[PATCH bpf-next 0/4] bpf: arm64: Indirect jumps

[Puranjay Mohan <puranjay@kernel.org>]

This set adds the support of indirect jumps to the arm64 JIT. It
involves calling bpf_prog_update_insn_ptrs() to support instructions
array map. The second piece is supporting BPF_JMP|BPF_X|BPF_JA, SRC=0,
DST=Rx, off=0, imm=0 instruction that is trivial to implement on arm64.

When running the selftests after doing the above changes, I found that
on arm64 builds of llvm, a relocation section was being generated for
.jumptables sections and it was making libbpf fail like:

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)

Which is due to:

Relocation section '.rel.jumptables' at offset 0x5b50 contains 263 entries:
    Offset             Info             Type               Symbol's Value  Symbol's Name
0000000000000000  0000000300000002 R_BPF_64_ABS64         0000000000000000 syscall
0000000000000008  0000000300000002 R_BPF_64_ABS64         0000000000000000 syscall
0000000000000010  0000000300000002 R_BPF_64_ABS64         0000000000000000 syscall

This rel section is not generated by x86 builds of LLVM. The third patch
of this set makes libbpf ignore relocation sections for .jumptables.

The final patch enables selftests on arm64:

 [root@localhost bpf]# ./test_progs-cpuv4 -a "*gotox*"
 #20/1    bpf_gotox/one-switch:OK
 #20/2    bpf_gotox/one-switch-non-zero-sec-offset:OK
 #20/3    bpf_gotox/two-switches:OK
 #20/4    bpf_gotox/big-jump-table:OK
 #20/5    bpf_gotox/static-global:OK
 #20/6    bpf_gotox/nonstatic-global:OK
 #20/7    bpf_gotox/other-sec:OK
 #20/8    bpf_gotox/static-global-other-sec:OK
 #20/9    bpf_gotox/nonstatic-global-other-sec:OK
 #20/10   bpf_gotox/one-jump-two-maps:OK
 #20/11   bpf_gotox/one-map-two-jumps:OK
 #20      bpf_gotox:OK
 #537/1   verifier_gotox/jump_table_ok:OK
 #537/2   verifier_gotox/jump_table_reserved_field_src_reg:OK
 #537/3   verifier_gotox/jump_table_reserved_field_non_zero_off:OK
 #537/4   verifier_gotox/jump_table_reserved_field_non_zero_imm:OK
 #537/5   verifier_gotox/jump_table_no_jump_table:OK
 #537/6   verifier_gotox/jump_table_incorrect_dst_reg_type:OK
 #537/7   verifier_gotox/jump_table_invalid_read_size_u32:OK
 #537/8   verifier_gotox/jump_table_invalid_read_size_u16:OK
 #537/9   verifier_gotox/jump_table_invalid_read_size_u8:OK
 #537/10  verifier_gotox/jump_table_misaligned_access:OK
 #537/11  verifier_gotox/jump_table_invalid_mem_acceess_pos:OK
 #537/12  verifier_gotox/jump_table_invalid_mem_acceess_neg:OK
 #537/13  verifier_gotox/jump_table_add_sub_ok:OK
 #537/14  verifier_gotox/jump_table_no_writes:OK
 #537/15  verifier_gotox/jump_table_use_reg_r0:OK
 #537/16  verifier_gotox/jump_table_use_reg_r1:OK
 #537/17  verifier_gotox/jump_table_use_reg_r2:OK
 #537/18  verifier_gotox/jump_table_use_reg_r3:OK
 #537/19  verifier_gotox/jump_table_use_reg_r4:OK
 #537/20  verifier_gotox/jump_table_use_reg_r5:OK
 #537/21  verifier_gotox/jump_table_use_reg_r6:OK
 #537/22  verifier_gotox/jump_table_use_reg_r7:OK
 #537/23  verifier_gotox/jump_table_use_reg_r8:OK
 #537/24  verifier_gotox/jump_table_use_reg_r9:OK
 #537/25  verifier_gotox/jump_table_outside_subprog:OK
 #537/26  verifier_gotox/jump_table_contains_non_unique_values:OK
 #537     verifier_gotox:OK
 Summary: 2/37 PASSED, 0 SKIPPED, 0 FAILED

Puranjay Mohan (4):
  bpf: arm64: Add support for instructions array
  bpf: arm64: Add support for indirect jumps
  libbpf: Ignore relocations for .jumptables sections
  selftests: bpf: Enable gotox tests from arm64

 arch/arm64/net/bpf_jit_comp.c                      | 11 +++++++++++
 tools/lib/bpf/linker.c                             |  4 ++++
 tools/testing/selftests/bpf/progs/verifier_gotox.c |  4 ++--
 3 files changed, 17 insertions(+), 2 deletions(-)

-- 
2.47.3