Re: [PATCH] /proc/kcore: Update physical address for kcore ram and text

From: Dave Young
Date: Wed Jan 25 2017 - 01:38:40 EST


Hi Pratyush
On 01/25/17 at 10:14am, Pratyush Anand wrote:
> Currently all the p_paddr of PT_LOAD headers are assigned to 0, which is
> not true and could be misleading, since 0 is a valid physical address.

I do not know the history of /proc/kcore, so a question is why the
p_addr was set as 0, if there were some reasons and if this could cause
some risk or breakage.

>
> User space tools like makedumpfile needs to know physical address for
> PT_LOAD segments of direct mapped regions. Therefore this patch updates
> paddr for such regions. It also sets an invalid paddr (-1) for other
> regions, so that user space tool can know whether a physical address
> provided in PT_LOAD is correct or not.
>
> Signed-off-by: Pratyush Anand <panand@xxxxxxxxxx>
> ---
> fs/proc/kcore.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c
> index 0b80ad87b4d6..ea9f3d1ae830 100644
> --- a/fs/proc/kcore.c
> +++ b/fs/proc/kcore.c
> @@ -373,7 +373,10 @@ static void elf_kcore_store_hdr(char *bufp, int nphdr, int dataoff)
> phdr->p_flags = PF_R|PF_W|PF_X;
> phdr->p_offset = kc_vaddr_to_offset(m->addr) + dataoff;
> phdr->p_vaddr = (size_t)m->addr;
> - phdr->p_paddr = 0;
> + if (m->type == KCORE_RAM || m->type == KCORE_TEXT)
> + phdr->p_paddr = __pa(m->addr);
> + else
> + phdr->p_paddr = (elf_addr_t)-1;
> phdr->p_filesz = phdr->p_memsz = m->size;
> phdr->p_align = PAGE_SIZE;
> }
> --
> 2.9.3
>

Thanks
Dave