Subject: [PATCH v4 bpf-next 4/7] bpf: add a pointer of bpf_binary_header to bpf_prog

From: Song Liu <[email-masked]>
Date: Wed, 19 Jan 2022 15:06:17 -0800

With sub page allocation, we cannot simply use bpf_func & PAGE_MASK to
find the bpf_binary_header. Add a pointer to struct bpf_prog to avoid
this logic.

Use this point for x86_64. If the pointer is not set by the jit engine,
fall back to original logic.

Signed-off-by: Song Liu <[email-masked]>
---
 arch/x86/net/bpf_jit_comp.c |  2 ++
 include/linux/filter.h      | 10 ++++++++--
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index ce1f86f245c9..fe4f08e25a1d 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -2339,6 +2339,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
 			if (header)
 				bpf_jit_binary_free(header);
 			prog = orig_prog;
+			header = NULL;
 			goto out_addrs;
 		}
 		if (image) {
@@ -2406,6 +2407,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
 	if (tmp_blinded)
 		bpf_jit_prog_release_other(prog, prog == orig_prog ?
 					   tmp : orig_prog);
+	prog->hdr = header;
 	return prog;
 }
 
diff --git a/include/linux/filter.h b/include/linux/filter.h
index 6cc1ebf1f840..6bb00f343cc5 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -584,6 +584,7 @@ struct bpf_prog {
 					    const struct bpf_insn *insn);
 	struct bpf_prog_aux	*aux;		/* Auxiliary fields */
 	struct sock_fprog_kern	*orig_prog;	/* Original BPF program */
+	struct bpf_binary_header *hdr;
 	/* Instructions for interpreter */
 	union {
 		DECLARE_FLEX_ARRAY(struct sock_filter, insns);
@@ -893,9 +894,14 @@ static inline void bpf_jit_binary_lock_ro(struct bpf_binary_header *hdr)
 static inline struct bpf_binary_header *
 bpf_jit_binary_hdr(const struct bpf_prog *fp)
 {
-	unsigned long real_start = (unsigned long)fp->bpf_func;
-	unsigned long addr = real_start & PAGE_MASK;
+	unsigned long real_start;
+	unsigned long addr;
 
+	if (fp->hdr)
+		return fp->hdr;
+
+	real_start = (unsigned long)fp->bpf_func;
+	addr = real_start & PAGE_MASK;
 	return (void *)addr;
 }
 
-- 
2.30.2