crt_pad_segment adds a NOTE to the ELF which is used by the binoic
loader to determine whether it should pad segments when mapping them
into the virtual address space, such that there are no gaps between
mappings of consecutive segments. This avoids an increase in
unreclaimable kernel slab memory usage for VMAs on devices where the
runtime-page-size > elf-segment-p_align.
Since -fandroid-pad-segment [1] respects -nostdlib used in android
platform builds, soong must link in crt_pad_segment to platform shared
libraries.
For simplicity, link crt_pad_segment everywhere that crtend_so is
applicable, ignoring nocrt property, as there is no other reason
to track these separately.
Example:
❯ readelf -WS /system/lib64/libc++.so [Output simplified]
...
Section Headers:
[Nr] Name Type Address Off Size ES Flg Lk Inf Al
...
[ 2] .note.android.pad_segment NOTE 0000000000000288 000288 000018 00 A 0 0 4
...
[1] https://github.com/llvm/llvm-project/pull/77244
Bug: 316403210
Test: readelf -WS <lib>.so
Change-Id: Icc06611376cfd5ee4de7281b4134f9f8ffe7ca60
Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
f4ffe0a026