sh: Initial vsyscall page support.

This implements initial support for the vsyscall page on SH.
At the moment we leave it configurable due to having nommu
to support from the same code base. We hook it up for the
signal trampoline return at present, with more to be added
later, once uClibc catches up.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

arch/sh/kernel/Makefile

@@ -9,6 +9,7 @@ obj-y	:= process.o signal.o entry.o traps.o irq.o \
 	io.o io_generic.o sh_ksyms.o syscalls.o
 
 obj-y				+= cpu/ timers/
+obj-$(CONFIG_VSYSCALL)		+= vsyscall/
 
 obj-$(CONFIG_SMP)		+= smp.o
 obj-$(CONFIG_CF_ENABLER)	+= cf-enabler.o

arch/sh/kernel/process.c

@@ -355,7 +355,7 @@ struct task_struct *__switch_to(struct task_struct *prev, struct task_struct *ne
 	else if (next->thread.ubc_pc && next->mm) {
 		int asid = 0;
 #ifdef CONFIG_MMU
-		asid |= next->mm->context & MMU_CONTEXT_ASID_MASK;
+		asid |= next->mm->context.id & MMU_CONTEXT_ASID_MASK;
 #endif
 		ubc_set_tracing(asid, next->thread.ubc_pc);
 	} else {

arch/sh/kernel/signal.c

@@ -8,7 +8,6 @@
  *  SuperH version:  Copyright (C) 1999, 2000  Niibe Yutaka & Kaz Kojima
  *
  */
-
 #include <linux/sched.h>
 #include <linux/mm.h>
 #include <linux/smp.h>
@@ -21,6 +20,7 @@
 #include <linux/unistd.h>
 #include <linux/stddef.h>
 #include <linux/tty.h>
+#include <linux/elf.h>
 #include <linux/personality.h>
 #include <linux/binfmts.h>
 
@@ -29,8 +29,6 @@
 #include <asm/pgtable.h>
 #include <asm/cacheflush.h>
 
-#undef DEBUG
-
 #define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))
 
 /*
@@ -312,6 +310,11 @@ get_sigframe(struct k_sigaction *ka, unsigned long sp, size_t frame_size)
 	return (void __user *)((sp - frame_size) & -8ul);
 }
 
+/* These symbols are defined with the addresses in the vsyscall page.
+   See vsyscall-trapa.S.  */
+extern void __user __kernel_sigreturn;
+extern void __user __kernel_rt_sigreturn;
+
 static int setup_frame(int sig, struct k_sigaction *ka,
 			sigset_t *set, struct pt_regs *regs)
 {
@@ -340,6 +343,10 @@ static int setup_frame(int sig, struct k_sigaction *ka,
 	   already in userspace.  */
 	if (ka->sa.sa_flags & SA_RESTORER) {
 		regs->pr = (unsigned long) ka->sa.sa_restorer;
+#ifdef CONFIG_VSYSCALL
+	} else if (likely(current->mm->context.vdso)) {
+		regs->pr = VDSO_SYM(&__kernel_sigreturn);
+#endif
 	} else {
 		/* Generate return code (system call to sigreturn) */
 		err |= __put_user(MOVW(7), &frame->retcode[0]);
@@ -416,6 +423,10 @@ static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
 	   already in userspace.  */
 	if (ka->sa.sa_flags & SA_RESTORER) {
 		regs->pr = (unsigned long) ka->sa.sa_restorer;
+#ifdef CONFIG_VSYSCALL
+	} else if (likely(current->mm->context.vdso)) {
+		regs->pr = VDSO_SYM(&__kernel_rt_sigreturn);
+#endif
 	} else {
 		/* Generate return code (system call to rt_sigreturn) */
 		err |= __put_user(MOVW(7), &frame->retcode[0]);

arch/sh/kernel/vsyscall/Makefile

@@ -0,0 +1,36 @@
+obj-y += vsyscall.o vsyscall-syscall.o
+
+$(obj)/vsyscall-syscall.o: \
+	$(foreach F,trapa,$(obj)/vsyscall-$F.so)
+
+# Teach kbuild about targets
+targets += $(foreach F,trapa,vsyscall-$F.o vsyscall-$F.so)
+targets += vsyscall-note.o vsyscall.lds
+
+# The DSO images are built using a special linker script
+quiet_cmd_syscall = SYSCALL $@
+      cmd_syscall = $(CC) -nostdlib $(SYSCFLAGS_$(@F)) \
+			   -Wl,-T,$(filter-out FORCE,$^) -o $@
+
+export CPPFLAGS_vsyscall.lds += -P -C -Ush
+
+vsyscall-flags = -shared -s -Wl,-soname=linux-gate.so.1 \
+		$(call ld-option, -Wl$(comma)--hash-style=sysv)
+
+SYSCFLAGS_vsyscall-trapa.so	= $(vsyscall-flags)
+
+$(obj)/vsyscall-trapa.so: \
+$(obj)/vsyscall-%.so: $(src)/vsyscall.lds $(obj)/vsyscall-%.o FORCE
+	$(call if_changed,syscall)
+
+# We also create a special relocatable object that should mirror the symbol
+# table and layout of the linked DSO.  With ld -R we can then refer to
+# these symbols in the kernel code rather than hand-coded addresses.
+extra-y += vsyscall-syms.o
+$(obj)/built-in.o: $(obj)/vsyscall-syms.o
+$(obj)/built-in.o: ld_flags += -R $(obj)/vsyscall-syms.o
+
+SYSCFLAGS_vsyscall-syms.o = -r
+$(obj)/vsyscall-syms.o: $(src)/vsyscall.lds \
+			$(obj)/vsyscall-trapa.o $(obj)/vsyscall-note.o FORCE
+	$(call if_changed,syscall)

