linux-kernel - [PATCH v3 17/21] vmcore: check NT_VMCORE_PAD as a mark indicating the end of ELF note buffer

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Date:	Sat, 16 Mar 2013 13:02:23 +0900
From:	HATAYAMA Daisuke <d.hatayama@...fujitsu.com>
To:	vgoyal@...hat.com, ebiederm@...ssion.com, cpw@....com,
	kumagai-atsushi@....nes.nec.co.jp, lisa.mitchell@...com,
	heiko.carstens@...ibm.com, akpm@...ux-foundation.org
Cc:	kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
	zhangyanfei@...fujitsu.com
Subject: [PATCH v3 17/21] vmcore: check NT_VMCORE_PAD as a mark indicating the
 end of ELF note buffer

Modern kernel marks the end of ELF note buffer with NT_VMCORE_PAD type
note in order to make the buffer satisfy mmap()'s page-size boundary
requirement. This patch makes finishing reading each buffer if the
note type now being read is NT_VMCORE_PAD type.

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

 fs/proc/vmcore.c |   24 ++++++++++++++++++++++++
 1 files changed, 24 insertions(+), 0 deletions(-)

diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
index b252d17..2a0f885 100644
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -258,12 +258,24 @@ static int __init merge_note_headers_elf64(char *elfptr, size_t *elfsz,
 		}
 		nhdr_ptr = notes_section;
 		while (real_sz < max_sz) {
+			char *name;
+
+			/* Old kernel marks the end of ELF note buffer
+			 * with empty header. */
 			if (nhdr_ptr->n_namesz == 0)
 				break;
 			sz = sizeof(Elf64_Nhdr) +
 				((nhdr_ptr->n_namesz + 3) & ~3) +
 				((nhdr_ptr->n_descsz + 3) & ~3);
 			real_sz += sz;
+
+			/* Modern kernel marks the end of ELF note
+			 * buffer with NT_VMCORE_PAD type note. */
+			name = (char *)(nhdr_ptr + 1);
+			if (strncmp(name, VMCOREINFO_NOTE_NAME,
+				    sizeof(VMCOREINFO_NOTE_NAME)) == 0
+			    && nhdr_ptr->n_type == NT_VMCORE_PAD)
+				break;
 			nhdr_ptr = (Elf64_Nhdr*)((char*)nhdr_ptr + sz);
 		}
 
@@ -367,12 +379,24 @@ static int __init merge_note_headers_elf32(char *elfptr, size_t *elfsz,
 		}
 		nhdr_ptr = notes_section;
 		while (real_sz < max_sz) {
+			char *name;
+
+			/* Old kernel marks the end of ELF note buffer
+			 * with empty header. */
 			if (nhdr_ptr->n_namesz == 0)
 				break;
 			sz = sizeof(Elf32_Nhdr) +
 				((nhdr_ptr->n_namesz + 3) & ~3) +
 				((nhdr_ptr->n_descsz + 3) & ~3);
 			real_sz += sz;
+
+			/* Modern kernel marks the end of ELF note
+			 * buffer with NT_VMCORE_PAD type note. */
+			name = (char *)(nhdr_ptr + 1);
+			if (strncmp(name, VMCOREINFO_NOTE_NAME,
+				    sizeof(VMCOREINFO_NOTE_NAME)) == 0
+			    && nhdr_ptr->n_type == NT_VMCORE_PAD)
+				break;
 			nhdr_ptr = (Elf32_Nhdr*)((char*)nhdr_ptr + sz);
 		}
 

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