Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
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From: Andy Lutomirski <luto@kernel.org>
Date: 2020-09-20 00:14:57
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On Sat, Sep 19, 2020 at 4:24 PM Al Viro [off-list ref] wrote:
On Sat, Sep 19, 2020 at 03:53:40PM -0700, Andy Lutomirski wrote:quoted
quoted
It would not be a win - most of the syscalls don't give a damn about 32bit vs. 64bit...Any reasonable implementation would optimize it out for syscalls that don’t care. Or it could be explicit: DEFINE_MULTIARCH_SYSCALL(...)1) what would that look like?
In effect, it would work like this:
/* Arch-specific, but there's a generic case for sane architectures. */
enum syscall_arch {
SYSCALL_NATIVE,
SYSCALL_COMPAT,
SYSCALL_X32,
};
DEFINE_MULTIARCH_SYSCALLn(args, arch)
{
args are the args here, and arch is the arch.
}
2) have you counted the syscalls that do and do not need that?
No.
3) how many of those realistically *can* be unified with their compat counterparts? [hint: ioctl(2) cannot]
There would be no requirement to unify anything. The idea is that we'd get rid of all the global state flags. For ioctl, we'd have a new file_operation: long ioctl(struct file *, unsigned int, unsigned long, enum syscall_arch); I'm not saying this is easy, but I think it's possible and the result would be more obviously correct than what we have now. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel