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, 17 insertions, 5 deletions

diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
index 8581693e62d3..35747fafde57 100644
--- a/arch/riscv/net/bpf_jit_comp64.c
+++ b/arch/riscv/net/bpf_jit_comp64.c
@@ -1029,6 +1029,21 @@ out:
 	return ret;
 }
 
+int arch_bpf_trampoline_size(const struct btf_func_model *m, u32 flags,
+			     struct bpf_tramp_links *tlinks, void *func_addr)
+{
+	struct bpf_tramp_image im;
+	struct rv_jit_context ctx;
+	int ret;
+
+	ctx.ninsns = 0;
+	ctx.insns = NULL;
+	ctx.ro_insns = NULL;
+	ret = __arch_prepare_bpf_trampoline(&im, m, tlinks, func_addr, flags, &ctx);
+
+	return ret < 0 ? ret : ninsns_rvoff(ctx.ninsns);
+}
+
 int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image,
 				void *image_end, const struct btf_func_model *m,
 				u32 flags, struct bpf_tramp_links *tlinks,
@@ -1037,14 +1052,11 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image,
 	int ret;
 	struct rv_jit_context ctx;
 
-	ctx.ninsns = 0;
-	ctx.insns = NULL;
-	ctx.ro_insns = NULL;
-	ret = __arch_prepare_bpf_trampoline(im, m, tlinks, func_addr, flags, &ctx);
+	ret = arch_bpf_trampoline_size(im, m, flags, tlinks, func_addr);
 	if (ret < 0)
 		return ret;
 
-	if (ninsns_rvoff(ret) > (long)image_end - (long)image)
+	if (ret > (long)image_end - (long)image)
 		return -EFBIG;
 
 	ctx.ninsns = 0;