RE: [PATCH 1/1] tracing: Support reading trace event format file larger than PAGE_SIZE

[Shiju Jose <shiju.jose@huawei.com>]

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>-----Original Message-----
>From: Steven Rostedt <rostedt@goodmis.org>
>Sent: 06 January 2025 22:12
>To: Shiju Jose <shiju.jose@huawei.com>
>Cc: mhiramat@kernel.org; mathieu.desnoyers@efficios.com; linux-trace-
>kernel@vger.kernel.org; linux-kernel@vger.kernel.org; Linuxarm
><linuxarm@huawei.com>; Jonathan Cameron
><jonathan.cameron@huawei.com>; tanxiaofei <tanxiaofei@huawei.com>;
>Zengtao (B) <prime.zeng@hisilicon.com>
>Subject: Re: [PATCH 1/1] tracing: Support reading trace event format file larger
>than PAGE_SIZE
>
>On Mon, 6 Jan 2025 18:15:36 +0000
>Shiju Jose <shiju.jose@huawei.com> wrote:
>
>> >You see, it requires multiple reads to pull in an entire kernel
>> >pseudo file. None of those reads are greater than PAGE_SIZE. Why
>> >should trace format files be any different?
>> Thanks for the reply.
>> Yes. I had a fix/workaround in the userspace rasdaemon with multiple
>> reads like above as reported previously in the  following thread.
>> https://lore.kernel.org/lkml/3c9808a694d242cab35bab67602edebf@huawei.c
>> om/ However thought a solution in the common kernel code for the
>> format file may be better.  I will go ahead with the user space
>> solution.
>
>That would make it different than every other pseudo file in the kernel. I rather
>not do that.
>
>>
>> Also shared an information in the above thread about libtraceevent
>> __parse_event() does not return error when parse_format() fail with
>> incomplete formt data, which resulted initialization for the trace event does
>not fail in the user space tool.
>
>Hmm, can you send me the the format file that failed?
>
>Just the output of "cat /sys/kernel/tracing/events/<system>/<event>/format"
>will do.

Please find attached format file, which might have failed to parse because of the
unsupported formats in the libtraceevent you mentioned in the following thread.
https://lore.kernel.org/lkml/20241127104132.6c1729e1@gandalf.local.home/#t    

Please find the improvement in the libraceevent which I mentioned for not returning error
when parsing failed,
===========================================
diff --git a/src/event-parse.c b/src/event-parse.c index 0427061..b9264cb 100644
--- a/src/event-parse.c
+++ b/src/event-parse.c
@@ -7905,9 +7905,14 @@ __parse_event(struct tep_handle *tep,
              const char *buf, unsigned long size,
              const char *sys)
 {
-       int ret = parse_format(eventp, tep, buf, size, sys);
-       struct tep_event *event = *eventp;
+       int ret;
+       struct tep_event *event;
+
+       ret = parse_format(eventp, tep, buf, size, sys);
+       if (ret)
+               return ret;
 
+       event = *eventp;
        if (event == NULL)
                return ret; 
 =========================================  
>
>-- Steve

Thanks,
Shiju

[-- Attachment #2: format_cxl_general_media --]
[-- Type: application/octet-stream, Size: 5089 bytes --]

name: cxl_general_media
ID: 1497
format:
	field:unsigned short common_type;	offset:0;	size:2;	signed:0;
	field:unsigned char common_flags;	offset:2;	size:1;	signed:0;
	field:unsigned char common_preempt_count;	offset:3;	size:1;	signed:0;
	field:int common_pid;	offset:4;	size:4;	signed:1;

	field:__data_loc char[] memdev;	offset:8;	size:4;	signed:0;
	field:__data_loc char[] host;	offset:12;	size:4;	signed:0;
	field:int log;	offset:16;	size:4;	signed:1;
	field:uuid_t hdr_uuid;	offset:20;	size:16;	signed:0;
	field:u64 serial;	offset:40;	size:8;	signed:0;
	field:u32 hdr_flags;	offset:48;	size:4;	signed:0;
	field:u16 hdr_handle;	offset:52;	size:2;	signed:0;
	field:u16 hdr_related_handle;	offset:54;	size:2;	signed:0;
	field:u64 hdr_timestamp;	offset:56;	size:8;	signed:0;
	field:u8 hdr_length;	offset:64;	size:1;	signed:0;
	field:u8 hdr_maint_op_class;	offset:65;	size:1;	signed:0;
	field:u8 hdr_maint_op_sub_class;	offset:66;	size:1;	signed:0;
	field:u64 dpa;	offset:72;	size:8;	signed:0;
	field:u8 descriptor;	offset:80;	size:1;	signed:0;
	field:u8 type;	offset:81;	size:1;	signed:0;
	field:u8 sub_type;	offset:82;	size:1;	signed:0;
	field:u8 transaction_type;	offset:83;	size:1;	signed:0;
	field:u8 channel;	offset:84;	size:1;	signed:0;
	field:u32 device;	offset:88;	size:4;	signed:0;
	field:u8 comp_id[16];	offset:92;	size:16;	signed:0;
	field:u64 hpa;	offset:112;	size:8;	signed:0;
	field:uuid_t region_uuid;	offset:120;	size:16;	signed:0;
	field:u16 validity_flags;	offset:136;	size:2;	signed:0;
	field:u8 rank;	offset:138;	size:1;	signed:0;
	field:u8 dpa_flags;	offset:139;	size:1;	signed:0;
	field:__data_loc char[] region_name;	offset:140;	size:4;	signed:0;
	field:u8 cme_threshold_ev_flags;	offset:144;	size:1;	signed:0;
	field:u32 cme_count;	offset:148;	size:4;	signed:0;

