linux-kernel - [PATCH v2 17/20] vmcore: check if vmcore objects satify mmap()'s page-size boundary requirement

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Date:	Sat, 02 Mar 2013 17:37:25 +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
Subject: [PATCH v2 17/20] vmcore: check if vmcore objects satify mmap()'s
 page-size boundary requirement

If there's some vmcore object that doesn't satisfy page-size boundary
requirement, remap_pfn_range() fails to remap it to user-space.

Objects that posisbly don't satisfy the requirement are ELF note
segments only. The memory chunks corresponding to PT_LOAD entries are
guaranteed to satisfy page-size boundary requirement by the copy from
old memory to buffer in 2nd kernel done in later patch.

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

 fs/proc/vmcore.c |   22 ++++++++++++++++++++++
 1 files changed, 22 insertions(+), 0 deletions(-)

diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
index e432946..5582aaa 100644
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -38,6 +38,8 @@ static u64 vmcore_size;
 
 static struct proc_dir_entry *proc_vmcore = NULL;
 
+static bool support_mmap_vmcore;
+
 /*
  * Returns > 0 for RAM pages, 0 for non-RAM pages, < 0 on error
  * The called function has to take care of module refcounting.
@@ -897,6 +899,7 @@ static int __init parse_crash_elf_headers(void)
 static int __init vmcore_init(void)
 {
 	int rc = 0;
+	struct vmcore *m;
 
 	/* If elfcorehdr= has been passed in cmdline, then capture the dump.*/
 	if (!(is_vmcore_usable()))
@@ -907,6 +910,25 @@ static int __init vmcore_init(void)
 		return rc;
 	}
 
+	/* If some object doesn't satisfy PAGE_SIZE boundary
+	 * requirement, mmap_vmcore() is not exported to
+	 * user-space. */
+	support_mmap_vmcore = true;
+	list_for_each_entry(m, &vmcore_list, list) {
+		u64 paddr;
+
+		if (m->flag & MEM_TYPE_CURRENT_KERNEL)
+			paddr = (u64)__pa(m->buf);
+		else
+			paddr = m->paddr;
+
+		if ((m->offset & ~PAGE_MASK) || (paddr & ~PAGE_MASK)
+		    || (m->size & ~PAGE_MASK)) {
+			support_mmap_vmcore = false;
+			break;
+		}
+	}
+
 	proc_vmcore = proc_create("vmcore", S_IRUSR, NULL, &proc_vmcore_operations);
 	if (proc_vmcore)
 		proc_vmcore->size = vmcore_size;

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