[Bug malloc/32996] i386 TLS helper functions don't preserve XMM registers

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=32996

--- Comment #24 from Sourceware Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by H.J. Lu <hjl@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=848f0e46f03f22404ed9a8aabf3fd5ce8809a1be

commit 848f0e46f03f22404ed9a8aabf3fd5ce8809a1be
Author: H.J. Lu <hjl.tools@gmail.com>
Date:   Mon Jun 9 05:22:10 2025 +0800

    i386: Update ___tls_get_addr to preserve vector registers

    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>

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