print fmt: "memdev=%s host=%s serial=%lld log=%s : time=%llu uuid=%pUb len=%d flags='%s' handle=%x related_handle=%x maint_op_class=%u maint_op_sub_class=%u : dpa=%llx dpa_flags='%s' descriptor='%s' type='%s' sub_type='%s' transaction_type='%s' channel=%u rank=%u device=%x validity_flags='%s' comp_id=%s comp_id_pldm_valid_flags='%s' pldm_entity_id=%s pldm_resource_id=%s hpa=%llx region=%s region_uuid=%pUb cme_threshold_ev_flags='%s' cme_count=%x", __get_str(memdev), __get_str(host), REC->serial, __print_symbolic(REC->log, { CXL_EVENT_TYPE_INFO, "Informational" }, { CXL_EVENT_TYPE_WARN, "Warning" }, { CXL_EVENT_TYPE_FAIL, "Failure" }, { CXL_EVENT_TYPE_FATAL, "Fatal" }), REC->hdr_timestamp, &REC->hdr_uuid, REC->hdr_length, __print_flags(REC->hdr_flags, " | ", { ((((1UL))) << (2)), "PERMANENT_CONDITION" }, { ((((1UL))) << (3)), "MAINTENANCE_NEEDED" }, { ((((1UL))) << (4)), "PERFORMANCE_DEGRADED" }, { ((((1UL))) << (5)), "HARDWARE_REPLACEMENT_NEEDED" }, { ((((1UL))) << (6)), "MAINT_OP_SUB_CLASS_VALID" } ), REC->hdr_handle, REC->hdr_related_handle, REC->hdr_maint_op_class, REC->hdr_maint_op_sub_class, REC->dpa, __print_flags(REC->dpa_flags, "|", { ((((1UL))) << (0)), "VOLATILE" }, { ((((1UL))) << (1)), "NOT_REPAIRABLE" } ), __print_flags(REC->descriptor, "|", { ((((1UL))) << (0)), "UNCORRECTABLE_EVENT" }, { ((((1UL))) << (1)), "THRESHOLD_EVENT" }, { ((((1UL))) << (2)), "POISON_LIST_OVERFLOW" } ), __print_symbolic(REC->type, { 0x00, "ECC Error" }, { 0x01, "Invalid Address" }, { 0x02, "Data Path Error" }, { 0x03, "TE State Violation" }, { 0x04, "Scrub Media ECC Error" }, { 0x05, "Adv Prog CME Counter Expiration" }, { 0x06, "CKID Violation" } ), __print_symbolic(REC->sub_type, { 0x00, "Not Reported" }, { 0x01, "Internal Datapath Error" }, { 0x02, "Media Link Command Training Error" }, { 0x03, "Media Link Control Training Error" }, { 0x04, "Media Link Data Training Error" }, { 0x05, "Media Link CRC Error" } ), __print_symbolic(REC->transaction_type, { 0x00, "Unknown" }, { 0x01, "Host Read" }, { 0x02, "Host Write" }, { 0x03, "Host Scan Media" }, { 0x04, "Host Inject Poison" }, { 0x05, "Internal Media Scrub" }, { 0x06, "Internal Media Management" }, { 0x07, "Internal Media Error Check Scrub" }, { 0x08, "Media Initialization" } ), REC->channel, REC->rank, REC->device, __print_flags(REC->validity_flags, "|", { ((((1UL))) << (0)), "CHANNEL" }, { ((((1UL))) << (1)), "RANK" }, { ((((1UL))) << (2)), "DEVICE" }, { ((((1UL))) << (3)), "COMPONENT" }, { ((((1UL))) << (4)), "COMPONENT PLDM FORMAT" } ), __print_hex(REC->comp_id, 0x10), __print_flags(REC->comp_id[0], " | ", { ((((1UL))) << (0)), "PLDM Entity ID" }, { ((((1UL))) << (1)), "Resource ID" } ), (REC->validity_flags & ((((1UL))) << (3)) && REC->validity_flags & ((((1UL))) << (4))) ? (REC->comp_id[0] & ((((1UL))) << (0))) ? __print_hex(&REC->comp_id[1], 6) : "0x00" : "0x00", (REC->validity_flags & ((((1UL))) << (3)) && REC->validity_flags & ((((1UL))) << (4))) ? (REC->comp_id[0] & ((((1UL))) << (1))) ? __print_hex(&REC->comp_id[7], 4) : "0x00" : "0x00", REC->hpa, __get_str(region_name), &REC->region_uuid, __print_flags(REC->cme_threshold_ev_flags, "|", { ((((1UL))) << (0)), "Corrected Memory Errors in Multiple Media Components" }, { ((((1UL))) << (1)), "Exceeded Programmable Threshold" } ), REC->cme_count