From: Masami Hiramatsu (Google) <[email protected]> This allows type casting to various fetchargs without parentheses by recursively calling parse_probe_arg on the target when type casting is used.
For example, this allows the following expressions: - (STRUCT)%REG->FIELD - (STRUCT)$stackN->FIELD - (STRUCT)@SYM->FIELD Note that @SYM+/-OFFSET with typecast needs parentheses like: - (STRUCT)(@SYM-8)->FIELD Signed-off-by: Masami Hiramatsu (Google) <[email protected]> --- Changes in v8: - Fix caret position in error case. - Add a comment about @SYM+/-OFFSET without parentheses. Changes in v7: - Prohibit using @SYM+/-OFFSET without parentheses. - Cleanup parse_btf_arg() since ctx->struct_btf is always NULL now. Changes in v6: - Newly added. --- kernel/trace/trace_probe.c | 123 ++++++++++++++++++++++++++------------------ kernel/trace/trace_probe.h | 4 + 2 files changed, 75 insertions(+), 52 deletions(-) diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c index 1d6afda39462..87a2bb1cd950 100644 --- a/kernel/trace/trace_probe.c +++ b/kernel/trace/trace_probe.c @@ -684,19 +684,6 @@ static int parse_btf_arg(char *varname, return -EOPNOTSUPP; } - if (ctx->flags & TPARG_FL_TEVENT) { - ret = parse_trace_event(varname, code, ctx); - if (ret < 0) { - trace_probe_log_err(ctx->offset, BAD_ATTACH_ARG); - return ret; - } - /* TEVENT is only here via a typecast */ - if (WARN_ON_ONCE(ctx->struct_btf == NULL)) - return -EINVAL; - type = ctx->last_struct; - goto found_type; - } - if (ctx->flags & TPARG_FL_RETURN && !strcmp(varname, "$retval")) { code->op = FETCH_OP_RETVAL; /* Check whether the function return type is not void, even with typecast. */ @@ -708,13 +695,6 @@ static int parse_btf_arg(char *varname, tid = ctx->proto->type; goto found; } - /* - * Even if we can not find appropriate BTF info, we can still access - * the field via typecast. - */ - if (ctx->struct_btf) - goto found; - if (field) { trace_probe_log_err(ctx->offset + field - varname, NO_BTF_ENTRY); @@ -759,11 +739,7 @@ static int parse_btf_arg(char *varname, return -ENOENT; found: - if (ctx->struct_btf) - type = ctx->last_struct; - else - type = btf_type_skip_modifiers(ctx->btf, tid, NULL); -found_type: + type = btf_type_skip_modifiers(ctx->btf, tid, NULL); if (!type) { trace_probe_log_err(ctx->offset, BAD_BTF_TID); return -EINVAL; @@ -860,7 +836,7 @@ static int handle_typecast(char *arg, struct fetch_insn **pcode, struct traceprobe_parse_context *ctx) { int orig_offset = ctx->offset; - bool nested = false; + char *close; char *tmp; int ret; @@ -871,6 +847,17 @@ static int handle_typecast(char *arg, struct fetch_insn **pcode, return -EOPNOTSUPP; } + /* + * Always consider the token after typecast as a nested call + * For example: (STRUCT)VAR->FIELD and (STRUCT)(VAR)->FIELD are same. + * VAR is solved in the nested call. + */ + ctx->nested_level++; + if (ctx->nested_level > TRACEPROBE_MAX_NESTED_LEVEL) { + trace_probe_log_err(ctx->offset, TOO_MANY_NESTED); + return -E2BIG; + } + tmp = strchr(arg, ')'); if (!tmp) { trace_probe_log_err(ctx->offset + strlen(arg), @@ -879,11 +866,10 @@ static int handle_typecast(char *arg, struct fetch_insn **pcode, } *tmp++ = '\0'; - /* Handle the nested structure like (STRUCT)(VAR->FIELD)->... */ + ctx->offset += tmp - arg; if (*tmp == '(') { - char *close = find_matched_close_paren(tmp); + close = find_matched_close_paren(tmp); - ctx->offset += tmp - arg; if (!close) { trace_probe_log_err(ctx->offset, DEREF_OPEN_BRACE); return -EINVAL; @@ -894,27 +880,66 @@ static int