(2013/12/18 22:34), WANG Chao wrote:
> We are using memset() to improve performance when creating 1st and 2nd
> bitmap. After doing round up the pfn_start and round down pfn_end, it's
> possible that pfn_start_roundup is greater than pfn_end_round. A segment
> fault could happen in that case because memset is taking roughly the
> value of (pfn_end_round << 3 - pfn_start_roundup << 3 ), which is
> negative, as its third argument.
>
> So we can skip the memset if start is greater than end. It's safe
> because we will set bit for the round up part and also round down part.
>
> Actually this happens on my EFI virtual machine:
>
> cat /proc/iomem:
> 00000000-00000fff : reserved
> 00001000-0009ffff : System RAM
> 000a0000-000bffff : PCI Bus 0000:00
> 000f0000-000fffff : System ROM
> 00100000-3d162017 : System RAM
> 01000000-015cab9b : Kernel code
> 015cab9c-019beb3f : Kernel data
> 01b4f000-01da9fff : Kernel bss
> 30000000-37ffffff : Crash kernel
> 3d162018-3d171e57 : System RAM
> 3d171e58-3d172017 : System RAM
> 3d172018-3d17ae57 : System RAM
> 3d17ae58-3dc10fff : System RAM
> 3dc11000-3dc18fff : reserved
> 3dc19000-3dc41fff : System RAM
> 3dc42000-3ddcefff : reserved
> 3ddcf000-3f7fefff : System RAM
> 3f7ff000-3f856fff : reserved
> [..]
>
> gdb ./makedumpfile core
> (gdb) bt full
> [..]
> #1 0x000000000042775d in create_1st_bitmap_cyclic () at makedumpfile.c:4543
> i = 0x5
> pfn = 0x3d190
> phys_start = 0x3d18ee58
> phys_end = 0x3d18f018
> pfn_start = 0x3d18e
> pfn_end = 0x3d18f
> pfn_start_roundup = 0x3d190
> pfn_end_round = 0x3d188
> pfn_start_byte = 0x7a32
> pfn_end_byte = 0x7a31
> [..]
> (gdb) list makedumpfile.c:4543
> 4538 return FALSE;
> 4539
> 4540 pfn_start_byte = (pfn_start_roundup - info->cyclic_start_pfn) >> 3;
> 4541 pfn_end_byte = (pfn_end_round - info->cyclic_start_pfn) >> 3;
> 4542
> 4543 memset(info->partial_bitmap2 + pfn_start_byte,
> 4544 0xff,
> 4545 pfn_end_byte - pfn_start_byte);
> 4546
> 4547 for (pfn = pfn_end_round; pfn < pfn_end; ++pfn)
>
> Signed-off-by: WANG Chao <chaowang at redhat.com>
> ---
> makedumpfile.c | 18 +++++++++++-------
> 1 file changed, 11 insertions(+), 7 deletions(-)
>
> diff --git a/makedumpfile.c b/makedumpfile.c
> index 23251a1..ef08d91 100644
> --- a/makedumpfile.c
> +++ b/makedumpfile.c
> @@ -4435,11 +4435,13 @@ create_1st_bitmap_cyclic()
> pfn_start_byte = (pfn_start_roundup - info->cyclic_start_pfn) >> 3;
> pfn_end_byte = (pfn_end_round - info->cyclic_start_pfn) >> 3;
>
> - memset(info->partial_bitmap1 + pfn_start_byte,
> - 0xff,
> - pfn_end_byte - pfn_start_byte);
> + if (pfn_start_byte < pfn_end_byte) {
> + memset(info->partial_bitmap1 + pfn_start_byte,
> + 0xff,
> + pfn_end_byte - pfn_start_byte);
>
> - pfn_bitmap1 += (pfn_end_byte - pfn_start_byte) * BITPERBYTE;
> + pfn_bitmap1 += (pfn_end_byte - pfn_start_byte) * BITPERBYTE;
> + }
>
> for (pfn = pfn_end_round; pfn < pfn_end; pfn++) {
> if (set_bit_on_1st_bitmap(pfn))
> @@ -4540,9 +4542,11 @@ initialize_2nd_bitmap_cyclic(void)
> pfn_start_byte = (pfn_start_roundup - info->cyclic_start_pfn) >> 3;
> pfn_end_byte = (pfn_end_round - info->cyclic_start_pfn) >> 3;
>
> - memset(info->partial_bitmap2 + pfn_start_byte,
> - 0xff,
> - pfn_end_byte - pfn_start_byte);
> + if (pfn_start_byte < pfn_end_byte) {
> + memset(info->partial_bitmap2 + pfn_start_byte,
> + 0xff,
> + pfn_end_byte - pfn_start_byte);
> + }
>
> for (pfn = pfn_end_round; pfn < pfn_end; ++pfn)
> if (!set_bit_on_2nd_bitmap_for_kernel(pfn))
>
Acked-by: HATAYAMA Daisuke <d.hatayama at jp.fujitsu.com>
Also, I'm interested in the memory map passed to from EFI in that
> cat /proc/iomem:
> 00000000-00000fff : reserved
> 00001000-0009ffff : System RAM
> 000a0000-000bffff : PCI Bus 0000:00
> 000f0000-000fffff : System ROM
> 00100000-3d162017 : System RAM
> 01000000-015cab9b : Kernel code
> 015cab9c-019beb3f : Kernel data
> 01b4f000-01da9fff : Kernel bss
> 30000000-37ffffff : Crash kernel
> 3d162018-3d171e57 : System RAM
> 3d171e58-3d172017 : System RAM
> 3d172018-3d17ae57 : System RAM
> 3d17ae58-3dc10fff : System RAM
this part is consecutive but somehow is divided into 4 entries.
You called your environment as ``EFI virtual machine'', could you tell
me precisely what it mean? qemu/KVM or VMware guest system? I do want
to understand how this kind of memory map was created. I think this
kind of memory mapping is odd and I guess this is caused by the fact
that the system is a virtual environment.
And for Vivek, this case is a concrete example of multiple RAM entries
appearing in a single page I suspected in the mmap failure patch,
although these entries are consecutive in physical address and can be
represented by a single entry by merging them in a single entry. But
then it seems to me that there could be more odd case that multiple
RAM entries but not consecutive. I again think this should be addressed
in the patch for the mmap failure issue. How do you think?
> 3dc11000-3dc18fff : reserved
> 3dc19000-3dc41fff : System RAM
> 3dc42000-3ddcefff : reserved
> 3ddcf000-3f7fefff : System RAM
> 3f7ff000-3f856fff : reserved
> [..]
--
Thanks.
HATAYAMA, Daisuke
