Messages in this thread Patch in this message | | | From | Masami Hiramatsu <> | Subject | [RFC PATCH] tracing/kprobes: Avoid parsing symbol+offset when updating arguments | Date | Sun, 4 Nov 2018 01:03:34 +0900 |
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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. 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 <mhiramat@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; }; };
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