Date: Thu, 12 Feb 2015 17:07:15 +0000 From: Catalin Marinas <catalin.marinas@....com> To: Szabolcs Nagy <nsz@...t70.net> Cc: musl@...ts.openwall.com, Rich Felker <dalias@...c.org>, Andrew Pinski <apinski@...ium.com>, "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "pinskia@...il.com" <pinskia@...il.com>, "libc-alpha@...rceware.org" <libc-alpha@...rceware.org>, Marcus Shawcroft <Marcus.Shawcroft@....com> Subject: Re: Re: [PATCHv3 00/24] ILP32 support in ARM64 On Thu, Feb 12, 2015 at 09:12:34AM +0100, Szabolcs Nagy wrote: > * Szabolcs Nagy <nsz@...t70.net> [2015-02-11 20:05:37 +0100]: > > (i think this is also a problem if userspace code uses syscall(2) directly, > > libc cannot possibly know where to signextend and the kernel side does not > > do the fixup right now) > > nobody picked up this issue, is this resolved? > > ie. if userspace calls syscall(SYS_foo,...) directly with 32bit > longs does it always work out correctly on the kernel side? I think the only way to solve this is to have syscall wrappers in the kernel rather than glibc. > the sign extension is a problem for signed long arguments, > i only found these in the kernel: > > fs/buffer.c:SYSCALL_DEFINE2(bdflush, int, func, long, data) This is part of the deprecated syscalls, it is not used on new user ABIs. > fs/open.c:SYSCALL_DEFINE2(truncate, const char __user *, path, long, length) The kernel uses a long (64-bit) here and the user ABI defines this as an off_t. With x32, this should be a long long (__kernel_long_t), so not a problem. > fs/aio.c:SYSCALL_DEFINE3(io_submit, aio_context_t, ctx_id, long, nr, > fs/aio.c- struct iocb __user * __user *, iocbpp) > > fs/aio.c:SYSCALL_DEFINE5(io_getevents, aio_context_t, ctx_id, > fs/aio.c- long, min_nr, > fs/aio.c- long, nr, These would need some int->long conversion for nr, min_nr (it may be done in x32 glibc already but as you said it would not work via syscall() directly). > kernel/ptrace.c:SYSCALL_DEFINE4(ptrace, long, request, long, pid, unsigned long, addr, > kernel/ptrace.c- unsigned long, data) The pid in user space would be pid_t which is 32-bit. The kernel seems to use it as pid_t afterwards, so looks safe. For addr and data, I guess it needs wrappers to zero the top part. > ipc/syscall.c:SYSCALL_DEFINE6(ipc, unsigned int, call, int, first, unsigned long, second, > ipc/syscall.c- unsigned long, third, void __user *, ptr, long, fifth) ipc(2) shows the first, second, third as ints. I guess some kernel wrapper is needed here as well. -- Catalin
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