Re: [PATCH v2 07/20] vmcore: copy non page-size aligned head and tail pages in 2nd kernel

Zhang Yanfei
2013-03-10T07:12:05Z

于 2013年03月02日 16:36, HATAYAMA Daisuke 写道:
> 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

00010000-0009efff

> 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 | 192 ++++++++++++++++++++++++++++++++++++++++++++++++------
> 1 files changed, 172 insertions(+), 20 deletions(-)
>
> diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
> index c511cf4..6b071b4 100644
> --- a/fs/proc/vmcore.c
> +++ b/fs/proc/vmcore.c
> @@ -474,11 +474,10 @@ 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 + ehdr_ptr->e_phoff); /* PT_NOTE hdr */
> @@ -488,20 +487,97 @@ 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->flag |= MEM_TYPE_CURRENT_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->paddr = paddr;
> + new->size = len;
> + list_add_tail(&new->list, vc_list);
> +
> + rest -= len;
> + }
> +
> + 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->flag |= MEM_TYPE_CURRENT_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);

Here the code changes phdr_ptr->p_offset to a new page-size aligned offset.
But it seems the phdr_ptr->p_paddr is still the non page-size aligned
physical address? Does the mismatch of a PT_LOAD segment and the physical
memory occur?

Or, later in makedumpfile, it will check the phdr_ptr->paddr to see if it
is page-size aligned and also phdr_ptr->p_memsz to get the real memory size,
not including padding?

> }
> return 0;
> }
> @@ -510,11 +586,10 @@ static int __init process_ptload_program_headers_elf32(char *elfptr,
> size_t elfsz,
> struct list_head *vc_list)
> {
> - int i;
> + int i, rc;
> Elf32_Ehdr *ehdr_ptr;
> Elf32_Phdr *phdr_ptr;
> loff_t vmcore_off;
> - struct vmcore *new;
>
> ehdr_ptr = (Elf32_Ehdr *)elfptr;
> phdr_ptr = (Elf32_Phdr*)(elfptr + ehdr_ptr->e_phoff); /* PT_NOTE hdr */
> @@ -524,20 +599,97 @@ static int __init process_ptload_program_headers_elf32(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->flag |= MEM_TYPE_CURRENT_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->paddr = paddr;
> + new->size = len;
> + list_add_tail(&new->list, vc_list);
> +
> + rest -= len;
> + }
> +
> + 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->flag |= MEM_TYPE_CURRENT_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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