From 05770dd0ad110854c7157d95700d7c89979cdb3e Mon Sep 17 00:00:00 2001 From: Masami Hiramatsu Date: Mon, 22 Nov 2021 18:30:12 +0900 Subject: tracing: Support __rel_loc relative dynamic data location attribute Add '__rel_loc' new dynamic data location attribute which encodes the data location from the next to the field itself. The '__data_loc' is used for encoding the dynamic data location on the trace event record. But '__data_loc' is not useful if the writer doesn't know the event header (e.g. user event), because it records the dynamic data offset from the entry of the record, not the field itself. This new '__rel_loc' attribute encodes the data location relatively from the next of the field. For example, when there is a record like below (the number in the parentheses is the size of fields) |header(N)|common(M)|fields(K)|__data_loc(4)|fields(L)|data(G)| In this case, '__data_loc' field will be __data_loc = (G << 16) | (N+M+K+4+L) If '__rel_loc' is used, this will be |header(N)|common(M)|fields(K)|__rel_loc(4)|fields(L)|data(G)| where __rel_loc = (G << 16) | (L) This case shows L bytes after the '__rel_loc' attribute field, if there is no fields after the __rel_loc field, L must be 0. This is relatively easy (and no need to consider the kernel header change) when the event data fields are composed by user who doesn't know header and common fields. Link: https://lkml.kernel.org/r/163757341258.510314.4214431827833229956.stgit@devnote2 Cc: Beau Belgrave Cc: Namhyung Kim Cc: Tom Zanussi Signed-off-by: Masami Hiramatsu Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/trace_events_inject.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) (limited to 'kernel/trace/trace_events_inject.c') diff --git a/kernel/trace/trace_events_inject.c b/kernel/trace/trace_events_inject.c index c188045c5f97..d6b4935a78c0 100644 --- a/kernel/trace/trace_events_inject.c +++ b/kernel/trace/trace_events_inject.c @@ -168,10 +168,14 @@ static void *trace_alloc_entry(struct trace_event_call *call, int *size) continue; if (field->filter_type == FILTER_STATIC_STRING) continue; - if (field->filter_type == FILTER_DYN_STRING) { + if (field->filter_type == FILTER_DYN_STRING || + field->filter_type == FILTER_RDYN_STRING) { u32 *str_item; int str_loc = entry_size & 0xffff; + if (field->filter_type == FILTER_RDYN_STRING) + str_loc -= field->offset + field->size; + str_item = (u32 *)(entry + field->offset); *str_item = str_loc; /* string length is 0. */ } else { @@ -214,7 +218,8 @@ static int parse_entry(char *str, struct trace_event_call *call, void **pentry) if (field->filter_type == FILTER_STATIC_STRING) { strlcpy(entry + field->offset, addr, field->size); - } else if (field->filter_type == FILTER_DYN_STRING) { + } else if (field->filter_type == FILTER_DYN_STRING || + field->filter_type == FILTER_RDYN_STRING) { int str_len = strlen(addr) + 1; int str_loc = entry_size & 0xffff; u32 *str_item; @@ -229,6 +234,8 @@ static int parse_entry(char *str, struct trace_event_call *call, void **pentry) strlcpy(entry + (entry_size - str_len), addr, str_len); str_item = (u32 *)(entry + field->offset); + if (field->filter_type == FILTER_RDYN_STRING) + str_loc -= field->offset + field->size; *str_item = (str_len << 16) | str_loc; } else { char **paddr; -- cgit v1.2.3