arch/sh/kernel/vsyscall/vsyscall-note.S

@@ -0,0 +1,25 @@
+/*
+ * This supplies .note.* sections to go into the PT_NOTE inside the vDSO text.
+ * Here we can supply some information useful to userland.
+ */
+
+#include <linux/uts.h>
+#include <linux/version.h>
+
+#define ASM_ELF_NOTE_BEGIN(name, flags, vendor, type)			      \
+	.section name, flags;						      \
+	.balign 4;							      \
+	.long 1f - 0f;		/* name length */			      \
+	.long 3f - 2f;		/* data length */			      \
+	.long type;		/* note type */				      \
+0:	.asciz vendor;		/* vendor name */			      \
+1:	.balign 4;							      \
+2:
+
+#define ASM_ELF_NOTE_END						      \
+3:	.balign 4;		/* pad out section */			      \
+	.previous
+
+	ASM_ELF_NOTE_BEGIN(".note.kernel-version", "a", UTS_SYSNAME, 0)
+	.long LINUX_VERSION_CODE
+	ASM_ELF_NOTE_END

arch/sh/kernel/vsyscall/vsyscall-sigreturn.S

@@ -0,0 +1,39 @@
+#include <asm/unistd.h>
+
+	.text
+	.balign 32
+	.globl __kernel_sigreturn
+	.type __kernel_sigreturn,@function
+__kernel_sigreturn:
+.LSTART_sigreturn:
+	mov.w	1f, r3
+	trapa	#0x10
+	or	r0, r0
+	or	r0, r0
+	or	r0, r0
+	or	r0, r0
+	or	r0, r0
+
+1:	.short	__NR_sigreturn
+.LEND_sigreturn:
+	.size __kernel_sigreturn,.-.LSTART_sigreturn
+
+	.balign 32
+	.globl __kernel_rt_sigreturn
+	.type __kernel_rt_sigreturn,@function
+__kernel_rt_sigreturn:
+.LSTART_rt_sigreturn:
+	mov.w	1f, r3
+	trapa	#0x10
+	or	r0, r0
+	or	r0, r0
+	or	r0, r0
+	or	r0, r0
+	or	r0, r0
+
+1:	.short	__NR_rt_sigreturn
+.LEND_rt_sigreturn:
+	.size __kernel_rt_sigreturn,.-.LSTART_rt_sigreturn
+
+	.section .eh_frame,"a",@progbits
+	.previous

arch/sh/kernel/vsyscall/vsyscall-syscall.S

@@ -0,0 +1,10 @@
+#include <linux/init.h>
+
+__INITDATA
+
+	.globl vsyscall_trapa_start, vsyscall_trapa_end
+vsyscall_trapa_start:
+	.incbin "arch/sh/kernel/vsyscall/vsyscall-trapa.so"
+vsyscall_trapa_end:
+
+__FINIT

arch/sh/kernel/vsyscall/vsyscall-trapa.S

@@ -0,0 +1,42 @@
+	.text
+	.globl __kernel_vsyscall
+	.type __kernel_vsyscall,@function
+__kernel_vsyscall:
+.LSTART_vsyscall:
+	/* XXX: We'll have to do something here once we opt to use the vDSO
+	 * page for something other than the signal trampoline.. as well as
+	 * fill out .eh_frame -- PFM. */
+.LEND_vsyscall:
+	.size __kernel_vsyscall,.-.LSTART_vsyscall
+	.previous
+
+	.section .eh_frame,"a",@progbits
+.LCIE:
+	.ualong	.LCIE_end - .LCIE_start
+.LCIE_start:
+	.ualong	0		/* CIE ID */
+	.byte	0x1		/* Version number */
+	.string	"zRS"		/* NUL-terminated augmentation string */
+	.uleb128 0x1		/* Code alignment factor */
+	.sleb128 -4		/* Data alignment factor */
+	.byte	0x11		/* Return address register column */
+				/* Augmentation length and data (none) */
+	.byte	0xc		/* DW_CFA_def_cfa */
+	.uleb128 0xf		/* r15 */
+	.uleb128 0x0		/* offset 0 */
+
+	.align 2
+.LCIE_end:
+
+	.ualong	.LFDE_end-.LFDE_start	/* Length FDE */
+.LFDE_start:
+	.ualong	.LCIE			/* CIE pointer */
+	.ualong	.LSTART_vsyscall-.	/* start address */
+	.ualong	.LEND_vsyscall-.LSTART_vsyscall
+	.uleb128 0
+	.align 2
+.LFDE_end:
+	.previous
+
+/* Get the common code for the sigreturn entry points */
+#include "vsyscall-sigreturn.S"

