[PATCH 03/11] s390: vmlinux.lds.S: Explicitly handle '.got' and '.plt' sections

Nathan Chancellor
2024-02-08T00:15:07Z

When building with CONFIG_LD_ORPHAN_WARN after selecting
CONFIG_ARCH_HAS_LD_ORPHAN_WARN, there are a lot of warnings around the
GOT and PLT sections:

s390-linux-ld: warning: orphan section `.plt' from `arch/s390/kernel/head64.o' being placed in section `.plt'
s390-linux-ld: warning: orphan section `.got' from `arch/s390/kernel/head64.o' being placed in section `.got'
s390-linux-ld: warning: orphan section `.got.plt' from `arch/s390/kernel/head64.o' being placed in section `.got.plt'
s390-linux-ld: warning: orphan section `.iplt' from `arch/s390/kernel/head64.o' being placed in section `.iplt'
s390-linux-ld: warning: orphan section `.igot.plt' from `arch/s390/kernel/head64.o' being placed in section `.igot.plt'

s390-linux-ld: warning: orphan section `.iplt' from `arch/s390/boot/head.o' being placed in section `.iplt'
s390-linux-ld: warning: orphan section `.igot.plt' from `arch/s390/boot/head.o' being placed in section `.igot.plt'
s390-linux-ld: warning: orphan section `.got' from `arch/s390/boot/head.o' being placed in section `.got'

Currently, only the '.got' section is actually emitted in the final
binary. In a manner similar to other architectures, put the '.got'
section near the '.data' section and coalesce the PLT sections,
checking that the final section is zero sized, which is a safe/tested
approach versus full discard.

Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---
arch/s390/boot/vmlinux.lds.S | 19 +++++++++++++++++++
arch/s390/kernel/vmlinux.lds.S | 19 +++++++++++++++++++
2 files changed, 38 insertions(+)

diff --git a/arch/s390/boot/vmlinux.lds.S b/arch/s390/boot/vmlinux.lds.S
index 389df0e0d9e5..4aa2f340c8d9 100644
--- a/arch/s390/boot/vmlinux.lds.S
+++ b/arch/s390/boot/vmlinux.lds.S
@@ -39,6 +39,9 @@ SECTIONS
*(.rodata.*)
_erodata = . ;
}
+ .got : {
+ *(.got)
+ }
NOTES
.data : {
_data = . ;
@@ -118,6 +121,22 @@ SECTIONS
}
_end = .;

+ /*
+ * Sections that should stay zero sized, which is safer to
+ * explicitly check instead of blindly discarding.
+ */
+ .got.plt : {
+ *(.got.plt)
+ }
+ ASSERT(SIZEOF(.got.plt) == 0, "Unexpected GOT/PLT entries detected!")
+ .plt : {
+ *(.plt)
+ *(.plt.*)
+ *(.iplt)
+ *(.igot .igot.plt)
+ }
+ ASSERT(SIZEOF(.plt) == 0, "Unexpected run-time procedure linkages detected!")
+
/* Sections to be discarded */
/DISCARD/ : {
*(.eh_frame)
diff --git a/arch/s390/kernel/vmlinux.lds.S b/arch/s390/kernel/vmlinux.lds.S
index d231a3faf981..661a487a3048 100644
--- a/arch/s390/kernel/vmlinux.lds.S
+++ b/arch/s390/kernel/vmlinux.lds.S
@@ -62,6 +62,9 @@ SECTIONS
.data.rel.ro : {
*(.data.rel.ro .data.rel.ro.*)
}
+ .got : {
+ *(.got)
+ }

. = ALIGN(PAGE_SIZE);
_sdata = .; /* Start of data section */
@@ -241,6 +244,22 @@ SECTIONS
DWARF_DEBUG
ELF_DETAILS

+ /*
+ * Sections that should stay zero sized, which is safer to
+ * explicitly check instead of blindly discarding.
+ */
+ .got.plt : {
+ *(.got.plt)
+ }
+ ASSERT(SIZEOF(.got.plt) == 0, "Unexpected GOT/PLT entries detected!")
+ .plt : {
+ *(.plt)
+ *(.plt.*)
+ *(.iplt)
+ *(.igot .igot.plt)
+ }
+ ASSERT(SIZEOF(.plt) == 0, "Unexpected run-time procedure linkages detected!")
+
/* Sections to be discarded */
DISCARDS
/DISCARD/ : {

--
2.43.0