Messages in this thread | | | From | Linus Torvalds <> | Date | Thu, 25 Apr 2024 12:18:17 -0700 | Subject | Re: [GIT PULL] ACPI fixes for v6.9-rc6 |
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On Thu, 25 Apr 2024 at 11:58, Linus Torvalds <torvalds@linux-foundation.org> wrote: > > And maybe this time, it's not a buggy mess?
Actually, even with MASK_VAL() fixed, I think it's *STILL* a buggy mess.
Why? Beuse the *uses* of MASK_VAL() seem entirely bogus.
In particular, we have this in cpc_write():
if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) val = MASK_VAL(reg, val);
switch (size) { case 8: writeb_relaxed(val, vaddr); break; case 16: writew_relaxed(val, vaddr); break; ...
and I strongly suspect that it needs to update the 'vaddr' too. Something like
if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) { val = MASK_VAL(reg, val); #ifdef __LITTLE_ENDIAN vaddr += reg->bit_offset >> 3; if (reg->bit_offset & 7) return -EFAULT; #else /* Fixme if we ever care */ if (reg->bit_offset) return -EFAULT; #endif }
*might* be changing this in the right direction, but it's unclear and I neither know that CPC rules, nor did I think _that_ much about it.
Anyway, the take-away should be that all this code is entirely broken and somebody didn't think enough about it.
It's possible that that whole cpc_write() ACPI_ADR_SPACE_SYSTEM_MEMORY case should be done as a 64-bit "read-mask-write" sequence.
Possibly with "reg->bit_offset == 0" and the 8/16/32/64-bit cases as a special case for "just do the write".
Or, maybe writes with a non-zero bit offset shouldn't be allowed at all, and there are CPC rules that aren't checked. I don't know. I only know that the current code is seriously broken.
Linus
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