From 69535186297b37e6e0a16290766666f4e8a55793 Mon Sep 17 00:00:00 2001 From: Will Hawkins Date: Thu, 27 Apr 2023 22:30:15 -0400 Subject: [PATCH] bpf, docs: Update llvm_relocs.rst with typo fixes Correct a few typographical errors and fix some mistakes in examples. Signed-off-by: Will Hawkins Acked-by: Yonghong Song Link: https://lore.kernel.org/r/20230428023015.1698072-2-hawkinsw@obs.cr Signed-off-by: Alexei Starovoitov --- Documentation/bpf/llvm_reloc.rst | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) diff --git a/Documentation/bpf/llvm_reloc.rst b/Documentation/bpf/llvm_reloc.rst index ca8957d5b671..e4a777a6a3a2 100644 --- a/Documentation/bpf/llvm_reloc.rst +++ b/Documentation/bpf/llvm_reloc.rst @@ -48,7 +48,7 @@ the code with ``llvm-objdump -dr test.o``:: 14: 0f 10 00 00 00 00 00 00 r0 += r1 15: 95 00 00 00 00 00 00 00 exit -There are four relations in the above for four ``LD_imm64`` instructions. +There are four relocations in the above for four ``LD_imm64`` instructions. The following ``llvm-readelf -r test.o`` shows the binary values of the four relocations:: @@ -79,14 +79,16 @@ The following is the symbol table with ``llvm-readelf -s test.o``:: The 6th entry is global variable ``g1`` with value 0. Similarly, the second relocation is at ``.text`` offset ``0x18``, instruction 3, -for global variable ``g2`` which has a symbol value 4, the offset -from the start of ``.data`` section. +has a type of ``R_BPF_64_64`` and refers to entry 7 in the symbol table. +The second relocation resolves to global variable ``g2`` which has a symbol +value 4. The symbol value represents the offset from the start of ``.data`` +section where the initial value of the global variable ``g2`` is stored. -The third and fourth relocations refers to static variables ``l1`` -and ``l2``. From ``.rel.text`` section above, it is not clear -which symbols they really refers to as they both refers to +The third and fourth relocations refer to static variables ``l1`` +and ``l2``. From the ``.rel.text`` section above, it is not clear +to which symbols they really refer as they both refer to symbol table entry 4, symbol ``sec``, which has ``STT_SECTION`` type -and represents a section. So for static variable or function, +and represents a section. So for a static variable or function, the section offset is written to the original insn buffer, which is called ``A`` (addend). Looking at above insn ``7`` and ``11``, they have section offset ``8`` and ``12``.