[PATCH] i386: Update ___tls_get_addr to preserve vector register

[H.J. Lu]

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:

_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.

This fixes BZ #32996.

-- 
H.J.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 0001-i386-Update-___tls_get_addr-to-preserve-vector-regis.patch
Type: text/x-patch
Size: 30616 bytes
Desc: not available
URL: <https://sourceware.org/pipermail/libc-alpha/attachments/20250609/3f414747/attachment-0001.bin>