On Sat, Apr 13, 2013 at 09:21:46AM +0900, HATAYAMA Daisuke wrote:
> 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)].
Sorry did not understand this part. So if end is not page aligned, then
we roundup(end, PAGE_SIZE) and increase the PT_LOAD size accordingly?
Similarly for start, we do roundown().
- Can you really rounddown() start? Then you will have to change start
virtual address in program header and that's not really a good idea.
- So this extra memory for end, we read from old memory and not fill
with zeros?
>
> Signed-off-by: HATAYAMA Daisuke <d.hatay...@jp.fujitsu.com>
> ---
>
> fs/proc/vmcore.c | 26 ++++++++++++++++++++------
> 1 files changed, 20 insertions(+), 6 deletions(-)
>
> diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
> index 029bdc0..cd0f9d9 100644
> --- a/fs/proc/vmcore.c
> +++ b/fs/proc/vmcore.c
> @@ -477,16 +477,23 @@ static int __init
> process_ptload_program_headers_elf64(char *elfptr,
> vmcore_off = elfsz + roundup(phdr_ptr->p_memsz, PAGE_SIZE);
>
> 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.*/
> - if (vmcore_add(vc_list, phdr_ptr->p_offset, phdr_ptr->p_memsz))
> + if (vmcore_add(vc_list, start, size))
> return -ENOMEM;
>
> /* 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);
What's paddr-start. Why following is not sufficient.
phdr_ptr->p_offset = vmcore_off
Thanks
Vivek
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