Re: [RFC PATCH V3 00/43] rv64ilp32_abi: Build CONFIG_64BIT kernel-self with ILP32 ABI
From: David Laight <hidden>
Date: 2025-03-27 21:06:33
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On Tue, 25 Mar 2025 08:15:41 -0400 guoren@kernel.org wrote:
From: "Guo Ren (Alibaba DAMO Academy)" <guoren@kernel.org> 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 for construction to reduce cache & memory footprint (Compared to kernel-lp64-abi, kernel-rv64ilp32-abi decreased the used memory by about 20%, as shown in "free -h" in the following demo.)
... Why on earth would you want to run a 64bit application on a 32bit kernel. IIRC the main justification for 64bit was to get a larger address space. Now you might want to compile a 32bit (ILP32) system that actually runs in 64bit mode (c/f x32) so that 64bit maths (long long) is more efficient - but that is a different issue. (I suspect you'd need to change the process switch code to save all 64bits of the registers - but maybe not much else??) David