ANDROID: 16K: Don't copy data vma for maps/smaps output

Remove get_data_vma() which made a copy of the original VMA containing
padding and modified vm_end to exclude the trailing padding (if any).

Avoid this copy to avoid races due to stale data relating to
vma->vm_file.

Instead use VMA_PAD_START(vma) directly to get the correct end excluding
padding if any.

Add additional check to verify the padding VMA is as expected and also
check for allocation failure of the pad VMA.

ELFs with padding can be loaded from tmpfs. For simplicity swapped out
shmem accounting in smaps, skips the fast path for read only files and
walks the page table with the range adjusted for padding.

Example output:

===== Maps =====

7ff6306c2000-7ff6306c3000 r--p 00000000 fe:09 1912                       /system/lib64/bootstrap/libdl.so
7ff6306c3000-7ff6306c6000 ---p 00000000 00:00 0                          [page size compat]
7ff6306c6000-7ff6306c7000 r-xp 00004000 fe:09 1912                       /system/lib64/bootstrap/libdl.so
7ff6306c7000-7ff6306ca000 ---p 00000000 00:00 0                          [page size compat]
7ff6306ca000-7ff6306cb000 r--p 00008000 fe:09 1912                       /system/lib64/bootstrap/libdl.so

===== Smaps =====

7ff6306c2000-7ff6306c3000 r--p 00000000 fe:09 1912                       /system/lib64/bootstrap/libdl.so
Size:                  4 kB
KernelPageSize:        4 kB
MMUPageSize:           4 kB
Rss:                   4 kB
Pss:                   0 kB
Pss_Dirty:             0 kB
Shared_Clean:          4 kB
Shared_Dirty:          0 kB
Private_Clean:         0 kB
Private_Dirty:         0 kB
Referenced:            4 kB
Anonymous:             0 kB
KSM:                   0 kB
LazyFree:              0 kB
AnonHugePages:         0 kB
ShmemPmdMapped:        0 kB
FilePmdMapped:         0 kB
Shared_Hugetlb:        0 kB
Private_Hugetlb:       0 kB
Swap:                  0 kB
SwapPss:               0 kB
Locked:                0 kB
THPeligible:           0
VmFlags: rd mr mw me ??
7ff6306c3000-7ff6306c6000 ---p 00000000 00:00 0                          [page size compat]
Size:                 12 kB
KernelPageSize:        4 kB
MMUPageSize:           4 kB
Rss:                   0 kB
Pss:                   0 kB
Pss_Dirty:             0 kB
Shared_Clean:          0 kB
Shared_Dirty:          0 kB
Private_Clean:         0 kB
Private_Dirty:         0 kB
Referenced:            0 kB
Anonymous:             0 kB
KSM:                   0 kB
LazyFree:              0 kB
AnonHugePages:         0 kB
ShmemPmdMapped:        0 kB
FilePmdMapped:         0 kB
Shared_Hugetlb:        0 kB
Private_Hugetlb:       0 kB
Swap:                  0 kB
SwapPss:               0 kB
Locked:                0 kB
THPeligible:           0
VmFlags: mr mw me
7ff6306c6000-7ff6306c7000 r-xp 00004000 fe:09 1912                       /system/lib64/bootstrap/libdl.so
Size:                  4 kB
KernelPageSize:        4 kB
MMUPageSize:           4 kB
Rss:                   4 kB
Pss:                   0 kB
Pss_Dirty:             0 kB
Shared_Clean:          4 kB
Shared_Dirty:          0 kB
Private_Clean:         0 kB
Private_Dirty:         0 kB
Referenced:            4 kB
Anonymous:             0 kB
KSM:                   0 kB
LazyFree:              0 kB
AnonHugePages:         0 kB
ShmemPmdMapped:        0 kB
FilePmdMapped:         0 kB
Shared_Hugetlb:        0 kB
Private_Hugetlb:       0 kB
Swap:                  0 kB
SwapPss:               0 kB
Locked:                0 kB
THPeligible:           0
VmFlags: rd ex mr mw me ??
7ff6306c7000-7ff6306ca000 ---p 00000000 00:00 0                          [page size compat]
Size:                 12 kB
KernelPageSize:        4 kB
MMUPageSize:           4 kB
Rss:                   0 kB
Pss:                   0 kB
Pss_Dirty:             0 kB
Shared_Clean:          0 kB
Shared_Dirty:          0 kB
Private_Clean:         0 kB
Private_Dirty:         0 kB
Referenced:            0 kB
Anonymous:             0 kB
KSM:                   0 kB
LazyFree:              0 kB
AnonHugePages:         0 kB
ShmemPmdMapped:        0 kB
FilePmdMapped:         0 kB
Shared_Hugetlb:        0 kB
Private_Hugetlb:       0 kB
Swap:                  0 kB
SwapPss:               0 kB
Locked:                0 kB
THPeligible:           0
VmFlags: mr mw me
7ff6306ca000-7ff6306cb000 r--p 00008000 fe:09 1912                       /system/lib64/bootstrap/libdl.so
Size:                  4 kB
KernelPageSize:        4 kB
MMUPageSize:           4 kB
Rss:                   4 kB
Pss:                   4 kB
Pss_Dirty:             4 kB
Shared_Clean:          0 kB
Shared_Dirty:          0 kB
Private_Clean:         0 kB
Private_Dirty:         4 kB
Referenced:            4 kB
Anonymous:             4 kB
KSM:                   0 kB
LazyFree:              0 kB
AnonHugePages:         0 kB
ShmemPmdMapped:        0 kB
FilePmdMapped:         0 kB
Shared_Hugetlb:        0 kB
Private_Hugetlb:       0 kB
Swap:                  0 kB
SwapPss:               0 kB
Locked:                0 kB
THPeligible:           0
VmFlags: rd mr mw me ac

Bug: 427145188
Bug: 409239984
Change-Id: Ic54e89571276db62ffc01681e7ca8986bb1ca7c4
Signed-off-by: Kalesh Singh <kaleshsingh@google.com>