[RFC PATCH bpf-next 6/7] bpf, arm64: Make program update work for trampoline ops

[Jordan Rife]

Use update_prog in place of current link prog when link matches
update_link.

Signed-off-by: Jordan Rife <jordan at jrife.io>
---
 arch/arm64/net/bpf_jit_comp.c | 23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
index 0c9a50a1e73e..1725d4cebdf2 100644
--- a/arch/arm64/net/bpf_jit_comp.c
+++ b/arch/arm64/net/bpf_jit_comp.c
@@ -2284,24 +2284,23 @@ bool bpf_jit_supports_subprog_tailcalls(void)
 	return true;
 }
 
-static void invoke_bpf_prog(struct jit_ctx *ctx, struct bpf_tramp_link *l,
+static void invoke_bpf_prog(struct jit_ctx *ctx, struct bpf_prog *p, u64 cookie,
 			    int bargs_off, int retval_off, int run_ctx_off,
 			    bool save_ret)
 {
 	__le32 *branch;
 	u64 enter_prog;
 	u64 exit_prog;
-	struct bpf_prog *p = l->link.prog;
 	int cookie_off = offsetof(struct bpf_tramp_run_ctx, bpf_cookie);
 
 	enter_prog = (u64)bpf_trampoline_enter(p);
 	exit_prog = (u64)bpf_trampoline_exit(p);
 
-	if (l->cookie == 0) {
+	if (cookie == 0) {
 		/* if cookie is zero, one instruction is enough to store it */
 		emit(A64_STR64I(A64_ZR, A64_SP, run_ctx_off + cookie_off), ctx);
 	} else {
-		emit_a64_mov_i64(A64_R(10), l->cookie, ctx);
+		emit_a64_mov_i64(A64_R(10), cookie, ctx);
 		emit(A64_STR64I(A64_R(10), A64_SP, run_ctx_off + cookie_off),
 		     ctx);
 	}
@@ -2362,7 +2361,8 @@ static void invoke_bpf_mod_ret(struct jit_ctx *ctx, struct bpf_tramp_links *tl,
 	 */
 	emit(A64_STR64I(A64_ZR, A64_SP, retval_off), ctx);
 	for (i = 0; i < tl->nr_links; i++) {
-		invoke_bpf_prog(ctx, tl->links[i], bargs_off, retval_off,
+		invoke_bpf_prog(ctx, bpf_tramp_links_prog(tl, i),
+				tl->links[i]->cookie, bargs_off, retval_off,
 				run_ctx_off, true);
 		/* if (*(u64 *)(sp + retval_off) !=  0)
 		 *	goto do_fexit;
@@ -2656,8 +2656,9 @@ static int prepare_trampoline(struct jit_ctx *ctx, struct bpf_tramp_image *im,
 	}
 
 	for (i = 0; i < fentry->nr_links; i++)
-		invoke_bpf_prog(ctx, fentry->links[i], bargs_off,
-				retval_off, run_ctx_off,
+		invoke_bpf_prog(ctx, bpf_tramp_links_prog(fentry, i),
+				fentry->links[i]->cookie, bargs_off, retval_off,
+				run_ctx_off,
 				flags & BPF_TRAMP_F_RET_FENTRY_RET);
 
 	if (fmod_ret->nr_links) {
@@ -2691,7 +2692,8 @@ static int prepare_trampoline(struct jit_ctx *ctx, struct bpf_tramp_image *im,
 	}
 
 	for (i = 0; i < fexit->nr_links; i++)
-		invoke_bpf_prog(ctx, fexit->links[i], bargs_off, retval_off,
+		invoke_bpf_prog(ctx, bpf_tramp_links_prog(fexit, i),
+				fexit->links[i]->cookie, bargs_off, retval_off,
 				run_ctx_off, false);
 
 	if (flags & BPF_TRAMP_F_CALL_ORIG) {
@@ -2829,6 +2831,11 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *ro_image,
 	return ret;
 }
 
+bool bpf_trampoline_supports_update_prog(void)
+{
+	return true;
+}
+
 static bool is_long_jump(void *ip, void *target)
 {
 	long offset;
-- 
2.43.0