AMD supports both 32-bit and 64-bit SYSCALL/SYSRET, but the TCG only
exposes it for 64-bit targets. For system emulation just reuse the
helper; for user-mode emulation the ABI is the same as "int $80".
The BSDs does not support any fast system call mechanism in 32-bit
mode so add to bsd-user the same stub that FreeBSD has for 64-bit
compatibility mode.
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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