[PATCH] riscv: Fix kernel crash due to PR_SET_TAGGED_ADDR_CTRL

[Nam Cao]

Hi Alex,

On Mon, May 05, 2025 at 06:02:26PM +0200, Alexandre Ghiti wrote:
> On 04/05/2025 12:19, Nam Cao wrote:
> > When userspace does PR_SET_TAGGED_ADDR_CTRL, but Supm extension is not
> > available, the kernel crashes:
> > 
> > Oops - illegal instruction [#1]
> >      [snip]
> > epc : set_tagged_addr_ctrl+0x112/0x15a
> >   ra : set_tagged_addr_ctrl+0x74/0x15a
> > epc : ffffffff80011ace ra : ffffffff80011a30 sp : ffffffc60039be10
> >      [snip]
> > status: 0000000200000120 badaddr: 0000000010a79073 cause: 0000000000000002
> >      set_tagged_addr_ctrl+0x112/0x15a
> >      __riscv_sys_prctl+0x352/0x73c
> >      do_trap_ecall_u+0x17c/0x20c
> >      andle_exception+0x150/0x15c
> 
> 
> It seems like the csr write is triggering this illegal instruction, can you
> confirm it is?

Yes, it is the "csr_write(CSR_ENVCFG, envcfg);" in envcfg_update_bits().

> If so, I can't find in the specification that an implementation should do
> that when writing envcfg and I can't reproduce it on qemu. Where did you
> see this oops?

I can't find it in the spec either. I think it is up to the implementation.

I got this crash on the MangoPI board:
https://mangopi.org/mqpro

Best regards,
Nam