Initial building of the vdso.

Not actually integrating with the kernel yet.

modules.yaml

@@ -9,6 +9,7 @@ modules:
             - elf
             - initrd
             - kutil
+            - vdso
         includes:
             - src/kernel
         source:
@@ -64,6 +65,16 @@ modules:
             - src/boot/reloc.cpp
             - src/boot/utility.cpp
 
+    vdso:
+        kind: exe
+        target: host
+        output: libvdso.so
+        extra:
+            - src/arch/x86_64/vdso.ld
+        source:
+            - src/vdso/syscalls.cpp
+            - src/vdso/overrides.cpp
+
     nulldrv:
         kind: exe
         target: user

scripts/templates/build.ninja.j2

@@ -43,6 +43,7 @@ ccflags = $
     $warnflags
 
 asflags = $
+    -I${srcroot}/src/include $
     -DVERSION_MAJOR={{ version_major }} $
     -DVERSION_MINOR={{ version_minor }} $
     -DVERSION_PATCH={{ version_patch }} $

scripts/templates/exe.vdso.j2

@@ -0,0 +1,9 @@
+{% extends "exe.default.j2" %}
+{% block variables %}
+{{ super() }}
+ccflags = $ccflags -fPIC -mcmodel=large
+ldflags = $ldflags -shared -znotext -T ${srcroot}/src/arch/x86_64/vdso.ld
+{% endblock %}
+
+# vim: ft=ninja et ts=4 sts=4 sw=4
+

src/arch/x86_64/vdso.ld

@@ -0,0 +1,67 @@
+PHDRS {
+	rodata PT_LOAD FLAGS(4) FILEHDR PHDRS ;
+	text PT_LOAD FLAGS(5) ;
+	dynamic PT_DYNAMIC FLAGS(4) ;
+	note PT_NOTE ;
+	eh_frame PT_GNU_EH_FRAME ;
+}
+
+SECTIONS {
+	. = SIZEOF_HEADERS;
+
+	/DISCARD/ : {
+		*(.got*)
+		*(.plt*)
+		*(.note.*)
+		*(.hash*)
+	}
+
+	.illegal.relocations : {
+		*(.rel*)
+	}
+
+	.illegal.writeable : {
+		*(.data*)
+		*(.bss*)
+	}
+
+	.rodata : {
+		*(.rodata*)
+	} :rodata
+
+	.dynamic : {
+		*(.dynamic)
+	} :dynamic
+
+	.dynsym : {
+		*(.dynsym*)
+	} :rodata :dynamic
+
+	.dynstr : {
+		*(.dynstr*)
+	} :rodata :dynamic
+
+	.gnu.hash : {
+		*(.gnu.hash*)
+	} :rodata
+
+	.eh_frame_hdr : {
+		__eh_frame_start = .;
+		KEEP(*(.eh_frame))
+		__eh_frame_end = .;
+
+		KEEP(*(.eh_frame_hdr))
+	} :eh_frame
+
+	.text ALIGN(0x1000) : {
+		*(.text*)
+		*(.init*)
+		*(.fini*)
+		. = ALIGN(0x1000);
+	} :text
+
+	ASSERT(SIZEOF(.illegal.relocations) == 0,
+			"Code has introduced relocations into the VDSO")
+	ASSERT(SIZEOF(.illegal.writeable) == 0,
+			"Code has introduced writeable data into the VDSO")
+}

src/include/syscalls.inc

@@ -2,8 +2,8 @@ SYSCALL(0x00, object_noop,      void)
 SYSCALL(0x01, object_wait,      j6_handle_t, j6_signal_t, j6_signal_t *)
 
 SYSCALL(0x11, process_exit,     int64_t)
-SYSCALL(0x12, process_fork,     pid_t*)
-SYSCALL(0x13, process_getpid,   pid_t*)
+//SYSCALL(0x12, process_fork,     j6_koid_t*)
+//SYSCALL(0x13, process_getpid,   j6_koid_t*)
 SYSCALL(0x14, process_log,      const char *)
 SYSCALL(0x15, process_pause,    void)
 SYSCALL(0x16, process_sleep,    uint64_t)

src/vdso/overrides.cpp

@@ -0,0 +1,17 @@
+#include <j6/errors.h>
+#include <j6/types.h>
+#include "vdso_internal.h"
+
+extern "C" {
+
+j6_status_t j6_object_noop() {
+	// Skip the kernel
+	return j6_status_ok;
+}
+
+// An example of overriding a weak default symbol with a custom function
+j6_status_t j6_object_wait(j6_handle_t target, j6_signal_t signals, j6_signal_t *triggered) {
+	return __sys_j6_object_wait(target, signals, triggered);
+}
+
+}

src/vdso/syscalls.cpp

@@ -0,0 +1,17 @@
+#include <j6/errors.h>
+#include <j6/types.h>
+#include "vdso_internal.h"
+
+#define SYSCALL(num, name, ...) \
+	j6_status_t __sys_j6_##name (__VA_ARGS__) { \
+		j6_status_t result = 0; \
+		__asm__ __volatile__ ( "syscall" : "=a"(result) : "a"(num) ); \
+		return result; \
+	} \
+	j6_status_t j6_ ## name(__VA_ARGS__) __weak_alias("__sys_j6_" #name);
+
+extern "C" {
+#include "syscalls.inc"
+}
+
+#undef SYSCALL

src/vdso/vdso_internal.h

@@ -0,0 +1,16 @@
+#pragma once
+/// \file vdso_internal.h
+/// VDSO syscall forward-declares and linker utils
+
+#define __weak_alias(name) __attribute__((weak, alias(name)));
+#define __local __attribute__((__visibility__("hidden")))
+
+#define SYSCALL(num, name, ...) \
+	j6_status_t __sys_j6_ ## name (__VA_ARGS__) __local; \
+
+extern "C" {
+#include "syscalls.inc"
+}
+
+#undef SYSCALL
+