Thread (5 messages) 5 messages, 2 authors, 2012-12-20
STALE4946d

[PATCH 3/3] kgdb/kgdbts: support ppc64

From: Tiejun Chen <hidden>
Date: 2012-10-25 06:44:04
Also in: lkml
Subsystem: char and misc drivers, kgdb / kdb /debug_core, the rest · Maintainers: Arnd Bergmann, Greg Kroah-Hartman, Jason Wessel, Daniel Thompson, Linus Torvalds

We can't look up the address of the entry point of the function simply
via that function symbol for all architectures.

For PPC64 ABI, actually there is a function descriptors structure.

A function descriptor is a three doubleword data structure that contains
the following values:
	* The first doubleword contains the address of the entry point of
		the function.
	* The second doubleword contains the TOC base address for
		the function.
	* The third doubleword contains the environment pointer for
		languages such as Pascal and PL/1.

So we should call a wapperred dereference_function_descriptor() to get
the address of the entry point of the function.

Note this is also safe for other architecture after refer to
"include/asm-generic/sections.h" since:

dereference_function_descriptor(p) always is (p) if without arched definition.

Signed-off-by: Tiejun Chen <redacted>
---
 drivers/misc/kgdbts.c |    2 ++
 1 file changed, 2 insertions(+)
diff --git a/drivers/misc/kgdbts.c b/drivers/misc/kgdbts.c
index 3aa9a96..4799e1f 100644
--- a/drivers/misc/kgdbts.c
+++ b/drivers/misc/kgdbts.c
@@ -103,6 +103,7 @@
 #include <linux/delay.h>
 #include <linux/kthread.h>
 #include <linux/module.h>
+#include <asm/sections.h>
 
 #define v1printk(a...) do { \
 	if (verbose) \
@@ -222,6 +223,7 @@ static unsigned long lookup_addr(char *arg)
 		addr = (unsigned long)do_fork;
 	else if (!strcmp(arg, "hw_break_val"))
 		addr = (unsigned long)&hw_break_val;
+	addr = (unsigned long )dereference_function_descriptor((void *)addr);
 	return addr;
 }
 
-- 
1.7.9.5
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