On Tue, Mar 25, 2025 at 8:27 PM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > > On Tue, Mar 25, 2025 at 08:15:41AM -0400, guoren@xxxxxxxxxx wrote: > > From: "Guo Ren (Alibaba DAMO Academy)" <guoren@xxxxxxxxxx> > > > > Since 2001, the CONFIG_64BIT kernel has been built with the LP64 ABI, > > but this patchset allows the CONFIG_64BIT kernel to use an ILP32 ABI > > I'm thinking you're going to be finding a metric ton of assumptions > about 'unsigned long' being 64bit when 64BIT=y throughout the kernel. Less than you imagined. Most code is compatible with ILP32 ABI due to the CONFIG_32BIT. In my practice, it's deemed acceptable. > > I know of a couple of places where 64BIT will result in different math > such that a 32bit 'unsigned long' will trivially overflow. I would be grateful if you could share some with me. > > Please, don't do this. This adds a significant maintenance burden on all > of us. The 64ILP32 ABI would bear the maintenance burden, not traditional 64-bit or 32-bit ABIs. The patch set won't impact other CONFIG_64BIT or CONFIG_32BIT. Numerous RV64 chips require the RV64ILP32 ABI to reduce the memory and cache footprint; we will bear the burden. The core code maintainers would receive patches that would make them use BITS_PER_LONG and CONFIG_64BIT more accurately. -- Best Regards Guo Ren
