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| author | Andrii Nakryiko <andrii@kernel.org> | 2021-01-11 23:55:18 -0800 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2021-01-12 17:24:30 -0800 |
| commit | 541c3bad8dc51b253ba8686d0cd7628e6b9b5f4c (patch) | |
| tree | 4ba7ff0adceb638a353df96eeded5ac9586460b1 /kernel/bpf/core.c | |
| parent | 635599bace259a2c42741c3ea61bfa7be6f15556 (diff) | |
| download | linux-stable-541c3bad8dc51b253ba8686d0cd7628e6b9b5f4c.tar.gz linux-stable-541c3bad8dc51b253ba8686d0cd7628e6b9b5f4c.tar.bz2 linux-stable-541c3bad8dc51b253ba8686d0cd7628e6b9b5f4c.zip | |
bpf: Support BPF ksym variables in kernel modules
Add support for directly accessing kernel module variables from BPF programs
using special ldimm64 instructions. This functionality builds upon vmlinux
ksym support, but extends ldimm64 with src_reg=BPF_PSEUDO_BTF_ID to allow
specifying kernel module BTF's FD in insn[1].imm field.
During BPF program load time, verifier will resolve FD to BTF object and will
take reference on BTF object itself and, for module BTFs, corresponding module
as well, to make sure it won't be unloaded from under running BPF program. The
mechanism used is similar to how bpf_prog keeps track of used bpf_maps.
One interesting change is also in how per-CPU variable is determined. The
logic is to find .data..percpu data section in provided BTF, but both vmlinux
and module each have their own .data..percpu entries in BTF. So for module's
case, the search for DATASEC record needs to look at only module's added BTF
types. This is implemented with custom search function.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Hao Luo <haoluo@google.com>
Link: https://lore.kernel.org/bpf/20210112075520.4103414-6-andrii@kernel.org
Diffstat (limited to 'kernel/bpf/core.c')
| -rw-r--r-- | kernel/bpf/core.c | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index 261f8692d0d2..69c3c308de5e 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -2119,6 +2119,28 @@ static void bpf_free_used_maps(struct bpf_prog_aux *aux) kfree(aux->used_maps); } +void __bpf_free_used_btfs(struct bpf_prog_aux *aux, + struct btf_mod_pair *used_btfs, u32 len) +{ +#ifdef CONFIG_BPF_SYSCALL + struct btf_mod_pair *btf_mod; + u32 i; + + for (i = 0; i < len; i++) { + btf_mod = &used_btfs[i]; + if (btf_mod->module) + module_put(btf_mod->module); + btf_put(btf_mod->btf); + } +#endif +} + +static void bpf_free_used_btfs(struct bpf_prog_aux *aux) +{ + __bpf_free_used_btfs(aux, aux->used_btfs, aux->used_btf_cnt); + kfree(aux->used_btfs); +} + static void bpf_prog_free_deferred(struct work_struct *work) { struct bpf_prog_aux *aux; @@ -2126,6 +2148,7 @@ static void bpf_prog_free_deferred(struct work_struct *work) aux = container_of(work, struct bpf_prog_aux, work); bpf_free_used_maps(aux); + bpf_free_used_btfs(aux); if (bpf_prog_is_dev_bound(aux)) bpf_prog_offload_destroy(aux->prog); #ifdef CONFIG_PERF_EVENTS |