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Merge branch 'Apply suggestions for typeless/weak ksym series'

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Kumar Kartikeya says:

====================

Three commits addressing comments for the typeless/weak ksym set. No functional
change intended. Hopefully this is simpler to read for kfunc as well.
====================

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
This commit is contained in:
Andrii Nakryiko 2021-11-30 15:48:15 -08:00
commit e30c8fd310
2 changed files with 24 additions and 20 deletions
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2
kernel/bpf/syscall.c
View File

@ -4804,7 +4804,7 @@ const struct bpf_func_proto bpf_kallsyms_lookup_name_proto = {
.gpl_only = false,
.ret_type = RET_INTEGER,
.arg1_type = ARG_PTR_TO_MEM,
.arg2_type = ARG_CONST_SIZE,
.arg2_type = ARG_CONST_SIZE_OR_ZERO,
.arg3_type = ARG_ANYTHING,
.arg4_type = ARG_PTR_TO_LONG,
};

42
tools/lib/bpf/gen_loader.c
View File

@ -674,27 +674,29 @@ static void emit_relo_kfunc_btf(struct bpf_gen *gen, struct ksym_relo_desc *relo
return;
}
kdesc->off = btf_fd_idx;
/* set a default value for imm */
/* jump to success case */
emit(gen, BPF_JMP_IMM(BPF_JSGE, BPF_REG_7, 0, 3));
/* set value for imm, off as 0 */
emit(gen, BPF_ST_MEM(BPF_W, BPF_REG_8, offsetof(struct bpf_insn, imm), 0));
/* skip success case store if ret < 0 */
emit(gen, BPF_JMP_IMM(BPF_JSLT, BPF_REG_7, 0, 1));
emit(gen, BPF_ST_MEM(BPF_H, BPF_REG_8, offsetof(struct bpf_insn, off), 0));
/* skip success case for ret < 0 */
emit(gen, BPF_JMP_IMM(BPF_JA, 0, 0, 10));
/* store btf_id into insn[insn_idx].imm */
emit(gen, BPF_STX_MEM(BPF_W, BPF_REG_8, BPF_REG_7, offsetof(struct bpf_insn, imm)));
/* obtain fd in BPF_REG_9 */
emit(gen, BPF_MOV64_REG(BPF_REG_9, BPF_REG_7));
emit(gen, BPF_ALU64_IMM(BPF_RSH, BPF_REG_9, 32));
/* jump to fd_array store if fd denotes module BTF */
emit(gen, BPF_JMP_IMM(BPF_JNE, BPF_REG_9, 0, 2));
/* set the default value for off */
emit(gen, BPF_ST_MEM(BPF_H, BPF_REG_8, offsetof(struct bpf_insn, off), 0));
/* skip BTF fd store for vmlinux BTF */
emit(gen, BPF_JMP_IMM(BPF_JA, 0, 0, 4));
/* load fd_array slot pointer */
emit2(gen, BPF_LD_IMM64_RAW_FULL(BPF_REG_0, BPF_PSEUDO_MAP_IDX_VALUE,
0, 0, 0, blob_fd_array_off(gen, btf_fd_idx)));
/* skip store of BTF fd if ret < 0 */
emit(gen, BPF_JMP_IMM(BPF_JSLT, BPF_REG_7, 0, 3));
/* store BTF fd in slot */
emit(gen, BPF_MOV64_REG(BPF_REG_9, BPF_REG_7));
emit(gen, BPF_ALU64_IMM(BPF_RSH, BPF_REG_9, 32));
emit(gen, BPF_STX_MEM(BPF_W, BPF_REG_0, BPF_REG_9, 0));
/* set a default value for off */
emit(gen, BPF_ST_MEM(BPF_H, BPF_REG_8, offsetof(struct bpf_insn, off), 0));
/* skip insn->off store if ret < 0 */
emit(gen, BPF_JMP_IMM(BPF_JSLT, BPF_REG_7, 0, 2));
/* skip if vmlinux BTF */
emit(gen, BPF_JMP_IMM(BPF_JEQ, BPF_REG_9, 0, 1));
/* store index into insn[insn_idx].off */
emit(gen, BPF_ST_MEM(BPF_H, BPF_REG_8, offsetof(struct bpf_insn, off), btf_fd_idx));
log:
@ -793,9 +795,8 @@ static void emit_relo_ksym_btf(struct bpf_gen *gen, struct ksym_relo_desc *relo,
kdesc->insn + offsetof(struct bpf_insn, imm));
move_blob2blob(gen, insn + sizeof(struct bpf_insn) + offsetof(struct bpf_insn, imm), 4,
kdesc->insn + sizeof(struct bpf_insn) + offsetof(struct bpf_insn, imm));
emit(gen, BPF_LDX_MEM(BPF_W, BPF_REG_9, BPF_REG_8, offsetof(struct bpf_insn, imm)));
/* jump over src_reg adjustment if imm is not 0 */
emit(gen, BPF_JMP_IMM(BPF_JNE, BPF_REG_9, 0, 3));
/* jump over src_reg adjustment if imm is not 0, reuse BPF_REG_0 from move_blob2blob */
emit(gen, BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 3));
goto clear_src_reg;
}
/* remember insn offset, so we can copy BTF ID and FD later */
@ -803,17 +804,20 @@ static void emit_relo_ksym_btf(struct bpf_gen *gen, struct ksym_relo_desc *relo,
emit_bpf_find_by_name_kind(gen, relo);
if (!relo->is_weak)
emit_check_err(gen);
/* set default values as 0 */
/* jump to success case */
emit(gen, BPF_JMP_IMM(BPF_JSGE, BPF_REG_7, 0, 3));
/* set values for insn[insn_idx].imm, insn[insn_idx + 1].imm as 0 */
emit(gen, BPF_ST_MEM(BPF_W, BPF_REG_8, offsetof(struct bpf_insn, imm), 0));
emit(gen, BPF_ST_MEM(BPF_W, BPF_REG_8, sizeof(struct bpf_insn) + offsetof(struct bpf_insn, imm), 0));
/* skip success case stores if ret < 0 */
emit(gen, BPF_JMP_IMM(BPF_JSLT, BPF_REG_7, 0, 4));
/* skip success case for ret < 0 */
emit(gen, BPF_JMP_IMM(BPF_JA, 0, 0, 4));
/* store btf_id into insn[insn_idx].imm */
emit(gen, BPF_STX_MEM(BPF_W, BPF_REG_8, BPF_REG_7, offsetof(struct bpf_insn, imm)));
/* store btf_obj_fd into insn[insn_idx + 1].imm */
emit(gen, BPF_ALU64_IMM(BPF_RSH, BPF_REG_7, 32));
emit(gen, BPF_STX_MEM(BPF_W, BPF_REG_8, BPF_REG_7,
sizeof(struct bpf_insn) + offsetof(struct bpf_insn, imm)));
/* skip src_reg adjustment */
emit(gen, BPF_JMP_IMM(BPF_JSGE, BPF_REG_7, 0, 3));
clear_src_reg:
/* clear bpf_object__relocate_data's src_reg assignment, otherwise we get a verifier failure */