bpf: Add arch_bpf_trampoline_size()

This helper will be used to calculate the size of the trampoline before
allocating the memory.

arch_prepare_bpf_trampoline() for arm64 and riscv64 can use
arch_bpf_trampoline_size() to check the trampoline fits in the image.

OTOH, arch_prepare_bpf_trampoline() for s390 has to call the JIT process
twice, so it cannot use arch_bpf_trampoline_size().

Signed-off-by: Song Liu <song@kernel.org>
Acked-by: Ilya Leoshkevich <iii@linux.ibm.com>
Tested-by: Ilya Leoshkevich <iii@linux.ibm.com>  # on s390x
Acked-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Björn Töpel <bjorn@rivosinc.com>
Tested-by: Björn Töpel <bjorn@rivosinc.com> # on riscv
Link: https://lore.kernel.org/r/20231206224054.492250-6-song@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index affbcbf7e76e1..b553cbd89e55b 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -1072,6 +1072,12 @@ void __weak arch_unprotect_bpf_trampoline(void *image, unsigned int size)
 	set_memory_rw((long)image, 1);
 }
 
+int __weak arch_bpf_trampoline_size(const struct btf_func_model *m, u32 flags,
+				    struct bpf_tramp_links *tlinks, void *func_addr)
+{
+	return -ENOTSUPP;
+}
+
 static int __init init_trampolines(void)
 {
 	int i;