selftests/bpf: Stop using static variables for passing data to/from user-space

In preparation of skipping emitting static variables in BPF skeletons, switch
all current selftests uses of static variables to pass data between BPF and
user-space to use global variables.

All non-read-only `static volatile` variables become just plain global
variables by dropping `static volatile` part.

Read-only `static volatile const` variables, though, still require `volatile`
modifier, otherwise compiler will ignore whatever values are set from
user-space.

Few static linker tests are using name-conflicting static variables to
validate that static linker still properly handles static variables and
doesn't trip up on name conflicts.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210507054119.270888-4-andrii@kernel.org

tools/testing/selftests/bpf/prog_tests/send_signal.c

@@ -2,7 +2,7 @@
 #include <test_progs.h>
 #include "test_send_signal_kern.skel.h"
 
-static volatile int sigusr1_received = 0;
+int sigusr1_received = 0;
 
 static void sigusr1_handler(int signum)
 {

tools/testing/selftests/bpf/prog_tests/skeleton.c

@@ -82,10 +82,8 @@ void test_skeleton(void)
 	CHECK(data->out2 != 2, "res2", "got %lld != exp %d\n", data->out2, 2);
 	CHECK(bss->out3 != 3, "res3", "got %d != exp %d\n", (int)bss->out3, 3);
 	CHECK(bss->out4 != 4, "res4", "got %lld != exp %d\n", bss->out4, 4);
-	CHECK(bss->handler_out5.a != 5, "res5", "got %d != exp %d\n",
-	      bss->handler_out5.a, 5);
-	CHECK(bss->handler_out5.b != 6, "res6", "got %lld != exp %d\n",
-	      bss->handler_out5.b, 6);
+	CHECK(bss->out5.a != 5, "res5", "got %d != exp %d\n", bss->out5.a, 5);
+	CHECK(bss->out5.b != 6, "res6", "got %lld != exp %d\n", bss->out5.b, 6);
 	CHECK(bss->out6 != 14, "res7", "got %d != exp %d\n", bss->out6, 14);
 
 	CHECK(bss->bpf_syscall != kcfg->CONFIG_BPF_SYSCALL, "ext1",

tools/testing/selftests/bpf/prog_tests/static_linked.c

@@ -14,12 +14,7 @@ void test_static_linked(void)
 		return;
 
 	skel->rodata->rovar1 = 1;
-	skel->bss->static_var1 = 2;
-	skel->bss->static_var11 = 3;
-
 	skel->rodata->rovar2 = 4;
-	skel->bss->static_var2 = 5;
-	skel->bss->static_var22 = 6;
 
 	err = test_static_linked__load(skel);
 	if (!ASSERT_OK(err, "skel_load"))

tools/testing/selftests/bpf/progs/bpf_iter_test_kern4.c

@@ -9,8 +9,8 @@ __u32 map1_id = 0, map2_id = 0;
 __u32 map1_accessed = 0, map2_accessed = 0;
 __u64 map1_seqnum = 0, map2_seqnum1 = 0, map2_seqnum2 = 0;
 
-static volatile const __u32 print_len;
-static volatile const __u32 ret1;
+volatile const __u32 print_len;
+volatile const __u32 ret1;
 
 SEC("iter/bpf_map")
 int dump_bpf_map(struct bpf_iter__bpf_map *ctx)

tools/testing/selftests/bpf/progs/kfree_skb.c

@@ -109,10 +109,10 @@ int BPF_PROG(trace_kfree_skb, struct sk_buff *skb, void *location)
 	return 0;
 }
 
-static volatile struct {
+struct {
 	bool fentry_test_ok;
 	bool fexit_test_ok;
-} result;
+} result = {};
 
 SEC("fentry/eth_type_trans")
 int BPF_PROG(fentry_eth_type_trans, struct sk_buff *skb, struct net_device *dev,

tools/testing/selftests/bpf/progs/tailcall3.c

@@ -10,7 +10,7 @@ struct {
 	__uint(value_size, sizeof(__u32));
 } jmp_table SEC(".maps");
 
-static volatile int count;
+int count = 0;
 
 SEC("classifier/0")
 int bpf_func_0(struct __sk_buff *skb)

tools/testing/selftests/bpf/progs/tailcall4.c

@@ -10,7 +10,7 @@ struct {
 	__uint(value_size, sizeof(__u32));
 } jmp_table SEC(".maps");
 
-static volatile int selector;
+int selector = 0;
 
 #define TAIL_FUNC(x)				\
 	SEC("classifier/" #x)			\

tools/testing/selftests/bpf/progs/tailcall5.c

@@ -10,7 +10,7 @@ struct {
 	__uint(value_size, sizeof(__u32));
 } jmp_table SEC(".maps");
 
-static volatile int selector;
+int selector = 0;
 
 #define TAIL_FUNC(x)				\
 	SEC("classifier/" #x)			\

tools/testing/selftests/bpf/progs/tailcall_bpf2bpf2.c

@@ -20,7 +20,7 @@ int subprog_tail(struct __sk_buff *skb)
 	return 1;
 }
 
-static volatile int count;
+int count = 0;
 
 SEC("classifier/0")
 int bpf_func_0(struct __sk_buff *skb)

tools/testing/selftests/bpf/progs/tailcall_bpf2bpf4.c

@@ -9,7 +9,7 @@ struct {
 	__uint(value_size, sizeof(__u32));
 } jmp_table SEC(".maps");
 
