On Mon, Aug 25, 2025, Yan Zhao wrote: > > + /* > > + * Handcode "JMP rel8" at the RESET vector to jump back to the TD boot > > + * code, as there are only 16 bytes at the RESET vector before RIP will > > + * wrap back to zero. Insert a trailing int3 so that the vCPU crashes > > + * in case the JMP somehow falls through. Note! The target address is > > + * relative to the end of the instruction! > > + */ > > + TEST_ASSERT(TD_BOOT_CODE_SIZE < 256, > Looks TD_BOOT_CODE_SIZE needs to be <= 126, as the jump range is limited to -128 > to +127 for JMP rel8. Gah, I managed to forget that relative targets obviously need to be signed values, and I also forgot to account for the size of the JMP in the assert. Go me. Maybe express this as: TEST_ASSERT(TD_BOOT_CODE_SIZE + 2 < 128, "TD boot code not addressable by 'JMP rel8'"); > > + "TD boot code not addressable by 'JMP rel8'"); > > + hva[0] = 0xeb; > > + hva[1] = 256 - 2 - TD_BOOT_CODE_SIZE; I think I lucked into getting this right though? > > + hva[2] = 0xcc; > > +} > > -- > > 2.51.0.rc1.193.gad69d77794-goog > > > >
