On Sat, Jul 6, 2019 at 5:00 PM Aleksa Sarai cyphar@cyphar.com wrote:
diff --git a/arch/alpha/kernel/syscalls/syscall.tbl b/arch/alpha/kernel/syscalls/syscall.tbl index 9e7704e44f6d..1703d048c141 100644 --- a/arch/alpha/kernel/syscalls/syscall.tbl +++ b/arch/alpha/kernel/syscalls/syscall.tbl @@ -461,6 +461,7 @@ 530 common getegid sys_getegid 531 common geteuid sys_geteuid 532 common getppid sys_getppid +533 common openat2 sys_openat2 # all other architectures have common numbers for new syscall, alpha # is the exception. 534 common pidfd_send_signal sys_pidfd_send_signal
My plan here was to add new syscalls in the same order as everwhere else, just with the number 110 higher. In the long run, I hope we can automate this.
diff --git a/arch/arm/tools/syscall.tbl b/arch/arm/tools/syscall.tbl index aaf479a9e92d..4ad262698396 100644 --- a/arch/arm/tools/syscall.tbl +++ b/arch/arm/tools/syscall.tbl @@ -447,3 +447,4 @@ 431 common fsconfig sys_fsconfig 432 common fsmount sys_fsmount 433 common fspick sys_fspick +434 common openat2 sys_openat2
434 is already used in linux-next, I suggest you use 437 (Palmer just submitted fchmodat4, which could become 436).
+/**
- Arguments for how openat2(2) should open the target path. If @extra is zero,
- then openat2(2) is identical to openat(2).
- @flags: O_* flags (unknown flags ignored).
- @mode: O_CREAT file mode (ignored otherwise).
- @upgrade_mask: restrict how the O_PATH may be re-opened (ignored otherwise).
- @resolve: RESOLVE_* flags (-EINVAL on unknown flags).
- @reserved: reserved for future extensions, must be zeroed.
- */
+struct open_how {
__u32 flags;union {__u16 mode;__u16 upgrade_mask;};__u16 resolve;__u64 reserved[7]; /* must be zeroed */+};
We can have system calls with up to six arguments on all architectures, so this could still be done more conventionally without the indirection: like
long openat2(int dfd, const char __user * filename, int flags, mode_t mode_mask, __u16 resolve);
In fact, that seems similar enough to the existing openat() that I think you could also just add the fifth argument to the existing call when a newly defined flag is set, similarly to how we only use the 'mode' argument when O_CREAT or O_TMPFILE are set.
--- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h
This file seems to lack a declaration for the system call, which means it will cause a build failure on some architectures, e.g. arch/arc/kernel/sys.c:
#define __SYSCALL(nr, call) [nr] = (call), void *sys_call_table[NR_syscalls] = { [0 ... NR_syscalls-1] = sys_ni_syscall, #include <asm/unistd.h> };
Arnd