Arm64 indirect jump #10300
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Arm64 indirect jump #10300
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Add support for the instructions array map type in the arm64 JIT by calling bpf_prog_update_insn_ptrs() with the offsets that map xlated_offset to the jited_offset in the final image. arm64 JIT already has this offset array which was being used for bpf_prog_fill_jited_linfo() and can be used directly for bpf_prog_update_insn_ptrs. Signed-off-by: Puranjay Mohan <[email protected]>
Add support for a new instruction BPF_JMP|BPF_X|BPF_JA, SRC=0, DST=Rx, off=0, imm=0 which does an indirect jump to a location stored in Rx. The register Rx should have type PTR_TO_INSN. This new type assures that the Rx register contains a value (or a range of values) loaded from a correct jump table – map of type instruction array. ARM64 JIT supports indirect jumps to all registers through the A64_BR() macro, use it to implement this new instruction. Signed-off-by: Puranjay Mohan <[email protected]>
.jumptables sections generated by LLVM store byte offsets from the start of the section to the jump's target instruction. On arm64 builds of LLVM, it generates a rel section to add the section address to each entry in the jump table, therefore storing the absolute address of the jump target into the table. For BPF usage of .jumptables, we only care about the instruction offsets and calculate the final address much later after the JIT has finished, and called bpf_prog_update_insn_ptrs() Without the change in this commit, compilation fails with: libbpf: relocation against STT_SECTION in non-exec section is not supported! Error: failed to link 'tools/testing/selftests/bpf/cpuv4/bpf_gotox.bpf.o': Invalid argument (22) This is due to the presence of a relocation section for .jumptables (non-exec) against syscall (STT_SECTION): Relocation section '.rel.jumptables' at offset 0x5b50 contains 263 entries: Offset Info Type Symbol's Value Symbol's Name 000000000000 0000000300000002 R_BPF_64_ABS64 0000000000000000 syscall 000000000008 0000000300000002 R_BPF_64_ABS64 0000000000000000 syscall [...] Signed-off-by: Puranjay Mohan <[email protected]>
arm64 JIT now supports gotox instruction and jumptables, so run tests in verifier_gotox.c for arm64. Signed-off-by: Puranjay Mohan <[email protected]>
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