Change Details

- Completely rewrite TLSDESC relocation. The original code did not support dynamically loaded libraries and used suboptimal access to TLS variables. New implementation removes lazy resolving of TLS relocation - due to flaw in TLSDESC design is impossible to switch resolver function at runtime without expensive locking. The new implementation uses load time resolving, with specialized fast resolver for TLS relocation from libraries loaded with main binary (thus with known TLS offset). For dynamically loaded libraries it uses runtime resolver with fast path. It correctly handles undefined thread weak symbols (it should be resolved to NULL). - don't double relocate jump slots if LD_BIND_NOW is defined - handle TLS_DTPMOD64, TLS_DTPREL64 and NULL relocations - implement aarch64 specific version of __tls_get_addr() --------------------------------------------------------------------------- Unfortunately, here are still some issues which I unable to solve: - TLSDESC ABI for resolver function requires preserving all (but X0) registers, including all floating point and optional SVE registers. This is not possible (in universal way) so current code expects that nobody in rtld-elf code uses it, including compiler instrict and/or used libraries. I'm not sure if there is any compiler switch that ensure this. - memory allocated by reloc_tlsdesc_alloc() is not freed - for TLS_TPREL64 relocation, we don't handle undefined thread weak symbols, but this problem exist in all other architectures. - TLSDESC case in reloc_plt() is nonsense, this kind of relocation relocates data, not code. But (GNU compiled) /usr/local/lib/libuuid.so.1.2 have TLSDESC relocation in .rela.plt section. I have no idea why.

The original code did not support dynamically loaded libraries and use suboptimal access to TLS variables. New implementation removes lazy resolving of TLS relocation - due to flaw in TLSDESC design is impossible to switch resolver function at runtime without expensive locking. Due to this, 3 specialized resolvers are used. - load time resolver, for TLS relocation from libraries loaded with main binary (thus with known TLS offset). - undefined thread weak symbol resolved for initial exec symbols. - slower lazy resolving for dynamically loaded libraries with fast path for already resolved symbols. It correctly handles undefined thread weak symbols (it should be resolved to NULL). --------------------------------------------------------------------------- Unfortunately, here are still some issues which I unable to solve: - TLSDESC ABI for resolver function requires preserving all (but X0) registers, including all floating point and optional SVE registers. This is not possible (in universal way) so current code expects that nobody in rtld-elf code uses it, including compiler instrict and/or used libraries. I'm not sure if there is any compiler switch that ensure this. - memory allocated by reloc_tlsdesc_alloc() is not freed - for TLS_TPREL64 relocation, we don't handle undefined thread weak symbols, but this problem exist in all other architectures. - TLSDESC case in reloc_plt() is nonsense, this kind of relocation relocates data, not code. But (GNU compiled) /usr/local/lib/libuuid.so.1.2 have TLSDESC relocation in .rela.plt section. I have no idea why.

- Completely rewrite TLSDESC relocation. The original code did not supportThe original code did not support dynamically loaded libraries and use dynamically loaded libraries and used suboptimal access to TLS variables. New implementation removes lazy resolving of TLS relocation - due to flaw in TLSDESC design is impossible to switch resolver function at runtime without expensive locking. Due to this, 3 specialized resolvers are used. The new implementation uses- load time resolvinger, with specialized fastfor TLS relocation from libraries loaded with main resolver for binary (thus with known TLS relocation from libraries loaded with main binary (thusoffset). - undefined thread weak symbol resolved for initial exec symbols. with known TLS offset). F- slower lazy resolving for dynamically loaded libraries it uses runtimewith fast path for resolver with fast path already resolved symbols. It correctly handles undefined thread weak symbols (it should be resolved to NULL). - don't double relocate jump slots if LD_BIND_NOW is defined - handle TLS_DTPMOD64, TLS_DTPREL64 and NULL relocations - implement aarch64 specific version of __tls_get_addr() --------------------------------------------------------------------------- Unfortunately, here are still some issues which I unable to solve: - TLSDESC ABI for resolver function requires preserving all (but X0) registers, including all floating point and optional SVE registers. This is not possible (in universal way) so current code expects that nobody in rtld-elf code uses it, including compiler instrict and/or used libraries. I'm not sure if there is any compiler switch that ensure this. - memory allocated by reloc_tlsdesc_alloc() is not freed - for TLS_TPREL64 relocation, we don't handle undefined thread weak symbols, but this problem exist in all other architectures. - TLSDESC case in reloc_plt() is nonsense, this kind of relocation relocates data, not code. But (GNU compiled) /usr/local/lib/libuuid.so.1.2 have TLSDESC relocation in .rela.plt section. I have no idea why.