-static volatile int count;
+int count = 0;
 
 __noinline
 int subprog_tail_2(struct __sk_buff *skb)

tools/testing/selftests/bpf/progs/test_check_mtu.c

@@ -11,8 +11,8 @@
 char _license[] SEC("license") = "GPL";
 
 /* Userspace will update with MTU it can see on device */
-static volatile const int GLOBAL_USER_MTU;
-static volatile const __u32 GLOBAL_USER_IFINDEX;
+volatile const int GLOBAL_USER_MTU;
+volatile const __u32 GLOBAL_USER_IFINDEX;
 
 /* BPF-prog will update these with MTU values it can see */
 __u32 global_bpf_mtu_xdp = 0;

tools/testing/selftests/bpf/progs/test_cls_redirect.c

@@ -39,8 +39,8 @@ char _license[] SEC("license") = "Dual BSD/GPL";
 /**
  * Destination port and IP used for UDP encapsulation.
  */
-static volatile const __be16 ENCAPSULATION_PORT;
-static volatile const __be32 ENCAPSULATION_IP;
+volatile const __be16 ENCAPSULATION_PORT;
+volatile const __be32 ENCAPSULATION_IP;
 
 typedef struct {
 	uint64_t processed_packets_total;

tools/testing/selftests/bpf/progs/test_global_func_args.c

@@ -8,7 +8,7 @@ struct S {
 	int v;
 };
 
-static volatile struct S global_variable;
+struct S global_variable = {};
 
 struct {
 	__uint(type, BPF_MAP_TYPE_ARRAY);

tools/testing/selftests/bpf/progs/test_rdonly_maps.c

@@ -5,7 +5,7 @@
 #include <linux/bpf.h>
 #include <bpf/bpf_helpers.h>
 
-static volatile const struct {
+const struct {
 	unsigned a[4];
 	/*
 	 * if the struct's size is multiple of 16, compiler will put it into
@@ -15,11 +15,11 @@ static volatile const struct {
 	char _y;
 } rdonly_values = { .a = {2, 3, 4, 5} };
 
-static volatile struct {
+struct {
 	unsigned did_run;
 	unsigned iters;
 	unsigned sum;
-} res;
+} res = {};
 
 SEC("raw_tracepoint/sys_enter:skip_loop")
 int skip_loop(struct pt_regs *ctx)

tools/testing/selftests/bpf/progs/test_skeleton.c

@@ -38,11 +38,11 @@ extern int LINUX_KERNEL_VERSION __kconfig;
 bool bpf_syscall = 0;
 int kern_ver = 0;
 
+struct s out5 = {};
+
 SEC("raw_tp/sys_enter")
 int handler(const void *ctx)
 {
-	static volatile struct s out5;
-
 	out1 = in1;
 	out2 = in2;
 	out3 = in3;

tools/testing/selftests/bpf/progs/test_snprintf_single.c

@@ -5,7 +5,7 @@
 #include <bpf/bpf_helpers.h>
 
 /* The format string is filled from the userspace such that loading fails */
-static const char fmt[10];
+const char fmt[10];
 
 SEC("raw_tp/sys_enter")
 int handler(const void *ctx)

tools/testing/selftests/bpf/progs/test_sockmap_listen.c

@@ -28,8 +28,8 @@ struct {
 	__type(value, unsigned int);
 } verdict_map SEC(".maps");
 
-static volatile bool test_sockmap; /* toggled by user-space */
-static volatile bool test_ingress; /* toggled by user-space */
+bool test_sockmap = false; /* toggled by user-space */
+bool test_ingress = false; /* toggled by user-space */
 
 SEC("sk_skb/stream_parser")
 int prog_stream_parser(struct __sk_buff *skb)

tools/testing/selftests/bpf/progs/test_static_linked1.c

@@ -4,9 +4,9 @@
 #include <linux/bpf.h>
 #include <bpf/bpf_helpers.h>
 
-/* 8-byte aligned .bss */
-static volatile long static_var1;
-static volatile int static_var11;
+/* 8-byte aligned .data */
+static volatile long static_var1 = 2;
+static volatile int static_var2 = 3;
 int var1 = 0;
 /* 4-byte aligned .rodata */
 const volatile int rovar1;
@@ -21,7 +21,7 @@ static __noinline int subprog(int x)
 SEC("raw_tp/sys_enter")
 int handler1(const void *ctx)
 {
-	var1 = subprog(rovar1) + static_var1 + static_var11;
+	var1 = subprog(rovar1) + static_var1 + static_var2;
 
 	return 0;
 }

tools/testing/selftests/bpf/progs/test_static_linked2.c

@@ -4,9 +4,9 @@
 #include <linux/bpf.h>
 #include <bpf/bpf_helpers.h>
 
-/* 4-byte aligned .bss */
-static volatile int static_var2;
-static volatile int static_var22;
+/* 4-byte aligned .data */
+static volatile int static_var1 = 5;
+static volatile int static_var2 = 6;
 int var2 = 0;
 /* 8-byte aligned .rodata */
 const volatile long rovar2;
@@ -21,7 +21,7 @@ static __noinline int subprog(int x)
 SEC("raw_tp/sys_enter")
 int handler2(const void *ctx)
 {
-	var2 = subprog(rovar2) + static_var2 + static_var22;
+	var2 = subprog(rovar2) + static_var1 + static_var2;
 
 	return 0;
 }