On Wed, Mar 26, 2025 at 4:41 AM Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > > On Tue, 25 Mar 2025 at 05:17, <guoren@xxxxxxxxxx> wrote: > > > > The rv64ilp32 abi kernel accommodates the lp64 abi userspace and > > leverages the lp64 abi Linux interface. Hence, unify the > > BITS_PER_LONG = 32 memory layout to match BITS_PER_LONG = 64. > > No. > > This isn't happening. > > You can't do crazy things in the RISC-V code and then expect the rest > of the kernel to just go "ok, we'll do crazy things". > > We're not doing crazy __riscv_xlen hackery with random structures > containing 64-bit values that the kernel then only looks at the low 32 > bits. That's wrong on *so* many levels. > > I'm willing to say "big-endian is dead", but I'm not willing to accept > this kind of crazy hackery. > > Not today, not ever. > > If you want to run a ilp32 kernel on 64-bit hardware (and support > 64-bit ABI just in a 32-bit virtual memory size), I would suggest you > > (a) treat the kernel as natively 32-bit (obviously you can then tell > the compiler to use the rv64 instructions, which I presume you're > already doing - I didn't look) I used CONFIG_32BIT in v1 and v2, but I've abandoned them because, based on CONFIG_64BIT, I gain more functionality by inheriting the lp64-abi kernel. I want the full functionality of the CONFIG_64BIT Linux kernel, which can be equivalent, used interchangeably, and seamlessly. > > (b) look at making the compat stuff do the conversion the "wrong way". > > And btw, that (b) implies *not* just ignoring the high bits. If > user-space gives 64-bit pointer, you don't just treat it as a 32-bit > one by dropping the high bits. You add some logic to convert it to an > invalid pointer so that user space gets -EFAULT. Thanks for the advice. I'm looking at how to make the compat stuff. -- Best Regards Guo Ren
