feat(1808): migrate to linux 6.8.9 #2124
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Problems: 1. In the new kernel, assembly functions uniformly return from `__x86_return_thunk`. However, our assembly code uses the original `ret` instruction, so objtool in the kernel will notice this is a naked return during compilation. 2. `SYM_FUNC_START` in the new kernel will add endbr64 to the head of the assembly function, and all indirect jumps to ENDBR instructions, that is, the code snippet within the same function, will fail, but we use jump tables in the assembly function to perform indirect jumps. It will raise CET exception: https://en.wikipedia.org/wiki/X86_instruction_listings#Added_with_Intel_CET). Solutions: 1. Substitute the `ret` with `RET`, a macro in the new kernel to ensure the correct return. 2. `notrack jmp` and enable notrack in CPU setting: `wrmsrl(MSR_IA32_S_CET, CET_ENDBR_EN | CET_NO_TRACK_EN)` As an aside, interestingly, if a user-mode C program uses a switch statement that meets the conditions for generating a jump table (gcc uses `-fcf-protection=full` by default), the generated jump table will use a `jmp` with the `notrack` prefix, and IBT will be marked as `true` in the `.note.gnu.property` section of the compiled elf file, so that the `NO_TRACK_EN` of the `MSR` will be set to `true` in user mode when the kernel is loaded. So user mode can use `notrack` to bypass CET without caring about setting or not setting `NO_TRACK_EN`.
…grate-to-linux-6.8.9
This reverts commit 89d2f30.
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During tests sometimes occurs this crash. Full log |
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@biathlon3 Please describe which commit of this branch the crash happens at. |
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And a very rare case of OOM during compilation, VM with 4 cpu, make -j4 Full log |
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@biathlon3 have you made changes beyond this PR to adapt #2131? If so, please record the error in #2131 instead of this one. I cannot reproduce your error. |
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close #1808