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authorIlya Leoshkevich <iii@linux.ibm.com>2024-07-31 16:44:12 +0200
committerWarner Losh <imp@bsdimp.com>2024-11-04 20:26:40 -0700
commit1f31243a8c80fac27e52cc362cb1e2c922cf0e1b (patch)
tree290b827b2b75619b423f2f00fc0145598bffdf45
parentdaaf51001a13da007d7dde72e1ed3b06bc490791 (diff)
downloadfocaccia-qemu-1f31243a8c80fac27e52cc362cb1e2c922cf0e1b.tar.gz
focaccia-qemu-1f31243a8c80fac27e52cc362cb1e2c922cf0e1b.zip
bsd-user/x86_64/target_arch_thread.h: Align stack
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>
-rw-r--r--bsd-user/x86_64/target_arch_thread.h2
1 files changed, 1 insertions, 1 deletions
diff --git a/bsd-user/x86_64/target_arch_thread.h b/bsd-user/x86_64/target_arch_thread.h
index 52c28906d6..7739bb2154 100644
--- a/bsd-user/x86_64/target_arch_thread.h
+++ b/bsd-user/x86_64/target_arch_thread.h
@@ -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;
 }