes is going away?
} /* * If pre_handler returns !0, it sets regs->ip and * resets current kprobe, and keep preempt count +1. */} }
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