selftests/bpf: Allow macros in __retval

Allow macro expansion for values passed to the `__retval` and
`__retval_unpriv` attributes. This is especially useful for testing
programs which return various error codes.

With this change, the code for parsing special literals can be made
simpler, as the literals are defined via macros. The only exception is
INT_MIN which expands to (-INT_MAX -1), which is not single number and
cannot be parsed by strtol. So, we instead use a prefixed literal
_INT_MIN in __retval and handle it separately (assign the expected
return to INT_MIN). Also, strtol cannot handle the "ll" suffix so change
the value of POINTER_VALUE from 0xcafe4all to 0xbadcafe.

Signed-off-by: Viktor Malik <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Alexei Starovoitov <[e-mail]>

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

···
  *                   expect return value to match passed parameter:
  *                   - a decimal number
  *                   - a hexadecimal number, when starts from 0x
- *                   - literal INT_MIN
- *                   - literal POINTER_VALUE (see definition below)
- *                   - literal TEST_DATA_LEN (see definition below)
+ *                   - a macro which expands to one of the above
+ *                   - literal _INT_MIN (expands to INT_MIN)
+ *                   In addition, two special macros are defined below:
+ *                   - POINTER_VALUE
+ *                   - TEST_DATA_LEN
  * __retval_unpriv   Same, but load program in unprivileged mode.
  *
  * __description     Text to be used instead of a program name for display
···
 #define __success_unpriv	__attribute__((btf_decl_tag("comment:test_expect_success_unpriv")))
 #define __log_level(lvl)	__attribute__((btf_decl_tag("comment:test_log_level="#lvl)))
 #define __flag(flag)		__attribute__((btf_decl_tag("comment:test_prog_flags="#flag)))
-#define __retval(val)		__attribute__((btf_decl_tag("comment:test_retval="#val)))
-#define __retval_unpriv(val)	__attribute__((btf_decl_tag("comment:test_retval_unpriv="#val)))
+#define __retval(val)		__attribute__((btf_decl_tag("comment:test_retval="XSTR(val))))
+#define __retval_unpriv(val)	__attribute__((btf_decl_tag("comment:test_retval_unpriv="XSTR(val))))
 #define __auxiliary		__attribute__((btf_decl_tag("comment:test_auxiliary")))
 #define __auxiliary_unpriv	__attribute__((btf_decl_tag("comment:test_auxiliary_unpriv")))
 #define __btf_path(path)	__attribute__((btf_decl_tag("comment:test_btf_path=" path)))
···
 #define __imm_insn(name, expr) [name]"i"(*(long *)&(expr))
 
 /* Magic constants used with __retval() */
-#define POINTER_VALUE	0xcafe4all
+#define POINTER_VALUE	0xbadcafe
 #define TEST_DATA_LEN	64
 
 #ifndef __used

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

···
 
 SEC("tc")
 __description("MOD32 overflow, check 1")
-__success __retval(INT_MIN)
+__success __retval(_INT_MIN)
 __naked void mod32_overflow_check_1(void)
 {
 	asm volatile ("					\
···
 
 SEC("tc")
 __description("MOD32 overflow, check 2")
-__success __retval(INT_MIN)
+__success __retval(_INT_MIN)
 __naked void mod32_overflow_check_2(void)
 {
 	asm volatile ("					\

tools/testing/selftests/bpf/test_loader.c

···
 #define TEST_TAG_LOAD_MODE_PFX "comment:load_mode="
 
 /* Warning: duplicated in bpf_misc.h */
-#define POINTER_VALUE	0xcafe4all
+#define POINTER_VALUE	0xbadcafe
 #define TEST_DATA_LEN	64
 
 #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
···
 
 static int parse_retval(const char *str, int *val, const char *name)
 {
-	struct {
-		char *name;
-		int val;
-	} named_values[] = {
-		{ "INT_MIN"      , INT_MIN },
-		{ "POINTER_VALUE", POINTER_VALUE },
-		{ "TEST_DATA_LEN", TEST_DATA_LEN },
-	};
-	int i;
-
-	for (i = 0; i < ARRAY_SIZE(named_values); ++i) {
-		if (strcmp(str, named_values[i].name) != 0)
-			continue;
-		*val = named_values[i].val;
+	/*
+	 * INT_MIN is defined as (-INT_MAX -1), i.e. it doesn't expand to a
+	 * single int and cannot be parsed with strtol, so we handle it
+	 * separately here. In addition, it expands to different expressions in
+	 * different compilers so we use a prefixed _INT_MIN instead.
+	 */
+	if (strcmp(str, "_INT_MIN") == 0) {
+		*val = INT_MIN;
 		return 0;
 	}