Klib linker scripts: use ELF segments with appropriate permissions

This change amends the linker scripts for the klibs so that each
klib ELF file has 3 segments: a text segment with read and execute
permissions, a data segment with read-only permissions, and a data
segment with read/write permissions. This avoids mapping an entire
klib image with both write and execute permissions when the kernel
loads a klib.
In addition, the SECTIONS directive in the linker scripts has been
fixed so that all the read-only input sections are mapped to the
.text and .rodata output sections; this decreases the size of the
klib ELF files.

src/aarch64/klib.lds

@@ -2,14 +2,23 @@ OUTPUT_FORMAT("elf64-littleaarch64")
 
 ENTRY(init)
 
+PHDRS
+{
+        text PT_LOAD FLAGS(5);          /* R E */
+        rodata PT_LOAD FLAGS(4);        /* R */
+        data PT_LOAD FLAGS(6);          /* RW */
+}
+
 SECTIONS
 {
         . = SIZEOF_HEADERS;
-        .text : { *(.text)}
-        .rodata : { *(.rodata)}
+        .text : { *(.text) *(.text.*) } :text
+        . = ALIGN(4096);
+        .rodata : { *(.rodata) *(.rodata.*) } :rodata
 
-        .data ALIGN(4096) : { *(.data) *(.data.*) }
-        .bss ALIGN(32): { *(.bss) *(.bss.*) }
+        . = ALIGN(4096);
+        .data : { *(.data) *(.data.*) } :data
+        .bss : { *(.bss) *(.bss.*) } :data
 
         /DISCARD/ : { *(.interp) }
 }

src/riscv64/klib.lds

@@ -2,14 +2,23 @@ OUTPUT_FORMAT("elf64-littleriscv")
 
 ENTRY(init)
 
+PHDRS
+{
+        text PT_LOAD FLAGS(5);          /* R E */
+        rodata PT_LOAD FLAGS(4);        /* R */
+        data PT_LOAD FLAGS(6);          /* RW */
+}
+
 SECTIONS
 {
         . = SIZEOF_HEADERS;
-        .text : { *(.text)}
-        .rodata : { *(.rodata)}
+        .text : { *(.text) *(.text.*) } :text
+        . = ALIGN(4096);
+        .rodata : { *(.rodata) *(.rodata.*) } :rodata
 
-        .data ALIGN(4096) : { *(.data) *(.data.*) }
-        .bss ALIGN(32): { *(.bss) *(.bss.*) }
+        . = ALIGN(4096);
+        .data : { *(.data) *(.data.*) } :data
+        .bss : { *(.bss) *(.bss.*) } :data
 
         /DISCARD/ : { *(.interp) }
 }

src/x86_64/klib.lds

@@ -2,14 +2,23 @@ OUTPUT_FORMAT("elf64-x86-64")
 
 ENTRY(init)
 
+PHDRS
+{
+        text PT_LOAD FLAGS(5);          /* R E */
+        rodata PT_LOAD FLAGS(4);        /* R */
+        data PT_LOAD FLAGS(6);          /* RW */
+}
+
 SECTIONS
 {
         . = SIZEOF_HEADERS;
-        .text : { *(.text)}
-        .rodata : { *(.rodata)}
+        .text : { *(.text) *(.text.*) } :text
+        . = ALIGN(4096);
+        .rodata : { *(.rodata) *(.rodata.*) } :rodata
 
-        .data ALIGN(4096) : { *(.data) *(.data.*) }
-        .bss ALIGN(32): { *(.bss) *(.bss.*) }
+        . = ALIGN(4096);
+        .data : { *(.data) *(.data.*) } :data
+        .bss : { *(.bss) *(.bss.*) } :data
 
         /DISCARD/ : { *(.interp) }
 }