arch/sh/kernel/vsyscall/vsyscall.c

@@ -0,0 +1,150 @@
+/*
+ * arch/sh/kernel/vsyscall.c
+ *
+ *  Copyright (C) 2006 Paul Mundt
+ *
+ * vDSO randomization
+ * Copyright(C) 2005-2006, Red Hat, Inc., Ingo Molnar
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/gfp.h>
+#include <linux/module.h>
+#include <linux/elf.h>
+
+/*
+ * Should the kernel map a VDSO page into processes and pass its
+ * address down to glibc upon exec()?
+ */
+unsigned int __read_mostly vdso_enabled = 1;
+EXPORT_SYMBOL_GPL(vdso_enabled);
+
+static int __init vdso_setup(char *s)
+{
+	vdso_enabled = simple_strtoul(s, NULL, 0);
+	return 1;
+}
+__setup("vdso=", vdso_setup);
+
+/*
+ * These symbols are defined by vsyscall.o to mark the bounds
+ * of the ELF DSO images included therein.
+ */
+extern const char vsyscall_trapa_start, vsyscall_trapa_end;
+static void *syscall_page;
+
+int __init vsyscall_init(void)
+{
+	syscall_page = (void *)get_zeroed_page(GFP_ATOMIC);
+
+	/*
+	 * XXX: Map this page to a fixmap entry if we get around
+	 * to adding the page to ELF core dumps
+	 */
+
+	memcpy(syscall_page,
+	       &vsyscall_trapa_start,
+	       &vsyscall_trapa_end - &vsyscall_trapa_start);
+
+	return 0;
+}
+
+static struct page *syscall_vma_nopage(struct vm_area_struct *vma,
+				       unsigned long address, int *type)
+{
+	unsigned long offset = address - vma->vm_start;
+	struct page *page;
+
+	if (address < vma->vm_start || address > vma->vm_end)
+		return NOPAGE_SIGBUS;
+
+	page = virt_to_page(syscall_page + offset);
+
+	get_page(page);
+
+	return page;
+}
+
+/* Prevent VMA merging */
+static void syscall_vma_close(struct vm_area_struct *vma)
+{
+}
+
+static struct vm_operations_struct syscall_vm_ops = {
+	.nopage	= syscall_vma_nopage,
+	.close	= syscall_vma_close,
+};
+
+/* Setup a VMA at program startup for the vsyscall page */
+int arch_setup_additional_pages(struct linux_binprm *bprm,
+				int executable_stack)
+{
+	struct vm_area_struct *vma;
+	struct mm_struct *mm = current->mm;
+	unsigned long addr;
+	int ret;
+
+	down_write(&mm->mmap_sem);
+	addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
+	if (IS_ERR_VALUE(addr)) {
+		ret = addr;
+		goto up_fail;
+	}
+
+	vma = kmem_cache_zalloc(vm_area_cachep, SLAB_KERNEL);
+	if (!vma) {
+		ret = -ENOMEM;
+		goto up_fail;
+	}
+
+	vma->vm_start = addr;
+	vma->vm_end = addr + PAGE_SIZE;
+	/* MAYWRITE to allow gdb to COW and set breakpoints */
+	vma->vm_flags = VM_READ|VM_EXEC|VM_MAYREAD|VM_MAYEXEC|VM_MAYWRITE;
+	vma->vm_flags |= mm->def_flags;
+	vma->vm_page_prot = protection_map[vma->vm_flags & 7];
+	vma->vm_ops = &syscall_vm_ops;
+	vma->vm_mm = mm;
+
+	ret = insert_vm_struct(mm, vma);
+	if (unlikely(ret)) {
+		kmem_cache_free(vm_area_cachep, vma);
+		goto up_fail;
+	}
+
+	current->mm->context.vdso = (void *)addr;
+
+	mm->total_vm++;
+up_fail:
+	up_write(&mm->mmap_sem);
+	return ret;
+}
+
+const char *arch_vma_name(struct vm_area_struct *vma)
+{
+	if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
+		return "[vdso]";
+
+	return NULL;
+}
+
+struct vm_area_struct *get_gate_vma(struct task_struct *task)
+{
+	return NULL;
+}
+
+int in_gate_area(struct task_struct *task, unsigned long address)
+{
+	return 0;
+}
+
+int in_gate_area_no_task(unsigned long address)
+{
+	return 0;
+}