GCC assumes that the call to the descriptor function does not clobber vector registers. I think this means we can't enable -mtls-dialect=gnu2 for Fedora 40. Reproducible: Always
Upstream consensus appears to be that this is a glibc bug.
Upstream glibc bug is not marked done, but upstream has made forward progress. commit 0aac205a814a8511e98d02b91a8dc908f1c53cde Author: H.J. Lu <hjl.tools> Date: Mon Feb 26 06:37:03 2024 -0800 x86: Update _dl_tlsdesc_dynamic to preserve caller-saved registers Compiler generates the following instruction sequence for GNU2 dynamic TLS access: leaq tls_var@TLSDESC(%rip), %rax call *tls_var@TLSCALL(%rax) or leal tls_var@TLSDESC(%ebx), %eax call *tls_var@TLSCALL(%eax) CALL instruction is transparent to compiler which assumes all registers, except for EFLAGS and RAX/EAX, are unchanged after CALL. When _dl_tlsdesc_dynamic is called, it calls __tls_get_addr on the slow path. __tls_get_addr is a normal function which doesn't preserve any caller-saved registers. _dl_tlsdesc_dynamic saved and restored integer caller-saved registers, but didn't preserve any other caller-saved registers. Add _dl_tlsdesc_dynamic IFUNC functions for FNSAVE, FXSAVE, XSAVE and XSAVEC to save and restore all caller-saved registers. This fixes BZ #31372. Add GLRO(dl_x86_64_runtime_resolve) with GLRO(dl_x86_tlsdesc_dynamic) to optimize elf_machine_runtime_setup. Reviewed-by: Noah Goldstein <goldstein.w.n> commit 9b7091415af47082664717210ac49d51551456ab Author: H.J. Lu <hjl.tools> Date: Wed Feb 28 12:08:03 2024 -0800 x86-64: Update _dl_tlsdesc_dynamic to preserve AMX registers _dl_tlsdesc_dynamic should also preserve AMX registers which are caller-saved. Add X86_XSTATE_TILECFG_ID and X86_XSTATE_TILEDATA_ID to x86-64 TLSDESC_CALL_STATE_SAVE_MASK. Compute the AMX state size and save it in xsave_state_full_size which is only used by _dl_tlsdesc_dynamic_xsave and _dl_tlsdesc_dynamic_xsavec. This fixes the AMX part of BZ #31372. Tested on AMX processor. AMX test is enabled only for compilers with the fix for https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114098 GCC 14 and GCC 11/12/13 branches have the bug fix. Reviewed-by: Sunil K Pandey <skpgkp2>
Additional fixes: commit fd7ee2e6c5eb49e4a630a9978b4d668bff6354ee Author: Andreas Schwab <schwab> Date: Tue Mar 19 13:49:50 2024 +0100 Add tst-gnu2-tls2mod1 to test-internal-extras That allows sysdeps/x86_64/tst-gnu2-tls2mod1.S to use internal headers. Fixes: 717ebfa85c ("x86-64: Allocate state buffer space for RDI, RSI and RBX") commit 717ebfa85c8240d32d0d19d86a484c31c55c9617 Author: H.J. Lu <hjl.tools> Date: Mon Mar 18 06:40:16 2024 -0700 x86-64: Allocate state buffer space for RDI, RSI and RBX _dl_tlsdesc_dynamic preserves RDI, RSI and RBX before realigning stack. After realigning stack, it saves RCX, RDX, R8, R9, R10 and R11. Define TLSDESC_CALL_REGISTER_SAVE_AREA to allocate space for RDI, RSI and RBX to avoid clobbering saved RDI, RSI and RBX values on stack by xsave to STATE_SAVE_OFFSET(%rsp). +==================+<- stack frame start aligned at 8 or 16 bytes | |<- RDI saved in the red zone | |<- RSI saved in the red zone | |<- RBX saved in the red zone | |<- paddings for stack realignment of 64 bytes |------------------|<- xsave buffer end aligned at 64 bytes | |<- | |<- | |<- |------------------|<- xsave buffer start at STATE_SAVE_OFFSET(%rsp) | |<- 8-byte padding for 64-byte alignment | |<- 8-byte padding for 64-byte alignment | |<- R11 | |<- R10 | |<- R9 | |<- R8 | |<- RDX | |<- RCX +==================+<- RSP aligned at 64 bytes Define TLSDESC_CALL_REGISTER_SAVE_AREA, the total register save area size for all integer registers by adding 24 to STATE_SAVE_OFFSET since RDI, RSI and RBX are saved onto stack without adjusting stack pointer first, using the red-zone. This fixes BZ #31501. Reviewed-by: Sunil K Pandey <skpgkp2>
This is fixed in Fedora 40 via the bodhi update: https://bodhi.fedoraproject.org/updates/FEDORA-2024-eafbf519ec