From: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Date: Thu, 28 Oct 2021 12:04:55 +0530
Subject: libbpf: Add typeless ksym support to gen_loader
Patch-mainline: v5.16-rc1
Git-commit: c24941cd3766b6de682dbe6809bd6af12271ab5b
References: jsc#PED-1377
This uses the bpf_kallsyms_lookup_name helper added in previous patches
to relocate typeless ksyms. The return value ENOENT can be ignored, and
the value written to 'res' can be directly stored to the insn, as it is
overwritten to 0 on lookup failure. For repeating symbols, we can simply
copy the previously populated bpf_insn.
Also, we need to take care to not close fds for typeless ksym_desc, so
reuse the 'off' member's space to add a marker for typeless ksym and use
that to skip them in cleanup_relos.
We add a emit_ksym_relo_log helper that avoids duplicating common
logging instructions between typeless and weak ksym (for future commit).
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211028063501.2239335-3-memxor@gmail.com
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
---
tools/lib/bpf/bpf_gen_internal.h | 12 +++-
tools/lib/bpf/gen_loader.c | 97 ++++++++++++++++++++++++++++++++++-----
tools/lib/bpf/libbpf.c | 13 ++---
3 files changed, 99 insertions(+), 23 deletions(-)
--- a/tools/lib/bpf/bpf_gen_internal.h
+++ b/tools/lib/bpf/bpf_gen_internal.h
@@ -8,13 +8,19 @@ struct ksym_relo_desc {
int kind;
int insn_idx;
bool is_weak;
+ bool is_typeless;
};
struct ksym_desc {
const char *name;
int ref;
int kind;
- int off;
+ union {
+ /* used for kfunc */
+ int off;
+ /* used for typeless ksym */
+ bool typeless;
+ };
int insn;
};
@@ -49,7 +55,7 @@ void bpf_gen__prog_load(struct bpf_gen *
void bpf_gen__map_update_elem(struct bpf_gen *gen, int map_idx, void *value, __u32 value_size);
void bpf_gen__map_freeze(struct bpf_gen *gen, int map_idx);
void bpf_gen__record_attach_target(struct bpf_gen *gen, const char *name, enum bpf_attach_type type);
-void bpf_gen__record_extern(struct bpf_gen *gen, const char *name, bool is_weak, int kind,
- int insn_idx);
+void bpf_gen__record_extern(struct bpf_gen *gen, const char *name, bool is_weak,
+ bool is_typeless, int kind, int insn_idx);
#endif
--- a/tools/lib/bpf/gen_loader.c
+++ b/tools/lib/bpf/gen_loader.c
@@ -560,7 +560,7 @@ static void emit_find_attach_target(stru
}
void bpf_gen__record_extern(struct bpf_gen *gen, const char *name, bool is_weak,
- int kind, int insn_idx)
+ bool is_typeless, int kind, int insn_idx)
{
struct ksym_relo_desc *relo;
@@ -573,6 +573,7 @@ void bpf_gen__record_extern(struct bpf_g
relo += gen->relo_cnt;
relo->name = name;
relo->is_weak = is_weak;
+ relo->is_typeless = is_typeless;
relo->kind = kind;
relo->insn_idx = insn_idx;
gen->relo_cnt++;
@@ -622,6 +623,29 @@ static void emit_bpf_find_by_name_kind(s
