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Compiler generates the following instruction sequence for dynamic TLS access: leal tls_var@tlsgd(,%ebx,1), %eax call ___tls_get_addr@PLT CALL instruction is transparent to compiler which assumes all registers, except for EFLAGS, AX, CX, and DX, are unchanged after CALL. But ___tls_get_addr is a normal function which doesn't preserve any vector registers. 1. Rename the generic __tls_get_addr function to ___tls_get_addr_internal. 2. Change ___tls_get_addr to a wrapper function with implementations for FNSAVE, FXSAVE, XSAVE and XSAVEC to save and restore all vector registers. 3. dl-tlsdesc-dynamic.h has: _dl_tlsdesc_dynamic: /* Like all TLS resolvers, preserve call-clobbered registers. We need two scratch regs anyway. */ subl $32, %esp cfi_adjust_cfa_offset (32) It is wrong to use movl %ebx, -28(%esp) movl %esp, %ebx cfi_def_cfa_register(%ebx) ... mov %ebx, %esp cfi_def_cfa_register(%esp) movl -28(%esp), %ebx to preserve EBX on stack. Fix it with: movl %ebx, 28(%esp) movl %esp, %ebx cfi_def_cfa_register(%ebx) ... mov %ebx, %esp cfi_def_cfa_register(%esp) movl 28(%esp), %ebx 4. Update _dl_tlsdesc_dynamic to call ___tls_get_addr_internal directly. 5. Add have-test-mtls-traditional to compile tst-tls23-mod.c with traditional TLS variant to verify the fix. 6. Define DL_RUNTIME_RESOLVE_REALIGN_STACK in sysdeps/x86/sysdep.h. This fixes BZ #32996. Co-Authored-By: Adhemerval Zanella <adhemerval.zanella@linaro.org> Signed-off-by: H.J. Lu <hjl.tools@gmail.com> Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
69 lines
2.3 KiB
C
69 lines
2.3 KiB
C
/* Ifunc selector for ___tls_get_addr.
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Copyright (C) 2025 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#ifdef SHARED
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# define ___tls_get_addr __redirect____tls_get_addr
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# include <dl-tls.h>
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# undef ___tls_get_addr
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# undef __tls_get_addr
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# define SYMBOL_NAME ___tls_get_addr
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# include <init-arch.h>
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extern __typeof (REDIRECT_NAME) OPTIMIZE (fnsave) attribute_hidden;
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extern __typeof (REDIRECT_NAME) OPTIMIZE (fxsave) attribute_hidden;
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extern __typeof (REDIRECT_NAME) OPTIMIZE (xsave) attribute_hidden;
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extern __typeof (REDIRECT_NAME) OPTIMIZE (xsavec) attribute_hidden;
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static inline void *
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IFUNC_SELECTOR (void)
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{
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const struct cpu_features* cpu_features = __get_cpu_features ();
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if (cpu_features->xsave_state_size != 0)
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{
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if (CPU_FEATURE_USABLE_P (cpu_features, XSAVEC))
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return OPTIMIZE (xsavec);
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else
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return OPTIMIZE (xsave);
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}
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else if (CPU_FEATURE_USABLE_P (cpu_features, FXSR))
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return OPTIMIZE (fxsave);
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return OPTIMIZE (fnsave);
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}
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libc_ifunc_redirected (__redirect____tls_get_addr, ___tls_get_addr,
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IFUNC_SELECTOR ());
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/* The special thing about the x86 TLS ABI is that we have two
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variants of the __tls_get_addr function with different calling
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conventions. The GNU version, which we are mostly concerned here,
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takes the parameter in a register. The name is changed by adding
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an additional underscore at the beginning. The Sun version uses
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the normal calling convention. */
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rtld_hidden_proto (___tls_get_addr)
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rtld_hidden_def (___tls_get_addr)
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void *
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__tls_get_addr (tls_index *ti)
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{
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return ___tls_get_addr (ti);
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}
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#endif
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