mirrors/linux
2
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git synced 2026-08-27 16:28:58 -04:00
Code Issues Packages Projects Releases Wiki Activity

tracing/probes: Type casting always involves nested calls

Browse Source 
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

Link: https://lore.kernel.org/all/178271364804.1176915.17600229399446264813.stgit@devnote2/

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
This commit is contained in:
Masami Hiramatsu (Google)
2026-07-02 21:12:41 +09:00
parent 60432df556
commit 52c76ec18e
2 changed files with 75 additions and 52 deletions
Download Patch File Download Diff File Expand all files Collapse all files

123
kernel/trace/trace_probe.c
View File

@@ -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;
}
/* Skip '(' */
ctx->offset += 1;
tmp++;
} else if (*tmp == '+' || *tmp == '-') {
/* Dereference can have another field access inside it. */
char *open = strchr(tmp + 1, '(');
ctx->nested_level++;
if (ctx->nested_level > TRACEPROBE_MAX_NESTED_LEVEL) {
trace_probe_log_err(ctx->offset, TOO_MANY_NESTED);
return -E2BIG;
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;
}
}
/* 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);
tmp = close + 3;/* Skip "->" after closing parenthesis */
nested = true;
}
*close = '\0';
/* 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);
/* 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;
}

4
kernel/trace/trace_probe.h
View File

@@ -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