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

Tiejun Chen tiejun.chen at windriver.com
Thu Oct 25 17:43:30 EST 2012

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 <tiejun.chen at windriver.com>
 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;

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