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bsd-user/x86_64/target_arch_thread.h: Align stack

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bsd-user qemu-x86_64 almost immediately dies with:

    qemu: 0x4002201a68: unhandled CPU exception 0xd - aborting

on FreeBSD 14.1-RELEASE. This is an instruction that requires
alignment:

    (gdb) x/i 0x4002201a68
       0x4002201a68:        movaps %xmm0,-0x40(%rbp)

and the argument is not aligned:

    (gdb) p/x env->regs[5]
    $1 = 0x822443b58

A quick experiment shows that the userspace entry point expects
misaligned rsp:

    (gdb) starti
    (gdb) p/x $rsp
    $1 = 0x7fffffffeaa8

Emulate this behavior in bsd-user.

[[ applied Richard's suggestion ]]

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Warner Losh <imp@bsdimp.com>
Signed-off-by: Warner Losh <imp@bsdimp.com>
This commit is contained in:
Ilya Leoshkevich 2024-07-31 16:44:12 +02:00 committed by Warner Losh
parent daaf51001a
commit 1f31243a8c
1 changed files with 1 additions and 1 deletions
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2
bsd-user/x86_64/target_arch_thread.h
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@ -31,7 +31,7 @@ static inline void target_thread_init(struct target_pt_regs *regs,
struct image_info *infop)
{
regs->rax = 0;
regs->rsp = infop->start_stack;
regs->rsp = ((infop->start_stack - 8) & ~0xfUL) + 8;
regs->rip = infop->entry;
regs->rdi = infop->start_stack;
}