Re: [PATCH 1/3] bpf: Move iterator functions into special init section

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Em Mon, Nov 09, 2020 at 03:06:55PM -0300, Arnaldo Carvalho de Melo escreveu:
> > I'm fixing it up by hand to try together with pahole's patches.
 
> Due to:
 
> 33def8498fdde180 ("treewide: Convert macro and uses of __section(foo) to __section("foo")")
> 

For convenience:

 asm-generic/vmlinux.lds.h |   16 +++++++++++++++-
 linux/bpf.h               |    8 +++++++-
 linux/init.h              |    1 +
 3 files changed, 23 insertions(+), 2 deletions(-)

---

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index b2b3d81b1535a5ab..f91029b3443bf0d2 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -685,8 +685,21 @@
 	.BTF_ids : AT(ADDR(.BTF_ids) - LOAD_OFFSET) {			\
 		*(.BTF_ids)						\
 	}
+
+/*
+ * .init.bpf.preserve_type
+ *
+ * This section store special BPF function and marks them
+ * with begin/end symbols pair for the sake of pahole tool.
+ */
+#define INIT_BPF_PRESERVE_TYPE						\
+	__init_bpf_preserve_type_begin = .;                             \
+	*(.init.bpf.preserve_type)                                      \
+	__init_bpf_preserve_type_end = .;				\
+	MEM_DISCARD(init.bpf.preserve_type)
 #else
 #define BTF
+#define INIT_BPF_PRESERVE_TYPE
 #endif
 
 /*
@@ -741,7 +754,8 @@
 #define INIT_TEXT							\
 	*(.init.text .init.text.*)					\
 	*(.text.startup)						\
-	MEM_DISCARD(init.text*)
+	MEM_DISCARD(init.text*)						\
+	INIT_BPF_PRESERVE_TYPE
 
 #define EXIT_DATA							\
 	*(.exit.data .exit.data.*)					\
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 2b16bf48aab61a1f..73e8ededde3e9c09 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1276,10 +1276,16 @@ struct bpf_link *bpf_link_get_from_fd(u32 ufd);
 int bpf_obj_pin_user(u32 ufd, const char __user *pathname);
 int bpf_obj_get_user(const char __user *pathname, int flags);
 
+#ifdef CONFIG_DEBUG_INFO_BTF
+#define BPF_INIT __init_bpf_preserve_type
+#else
+#define BPF_INIT __init
+#endif
+
 #define BPF_ITER_FUNC_PREFIX "bpf_iter_"
 #define DEFINE_BPF_ITER_FUNC(target, args...)			\
 	extern int bpf_iter_ ## target(args);			\
-	int __init bpf_iter_ ## target(args) { return 0; }
+	int BPF_INIT bpf_iter_ ## target(args) { return 0; }
 
 struct bpf_iter_aux_info {
 	struct bpf_map *map;
diff --git a/include/linux/init.h b/include/linux/init.h
index 7b53cb3092ee9956..a7c71e3b5f9a1d65 100644
--- a/include/linux/init.h
+++ b/include/linux/init.h
@@ -52,6 +52,7 @@
 #define __initconst	__section(".init.rodata")
 #define __exitdata	__section(".exit.data")
 #define __exit_call	__used __section(".exitcall.exit")
+#define __init_bpf_preserve_type __section(".init.bpf.preserve_type")
 
 /*
  * modpost check for section mismatches during the kernel build.