Hi Song,
On 9/20/2023 1:31 PM, Song Liu wrote:
This helper will be used to calculate the size of the trampoline before
allocating the memory.
Signed-off-by: Song Liu <song@xxxxxxxxxx>
---
arch/arm64/net/bpf_jit_comp.c | 56 ++++++++++++++++++++++++---------
arch/riscv/net/bpf_jit_comp64.c | 24 +++++++++-----
arch/s390/net/bpf_jit_comp.c | 52 +++++++++++++++++-------------
arch/x86/net/bpf_jit_comp.c | 40 ++++++++++++++++++++---
include/linux/bpf.h | 2 ++
kernel/bpf/trampoline.c | 6 ++++
6 files changed, 131 insertions(+), 49 deletions(-)
diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
index d81b886ea4df..a6671253b7ed 100644
--- a/arch/arm64/net/bpf_jit_comp.c
+++ b/arch/arm64/net/bpf_jit_comp.c
@@ -2026,18 +2026,10 @@ static int prepare_trampoline(struct jit_ctx *ctx, struct bpf_tramp_image *im,
return ctx->idx;
}
-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,
- void *func_addr)
+static int btf_func_model_nregs(const struct btf_func_model *m)
{
- int i, ret;
int nregs = m->nr_args;
- int max_insns = ((long)image_end - (long)image) / AARCH64_INSN_SIZE;
- struct jit_ctx ctx = {
- .image = NULL,
- .idx = 0,
- };
+ int i;
/* extra registers needed for struct argument */
for (i = 0; i < MAX_BPF_FUNC_ARGS; i++) {
@@ -2046,19 +2038,53 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image,
nregs += (m->arg_size[i] + 7) / 8 - 1;
}
+ return nregs;
+}
+
+int arch_bpf_trampoline_size(const struct btf_func_model *m, u32 flags,
+ struct bpf_tramp_links *tlinks, void *func_addr)
+{
+ struct jit_ctx ctx = {
+ .image = NULL,
+ .idx = 0,
+ };
+ struct bpf_tramp_image im;
+ int nregs, ret;
+
+ nregs = btf_func_model_nregs(m);
/* the first 8 registers are used for arguments */
if (nregs > 8)
return -ENOTSUPP;
- ret = prepare_trampoline(&ctx, im, tlinks, func_addr, nregs, flags);
+ ret = prepare_trampoline(&ctx, &im, tlinks, func_addr, nregs, flags);
if (ret < 0)
return ret;
- if (ret > max_insns)
- return -EFBIG;
+ return ret < 0 ? ret : ret * AARCH64_INSN_SIZE;
+}
- ctx.image = image;
- ctx.idx = 0;
+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,
+ void *func_addr)
+{
+ int ret, nregs;
+ struct jit_ctx ctx = {
+ .image = image,
+ .idx = 0,
+ };
+
+ nregs = btf_func_model_nregs(m);
+ /* the first 8 registers are used for arguments */
+ if (nregs > 8)
+ return -ENOTSUPP;
+
+ ret = arch_bpf_trampoline_size(m, flags, tlinks, func_addr);
+ if (ret < 0)
+ return ret;
Since arch_bpf_trampoline_size was already called before the trampoline
image was allocated, it seems this call to arch_bpf_trampoline_size is
unnecessary. If this call can be omitted, we can avoid one less dry run.
+
+ if (ret > ((long)image_end - (long)image))
+ return -EFBIG;
jit_fill_hole(image, (unsigned int)(image_end - image));
ret = prepare_trampoline(&ctx, im, tlinks, func_addr, nregs, flags);
[...]
