Messages in this thread | | | Date | Wed, 16 Aug 2023 14:42:13 -0400 | From | Steven Rostedt <> | Subject | Re: [RFC PATCH v1 1/1] tracing/kprobe: Add multi-probe support for 'perf_kprobe' PMU |
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On Wed, 16 Aug 2023 18:35:17 +0200 Francis Laniel <flaniel@linux.microsoft.com> wrote:
> When using sysfs, it is possible to create kprobe for several kernel functions > sharing the same name, but of course with different addresses, by writing their > addresses in kprobe_events file.
So this only happens if you write in the address?
> > When using PMU, if only the symbol name is given, the event will be created for > the first address which matches the symbol, as returned by > kallsyms_lookup_name(). > The idea here is to search all kernel functions which match this symbol and > create a trace_kprobe for each of them. > All these trace_kprobes are linked together by sharing the same trace_probe. >
So this makes the PMU version enable all by name, so there's still a disconnect between how sysfs works and how PMU does.
Why can't you just pass in the address like sysfs does?
-- Steve
> Signed-off-by: Francis Laniel <flaniel@linux.microsoft.com> > --- > kernel/trace/trace_kprobe.c | 86 +++++++++++++++++++++++++++++++++++++ > 1 file changed, 86 insertions(+) > > diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c > index 1b3fa7b854aa..08580f1466c7 100644 > --- a/kernel/trace/trace_kprobe.c > +++ b/kernel/trace/trace_kprobe.c > @@ -1682,13 +1682,42 @@ static int unregister_kprobe_event(struct trace_kprobe *tk) > } > > #ifdef CONFIG_PERF_EVENTS > + > +struct address_array { > + unsigned long *addrs; > + size_t size; > +}; > + > +static int add_addr(void *data, unsigned long addr) > +{ > + struct address_array *array = data; > + unsigned long *p; > + > + array->size++; > + p = krealloc(array->addrs, > + sizeof(*array->addrs) * array->size, > + GFP_KERNEL); > + if (!p) { > + kfree(array->addrs); > + return -ENOMEM; > + } > + > + array->addrs = p; > + array->addrs[array->size - 1] = addr; > + > + return 0; > +} > + > /* create a trace_kprobe, but don't add it to global lists */ > struct trace_event_call * > create_local_trace_kprobe(char *func, void *addr, unsigned long offs, > bool is_return) > { > enum probe_print_type ptype; > + struct address_array array; > struct trace_kprobe *tk; > + unsigned long func_addr; > + unsigned int i; > int ret; > char *event; > > @@ -1722,7 +1751,64 @@ create_local_trace_kprobe(char *func, void *addr, unsigned long offs, > if (ret < 0) > goto error; > > + array.addrs = NULL; > + array.size = 0; > + ret = kallsyms_on_each_match_symbol(add_addr, func, &array); > + if (ret) > + goto error_free; > + > + if (array.size == 1) > + goto end; > + > + /* > + * Below loop allocates a trace_kprobe for each function with the same > + * name in kernel source code. > + * All this differente trace_kprobes will be linked together through > + * append_trace_kprobe(). > + * NOTE append_trace_kprobe() is called in register_trace_kprobe() which > + * is called when a kprobe is added through sysfs. > + */ > + func_addr = kallsyms_lookup_name(func); > + for (i = 0; i < array.size; i++) { > + struct trace_kprobe *tk_same_name; > + unsigned long address; > + > + address = array.addrs[i]; > + /* Skip the function address as we already registered it. */ > + if (address == func_addr) > + continue; > + > + /* > + * alloc_trace_kprobe() first considers symbol name, so we set > + * this to NULL to allocate this kprobe on the given address. > + */ > + tk_same_name = alloc_trace_kprobe(KPROBE_EVENT_SYSTEM, event, > + (void *)address, NULL, offs, > + 0 /* maxactive */, > + 0 /* nargs */, is_return); > + > + if (IS_ERR(tk_same_name)) { > + ret = -ENOMEM; > + goto error_free; > + } > + > + init_trace_event_call(tk_same_name); > + > + if (traceprobe_set_print_fmt(&tk_same_name->tp, ptype) < 0) { > + ret = -ENOMEM; > + goto error_free; > + } > + > + ret = append_trace_kprobe(tk_same_name, tk); > + if (ret) > + goto error_free; > + } > + > +end: > + kfree(array.addrs); > return trace_probe_event_call(&tk->tp); > +error_free: > + kfree(array.addrs); > error: > free_trace_kprobe(tk); > return ERR_PTR(ret);
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