handle_typecast(char *arg, struct fetch_insn **pcode, TYPECAST_REQ_FIELD); return -EINVAL; } - - ctx->nested_level++; - if (ctx->nested_level > TRACEPROBE_MAX_NESTED_LEVEL) { - trace_probe_log_err(ctx->offset, TOO_MANY_NESTED); - return -E2BIG; + /* Skip '(' */ + ctx->offset += 1; + tmp++; + } else if (*tmp == '+' || *tmp == '-') { + /* Dereference can have another field access inside it. */ + char *open = strchr(tmp + 1, '('); + + if (!open) { + trace_probe_log_err(ctx->offset, + DEREF_NEED_BRACE); + return -EINVAL; + } + close = find_matched_close_paren(open); + if (!close) { + trace_probe_log_err(ctx->offset + strlen(tmp), + DEREF_OPEN_BRACE); + return -EINVAL; + } + close++; + /* We expect a field access for typecast */ + if (close[0] != '-' || close[1] != '>') { + trace_probe_log_err(ctx->offset + close - tmp, + TYPECAST_REQ_FIELD); + return -EINVAL; + } + } else { + if (tmp[0] == '@') { + /* @sym+offset is not allowed without parenthesized */ + close = strpbrk(tmp, "+-"); + if (close && isdigit(close[1])) { + trace_probe_log_err(ctx->offset, + TYPECAST_SYM_OFFSET); + return -EINVAL; + } } - *close = '\0'; + /* Inner variable name */ + close = strchr(tmp, '-'); + if (!close || close[1] != '>') { + trace_probe_log_err(ctx->offset + strlen(tmp), + TYPECAST_REQ_FIELD); + return -EINVAL; + } + } + *close = '\0'; - ctx->offset += 1; /* for the '(' */ - /* We need to parse the nested one */ - ret = parse_probe_arg(tmp + 1, find_fetch_type(NULL, ctx->flags), - pcode, end, ctx); - if (ret < 0) - return ret; - ctx->nested_level--; - clear_struct_btf(ctx); + /* We need to parse the nested one */ + ret = parse_probe_arg(tmp, find_fetch_type(NULL, ctx->flags), + pcode, end, ctx); + if (ret < 0) + return ret; + ctx->nested_level--; + clear_struct_btf(ctx); - tmp = close + 3;/* Skip "->" after closing parenthesis */ - nested = true; - } + /* Let tmp point the field name. */ + if (close[1] == '-') + tmp = close + 3; /* Skip "->" after closing parenthesis */ + else + tmp = close + 2; /* Skip ">" after inner variable name */ + /* resolve the typecast struct name */ ret = query_btf_struct(arg + 1, ctx); if (ret < 0) { trace_probe_log_err(orig_offset + 1, NO_PTR_STRCT); @@ -922,11 +947,7 @@ static int handle_typecast(char *arg, struct fetch_insn **pcode, } ctx->offset = orig_offset + tmp - arg; - /* If it is nested, tmp points to the field name. */ - if (nested) - ret = parse_btf_field(tmp, ctx->last_struct, pcode, end, ctx); - else - ret = parse_btf_arg(tmp, pcode, end, ctx); + ret = parse_btf_field(tmp, ctx->last_struct, pcode, end, ctx); return ret; } diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h index 7d71925244e8..f4fbe3010978 100644 --- a/kernel/trace/trace_probe.h +++ b/kernel/trace/trace_probe.h @@ -453,6 +453,7 @@ struct traceprobe_parse_context { int nested_level; }; +/* Each typecast consumes nested level. So the max number of typecast is 3. */ #define TRACEPROBE_MAX_NESTED_LEVEL 3 extern int traceprobe_parse_probe_arg(struct trace_probe *tp, int i, @@ -592,7 +593,8 @@ extern int traceprobe_define_arg_fields(struct trace_event_call *event_call, C(EVENT_TOO_BIG, "Event too big (too many fields?)"), \ C(TYPECAST_NOT_EVENT, "Typecasts are only for eprobe fields"), \ C(TYPECAST_REQ_FIELD, "Typecast requires a field access"), \ - C(TOO_MANY_NESTED, "Too many nested typecasts/dereferences"), + C(TOO_MANY_NESTED, "Too many nested typecasts/dereferences"), \ + C(TYPECAST_SYM_OFFSET, "@SYM+/-OFFSET with typecast needs parentheses") #undef C #define C(a, b) TP_ERR_##a
