makedumpfile -g with recent kernels

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Hello HATAYAMA-san,

On Thu, 02 Aug 2012 14:47:14 +0900 (JST)
HATAYAMA Daisuke <d.hatayama at jp.fujitsu.com> wrote:

> From: Atsushi Kumagai <kumagai-atsushi at mxc.nes.nec.co.jp>
> Subject: Re: makedumpfile -g with recent kernels
> Date: Thu, 2 Aug 2012 14:12:51 +0900
> 
> > Hello Stefan,
> > 
> > On Mon, 09 Jul 2012 11:17:13 +0200
> > Stefan Bader <stefan.bader at canonical.com> wrote:
> > 
> >> Hi,
> >> 
> >> I am not sure whether this really is the preferred way as I heard the required
> >> info now is in vmcore and vmcoreinfo would not be needed anymore. But just to
> >> have it produce some output I noticed that it trips again over some member of
> >> struct page that moved into some anonymous structure/union combo.
> >> There was some code that was quite specific for the page.mapping case (which now
> >> seems to be outside again). I changed the code to be more generic. It did fix my
> >> _count problem and should also handle the mapping case (though I could not test).
> >> So maybe this would be worth adding to the upstream code.
> >> 
> >> -Stefan
> >> 
> >> Please include me in cc's as I am not subscribed to this ml.
> > 
> > Thank you for your nice work!
> > 
> 
> Hello Kumagai-san,
> 
> I want to see a whole part of Stefan's patch. Could you post it on the
> ml?

This is the Stefan's patch. 


Thanks
Atsushi Kumagai

---
>From cde00fffeddddd1fcffd3085ded0947fdcd159ef Mon Sep 17 00:00:00 2001
From: Stefan Bader <stefan.bader@xxxxxxxxxxxxx>
Date: Thu, 5 Jul 2012 18:03:53 +0200
Subject: [PATCH] Generic search into anonymous members in search_member()

There was a special case to find page.mapping in case it would be
inside an anonymous union.struct. But recent kernel versions also
moved page._count into the depths of some unnamed elements.
Naturally not the same as page.mapping.
So this tries to approach the problem by implementing a generic
method of descending into anonymous sub-members. If this finds
a member and it is the member offset that is the target of the
search, that offset has to be adjusted on the way back out.

Signed-off-by: Stefan Bader <stefan.bader at canonical.com>
---
 dwarf_info.c   |  117 ++++++++++++++++++--------------------------------------
 dwarf_info.h   |    1 -
 makedumpfile.c |    8 ----
 makedumpfile.h |    6 ---
 4 files changed, 38 insertions(+), 94 deletions(-)

diff --git a/dwarf_info.c b/dwarf_info.c
index 1429858..583df53 100644
--- a/dwarf_info.c
+++ b/dwarf_info.c
@@ -64,7 +64,6 @@ is_search_structure(int cmd)
 	if ((cmd == DWARF_INFO_GET_STRUCT_SIZE)
 	    || (cmd == DWARF_INFO_GET_MEMBER_OFFSET)
 	    || (cmd == DWARF_INFO_GET_MEMBER_TYPE)
-	    || (cmd == DWARF_INFO_GET_MEMBER_OFFSET_IN_UNION)
 	    || (cmd == DWARF_INFO_GET_MEMBER_OFFSET_1ST_UNION)
 	    || (cmd == DWARF_INFO_GET_MEMBER_ARRAY_LENGTH))
 		return TRUE;
@@ -447,75 +446,40 @@ get_dwarf_base_type(Dwarf_Die *die)
 	return TRUE;
 }
 
