On Sun, 4 Nov 2018 01:03:34 +0900 Masami Hiramatsu <[email protected]> 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. -- 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 <[email protected]> > --- > 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; > }; > }; >
