On Sat, 3 Nov 2018 13:43:16 -0400 Steven Rostedt <rost...@goodmis.org> wrote:
> On Sun, 4 Nov 2018 01:03:34 +0900 > Masami Hiramatsu <mhira...@kernel.org> wrote: > > > Introduce symbol_offset data structure for avoiding symbol+offset > > parsing when updating arguments. > > > > For kprobe events, "@symbol+offset" is supported, that requires > > to be updated when new module is loaded because @symbol address > > can be solved at that point. Currently kprobe events saves > > the "symbol+offset" string and parse it repeatedly, but that > > is inefficient. > > Do we care if it's inefficient? It's only done on module load and at > the beginning. That's far from a fast path. > > If anything, the original solution saves memory, which is a bigger > concern than speed in this case. OK, and original one saves lines too. Please drop it :) Thank you, > > -- Steve > > > > This introduces symbol_offset data structure which can save the > > offset and symbol separated, so that we don't need to parse it > > anymore. > > > > Signed-off-by: Masami Hiramatsu <mhira...@kernel.org> > > --- > > kernel/trace/trace_probe.c | 49 > > +++++++++++++++++++++++++------------------- > > kernel/trace/trace_probe.h | 7 +++++- > > 2 files changed, 34 insertions(+), 22 deletions(-) > > > > diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c > > index bd30e9398d2a..0a3af7d6e133 100644 > > --- a/kernel/trace/trace_probe.c > > +++ b/kernel/trace/trace_probe.c > > @@ -201,6 +201,26 @@ static int parse_probe_vars(char *arg, const struct > > fetch_type *t, > > return ret; > > } > > > > +static struct symbol_offset *allocate_symbol_offset(char *sym_offs_str) > > +{ > > + int ret; > > + long offset = 0; > > + struct symbol_offset *sof; > > + > > + ret = traceprobe_split_symbol_offset(sym_offs_str, &offset); > > + if (ret) > > + return ERR_PTR(ret); > > + > > + sof = kzalloc(sizeof(struct symbol_offset) + strlen(sym_offs_str) + 1, > > + GFP_KERNEL); > > + if (!sof) > > + return ERR_PTR(-ENOMEM); > > + > > + sof->offset = offset; > > + strcpy(sof->symbol, sym_offs_str); > > + return sof; > > +} > > + > > /* Recursive argument parser */ > > static int > > parse_probe_arg(char *arg, const struct fetch_type *type, > > @@ -253,9 +273,9 @@ parse_probe_arg(char *arg, const struct fetch_type > > *type, > > > > /* Preserve symbol for updating */ > > code->op = FETCH_NOP_SYMBOL; > > - code->data = kstrdup(arg + 1, GFP_KERNEL); > > - if (!code->data) > > - return -ENOMEM; > > + code->symoffs = allocate_symbol_offset(arg + 1); > > + if (IS_ERR(code->symoffs)) > > + return PTR_ERR(code->symoffs); > > if (++code == end) > > return -E2BIG; > > > > @@ -483,7 +503,7 @@ int traceprobe_parse_probe_arg(char *arg, ssize_t *size, > > if (ret) { > > for (code = tmp; code < tmp + FETCH_INSN_MAX; code++) > > if (code->op == FETCH_NOP_SYMBOL) > > - kfree(code->data); > > + kfree(code->symoffs); > > } > > kfree(tmp); > > > > @@ -513,7 +533,7 @@ void traceprobe_free_probe_arg(struct probe_arg *arg) > > > > while (code && code->op != FETCH_OP_END) { > > if (code->op == FETCH_NOP_SYMBOL) > > - kfree(code->data); > > + kfree(code->symoffs); > > code++; > > } > > kfree(arg->code); > > @@ -525,31 +545,18 @@ void traceprobe_free_probe_arg(struct probe_arg *arg) > > int traceprobe_update_arg(struct probe_arg *arg) > > { > > struct fetch_insn *code = arg->code; > > - long offset; > > - char *tmp; > > - char c; > > - int ret = 0; > > > > while (code && code->op != FETCH_OP_END) { > > if (code->op == FETCH_NOP_SYMBOL) { > > if (code[1].op != FETCH_OP_IMM) > > return -EINVAL; > > > > - tmp = strpbrk(code->data, "+-"); > > - if (tmp) > > - c = *tmp; > > - ret = traceprobe_split_symbol_offset(code->data, > > - &offset); > > - if (ret) > > - return ret; > > - > > code[1].immediate = > > - (unsigned long)kallsyms_lookup_name(code->data); > > - if (tmp) > > - *tmp = c; > > + (unsigned long)kallsyms_lookup_name( > > + code->symoffs->symbol); > > if (!code[1].immediate) > > return -ENOENT; > > - code[1].immediate += offset; > > + code[1].immediate += code->symoffs->offset; > > } > > code++; > > } > > diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h > > index 974afc1a3e73..942424d05427 100644 > > --- a/kernel/trace/trace_probe.h > > +++ b/kernel/trace/trace_probe.h > > @@ -103,6 +103,11 @@ enum fetch_op { > > FETCH_NOP_SYMBOL, /* Unresolved Symbol holder */ > > }; > > > > +struct symbol_offset { > > + long offset; > > + char symbol[]; > > +}; > > + > > struct fetch_insn { > > enum fetch_op op; > > union { > > @@ -117,7 +122,7 @@ struct fetch_insn { > > unsigned char rshift; > > }; > > unsigned long immediate; > > - void *data; > > + struct symbol_offset *symoffs; > > }; > > }; > > > -- Masami Hiramatsu <mhira...@kernel.org>