Re: [PATCH v7] y2038: Introduce __ASSUME_TIME64_SYSCALLS define

[Joseph Myers <joseph at codesourcery dot com>]

On Tue, 11 Jun 2019, Lukasz Majewski wrote:

> Syscall's ABI compatibility checking:
> 
> 1. Code to check if syscalls are defined since v3.2 kernel on the
>    intersection of archs supported by v3.2 kernel and contemporary glibc
>    (SHA1: e6e24243905957c36596f50a22af0acfd83793e2):
> 
> (Assumption: syscall ABI change require changing the name - like __NR_epoll_create
> and __NR_epoll_create1)
> 
> export syscalls_table="\
> 	clock_gettime clock_settime clock_adjtime \
> 	clock_getres clock_nanosleep timer_gettime \
> 	timer_settime timerfd_gettime timerfd_settime \
> 	utimensat pselect6 ppoll io_pgetevents recvmmsg \
> 	mq_timedsend mq_timedreceive rt_sigtimedwait futex \
> 	sched_rr_get_interval"
> 
> for syscall in ${syscalls_table} ; do echo -n "syscall: ${syscall} -> "; \
> 	grep -rnIw "__NR_${syscall}" | grep ^arch/ | \
> 	grep -vE "mn10300|avr32|cris|m32r|frv|blackfin|xtensa|h8300|vdso" | \
> 	wc -l; done

This is not quite sufficient.  It's possible for a syscall to be mentioned 
in an architecture's asm/unistd.h but not in the actual syscall table, for 
example (or mentioned inside #if 0).

You do need to check the relevant files for each architecture.  *But* only 
architectures with 64-bit syscall interfaces are relevant, because those 
with 32-bit syscall interfaces won't get __ASSUME_TIME64_SYSCALLS defined 
for kernels before 5.1 anyway.  So it doesn't matter whether a syscall was 
present for arm or m68k, for example.

(For example: before 3.15, microblaze didn't have pselect6 in its syscall 
table, though it had it in asm/unistd.h.  But there's no reason to exclude 
pselect6 from this patch, because microblaze is a 32-bit architecture, and 
all 64-bit architectures / syscall ABIs had that syscall already in 3.2.)

So you care about (glibc architecture names): aarch64 alpha ia64 mips (n64 
and n32 syscall ABIs) powerpc (64-bit syscall ABI) riscv (64-bit syscall 
ABI) s390 (64-bit syscall ABI) sparc (64-bit syscall ABI) x86_64 (classic 
and x32 syscall ABIs).  The 64-bit versions of hppa and sh are not 
relevant because they aren't supported by glibc.

> 	- 32 bit: nios2, csky, hppa (is the same as parisc?) - no need to

Yes, hppa is called parisc in the Linux kernel.  There are a few such 
cases where the names are different (e.g. the Linux kernel uses "arm64" as 
the name for aarch64).

-- 
Joseph S. Myers
joseph@codesourcery.com