debug_ret(gen, "find_by_name_kind(%s,%d)", relo->name, relo->kind);
}
+/* Overwrites BPF_REG_{0, 1, 2, 3, 4, 7}
+ * Returns result in BPF_REG_7
+ * Returns u64 symbol addr in BPF_REG_9
+ */
+static void emit_bpf_kallsyms_lookup_name(struct bpf_gen *gen, struct ksym_relo_desc *relo)
+{
+ int name_off, len = strlen(relo->name) + 1, res_off;
+
+ name_off = add_data(gen, relo->name, len);
+ res_off = add_data(gen, NULL, 8); /* res is u64 */
+ emit2(gen, BPF_LD_IMM64_RAW_FULL(BPF_REG_1, BPF_PSEUDO_MAP_IDX_VALUE,
+ 0, 0, 0, name_off));
+ emit(gen, BPF_MOV64_IMM(BPF_REG_2, len));
+ emit(gen, BPF_MOV64_IMM(BPF_REG_3, 0));
+ emit2(gen, BPF_LD_IMM64_RAW_FULL(BPF_REG_4, BPF_PSEUDO_MAP_IDX_VALUE,
+ 0, 0, 0, res_off));
+ emit(gen, BPF_MOV64_REG(BPF_REG_7, BPF_REG_4));
+ emit(gen, BPF_EMIT_CALL(BPF_FUNC_kallsyms_lookup_name));
+ emit(gen, BPF_LDX_MEM(BPF_DW, BPF_REG_9, BPF_REG_7, 0));
+ emit(gen, BPF_MOV64_REG(BPF_REG_7, BPF_REG_0));
+ debug_ret(gen, "kallsyms_lookup_name(%s,%d)", relo->name, relo->kind);
+}
+
/* Expects:
* BPF_REG_8 - pointer to instruction
*
@@ -701,6 +725,58 @@ log:
relo->name, kdesc->ref);
}
+static void emit_ksym_relo_log(struct bpf_gen *gen, struct ksym_relo_desc *relo,
+ int ref)
+{
+ if (!gen->log_level)
+ return;
+ emit(gen, BPF_LDX_MEM(BPF_W, BPF_REG_7, BPF_REG_8,
+ offsetof(struct bpf_insn, imm)));
+ emit(gen, BPF_LDX_MEM(BPF_H, BPF_REG_9, BPF_REG_8, sizeof(struct bpf_insn) +
+ offsetof(struct bpf_insn, imm)));
+ debug_regs(gen, BPF_REG_7, BPF_REG_9, " var t=%d w=%d (%s:count=%d): imm[0]: %%d, imm[1]: %%d",
+ relo->is_typeless, relo->is_weak, relo->name, ref);
+ emit(gen, BPF_LDX_MEM(BPF_B, BPF_REG_9, BPF_REG_8, offsetofend(struct bpf_insn, code)));
+ debug_regs(gen, BPF_REG_9, -1, " var t=%d w=%d (%s:count=%d): insn.reg",
+ relo->is_typeless, relo->is_weak, relo->name, ref);
+}
+
+/* Expects:
+ * BPF_REG_8 - pointer to instruction
+ */
+static void emit_relo_ksym_typeless(struct bpf_gen *gen,
+ struct ksym_relo_desc *relo, int insn)
+{
+ struct ksym_desc *kdesc;
+
+ kdesc = get_ksym_desc(gen, relo);
+ if (!kdesc)
+ return;
+ /* try to copy from existing ldimm64 insn */
+ if (kdesc->ref > 1) {
+ move_blob2blob(gen, insn + offsetof(struct bpf_insn, imm), 4,
+ 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));
+ goto log;
+ }
+ /* remember insn offset, so we can copy ksym addr later */
+ kdesc->insn = insn;
+ /* skip typeless ksym_desc in fd closing loop in cleanup_relos */
+ kdesc->typeless = true;
+ emit_bpf_kallsyms_lookup_name(gen, relo);
+ emit(gen, BPF_JMP_IMM(BPF_JEQ, BPF_REG_7, -ENOENT, 1));
+ emit_check_err(gen);
+ /* store lower half of addr into insn[insn_idx].imm */
+ emit(gen, BPF_STX_MEM(BPF_W, BPF_REG_8, BPF_REG_9, offsetof(struct bpf_insn, imm)));
+ /* store upper half of addr into insn[insn_idx + 1].imm */
