selftests/bpf: Validate arch-specific argument registers limits

Update uprobe_autoattach selftest to validate architecture-specific
argument passing through registers. Use new BPF_UPROBE and
BPF_URETPROBE, and construct both BPF-side and user-space side in such
a way that for different architectures we are fetching and checking
different number of arguments, matching architecture-specific limit of
how many registers are available for argument passing.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: Alan Maguire <alan.maguire@oracle.com> # arm64
Tested-by: Ilya Leoshkevich <iii@linux.ibm.com> # s390x
Link: https://lore.kernel.org/bpf/20230120200914.3008030-12-andrii@kernel.org

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

@@ -3,18 +3,21 @@
 
 #include <test_progs.h>
 #include "test_uprobe_autoattach.skel.h"
+#include "progs/bpf_misc.h"
 
 /* uprobe attach point */
-static noinline int autoattach_trigger_func(int arg)
+static noinline int autoattach_trigger_func(int arg1, int arg2, int arg3,
+					    int arg4, int arg5, int arg6,
+					    int arg7, int arg8)
 {
 	asm volatile ("");
-	return arg + 1;
+	return arg1 + arg2 + arg3 + arg4 + arg5 + arg6 + arg7 + arg8 + 1;
 }
 
 void test_uprobe_autoattach(void)
 {
 	struct test_uprobe_autoattach *skel;
-	int trigger_val = 100, trigger_ret;
+	int trigger_ret;
 	size_t malloc_sz = 1;
 	char *mem;
 
@@ -28,22 +31,42 @@ void test_uprobe_autoattach(void)
 	skel->bss->test_pid = getpid();
 
 	/* trigger & validate uprobe & uretprobe */
-	trigger_ret = autoattach_trigger_func(trigger_val);
+	trigger_ret = autoattach_trigger_func(1, 2, 3, 4, 5, 6, 7, 8);
 
 	skel->bss->test_pid = getpid();
 
 	/* trigger & validate shared library u[ret]probes attached by name */
 	mem = malloc(malloc_sz);
 
-	ASSERT_EQ(skel->bss->uprobe_byname_parm1, trigger_val, "check_uprobe_byname_parm1");
+	ASSERT_EQ(skel->bss->uprobe_byname_parm1, 1, "check_uprobe_byname_parm1");
 	ASSERT_EQ(skel->bss->uprobe_byname_ran, 1, "check_uprobe_byname_ran");
 	ASSERT_EQ(skel->bss->uretprobe_byname_rc, trigger_ret, "check_uretprobe_byname_rc");
+	ASSERT_EQ(skel->bss->uretprobe_byname_ret, trigger_ret, "check_uretprobe_byname_ret");
 	ASSERT_EQ(skel->bss->uretprobe_byname_ran, 2, "check_uretprobe_byname_ran");
 	ASSERT_EQ(skel->bss->uprobe_byname2_parm1, malloc_sz, "check_uprobe_byname2_parm1");
 	ASSERT_EQ(skel->bss->uprobe_byname2_ran, 3, "check_uprobe_byname2_ran");
 	ASSERT_EQ(skel->bss->uretprobe_byname2_rc, mem, "check_uretprobe_byname2_rc");
 	ASSERT_EQ(skel->bss->uretprobe_byname2_ran, 4, "check_uretprobe_byname2_ran");
 
+	ASSERT_EQ(skel->bss->a[0], 1, "arg1");
+	ASSERT_EQ(skel->bss->a[1], 2, "arg2");
+	ASSERT_EQ(skel->bss->a[2], 3, "arg3");
+#if FUNC_REG_ARG_CNT > 3
+	ASSERT_EQ(skel->bss->a[3], 4, "arg4");
+#endif
+#if FUNC_REG_ARG_CNT > 4
+	ASSERT_EQ(skel->bss->a[4], 5, "arg5");
+#endif
+#if FUNC_REG_ARG_CNT > 5
+	ASSERT_EQ(skel->bss->a[5], 6, "arg6");
+#endif
+#if FUNC_REG_ARG_CNT > 6
+	ASSERT_EQ(skel->bss->a[6], 7, "arg7");
+#endif
+#if FUNC_REG_ARG_CNT > 7
+	ASSERT_EQ(skel->bss->a[7], 8, "arg8");
+#endif
+
 	free(mem);
 cleanup:
 	test_uprobe_autoattach__destroy(skel);

