Skip to content

mpk: reenable MPK support with vendor string check #7513

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
abrown merged 2 commits into from
Nov 9, 2023
Merged

mpk: reenable MPK support with vendor string check #7513

Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
998c766
mpk: reenable MPK support with vendor string check
abrown Nov 9, 2023
ae96efc
review: use `u32::from_le_bytes` to self-document the string check
abrown Nov 9, 2023
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
24 changes: 16 additions & 8 deletions crates/runtime/src/mpk/pkru.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -53,16 +53,24 @@ pub fn write(pkru: u32) {
}
}

/// Check the `ECX.PKU` flag (bit 3) of the `07h` `CPUID` leaf; see the
/// Intel Software Development Manual, vol 3a, section 2.7.
/// Check the `ECX.PKU` flag (bit 3) of the `07h` `CPUID` leaf; see the Intel
/// Software Development Manual, vol 3a, section 2.7. This flag is only set on
/// Intel CPUs, so this function also checks the `CPUID` vendor string.
pub fn has_cpuid_bit_set() -> bool {
// TODO: disable MPK support until the following issue is resolved:
// https://github.com/bytecodealliance/wasmtime/issues/7445
if true {
return false;
}
let result = unsafe { std::arch::x86_64::__cpuid(0x07) };
(result.ecx & 0b100) != 0
is_intel_cpu() && (result.ecx & 0b100) != 0
}

/// Check the `CPUID` vendor string for `GenuineIntel`; see the Intel Software
/// Development Manual, vol 2a, `CPUID` description.
pub fn is_intel_cpu() -> bool {
// To read the CPU vendor string, we pass 0 in EAX and read 12 ASCII bytes
// from EBX, EDX, and ECX (in that order).
let result = unsafe { std::arch::x86_64::__cpuid(0) };
// Then we check if the vendor string matches "GenuineIntel".
result.ebx == u32::from_le_bytes(*b"Genu")
&& result.edx == u32::from_le_bytes(*b"ineI")
&& result.ecx == u32::from_le_bytes(*b"ntel")
}

#[cfg(test)]
Expand Down