Dynamically size sigaltstk in rustc #113528
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This is more-or-less a twin of #113525 but since the code winds up moduled-off from the rest of the world in either case and the two have different contexts, I figured I'd submit it separately. |
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workingjubilee
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Jul 10, 2023
| unsafe { | ||
| const ALT_STACK_SIZE: usize = libc::MINSIGSTKSZ + 64 * 1024; | ||
| let alt_stack_size: usize = min_sigstack_size() + 64 * 1024; |
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It might seem like 64KiB is greater than the largest number I mentioned, 16KiB.
...but it's up to 16KiB per vector register, and it has way more than one. 🫠
workingjubilee
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Jul 10, 2023
| @@ -1469,6 +1470,23 @@ mod signal_handler { | |||
| libc::sigaction(libc::SIGSEGV, &sa, std::ptr::null_mut()); | |||
| } | |||
| } | |||
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| /// Modern kernels on modern hardware can have dynamic signal stack sizes. | |||
| #[cfg(any(target_os = "linux", target_os = "android"))] | |||
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Yes, I have spoken to people who run rustc on Android.
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| #[cfg(any(target_os = "linux", target_os = "android"))] | ||
| fn min_sigstack_size() -> usize { | ||
| const AT_MINSIGSTKSZ: core::ffi::c_ulong = 51; | ||
| let dynamic_sigstksz = unsafe { libc::getauxval(AT_MINSIGSTKSZ) }; |
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doesn't need to block this PR, but does it make sense to upstream AT_MINSIGSTKSZ to the libc crate so we don't need to hardcode it here?
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you mean would it be good for rust-lang/libc#3125 to be reviewed and accepted? yes, I think so.
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rustc installs a signal stack that assumes that MINSIGSTKSZ is a constant, unchanging value. Newer hardware undermines that assumption greatly, with register files larger than MINSIGSTKZ. Properly handle this so that it is correct on all supported Linux versions with all CPUs.
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…in-rustc-signal-handler, r=WaffleLapkin Dynamically size sigaltstk in rustc rustc installs a signal stack that assumes that MINSIGSTKSZ is a constant, unchanging value. Newer hardware undermines that assumption greatly, with register files larger than glibc's traditional static MINSIGSTKZ. Properly handle this so that it is correct on all supported Linux versions with all CPUs.
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…in-rustc-signal-handler, r=WaffleLapkin Dynamically size sigaltstk in rustc rustc installs a signal stack that assumes that MINSIGSTKSZ is a constant, unchanging value. Newer hardware undermines that assumption greatly, with register files larger than glibc's traditional static MINSIGSTKZ. Properly handle this so that it is correct on all supported Linux versions with all CPUs.
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Jul 11, 2023
…iaskrgr Rollup of 7 pull requests Successful merges: - rust-lang#113386 (style-guide: Expand example of combinable expressions to include arrays) - rust-lang#113523 (Reuse LLVMConstInBoundsGEP2) - rust-lang#113528 (Dynamically size sigaltstk in rustc) - rust-lang#113543 (Remove `rustc_llvm` from llvm-stamp nags) - rust-lang#113548 (Update books) - rust-lang#113551 (bootstrap: Don't print "Skipping" twice) - rust-lang#113556 (Don't use serde-derive in the rls shim) r? `@ghost` `@rustbot` modify labels: rollup
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rustc installs a signal stack that assumes that MINSIGSTKSZ is a constant, unchanging value. Newer hardware undermines that assumption greatly, with register files larger than glibc's traditional static MINSIGSTKZ. Properly handle this so that it is correct on all supported Linux versions with all CPUs.