Brown bag time: offset 0 from esp is the return address,
offset 4 is the first argument.

Fixes: d7478d42 ("common-user: Fix tail calls to safe_syscall_set_errno_tail")
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

For the ABIs in which the syscall return register is not
also the first function argument register, move the errno
value into the correct place.

Fixes: a3310c03 ("linux-user: Move syscall error detection into safe_syscall_base")
Reported-by: Laurent Vivier <laurent@vivier.eu>
Tested-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20220104190454.542225-1-richard.henderson@linaro.org>

Signed-off-by: WANG Xuerui <git@xen0n.name>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20211221054105.178795-29-git@xen0n.name>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

FreeBSD system calls return positive errno.  On the 4 hosts for
which we have support, error is indicated by the C bit set or clear.

Reviewed-by: Warner Losh <imp@bsdimp.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

Move linux-user safe-syscall.S and safe-syscall-error.c to common-user
so that bsd-user can also use it.  Also move safe-syscall.h to
include/user/.  Since there is nothing here that is related to the guest,
as opposed to the host, build it once.

Reviewed-by: Warner Losh <imp@bsdimp.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>