Am 21.10.24 um 08:48 schrieb Muhammad Usama Anjum:
Hi,
The asm-generic/unistd.h file has wrong __NR_userfaultfd syscall number which
doesn't even depend on the architecture. This has caused failure of a selftest
which was fixed recently [1].
grep -rnIF "#define __NR_userfaultfd"
tools/include/uapi/asm-generic/unistd.h:681:#define __NR_userfaultfd 282
arch/x86/include/generated/uapi/asm/unistd_32.h:374:#define __NR_userfaultfd 374
arch/x86/include/generated/uapi/asm/unistd_64.h:327:#define __NR_userfaultfd 323
arch/x86/include/generated/uapi/asm/unistd_x32.h:282:#define __NR_userfaultfd (__X32_SYSCALL_BIT + 323)
arch/arm/include/generated/uapi/asm/unistd-eabi.h:347:#define __NR_userfaultfd (__NR_SYSCALL_BASE + 388)
arch/arm/include/generated/uapi/asm/unistd-oabi.h:359:#define __NR_userfaultfd (__NR_SYSCALL_BASE + 388)
include/uapi/asm-generic/unistd.h:681:#define __NR_userfaultfd 282
The number is dependent on the architecture. The above data shows that it
is different for different arch:
x86 374
x86_64 323
ARM 347/358
It seems include/uapi/asm-generic/unistd has wrong 282 value in it. Maybe I'm
missing some context.. Please have a look at it.
The __NR_userfaultfd was added to include/uapi/asm-generic/unistd.h in
09f7298100ea ("Subject: [PATCH] userfaultfd: register uapi generic syscall (aarch64)").
This is not specific to __NR_userfaultfd, just take a look at some of the other
syscalls (e.g., __NR_membarrier).
Now, some of the files you list above are "generated". Doing it on a clean tree:
$ grep -rnIF "#define __NR_userfaultfd"
arch/arm64/include/asm/unistd32.h:789:#define __NR_userfaultfd 388
tools/include/uapi/asm-generic/unistd.h:681:#define __NR_userfaultfd 282
include/uapi/asm-generic/unistd.h:681:#define __NR_userfaultfd 282
But now comes the tricky part: an architecture defines whether it wants to
(a) Use the asm-generic unistd.h
(b) Use a custom one
E.g.,
$ cat include/uapi/linux/unistd.h
/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
#ifndef _LINUX_UNISTD_H_
#define _LINUX_UNISTD_H_
/*
* Include machine specific syscall numbers
*/
#include <asm/unistd.h>
#endif /* _LINUX_UNISTD_H_ */
For example on riscv arch/riscv/include/asm/unistd.h will include
arch/riscv/include/uapi/asm/unistd.h which will include "asm-generic/unistd.h".
If you follow the flow on x86, you'll find that it will not include that
asm-generic one as default.
So the asm-generic variant only applies if an arch wants to do it in the generic
way.
$ find tools -name unistd.h
tools/arch/x86/include/uapi/asm/unistd.h
tools/arch/arc/include/uapi/asm/unistd.h
tools/arch/riscv/include/uapi/asm/unistd.h
tools/arch/hexagon/include/uapi/asm/unistd.h
tools/arch/arm64/include/uapi/asm/unistd.h
tools/arch/loongarch/include/uapi/asm/unistd.h
tools/include/uapi/asm-generic/unistd.h
tools/include/nolibc/unistd.h
Consequently, the asm-generic one should never be used directly.
--
Cheers,
David / dhildenb
