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Auto merge of #101442 - joboet:null_check_tcs, r=thomcc

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Check if TCS is a null pointer on SGX

The `EENTER` instruction only checks if the TCS is aligned, not if it zero. Saying the address returned is a `NonNull<u8>` (for which `Tcs` is a type alias) is unsound. As well-behaved runners will not put the TCS at address zero, so the definition of `Tcs` is correct. However, `std` should check the address before casting it to a `NonNull`.

ping `@jethrogb` `@raoulstrackx`
`@rustbot` label I-unsound
This commit is contained in:
bors 2022-09-11 22:19:24 +00:00
commit 98e1f041b6
1 changed files with 6 additions and 2 deletions
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8
library/std/src/sys/sgx/abi/thread.rs
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@ -7,7 +7,11 @@ use fortanix_sgx_abi::Tcs;
#[unstable(feature = "sgx_platform", issue = "56975")]
pub fn current() -> Tcs {
extern "C" {
fn get_tcs_addr() -> Tcs;
fn get_tcs_addr() -> *mut u8;
}
let addr = unsafe { get_tcs_addr() };
match Tcs::new(addr) {
Some(tcs) => tcs,
None => rtabort!("TCS must not be placed at address zero (this is a linker error)"),
}
unsafe { get_tcs_addr() }
}