-/*
- * Function for searching struct page.union.struct.mapping.
- */
 static int
-__search_mapping(Dwarf_Die *die, long *offset)
+is_anonymous_container(Dwarf_Die *die)
 {
-	int tag;
-	const char *name;
-	Dwarf_Die child, *walker;
-
-	if (dwarf_child(die, &child) != 0)
+	if (dwarf_diename(die))
 		return FALSE;
-
-	walker = &child;
-	do {
-		tag  = dwarf_tag(walker);
-		name = dwarf_diename(walker);
-
-		if (tag != DW_TAG_member)
-			continue;
-		if ((!name) || strcmp(name, dwarf_info.member_name))
-			continue;
-		if (!get_data_member_location(walker, offset))
-			continue;
+	if (dwarf_tag(die) == DW_TAG_union_type)
+		return TRUE;
+	if (dwarf_tag(die) == DW_TAG_structure_type)
 		return TRUE;
-
-	} while (!dwarf_siblingof(walker, walker));
-
 	return FALSE;
 }
 
-/*
- * Function for searching struct page.union.struct.
- */
-static int
-search_mapping(Dwarf_Die *die, long *offset)
+static void
+adjust_member_offset(Dwarf_Die *die)
 {
-	Dwarf_Die child, *walker;
-	Dwarf_Die die_struct;
-
-	if (dwarf_child(die, &child) != 0)
-		return FALSE;
+	long offset;
 
-	walker = &child;
-
-	do {
-		if (dwarf_tag(walker) != DW_TAG_member)
-			continue;
-		if (!get_die_type(walker, &die_struct))
-			continue;
-		if (dwarf_tag(&die_struct) != DW_TAG_structure_type)
-			continue;
-		if (__search_mapping(&die_struct, offset))
-			return TRUE;
-	} while (!dwarf_siblingof(walker, walker));
-
-	return FALSE;
+	if (dwarf_info.member_offset == NOT_FOUND_STRUCTURE)
+		return;
+	if (!get_data_member_location(die, &offset))
+		return;
+	dwarf_info.member_offset += offset;
 }
 
-static void
+static int
 search_member(Dwarf_Die *die)
 {
 	int tag;
-	long offset, offset_union;
+	long offset;
 	const char *name;
-	Dwarf_Die child, *walker, die_union;
+	Dwarf_Die child, *walker, die_type;
 
 	if (dwarf_child(die, &child) != 0)
-		return;
+		return FALSE;
 
 	walker = &child;
 
@@ -526,6 +490,20 @@ search_member(Dwarf_Die *die)
 		if (tag != DW_TAG_member)
 			continue;
 
+		/*
+		 * Descend into anonymous members and search for member
+		 * there.
+		 */
+		if (!name) {
+			if (!get_die_type(walker, &die_type))
+				continue;
+			if (is_anonymous_container(&die_type))
+				if (search_member(&die_type)) {
+					adjust_member_offset(walker);
+					return TRUE;
+				}
+		}
+
 		switch (dwarf_info.cmd) {
 		case DWARF_INFO_GET_MEMBER_TYPE:
 			if ((!name) || strcmp(name, dwarf_info.member_name))
@@ -535,7 +513,7 @@ search_member(Dwarf_Die *die)
 			 */
 			if (!get_dwarf_base_type(walker))
 				continue;
-			return;
+			return TRUE;
 		case DWARF_INFO_GET_MEMBER_OFFSET:
 			if ((!name) || strcmp(name, dwarf_info.member_name))
 				continue;
@@ -545,29 +523,11 @@ search_member(Dwarf_Die *die)
 			if (!get_data_member_location(walker, &offset))
 				continue;
 			dwarf_info.member_offset = offset;
-			return;
-		case DWARF_INFO_GET_MEMBER_OFFSET_IN_UNION:
-			if (!get_die_type(walker, &die_union))
-				continue;
-			if (dwarf_tag(&die_union) != DW_TAG_union_type)
-				continue;
-			/*
-			 * Search page.mapping in union.
-			 */
-			if (!search_mapping(&die_union, &offset_union))
-				continue;
-
-			/*
-			 * Get the member offset.
-			 */
-			if (!get_data_member_location(walker, &offset))
- 				continue;
-			dwarf_info.member_offset = offset + offset_union;
- 			return;
+			return TRUE;
 		case DWARF_INFO_GET_MEMBER_OFFSET_1ST_UNION:
-			if (!get_die_type(walker, &die_union))
+			if (!get_die_type(walker, &die_type))
 				continue;
-			if (dwarf_tag(&die_union) != DW_TAG_union_type)
+			if (dwarf_tag(&die_type) != DW_TAG_union_type)
 				continue;
 			/*
 			 * Get the member offset.
@@ -575,7 +535,7 @@ search_member(Dwarf_Die *die)
 			if (!get_data_member_location(walker, &offset))
 				continue;
 			dwarf_info.member_offset = offset;
-			return;
+			return TRUE;
 		case DWARF_INFO_GET_MEMBER_ARRAY_LENGTH:
 			if ((!name) || strcmp(name, dwarf_info.member_name))
 				continue;
@@ -584,14 +544,14 @@ search_member(Dwarf_Die *die)
 			 */
 			if (!get_data_array_length(walker))
 				continue;
-			return;
+			return TRUE;
 		}
 	} while (!dwarf_siblingof(walker, walker));
 
