nolibc updates for v6.2

This branch further improves nolibc testing.
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Merge tag 'nolibc.2022.12.02a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu

Pull nolibc updates from Paul McKenney:

 - Further improvements to nolibc testing

* tag 'nolibc.2022.12.02a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu:
  selftests/nolibc: Always rebuild the sysroot when running a test
  selftests/nolibc: Add 7 tests for memcmp()

tools/testing/selftests/nolibc/Makefile

@@ -95,6 +95,7 @@ all: run
 sysroot: sysroot/$(ARCH)/include
 
 sysroot/$(ARCH)/include:
+	$(Q)rm -rf sysroot/$(ARCH) sysroot/sysroot
 	$(QUIET_MKDIR)mkdir -p sysroot
 	$(Q)$(MAKE) -C ../../../include/nolibc ARCH=$(ARCH) OUTPUT=$(CURDIR)/sysroot/ headers_standalone
 	$(Q)mv sysroot/sysroot sysroot/$(ARCH)
@@ -133,3 +134,5 @@ clean:
 	$(Q)rm -rf initramfs
 	$(call QUIET_CLEAN, run.out)
 	$(Q)rm -rf run.out
+
+.PHONY: sysroot/$(ARCH)/include

tools/testing/selftests/nolibc/nolibc-test.c

@@ -565,6 +565,13 @@ int run_stdlib(int min, int max)
 		CASE_TEST(strchr_foobar_z);    EXPECT_STRZR(1, strchr("foobar", 'z')); break;
 		CASE_TEST(strrchr_foobar_o);   EXPECT_STREQ(1, strrchr("foobar", 'o'), "obar"); break;
 		CASE_TEST(strrchr_foobar_z);   EXPECT_STRZR(1, strrchr("foobar", 'z')); break;
+		CASE_TEST(memcmp_20_20);       EXPECT_EQ(1, memcmp("aaa\x20", "aaa\x20", 4), 0); break;
+		CASE_TEST(memcmp_20_60);       EXPECT_LT(1, memcmp("aaa\x20", "aaa\x60", 4), 0); break;
+		CASE_TEST(memcmp_60_20);       EXPECT_GT(1, memcmp("aaa\x60", "aaa\x20", 4), 0); break;
+		CASE_TEST(memcmp_20_e0);       EXPECT_LT(1, memcmp("aaa\x20", "aaa\xe0", 4), 0); break;
+		CASE_TEST(memcmp_e0_20);       EXPECT_GT(1, memcmp("aaa\xe0", "aaa\x20", 4), 0); break;
+		CASE_TEST(memcmp_80_e0);       EXPECT_LT(1, memcmp("aaa\x80", "aaa\xe0", 4), 0); break;
+		CASE_TEST(memcmp_e0_80);       EXPECT_GT(1, memcmp("aaa\xe0", "aaa\x80", 4), 0); break;
 		case __LINE__:
 			return ret; /* must be last */
 		/* note: do not set any defaults so as to permit holes above */