From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 516E01C8603; Sat, 20 Jun 2026 15:17:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781968666; cv=none; b=GnIs3uAjg9pksv1OYUHa3SQbCdMc2jXEzSN5pu30mkAWzS25KI9dM4sFOMi0PuCDKn+3GfrgRUk+cFgDxROD47iaJiwsDidM08pXnPZdlRiWg0dnDN6fwDuWCiiL1KwT1vRJiPTNOvJXzGX1yOQ/Xm58XwGvWJZpD1bAFLH8JNM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781968666; c=relaxed/simple; bh=zmnfADVRPpK/oeZ0siMG+ZNdyfRyUEavzeqAiiKIlkQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=MftQfTGuPEI/A7PVTlyCZ1UEQMICvkMzZpmy6qLREPFkGPuHnM2seojk3v3A2xmFJ+uN+aaztA5+gW7Kh8QuPueUKsNiSmoN85hQucwHWES/LohxTXhFf+yG+7oBr3RzTwbwgselvXs2HNDxTOdqhbB6tj+o43oTUKU2h+uLa6g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=V1pGZ527; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="V1pGZ527" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 254801F000E9; Sat, 20 Jun 2026 15:17:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1781968664; bh=e7+CbQvZItN7+BJLtmchrIMdNeoy0A8Qp/NedOJdSq0=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=V1pGZ527App9qoFvDPFWqbdhXOSd87WpEjfBfJxhcQ4RDUjAGn/APTk6prEvTbBOp sKTGykYhPlrzXsqDxb7siQJMf9ZaTw8nn1EEq7AwfDuK2C94IuABg9TmE/WpRBgnAW hvCJ3uPKUP0yT2O8DefEv01qYDfsntJJr0SHjYkXpUTp+4RWFHmmPCMabNv1GNGHgL Y1x5w0w0UoaKPKTyPJKG0NwcjFvRDnnTkXqx7QcNq4qXVVtnX3oJa4Tpeduvq4bls7 EnPUrPDyek5t5Dmg7V721+UqedGXpIXqxKZJcIYARoD8Mv4MQ2WnuVueOGven8u14b HcsToAwpDzVng== From: "Masami Hiramatsu (Google)" To: Steven Rostedt , Mathieu Desnoyers Cc: Jonathan Corbet , Shuah Khan , Masami Hiramatsu , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: [PATCH v6 4/8] tracing/probes: Type casting always involves nested calls Date: Sun, 21 Jun 2026 00:17:41 +0900 Message-ID: <178196866091.560995.825215766156265728.stgit@devnote2> X-Mailer: git-send-email 2.43.0 In-Reply-To: <178196862271.560995.5255615288323003663.stgit@devnote2> References: <178196862271.560995.5255615288323003663.stgit@devnote2> User-Agent: StGit/0.19 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit From: Masami Hiramatsu (Google) 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)$stackN->FIELD - (STRUCT)@SYM->FIELD Signed-off-by: Masami Hiramatsu (Google) --- Changes in v6: - Newly added. --- kernel/trace/trace_probe.c | 101 +++++++++++++++++++++++++++----------------- kernel/trace/trace_probe.h | 1 2 files changed, 63 insertions(+), 39 deletions(-) diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c index cebfba580922..b413bbe8c3af 100644 --- a/kernel/trace/trace_probe.c +++ b/kernel/trace/trace_probe.c @@ -691,19 +691,6 @@ static int parse_btf_arg(char *varname, return -EOPNOTSUPP; } - if (ctx->flags & TPARG_FL_TEVENT) { - ret = parse_trace_event(varname, code, ctx); - if (ret < 0) { - trace_probe_log_err(ctx->offset, BAD_ATTACH_ARG); - return ret; - } - /* TEVENT is only here via a typecast */ - if (WARN_ON_ONCE(ctx->struct_btf == NULL)) - return -EINVAL; - type = ctx->last_struct; - goto found_type; - } - if (ctx->flags & TPARG_FL_RETURN && !strcmp(varname, "$retval")) { code->op = FETCH_OP_RETVAL; /* Check whether the function return type is not void, even with typecast. */ @@ -867,7 +854,7 @@ 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; @@ -878,6 +865,17 @@ 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), @@ -886,11 +884,10 @@ 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; @@ -901,27 +898,57 @@ 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 = '\0'; + 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 + 1, + TYPECAST_REQ_FIELD); + return -EINVAL; + } + } else { + /* 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); @@ -929,11 +956,7 @@ 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 1515b3dda5be..e66e0fcb91a3 100644 --- a/kernel/trace/trace_probe.h +++ b/kernel/trace/trace_probe.h @@ -455,6 +455,7 @@ 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,