Linux kernel's rt_sigprocmask correctly handles an unaligned user address[1].
The original issue was for qemu-user, which seems long irrelevant.
Tested locally on an AArch64 CPU and qemu-aarch64-static.
The alignment operation actually serves another purpose: when addr resides in
the last 7 bytes of a page (unaligned), check only the current page and not the
next. Update the comment.
[1]:
kernel/signal.c `SYSCALL_DEFINE4(rt_sigprocmask`
arch/arm64/include/asm/uaccess.h:raw_copy_from_user
arch/arm64/lib/copy_template.S "alignment handled by the hardware"
PiperOrigin-RevId: 592618320
Change-Id: Ifbd05aba42f46e36e710cca940570213036b3ce0
