Re: [PATCH bpf-next 6/8] bpf: Add arch_bpf_trampoline_size()

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



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);


[...]





[Index of Archives]     [Linux Samsung SoC]     [Linux Rockchip SoC]     [Linux Actions SoC]     [Linux for Synopsys ARC Processors]     [Linux NFS]     [Linux NILFS]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]


  Powered by Linux