linux-kernel - [PATCH v2] tools lib traceevent: str addresses in heterogeneous arch environments

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Date:	Fri, 18 Sep 2015 11:57:29 +0100
From:	Kapileshwar Singh <kapileshwar.singh@....com>
To:	linux-kernel@...r.kernel.org
Cc:	Kapileshwar Singh <kapileshwar.singh@....com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Javi Merino <javi.merino@....com>,
	David Ahern <dsahern@...il.com>, Jiri Olsa <jolsa@...nel.org>
Subject: [PATCH v2] tools lib traceevent: str addresses in heterogeneous arch environments

When a trace recorded on a 32-bit device is processed with a 64-bit
binary, the higher 32-bits of the address need to ignored

The lack of this results in the output of the 64-bit pointer
value to the trace as the 32-bit address lookup fails in find_printk.

Before:
burn-1778  [003]   548.600305: bputs:   0xc0046db2s: 2cec5c058d98c

After:
burn-1778  [003]   548.600305: bputs:   0xc0046db2s: RT throttling activated

The problem occurs in PRINT_FEILD when the field is recognized as a pointer
to a string (of the type const char *)

Heterogeneous architectures cases below can arise and should be handled:

* Traces recorded using 32-bit addresses processed on a 64-bit machine
* Traces recorded using 64-bit addresses processed on a 32-bit machine

Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Javi Merino <javi.merino@....com>
Cc: David Ahern <dsahern@...il.com>
Cc: Jiri Olsa <jolsa@...nel.org>
Reported-by: Juri Lelli <juri.lelli@....com>
Signed-off-by: Kapileshwar Singh <kapileshwar.singh@....com>
---
 tools/lib/traceevent/event-parse.c | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/tools/lib/traceevent/event-parse.c b/tools/lib/traceevent/event-parse.c
index cc25f059ab3d..bb554e2ae70d 100644
--- a/tools/lib/traceevent/event-parse.c
+++ b/tools/lib/traceevent/event-parse.c
@@ -3721,7 +3721,7 @@ static void print_str_arg(struct trace_seq *s, void *data, int size,
 	struct format_field *field;
 	struct printk_map *printk;
 	long long val, fval;
-	unsigned long addr;
+	uint64_t addr;
 	char *str;
 	unsigned char *hex;
 	int print;
@@ -3754,7 +3754,24 @@ static void print_str_arg(struct trace_seq *s, void *data, int size,
 		 */
 		if (!(field->flags & FIELD_IS_ARRAY) &&
 		    field->size == pevent->long_size) {
-			addr = *(unsigned long *)(data + field->offset);
+
+			/* Handle heterogeneous recording and processing
+			 * architectures
+			 *
+			 * CASE I:
+			 * Traces recorded on 32-bit devices (32-bit
+			 * addressing) and processed on 64-bit devices:
+			 * In this case, the higher 32-bits of the address
+			 * need to be ignored.
+			 *
+			 * CASE II:
+			 * Traces recorded on 64 bit devices and processed
+			 * on 32-bit devices.
+			 * In this case the pointer must be 64-bit long
+			 */
+			addr = *(uint64_t *)(data + field->offset) &
+				((1ULL << pevent->long_size * 8) - 1);
+
 			/* Check if it matches a print format */
 			printk = find_printk(pevent, addr);
 			if (printk)
-- 
1.9.1

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