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charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-snps-arc" Errors-To: linux-snps-arc-bounces+linux-snps-arc=archiver.kernel.org@lists.infradead.org On 7/7/20 2:32 PM, Joseph Myers wrote: > On Tue, 7 Jul 2020, Vineet Gupta via Libc-alpha wrote: > >>> Each implementation has it ows requirements so I can't really say if >>> a helper function does make sense for all of them. For pause >>> specifically we can even simplify to since all architectures have >>> either ppoll or ppoll_time64: >>> >>> int >>> __libc_pause (void) >>> { >>> #ifdef __NR_ppoll_time64 >>> return SYSCALL_CANCEL (ppoll_time64, NULL, 0, NULL, NULL); >>> #else >>> return SYSCALL_CANCEL (ppoll, NULL, 0, NULL, NULL); >>> #endif >>> } >> >> But how is this compatible with older kernels (and perhaps this is a general >> question). I mean one/more ABIs minimum kernel would not have the ppoll or ppoll64 >> so how will new glibc work with such a kernel ? Is it not required to ? > > See commit 089b772f98afd9eb6264c6489bc96a30bf6af4ac, where I removed > __ASSUME_PPOLL because all supported kernel versions now had that syscall > for all glibc architectures. But that still doesn't explain how new glibc works with old kernels (for say when a port support was first merged, with say asm-generic ABI). Ah it seems any glibc is only required to work with "arch_minimum_kernel" (generic or architecture override) which over time itself keeps moving forward due to various reasons (e.g. 64-bit time support etc). So indeed a bleeding edge glibc of today won't necessarily work with an arch kernel for say when its glibc port was first merged, but will for the corresponding arch_minimum_kernel. > In general this sort of thing needs a review of whether a given syscall is > available for all glibc architectures in their minimum kernel versions. > For the old kernels in question, that means checking the > architecture-specific syscall table as used to dispatch syscalls at > runtime, which used to have an architecture-specific format before > unification work was done; it used to mean checking asm/unistd.h as well, > but now we have syscall tables in glibc that's probably no longer > required. It also involves checking compat syscall tables for 32-bit > binaries on 64-bit kernels, as sometimes a syscall didn't get added to the > native and compat syscall tables at the same time (see the comments in > sparc/kernel-features.h about various socket-related syscalls, for > example). > _______________________________________________ linux-snps-arc mailing list linux-snps-arc@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-snps-arc