Disable Android relocation packing in linker.
Newer versions of lld write ifunc relocations for PLT entries
to .rela.dyn instead of .rela.plt. This causes a problem because
.rela.dyn is subject to Android relocation packing and we don't
support relocation packing when calling the linker's own ifunc
resolvers. Resolve the problem by passing --pack-dyn-relocs=relr
which disables Android relocation packing but keeps RELR packing
enabled which covers most of the relocations in the linker.
With the current toolchain there are only two entries in the linker's
.rela.dyn (and these entries look like a bug anyway) so there should
be no substantial change to binary size as a result of this change.
Relocation section '.rela.dyn' at offset 0x8e8 contains 2 entries:
Offset Info Type Symbol's Value Symbol's Name + Addend
00000000001691d8 0000000100000401 R_AARCH64_GLOB_DAT 0000000000000000 ZSTD_trace_decompress_begin + 0
00000000001691e0 0000000200000401 R_AARCH64_GLOB_DAT 0000000000000000 ZSTD_trace_decompress_end + 0
Bug: 331450960
Change-Id: Idf403e775d134cbe208d6b1635a84a2a3e70b74b
diff --git a/linker/Android.bp b/linker/Android.bp
index f87a92e..e1a5a91 100644
--- a/linker/Android.bp
+++ b/linker/Android.bp
@@ -334,6 +334,13 @@
"-Wl,-Bsymbolic",
"-Wl,--exclude-libs,ALL",
"-Wl,-soname,ld-android.so",
+ // When the linker applies its own IRELATIVE relocations, it will only read DT_REL[A] and
+ // DT_JMPREL, not DT_ANDROID_REL[A], which can also theoretically contain IRELATIVE
+ // relocations. lld has been taught to not store them there as a bug workaround (see
+ // https://llvm.org/pr86751) but the workaround could be removed at some point in the
+ // future. So we explicitly prevent it from doing so by disabling DT_ANDROID_REL[A] when
+ // linking the linker (DT_RELR cannot encode IRELATIVE relocations).
+ "-Wl,--pack-dyn-relocs=relr",
],
// we are going to link libc++_static manually because