Merge branch 'Add USDT support for s390'

Ilya Leoshkevich says:

====================

This series adds USDT support for s390, making the "usdt" test pass
there. Patch 1 is a collection of minor cleanups, patch 2 adds
BPF-side support, patch 3 adds userspace-side support.
====================

Signed-off-by: Andrii Nakryiko <[email protected]>

Author: anakryiko

tools/lib/bpf/usdt.bpf.h

@@ -166,7 +166,7 @@ int bpf_usdt_arg(struct pt_regs *ctx, __u64 arg_num, long *res)
 	case BPF_USDT_ARG_REG_DEREF:
 		/* Arg is in memory addressed by register, plus some offset
 		 * (e.g., "-4@-1204(%rbp)" in USDT arg spec). Register is
-		 * identified lik with BPF_USDT_ARG_REG case, and the offset
+		 * identified like with BPF_USDT_ARG_REG case, and the offset
 		 * is in arg_spec->val_off. We first fetch register contents
 		 * from pt_regs, then do another user-space probe read to
 		 * fetch argument value itself.
@@ -177,6 +177,9 @@ int bpf_usdt_arg(struct pt_regs *ctx, __u64 arg_num, long *res)
 		err = bpf_probe_read_user(&val, sizeof(val), (void *)val + arg_spec->val_off);
 		if (err)
 			return err;
+#if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+		val >>= arg_spec->arg_bitshift;
+#endif
 		break;
 	default:
 		return -EINVAL;
@@ -198,7 +201,7 @@ int bpf_usdt_arg(struct pt_regs *ctx, __u64 arg_num, long *res)
 /* Retrieve user-specified cookie value provided during attach as
  * bpf_usdt_opts.usdt_cookie. This serves the same purpose as BPF cookie
  * returned by bpf_get_attach_cookie(). Libbpf's support for USDT is itself
- * utilizaing BPF cookies internally, so user can't use BPF cookie directly
+ * utilizing BPF cookies internally, so user can't use BPF cookie directly
  * for USDT programs and has to use bpf_usdt_cookie() API instead.
  */
 static inline __noinline

tools/lib/bpf/usdt.c

@@ -108,7 +108,7 @@
  * code through spec map. This allows BPF applications to quickly fetch the
  * actual value at runtime using a simple BPF-side code.
  *
- * With basics out of the way, let's go over less immeditately obvious aspects
+ * With basics out of the way, let's go over less immediately obvious aspects
  * of supporting USDTs.
  *
  * First, there is no special USDT BPF program type. It is actually just
@@ -189,14 +189,14 @@
 #define USDT_NOTE_TYPE 3
 #define USDT_NOTE_NAME "stapsdt"
 
-/* should match exactly enum __bpf_usdt_arg_type from bpf_usdt.bpf.h */
+/* should match exactly enum __bpf_usdt_arg_type from usdt.bpf.h */
 enum usdt_arg_type {
 	USDT_ARG_CONST,
 	USDT_ARG_REG,
 	USDT_ARG_REG_DEREF,
 };
 
-/* should match exactly struct __bpf_usdt_arg_spec from bpf_usdt.bpf.h */
+/* should match exactly struct __bpf_usdt_arg_spec from usdt.bpf.h */
 struct usdt_arg_spec {
 	__u64 val_off;
 	enum usdt_arg_type arg_type;
@@ -328,9 +328,9 @@ static int sanity_check_usdt_elf(Elf *elf, const char *path)
 		return -EBADF;
 	}
 
-#if __BYTE_ORDER == __LITTLE_ENDIAN
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
 	endianness = ELFDATA2LSB;
-#elif __BYTE_ORDER == __BIG_ENDIAN
+#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
 	endianness = ELFDATA2MSB;
 #else
 # error "Unrecognized __BYTE_ORDER__"
@@ -843,7 +843,7 @@ static int bpf_link_usdt_detach(struct bpf_link *link)
 						   sizeof(*new_free_ids));
 		/* If we couldn't resize free_spec_ids, we'll just leak
 		 * a bunch of free IDs; this is very unlikely to happen and if
-		 * system is so exausted on memory, it's the least of user's
+		 * system is so exhausted on memory, it's the least of user's
 		 * concerns, probably.
 		 * So just do our best here to return those IDs to usdt_manager.
 		 */
@@ -1269,6 +1269,63 @@ static int parse_usdt_arg(const char *arg_str, int arg_num, struct usdt_arg_spec
 	return len;
 }
 
+#elif defined(__s390x__)
+
+/* Do not support __s390__ for now, since user_pt_regs is broken with -m31. */
+
+static int parse_usdt_arg(const char *arg_str, int arg_num,
+			  struct usdt_arg_spec *arg)
+{
+	unsigned int reg;
+	int sz, len;
+	long off;
+
+	if (sscanf(arg_str, " %d @ %ld ( %%r%u ) %n", &sz, &off, &reg, &len) == 3) {
+		/* Memory dereference case, e.g., -2@-28(%r15) */
+		arg->arg_type = USDT_ARG_REG_DEREF;
+		arg->val_off = off;
+		if (reg > 15) {
+			pr_warn("usdt: unrecognized register '%%r%u'\n", reg);
+			return -EINVAL;
+		}
+		arg->reg_off = offsetof(user_pt_regs, gprs[reg]);
+	} else if (sscanf(arg_str, " %d @ %%r%u %n", &sz, &reg, &len) == 2) {
+		/* Register read case, e.g., -8@%r0 */
+		arg->arg_type = USDT_ARG_REG;
+		arg->val_off = 0;
+		if (reg > 15) {
+			pr_warn("usdt: unrecognized register '%%r%u'\n", reg);
+			return -EINVAL;
+		}
+		arg->reg_off = offsetof(user_pt_regs, gprs[reg]);
+	} else if (sscanf(arg_str, " %d @ %ld %n", &sz, &off, &len) == 2) {
+		/* Constant value case, e.g., 4@71 */
+		arg->arg_type = USDT_ARG_CONST;
+		arg->val_off = off;
+		arg->reg_off = -1;
+	} else {
+		pr_warn("usdt: unrecognized arg #%d spec '%s'\n", arg_num,
+			arg_str);
+		return -EINVAL;
+	}
+
+	arg->arg_signed = sz < 0;
+	if (sz < 0)
+		sz = -sz;
+
+	switch (sz) {
+	case 1: case 2: case 4: case 8:
+		arg->arg_bitshift = 64 - sz * 8;
+		break;
+	default:
+		pr_warn("usdt: unsupported arg #%d (spec '%s') size: %d\n",
+			arg_num, arg_str, sz);
+		return -EINVAL;
+	}
+
+	return len;
+}
+
 #else
 
 static int parse_usdt_arg(const char *arg_str, int arg_num, struct usdt_arg_spec *arg)