+ emit(gen, BPF_ALU64_IMM(BPF_RSH, BPF_REG_9, 32));
+ emit(gen, BPF_STX_MEM(BPF_W, BPF_REG_8, BPF_REG_9,
+ sizeof(struct bpf_insn) + offsetof(struct bpf_insn, imm)));
+log:
+ emit_ksym_relo_log(gen, relo, kdesc->ref);
+}
+
/* Expects:
* BPF_REG_8 - pointer to instruction
*/
@@ -730,14 +806,7 @@ static void emit_relo_ksym_btf(struct bp
emit(gen, BPF_STX_MEM(BPF_W, BPF_REG_8, BPF_REG_7,
sizeof(struct bpf_insn) + offsetof(struct bpf_insn, imm)));
log:
- if (!gen->log_level)
- return;
- emit(gen, BPF_LDX_MEM(BPF_W, BPF_REG_7, BPF_REG_8,
- offsetof(struct bpf_insn, imm)));
- emit(gen, BPF_LDX_MEM(BPF_H, BPF_REG_9, BPF_REG_8, sizeof(struct bpf_insn) +
- offsetof(struct bpf_insn, imm)));
- debug_regs(gen, BPF_REG_7, BPF_REG_9, " var (%s:count=%d): imm: %%d, fd: %%d",
- relo->name, kdesc->ref);
+ emit_ksym_relo_log(gen, relo, kdesc->ref);
}
static void emit_relo(struct bpf_gen *gen, struct ksym_relo_desc *relo, int insns)
@@ -749,7 +818,10 @@ static void emit_relo(struct bpf_gen *ge
emit2(gen, BPF_LD_IMM64_RAW_FULL(BPF_REG_8, BPF_PSEUDO_MAP_IDX_VALUE, 0, 0, 0, insn));
switch (relo->kind) {
case BTF_KIND_VAR:
- emit_relo_ksym_btf(gen, relo, insn);
+ if (relo->is_typeless)
+ emit_relo_ksym_typeless(gen, relo, insn);
+ else
+ emit_relo_ksym_btf(gen, relo, insn);
break;
case BTF_KIND_FUNC:
emit_relo_kfunc_btf(gen, relo, insn);
@@ -774,12 +846,13 @@ static void cleanup_relos(struct bpf_gen
int i, insn;
for (i = 0; i < gen->nr_ksyms; i++) {
- if (gen->ksyms[i].kind == BTF_KIND_VAR) {
+ /* only close fds for typed ksyms and kfuncs */
+ if (gen->ksyms[i].kind == BTF_KIND_VAR && !gen->ksyms[i].typeless) {
/* close fd recorded in insn[insn_idx + 1].imm */
insn = gen->ksyms[i].insn;
insn += sizeof(struct bpf_insn) + offsetof(struct bpf_insn, imm);
emit_sys_close_blob(gen, insn);
- } else { /* BTF_KIND_FUNC */
+ } else if (gen->ksyms[i].kind == BTF_KIND_FUNC) {
emit_sys_close_blob(gen, blob_fd_array_off(gen, gen->ksyms[i].off));
if (gen->ksyms[i].off < MAX_FD_ARRAY_SZ)
gen->nr_fd_array--;
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -6575,17 +6575,14 @@ static int bpf_program__record_externs(s
case RELO_EXTERN_VAR:
if (ext->type != EXT_KSYM)
continue;
- if (!ext->ksym.type_id) {
- pr_warn("typeless ksym %s is not supported yet\n",
- ext->name);
- return -ENOTSUP;
- }
- bpf_gen__record_extern(obj->gen_loader, ext->name, ext->is_weak,
+ bpf_gen__record_extern(obj->gen_loader, ext->name,
+ ext->is_weak, !ext->ksym.type_id,
BTF_KIND_VAR, relo->insn_idx);
break;
case RELO_EXTERN_FUNC:
- bpf_gen__record_extern(obj->gen_loader, ext->name, ext->is_weak,
- BTF_KIND_FUNC, relo->insn_idx);
+ bpf_gen__record_extern(obj->gen_loader, ext->name,
+ ext->is_weak, false, BTF_KIND_FUNC,
+ relo->insn_idx);
break;
default:
continue;