vmcore: treat memory chunks referenced by PT_LOAD program header entries in page-size boundary in vmcore_list

Treat memory chunks referenced by PT_LOAD program header entries in
page-size boundary in vmcore_list.  Formally, for each range [start,
end], we set up the corresponding vmcore object in vmcore_list to
[rounddown(start, PAGE_SIZE), roundup(end, PAGE_SIZE)].

This change affects layout of /proc/vmcore.  The gaps generated by the
rearrangement are newly made visible to applications as holes.
Concretely, they are two ranges [rounddown(start, PAGE_SIZE), start] and
[end, roundup(end, PAGE_SIZE)].

Suppose variable m points at a vmcore object in vmcore_list, and
variable phdr points at the program header of PT_LOAD type the variable
m corresponds to.  Then, pictorially:

  m->offset                    +---------------+
                               | hole          |
phdr->p_offset =               +---------------+
  m->offset + (paddr - start)  |               |\
                               | kernel memory | phdr->p_memsz
                               |               |/
                               +---------------+
                               | hole          |
  m->offset + m->size          +---------------+

where m->offset and m->offset + m->size are always page-size aligned.

Signed-off-by: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Atsushi Kumagai <kumagai-atsushi@mxc.nes.nec.co.jp>
Cc: Lisa Mitchell <lisa.mitchell@hp.com>
Cc: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 22 insertions, 8 deletions

diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
index 0b1c04e5e2c5..78c87a1ac01a 100644
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -407,20 +407,27 @@ static int __init process_ptload_program_headers_elf64(char *elfptr,
                         phdr_ptr->p_memsz; /* Note sections */
 
         for (i = 0; i < ehdr_ptr->e_phnum; i++, phdr_ptr++) {
+                u64 paddr, start, end, size;
+
                 if (phdr_ptr->p_type != PT_LOAD)
                         continue;
 
+                paddr = phdr_ptr->p_offset;
+                start = rounddown(paddr, PAGE_SIZE);
+                end = roundup(paddr + phdr_ptr->p_memsz, PAGE_SIZE);
+                size = end - start;
+
                 /* Add this contiguous chunk of memory to vmcore list.*/
                 new = get_new_element();
                 if (!new)
                         return -ENOMEM;
-                new->paddr = phdr_ptr->p_offset;
-                new->size = phdr_ptr->p_memsz;
+                new->paddr = start;
+                new->size = size;
                 list_add_tail(&new->list, vc_list);
 
                 /* Update the program header offset. */
-                phdr_ptr->p_offset = vmcore_off;
-                vmcore_off = vmcore_off + phdr_ptr->p_memsz;
+                phdr_ptr->p_offset = vmcore_off + (paddr - start);
+                vmcore_off = vmcore_off + size;
         }
         return 0;
 }
@@ -443,20 +450,27 @@ static int __init process_ptload_program_headers_elf32(char *elfptr,
                         phdr_ptr->p_memsz; /* Note sections */
 
         for (i = 0; i < ehdr_ptr->e_phnum; i++, phdr_ptr++) {
+                u64 paddr, start, end, size;
+
                 if (phdr_ptr->p_type != PT_LOAD)
                         continue;
 
+                paddr = phdr_ptr->p_offset;
+                start = rounddown(paddr, PAGE_SIZE);
+                end = roundup(paddr + phdr_ptr->p_memsz, PAGE_SIZE);
+                size = end - start;
+
                 /* Add this contiguous chunk of memory to vmcore list.*/
                 new = get_new_element();
                 if (!new)
                         return -ENOMEM;
-                new->paddr = phdr_ptr->p_offset;
-                new->size = phdr_ptr->p_memsz;
+                new->paddr = start;
+                new->size = size;
                 list_add_tail(&new->list, vc_list);
 
                 /* Update the program header offset */
-                phdr_ptr->p_offset = vmcore_off;
-                vmcore_off = vmcore_off + phdr_ptr->p_memsz;
+                phdr_ptr->p_offset = vmcore_off + (paddr - start);
+                vmcore_off = vmcore_off + size;
         }
         return 0;
 }