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Subject[PATCH 12/13] vmcore: copy non page-size aligned head and tail pages in 2nd kernel
Date
Due to mmap() requirement, we need to copy pages not starting or
ending with page-size aligned address in 2nd kernel and to map them to
user-space.

For example, see the map below:

00000000-0001ffff : reserved
00010000-0009f7ff : System RAM
0009f800-0009ffff : reserved

where the System RAM ends with 0x9f800 that is not page-size
aligned. This map is divided into two parts:

00010000-0009dfff
0009f000-0009f7ff

and the first one is kept in old memory and the 2nd one is copied into
buffer on 2nd kernel.

This kind of non-page-size-aligned area can always occur since any
part of System RAM can be converted into reserved area at runtime.

If not doing copying like this and if remapping non page-size aligned
pages on old memory directly, mmap() had to export memory which is not
dump target to user-space. In the above example this is reserved
0x9f800-0xa0000.

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

fs/proc/vmcore.c | 97 ++++++++++++++++++++++++++++++++++++++++++++++++------
1 files changed, 87 insertions(+), 10 deletions(-)

diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
index 2968e5a..99f5673 100644
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -446,11 +446,10 @@ static int __init process_ptload_program_headers_elf64(char *elfptr,
size_t elfsz,
struct list_head *vc_list)
{
- int i;
+ int i, rc;
Elf64_Ehdr *ehdr_ptr;
Elf64_Phdr *phdr_ptr;
loff_t vmcore_off;
- struct vmcore *new;

ehdr_ptr = (Elf64_Ehdr *)elfptr;
phdr_ptr = (Elf64_Phdr*)(elfptr + sizeof(Elf64_Ehdr)); /* PT_NOTE hdr */
@@ -460,20 +459,98 @@ static int __init process_ptload_program_headers_elf64(char *elfptr,
PAGE_SIZE);

for (i = 0; i < ehdr_ptr->e_phnum; i++, phdr_ptr++) {
+ u64 start, end, rest;
+
if (phdr_ptr->p_type != PT_LOAD)
continue;

- /* 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;
- list_add_tail(&new->list, vc_list);
+ start = phdr_ptr->p_offset;
+ end = phdr_ptr->p_offset + phdr_ptr->p_memsz;
+ rest = phdr_ptr->p_memsz;
+
+ if (start & ~PAGE_MASK) {
+ u64 paddr, len;
+ char *buf;
+ struct vmcore *new;
+
+ paddr = start;
+ len = min(roundup(start,PAGE_SIZE), end) - start;
+
+ buf = (char *)get_zeroed_page(GFP_KERNEL);
+ if (!buf)
+ return -ENOMEM;
+ rc = read_from_oldmem(buf + (start & ~PAGE_MASK), len,
+ &paddr, 0);
+ if (rc < 0) {
+ free_pages((unsigned long)buf, 0);
+ return rc;
+ }
+
+ new = get_new_element();
+ if (!new) {
+ free_pages((unsigned long)buf, 0);
+ return -ENOMEM;
+ }
+ new->type = VMCORE_2ND_KERNEL;
+ new->size = PAGE_SIZE;
+ new->buf = buf;
+ list_add_tail(&new->list, vc_list);
+
+ rest -= len;
+ }
+
+ if (rest > 0 &&
+ roundup(start, PAGE_SIZE) < rounddown(end, PAGE_SIZE)) {
+ u64 paddr, len;
+ struct vmcore *new;
+
+ paddr = roundup(start, PAGE_SIZE);
+ len =rounddown(end,PAGE_SIZE)-roundup(start,PAGE_SIZE);
+
+ new = get_new_element();
+ if (!new)
+ return -ENOMEM;
+ new->type = VMCORE_OLD_MEMORY;
+ new->paddr = paddr;
+ new->size = len;
+ list_add_tail(&new->list, vc_list);
+
+ rest -= new->size;
+ }
+
+ if (rest > 0) {
+ u64 paddr, len;
+ char *buf;
+ struct vmcore *new;
+
+ paddr = rounddown(end, PAGE_SIZE);
+ len = end - rounddown(end, PAGE_SIZE);
+
+ buf = (char *)get_zeroed_page(GFP_KERNEL);
+ if (!buf)
+ return -ENOMEM;
+ rc = read_from_oldmem(buf, len, &paddr, 0);
+ if (rc < 0) {
+ free_pages((unsigned long)buf, 0);
+ return rc;
+ }
+
+ new = get_new_element();
+ if (!new) {
+ free_pages((unsigned long)buf, 0);
+ return -ENOMEM;
+ }
+ new->type = VMCORE_2ND_KERNEL;
+ new->size = PAGE_SIZE;
+ new->buf = buf;
+ list_add_tail(&new->list, vc_list);
+
+ rest -= len;
+ }

/* Update the program header offset. */
phdr_ptr->p_offset = vmcore_off;
- vmcore_off = vmcore_off + phdr_ptr->p_memsz;
+ vmcore_off +=roundup(end,PAGE_SIZE)-rounddown(start,PAGE_SIZE);
}
return 0;
}


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