Patch "tools lib traceevent: Fix string handling in heterogeneous arch environments" has been added to the 4.2-stable tree

This is a note to let you know that I've just added the patch titled

tools lib traceevent: Fix string handling in heterogeneous arch environments

to the 4.2-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
tools-lib-traceevent-fix-string-handling-in-heterogeneous-arch-environments.patch
and it can be found in the queue-4.2 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Kapileshwar Singh <[email protected]>
Date: Tue, 22 Sep 2015 14:22:03 +0100
Subject: tools lib traceevent: Fix string handling in heterogeneous arch environments

From: Kapileshwar Singh <[email protected]>

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

---
 tools/lib/traceevent/event-parse.c |   23 ++++++++++++++++++++---
 1 file changed, 20 insertions(+), 3 deletions(-)

@@ -3721,7 +3721,7 @@ static void print_str_arg(struct trace_s
 	struct format_field *field;
 	struct printk_map *printk;
 	long long val, fval;
-	unsigned long addr;
+	unsigned long long addr;
 	char *str;
 	unsigned char *hex;
 	int print;

@@ -3754,13 +3754,30 @@ static void print_str_arg(struct trace_s
 		 */
 		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);

Patches currently in stable-queue which might be from [email protected] are

queue-4.2/tools-lib-traceevent-fix-string-handling-in-heterogeneous-arch-environments.patch