 	/*
 	 * Return even if not found.
 	 */
-	return;
+	return FALSE;
 }
 
 static void
@@ -636,7 +596,6 @@ search_structure(Dwarf_Die *die, int *found)
 		break;
 	case DWARF_INFO_GET_MEMBER_TYPE:
 	case DWARF_INFO_GET_MEMBER_OFFSET:
-	case DWARF_INFO_GET_MEMBER_OFFSET_IN_UNION:
 	case DWARF_INFO_GET_MEMBER_OFFSET_1ST_UNION:
 	case DWARF_INFO_GET_MEMBER_ARRAY_LENGTH:
 		search_member(die);
diff --git a/dwarf_info.h b/dwarf_info.h
index 1e07484..8d0084d 100644
--- a/dwarf_info.h
+++ b/dwarf_info.h
@@ -37,7 +37,6 @@
 enum {
 	DWARF_INFO_GET_STRUCT_SIZE,
 	DWARF_INFO_GET_MEMBER_OFFSET,
-	DWARF_INFO_GET_MEMBER_OFFSET_IN_UNION,
 	DWARF_INFO_GET_MEMBER_OFFSET_1ST_UNION,
 	DWARF_INFO_GET_MEMBER_ARRAY_LENGTH,
 	DWARF_INFO_GET_SYMBOL_ARRAY_LENGTH,
diff --git a/makedumpfile.c b/makedumpfile.c
index d024e95..d32ce55 100644
--- a/makedumpfile.c
+++ b/makedumpfile.c
@@ -874,17 +874,9 @@ get_structure_info(void)
 	SIZE_INIT(page, "page");
 	OFFSET_INIT(page.flags, "page", "flags");
 	OFFSET_INIT(page._count, "page", "_count");
-
 	OFFSET_INIT(page.mapping, "page", "mapping");
 ---
 	/*
-	 * On linux-2.6.16 or later, page.mapping is defined
-	 * in anonymous union.
-	 */
-	if (OFFSET(page.mapping) == NOT_FOUND_STRUCTURE)
-		OFFSET_IN_UNION_INIT(page.mapping, "page", "mapping");
-
-	/*
 	 * Some vmlinux(s) don't have debugging information about
 	 * page.mapping. Then, makedumpfile assumes that there is
 	 * "mapping" next to "private(unsigned long)" in the first
diff --git a/makedumpfile.h b/makedumpfile.h
index 6f5489d..4bf502f 100644
--- a/makedumpfile.h
+++ b/makedumpfile.h
@@ -239,12 +239,6 @@ do { \
 	     == FAILED_DWARFINFO) \
 		return FALSE; \
 } while (0)
-#define OFFSET_IN_UNION_INIT(X, Y, Z) \
-do { \
-	if ((OFFSET(X) = get_member_offset(Y, Z, DWARF_INFO_GET_MEMBER_OFFSET_IN_UNION)) \
-	     == FAILED_DWARFINFO) \
-		return FALSE; \
-} while (0)
 #define SYMBOL_ARRAY_LENGTH_INIT(X, Y) \
 do { \
 	if ((ARRAY_LENGTH(X) = get_array_length(Y, NULL, DWARF_INFO_GET_SYMBOL_ARRAY_LENGTH)) == FAILED_DWARFINFO) \
-- 
1.7.9.5



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