Daniel Verkamp b4244d3952 kernel_loader: load ELF kernels at the right paddr ... Previously, we were loading ELF kernels at the provided kernel_start address plus the p_paddr (physical address) field of each program header. This resulted in the kernel being loaded after a big gap of zero bytes, which accidentally worked on x86_64 because 0x00 0x00 encodes a valid instruction, and the entry point was at the beginning of the first section, so execution would effectively "nop slide" its way from the supposed entry point all the way to the actual beginning of the correct code. In addition, the Linux kernel entry point is compiled as position-independent code, so the mismatched address did not matter. Fix this by loading ELF kernels at whatever physical address they specify, without adding any extra offset. The load_kernel() function still accepts a start address, but this is now used simply to verify that the ELF file does not try to load any sections outside of the desired kernel region. As a demonstration, we can look at the instructions at the kernel's declared entry point (0x1000000 for a normal x86-64 Linux kernel in ELF format) by attaching to the gdb stub and running: (gdb) disas 0x1000000,+8 With the old behavior, we get purely 0x00 0x00 opcodes, decoding as: 0x0000000001000000: add BYTE PTR [rax],al 0x0000000001000002: add BYTE PTR [rax],al 0x0000000001000004: add BYTE PTR [rax],al 0x0000000001000006: add BYTE PTR [rax],al With the new behavior, we get the correct entry point instructions: 0x0000000001000000: lea rsp,[rip+0x1203f51] # 0x2203f58 0x0000000001000007: lea rdi,[rip+0xfffffffffffffff2] # 0x1000000 BUG=b:234155022 TEST=cargo test -p kernel_loader TEST=Boot x86-64 ELF vmlinux kernel Change-Id: Iae4c8db022674e6311e54dffe479a1ed430a1ef4 Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3673612 Tested-by: kokoro <noreply+kokoro@google.com> Reviewed-by: Anton Romanov <romanton@google.com> Commit-Queue: Daniel Verkamp <dverkamp@chromium.org> Reviewed-by: Alexandre Courbot <acourbot@chromium.org>		2022-06-23 22:30:37 +00:00
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src	kernel_loader: load ELF kernels at the right paddr	2022-06-23 22:30:37 +00:00
bindgen.sh
Cargo.toml	kernel_loader: load ELF kernels at the right paddr	2022-06-23 22:30:37 +00:00