linux-kernel - [PATCH v5 7/8] vmcore: calculate vmcore file size from buffer size and total size of vmcore objects

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Date:	Tue, 14 May 2013 10:57:46 +0900
From:	HATAYAMA Daisuke <d.hatayama@...fujitsu.com>
To:	vgoyal@...hat.com, ebiederm@...ssion.com, akpm@...ux-foundation.org
Cc:	cpw@....com, kumagai-atsushi@....nes.nec.co.jp,
	lisa.mitchell@...com, kexec@...ts.infradead.org,
	linux-kernel@...r.kernel.org, zhangyanfei@...fujitsu.com,
	jingbai.ma@...com, linux-mm@...ck.org
Subject: [PATCH v5 7/8] vmcore: calculate vmcore file size from buffer size
 and total size of vmcore objects

The previous patches newly added holes before each chunk of memory and
the holes need to be count in vmcore file size. There are two ways to
count file size in such a way:

1) supporse p as a poitner to the last program header entry with
PT_LOAD type, then roundup(p->p_offset + p->p_memsz, PAGE_SIZE), or

2) calculate sum of size of buffers for ELF header, program headers,
ELF note segments and objects in vmcore_list.

Although 1) is more direct and simpler than 2), 2) seems better in
that it reflects internal object structure of /proc/vmcore. Thus, this
patch changes get_vmcore_size_elf{64, 32} so that it calculates size
in the way of 2).

Signed-off-by: HATAYAMA Daisuke <d.hatayama@...fujitsu.com>
---

 fs/proc/vmcore.c |   40 ++++++++++++++++++----------------------
 1 files changed, 18 insertions(+), 22 deletions(-)

diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
index eb7ff29..ad6da17 100644
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -210,36 +210,28 @@ static struct vmcore* __init get_new_element(void)
 	return kzalloc(sizeof(struct vmcore), GFP_KERNEL);
 }
 
-static u64 __init get_vmcore_size_elf64(char *elfptr, size_t elfsz)
+static u64 __init get_vmcore_size_elf64(size_t elfsz, size_t elfnotesegsz,
+					struct list_head *vc_list)
 {
-	int i;
 	u64 size;
-	Elf64_Ehdr *ehdr_ptr;
-	Elf64_Phdr *phdr_ptr;
+	struct vmcore *m;
 
-	ehdr_ptr = (Elf64_Ehdr *)elfptr;
-	phdr_ptr = (Elf64_Phdr*)(elfptr + sizeof(Elf64_Ehdr));
-	size = elfsz;
-	for (i = 0; i < ehdr_ptr->e_phnum; i++) {
-		size += phdr_ptr->p_memsz;
-		phdr_ptr++;
+	size = elfsz + elfnotesegsz;
+	list_for_each_entry(m, vc_list, list) {
+		size += m->size;
 	}
 	return size;
 }
 
-static u64 __init get_vmcore_size_elf32(char *elfptr, size_t elfsz)
+static u64 __init get_vmcore_size_elf32(size_t elfsz, size_t elfnotesegsz,
+					struct list_head *vc_list)
 {
-	int i;
 	u64 size;
-	Elf32_Ehdr *ehdr_ptr;
-	Elf32_Phdr *phdr_ptr;
+	struct vmcore *m;
 
-	ehdr_ptr = (Elf32_Ehdr *)elfptr;
-	phdr_ptr = (Elf32_Phdr*)(elfptr + sizeof(Elf32_Ehdr));
-	size = elfsz;
-	for (i = 0; i < ehdr_ptr->e_phnum; i++) {
-		size += phdr_ptr->p_memsz;
-		phdr_ptr++;
+	size = elfsz + elfnotesegsz;
+	list_for_each_entry(m, vc_list, list) {
+		size += m->size;
 	}
 	return size;
 }
@@ -755,14 +747,18 @@ static int __init parse_crash_elf_headers(void)
 			return rc;
 
 		/* Determine vmcore size. */
-		vmcore_size = get_vmcore_size_elf64(elfcorebuf, elfcorebuf_sz);
+		vmcore_size = get_vmcore_size_elf64(elfcorebuf_sz,
+						    elfnotesegbuf_sz,
+						    &vmcore_list);
 	} else if (e_ident[EI_CLASS] == ELFCLASS32) {
 		rc = parse_crash_elf32_headers();
 		if (rc)
 			return rc;
 
 		/* Determine vmcore size. */
-		vmcore_size = get_vmcore_size_elf32(elfcorebuf, elfcorebuf_sz);
+		vmcore_size = get_vmcore_size_elf32(elfcorebuf_sz,
+						    elfnotesegbuf_sz,
+						    &vmcore_list);
 	} else {
 		pr_warn("Warning: Core image elf header is not sane\n");
 		return -EINVAL;

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