Subject: [PATCH bpf-next 1/2] bpf: Remove CONFIG_X86 and CONFIG_DYNAMIC_FTRACE guard from the tcp-cc kfuncs

From: Martin KaFai Lau <[email-masked]>
Date: Fri, 22 Mar 2024 12:14:32 -0700

From: Martin KaFai Lau <[email-masked]>

The commit 7aae231ac93b ("bpf: tcp: Limit calling some tcp cc functions to CONFIG_DYNAMIC_FTRACE")
added CONFIG_DYNAMIC_FTRACE guard because pahole was only generating
btf for ftrace-able functions. The ftrace filter had already been
removed from pahole, so the CONFIG_DYNAMIC_FTRACE guard can be
removed.

The commit 569c484f9995 ("bpf: Limit static tcp-cc functions in the .BTF_ids list to x86")
has added CONFIG_X86 guard because it failed the powerpc arch which
prepended a "." to the local static function, so "cubictcp_init" becomes
".cubictcp_init". "__bpf_kfunc" has been added to kfunc
since then and it uses the __unused compiler attribute.
There is an existing
"__bpf_kfunc static u32 bpf_kfunc_call_test_static_unused_arg(u32 arg, u32 unused)"
test in bpf_testmod.c to cover the static kfunc case.

cross compile on ppc64 with CONFIG_DYNAMIC_FTRACE disabled:
> readelf -s vmlinux | grep cubictcp_
56938: c00000000144fd00   184 FUNC    LOCAL  DEFAULT    2 cubictcp_cwnd_event 	    [<localentry>: 8]
56939: c00000000144fdb8   200 FUNC    LOCAL  DEFAULT    2 cubictcp_recalc_[...]   [<localentry>: 8]
56940: c00000000144fe80   296 FUNC    LOCAL  DEFAULT    2 cubictcp_init 	    [<localentry>: 8]
56941: c00000000144ffa8   228 FUNC    LOCAL  DEFAULT    2 cubictcp_state 	    [<localentry>: 8]
56942: c00000000145008c  1908 FUNC    LOCAL  DEFAULT    2 cubictcp_cong_avoid  [<localentry>: 8]
56943: c000000001450800  1644 FUNC    LOCAL  DEFAULT    2 cubictcp_acked 	    [<localentry>: 8]

> bpftool btf dump file vmlinux | grep cubictcp_
[51540] FUNC 'cubictcp_acked' type_id=38137 linkage=static
[51541] FUNC 'cubictcp_cong_avoid' type_id=38122 linkage=static
[51543] FUNC 'cubictcp_cwnd_event' type_id=51542 linkage=static
[51544] FUNC 'cubictcp_init' type_id=9186 linkage=static
[51545] FUNC 'cubictcp_recalc_ssthresh' type_id=35021 linkage=static
[51547] FUNC 'cubictcp_state' type_id=38141 linkage=static

The patch removed both config guards.

Cc: Jiri Olsa <[email-masked]>
Signed-off-by: Martin KaFai Lau <[email-masked]>
---
 net/ipv4/tcp_bbr.c   | 4 ----
 net/ipv4/tcp_cubic.c | 4 ----
 net/ipv4/tcp_dctcp.c | 4 ----
 3 files changed, 12 deletions(-)

diff --git a/net/ipv4/tcp_bbr.c b/net/ipv4/tcp_bbr.c
index 05dc2d05bc7c..7e52ab24e40a 100644
--- a/net/ipv4/tcp_bbr.c
+++ b/net/ipv4/tcp_bbr.c
@@ -1156,8 +1156,6 @@ static struct tcp_congestion_ops tcp_bbr_cong_ops __read_mostly = {
 };
 
 BTF_KFUNCS_START(tcp_bbr_check_kfunc_ids)
-#ifdef CONFIG_X86
-#ifdef CONFIG_DYNAMIC_FTRACE
 BTF_ID_FLAGS(func, bbr_init)
 BTF_ID_FLAGS(func, bbr_main)
 BTF_ID_FLAGS(func, bbr_sndbuf_expand)
@@ -1166,8 +1164,6 @@ BTF_ID_FLAGS(func, bbr_cwnd_event)
 BTF_ID_FLAGS(func, bbr_ssthresh)
 BTF_ID_FLAGS(func, bbr_min_tso_segs)
 BTF_ID_FLAGS(func, bbr_set_state)
-#endif
-#endif
 BTF_KFUNCS_END(tcp_bbr_check_kfunc_ids)
 
 static const struct btf_kfunc_id_set tcp_bbr_kfunc_set = {
diff --git a/net/ipv4/tcp_cubic.c b/net/ipv4/tcp_cubic.c
index 44869ea089e3..5dbed91c6178 100644
--- a/net/ipv4/tcp_cubic.c
+++ b/net/ipv4/tcp_cubic.c
@@ -486,16 +486,12 @@ static struct tcp_congestion_ops cubictcp __read_mostly = {
 };
 
 BTF_KFUNCS_START(tcp_cubic_check_kfunc_ids)
-#ifdef CONFIG_X86
-#ifdef CONFIG_DYNAMIC_FTRACE
 BTF_ID_FLAGS(func, cubictcp_init)
 BTF_ID_FLAGS(func, cubictcp_recalc_ssthresh)
 BTF_ID_FLAGS(func, cubictcp_cong_avoid)
 BTF_ID_FLAGS(func, cubictcp_state)
 BTF_ID_FLAGS(func, cubictcp_cwnd_event)
 BTF_ID_FLAGS(func, cubictcp_acked)
-#endif
-#endif
 BTF_KFUNCS_END(tcp_cubic_check_kfunc_ids)
 
 static const struct btf_kfunc_id_set tcp_cubic_kfunc_set = {
diff --git a/net/ipv4/tcp_dctcp.c b/net/ipv4/tcp_dctcp.c
index e33fbe4933e4..6b712a33d49f 100644
--- a/net/ipv4/tcp_dctcp.c
+++ b/net/ipv4/tcp_dctcp.c
@@ -261,16 +261,12 @@ static struct tcp_congestion_ops dctcp_reno __read_mostly = {
 };
 
 BTF_KFUNCS_START(tcp_dctcp_check_kfunc_ids)
-#ifdef CONFIG_X86
-#ifdef CONFIG_DYNAMIC_FTRACE
 BTF_ID_FLAGS(func, dctcp_init)
 BTF_ID_FLAGS(func, dctcp_update_alpha)
 BTF_ID_FLAGS(func, dctcp_cwnd_event)
 BTF_ID_FLAGS(func, dctcp_ssthresh)
 BTF_ID_FLAGS(func, dctcp_cwnd_undo)
 BTF_ID_FLAGS(func, dctcp_state)
-#endif
-#endif
 BTF_KFUNCS_END(tcp_dctcp_check_kfunc_ids)
 
 static const struct btf_kfunc_id_set tcp_dctcp_kfunc_set = {
-- 
2.43.0