s390: vmlinux.lds.S: fix .got.plt assertion

Naresh reported this build error on linux-next:

s390x-linux-gnu-ld: Unexpected GOT/PLT entries detected!
make[3]: *** [/builds/linux/arch/s390/boot/Makefile:87:
arch/s390/boot/vmlinux.syms] Error 1
make[3]: Target 'arch/s390/boot/bzImage' not remade because of errors.

The reason for the build error is an incorrect/incomplete assertion which
checks the size of the .got.plt section. Similar to x86 the size is either
zero or 24 bytes (three entries).

See commit 262b5cae ("x86/boot/compressed: Move .got.plt entries out of
the .got section") for more details. The three reserved/additional entries
for s390 are described in chapter 3.2.2 of the s390x ABI [1] (thanks to
Andreas Krebbel for pointing this out!).

[1] https://github.com/IBM/s390x-abi/releases/download/v1.6.1/lzsabi_s390x.pdfReported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
Closes: https://lore.kernel.org/all/CA+G9fYvWp8TY-fMEvc3UhoVtoR_eM5VsfHj3+n+kexcfJJ+Cvw@mail.gmail.com
Fixes: 30226853 ("s390: vmlinux.lds.S: explicitly handle '.got' and '.plt' sections")
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

arch/s390/boot/vmlinux.lds.S

@@ -144,13 +144,18 @@ SECTIONS
 	ELF_DETAILS
 
 	/*
-	 * Sections that should stay zero sized, which is safer to
-	 * explicitly check instead of blindly discarding.
+	 * Make sure that the .got.plt is either completely empty or it
+	 * contains only the three reserved double words.
 	 */
 	.got.plt : {
 		*(.got.plt)
 	}
-	ASSERT(SIZEOF(.got.plt) == 0, "Unexpected GOT/PLT entries detected!")
+	ASSERT(SIZEOF(.got.plt) == 0 || SIZEOF(.got.plt) == 0x18, "Unexpected GOT/PLT entries detected!")
+
+	/*
+	 * Sections that should stay zero sized, which is safer to
+	 * explicitly check instead of blindly discarding.
+	 */
 	.plt : {
 		*(.plt) *(.plt.*) *(.iplt) *(.igot .igot.plt)
 	}

arch/s390/kernel/vmlinux.lds.S

@@ -266,13 +266,18 @@ SECTIONS
 	ELF_DETAILS
 
 	/*
-	 * Sections that should stay zero sized, which is safer to
-	 * explicitly check instead of blindly discarding.
+	 * Make sure that the .got.plt is either completely empty or it
+	 * contains only the three reserved double words.
 	 */
 	.got.plt : {
 		*(.got.plt)
 	}
-	ASSERT(SIZEOF(.got.plt) == 0, "Unexpected GOT/PLT entries detected!")
+	ASSERT(SIZEOF(.got.plt) == 0 || SIZEOF(.got.plt) == 0x18, "Unexpected GOT/PLT entries detected!")
+
+	/*
+	 * Sections that should stay zero sized, which is safer to
+	 * explicitly check instead of blindly discarding.
+	 */
 	.plt : {
 		*(.plt) *(.plt.*) *(.iplt) *(.igot .igot.plt)
 	}