[3.16.y-ckt stable] Patch "tools lib traceevent: Fix string handling in heterogeneous arch environments" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    tools lib traceevent: Fix string handling in heterogeneous arch environments

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt19.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From c98cc93ee50f5386d337a7432cd4d7833c2a4e92 Mon Sep 17 00:00:00 2001
From: Kapileshwar Singh <kapileshwar.singh at arm.com>
Date: Tue, 22 Sep 2015 14:22:03 +0100
Subject: tools lib traceevent: Fix string handling in heterogeneous arch
 environments

commit c2e4b24ff848bb180f9b9cd873a38327cd219ad2 upstream.

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_FIELD 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

Reported-by: Juri Lelli <juri.lelli at arm.com>
Signed-off-by: Kapileshwar Singh <kapileshwar.singh at arm.com>
Reviewed-by: Steven Rostedt <rostedt at goodmis.org>
Cc: David Ahern <dsahern at gmail.com>
Cc: Javi Merino <javi.merino at arm.com>
Cc: Jiri Olsa <jolsa at kernel.org>
Cc: Namhyung Kim <namhyung at kernel.org>
Link: http://lkml.kernel.org/r/1442928123-13824-1-git-send-email-kapileshwar.singh@arm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme at redhat.com>
[ luis: backported to 3.16: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 tools/lib/traceevent/event-parse.c | 23 ++++++++++++++++++++---
 1 file changed, 20 insertions(+), 3 deletions(-)

diff --git a/tools/lib/traceevent/event-parse.c b/tools/lib/traceevent/event-parse.c
index 93825a17dcce..7959d66e1048 100644
--- a/tools/lib/traceevent/event-parse.c
+++ b/tools/lib/traceevent/event-parse.c
@@ -3658,7 +3658,7 @@ static void print_str_arg(struct trace_seq *s, void *data, int size,
 	struct format_field *field;
 	struct printk_map *printk;
 	unsigned long long val, fval;
-	unsigned long addr;
+	unsigned long long addr;
 	char *str;
 	unsigned char *hex;
 	int print;
@@ -3691,13 +3691,30 @@ 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, only 32 bits should be read.
+			 *
+			 * CASE II:
+			 * Traces recorded on 64 bit devices and processed
+			 * on 32-bit devices:
+			 * In this case, 64 bits must be read.
+			 */
+			addr = (pevent->long_size == 8) ?
+				*(unsigned long long *)(data + field->offset) :
+				(unsigned long long)*(unsigned int *)(data + field->offset);
+
 			/* Check if it matches a print format */
 			printk = find_printk(pevent, addr);
 			if (printk)
 				trace_seq_puts(s, printk->printk);
 			else
-				trace_seq_printf(s, "%lx", addr);
+				trace_seq_printf(s, "%llx", addr);
 			break;
 		}
 		str = malloc(len + 1);