tools/testing/selftests/bpf/progs/bpf_misc.h

@@ -28,4 +28,29 @@
 #define SYS_PREFIX "__se_"
 #endif
 
+/* How many arguments are passed to function in register */
+#if defined(__TARGET_ARCH_x86) || defined(__x86_64__)
+#define FUNC_REG_ARG_CNT 6
+#elif defined(__i386__)
+#define FUNC_REG_ARG_CNT 3
+#elif defined(__TARGET_ARCH_s390) || defined(__s390x__)
+#define FUNC_REG_ARG_CNT 5
+#elif defined(__TARGET_ARCH_arm) || defined(__arm__)
+#define FUNC_REG_ARG_CNT 4
+#elif defined(__TARGET_ARCH_arm64) || defined(__aarch64__)
+#define FUNC_REG_ARG_CNT 8
+#elif defined(__TARGET_ARCH_mips) || defined(__mips__)
+#define FUNC_REG_ARG_CNT 8
+#elif defined(__TARGET_ARCH_powerpc) || defined(__powerpc__) || defined(__powerpc64__)
+#define FUNC_REG_ARG_CNT 8
+#elif defined(__TARGET_ARCH_sparc) || defined(__sparc__)
+#define FUNC_REG_ARG_CNT 6
+#elif defined(__TARGET_ARCH_riscv) || defined(__riscv__)
+#define FUNC_REG_ARG_CNT 8
+#else
+/* default to 5 for others */
+#define FUNC_REG_ARG_CNT 5
+#endif
+
+
 #endif

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

@@ -6,10 +6,12 @@
 #include <bpf/bpf_core_read.h>
 #include <bpf/bpf_helpers.h>
 #include <bpf/bpf_tracing.h>
+#include "bpf_misc.h"
 
 int uprobe_byname_parm1 = 0;
 int uprobe_byname_ran = 0;
 int uretprobe_byname_rc = 0;
+int uretprobe_byname_ret = 0;
 int uretprobe_byname_ran = 0;
 size_t uprobe_byname2_parm1 = 0;
 int uprobe_byname2_ran = 0;
@@ -18,6 +20,8 @@ int uretprobe_byname2_ran = 0;
 
 int test_pid;
 
+int a[8];
+
 /* This program cannot auto-attach, but that should not stop other
  * programs from attaching.
  */
@@ -28,18 +32,58 @@ int handle_uprobe_noautoattach(struct pt_regs *ctx)
 }
 
 SEC("uprobe//proc/self/exe:autoattach_trigger_func")
-int handle_uprobe_byname(struct pt_regs *ctx)
+int BPF_UPROBE(handle_uprobe_byname
+	       , int arg1
+	       , int arg2
+	       , int arg3
+#if FUNC_REG_ARG_CNT > 3
+	       , int arg4
+#endif
+#if FUNC_REG_ARG_CNT > 4
+	       , int arg5
+#endif
+#if FUNC_REG_ARG_CNT > 5
+	       , int arg6
+#endif
+#if FUNC_REG_ARG_CNT > 6
+	       , int arg7
+#endif
+#if FUNC_REG_ARG_CNT > 7
+	       , int arg8
+#endif
+)
 {
 	uprobe_byname_parm1 = PT_REGS_PARM1_CORE(ctx);
 	uprobe_byname_ran = 1;
+
+	a[0] = arg1;
+	a[1] = arg2;
+	a[2] = arg3;
+#if FUNC_REG_ARG_CNT > 3
+	a[3] = arg4;
+#endif
+#if FUNC_REG_ARG_CNT > 4
+	a[4] = arg5;
+#endif
+#if FUNC_REG_ARG_CNT > 5
+	a[5] = arg6;
+#endif
+#if FUNC_REG_ARG_CNT > 6
+	a[6] = arg7;
+#endif
+#if FUNC_REG_ARG_CNT > 7
+	a[7] = arg8;
+#endif
 	return 0;
 }
 
 SEC("uretprobe//proc/self/exe:autoattach_trigger_func")
-int handle_uretprobe_byname(struct pt_regs *ctx)
+int BPF_URETPROBE(handle_uretprobe_byname, int ret)
 {
 	uretprobe_byname_rc = PT_REGS_RC_CORE(ctx);
+	uretprobe_byname_ret = ret;
 	uretprobe_byname_ran = 2;
+
 	return 0;
 }