x86/vdso: Allocate vvar page from C code

Allocate the vvar page through the standard union vdso_data_store
and remove the custom linker script logic.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20241010-vdso-generic-base-v1-14-b64f0842d512@linutronix.de

Author: t-8ch

arch/x86/entry/vdso/vma.c

@@ -20,25 +20,19 @@
 #include <asm/vgtod.h>
 #include <asm/proto.h>
 #include <asm/vdso.h>
-#include <asm/vvar.h>
 #include <asm/tlb.h>
 #include <asm/page.h>
 #include <asm/desc.h>
 #include <asm/cpufeature.h>
 #include <clocksource/hyperv_timer.h>
 
-#undef _ASM_X86_VVAR_H
-#define EMIT_VVAR(name, offset)	\
-	const size_t name ## _offset = offset;
-#include <asm/vvar.h>
-
 struct vdso_data *arch_get_vdso_data(void *vvar_page)
 {
-	return (struct vdso_data *)(vvar_page + _vdso_data_offset);
+	return (struct vdso_data *)vvar_page;
 }
-#undef EMIT_VVAR
 
-DEFINE_VVAR(struct vdso_data, _vdso_data);
+static union vdso_data_store vdso_data_store __page_aligned_data;
+struct vdso_data *vdso_data = vdso_data_store.data;
 
 unsigned int vclocks_used __read_mostly;
 
@@ -153,7 +147,7 @@ static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
 	if (sym_offset == image->sym_vvar_page) {
 		struct page *timens_page = find_timens_vvar_page(vma);
 
-		pfn = __pa_symbol(&__vvar_page) >> PAGE_SHIFT;
+		pfn = __pa_symbol(vdso_data) >> PAGE_SHIFT;
 
 		/*
 		 * If a task belongs to a time namespace then a namespace
@@ -200,7 +194,7 @@ static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
 		if (!timens_page)
 			return VM_FAULT_SIGBUS;
 
-		pfn = __pa_symbol(&__vvar_page) >> PAGE_SHIFT;
+		pfn = __pa_symbol(vdso_data) >> PAGE_SHIFT;
 		return vmf_insert_pfn(vma, vmf->address, pfn);
 	}
 

arch/x86/include/asm/vdso/vsyscall.h

@@ -8,20 +8,22 @@
 #include <asm/vgtod.h>
 #include <asm/vvar.h>
 
+extern struct vdso_data *vdso_data;
+
 /*
  * Update the vDSO data page to keep in sync with kernel timekeeping.
  */
 static __always_inline
 struct vdso_data *__x86_get_k_vdso_data(void)
 {
-	return _vdso_data;
+	return vdso_data;
 }
 #define __arch_get_k_vdso_data __x86_get_k_vdso_data
 
 static __always_inline
 struct vdso_rng_data *__x86_get_k_vdso_rng_data(void)
 {
-	return (void *)&__vvar_page + __VDSO_RND_DATA_OFFSET;
+	return (void *)vdso_data + __VDSO_RND_DATA_OFFSET;
 }
 #define __arch_get_k_vdso_rng_data __x86_get_k_vdso_rng_data
 

arch/x86/kernel/vmlinux.lds.S

@@ -193,29 +193,6 @@ SECTIONS
 
 	ORC_UNWIND_TABLE
 
-	. = ALIGN(PAGE_SIZE);
-	__vvar_page = .;
-
-	.vvar : AT(ADDR(.vvar) - LOAD_OFFSET) {
-		/* work around gold bug 13023 */
-		__vvar_beginning_hack = .;
-
-		/* Place all vvars at the offsets in asm/vvar.h. */
-#define EMIT_VVAR(name, offset)				\
-		. = __vvar_beginning_hack + offset;	\
-		*(.vvar_ ## name)
-#include <asm/vvar.h>
-#undef EMIT_VVAR
-
-		/*
-		 * Pad the rest of the page with zeros.  Otherwise the loader
-		 * can leave garbage here.
-		 */
-		. = __vvar_beginning_hack + PAGE_SIZE;
-	} :data
-
-	. = ALIGN(__vvar_page + PAGE_SIZE, PAGE_SIZE);
-
 	/* Init code and data - will be freed after init */
 	. = ALIGN(PAGE_SIZE);
 	.init.begin : AT(ADDR(.init.begin) - LOAD_OFFSET) {

arch/x86/tools/relocs.c

@@ -89,7 +89,6 @@ static const char * const	sym_regex_kernel[S_NSYMTYPES] = {
 	"init_per_cpu__.*|"
 	"__end_rodata_hpage_align|"
 #endif
-	"__vvar_page|"
 	"_end)$"
 };