x86 vDSO: vdso32 setup

This moves arch/x86/kernel/sysenter_32.c to arch/x86/vdso/vdso32-setup.c,
keeping all the code relating only to vDSO magic in the vdso/ subdirectory.
This is a pure renaming, but it paves the way to consolidating the code for
dealing with 32-bit vDSOs across CONFIG_X86_32 and CONFIG_IA32_EMULATION.

Signed-off-by: Roland McGrath <roland@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

2 files changed, 345 insertions, 1 deletions

diff --git a/arch/x86/vdso/Makefile b/arch/x86/vdso/Makefile
index ca2aabf..1efe785 100644
--- a/arch/x86/vdso/Makefile
+++ b/arch/x86/vdso/Makefile
@@ -15,7 +15,7 @@ vobjs-y := vdso-note.o vclock_gettime.o vgetcpu.o vvar.o
 
 # files to link into kernel
 obj-$(VDSO64-y)			+= vma.o vdso.o
-obj-$(CONFIG_X86_32)		+= vdso32.o
+obj-$(CONFIG_X86_32)		+= vdso32.o vdso32-setup.o
 
 vobjs := $(foreach F,$(vobjs-y),$(obj)/$F)
 
diff --git a/arch/x86/vdso/vdso32-setup.c b/arch/x86/vdso/vdso32-setup.c
new file mode 100644
index 0000000..85c52d2
--- /dev/null
+++ b/arch/x86/vdso/vdso32-setup.c
@@ -0,0 +1,344 @@
+/*
+ * (C) Copyright 2002 Linus Torvalds
+ * Portions based on the vdso-randomization code from exec-shield:
+ * Copyright(C) 2005-2006, Red Hat, Inc., Ingo Molnar
+ *
+ * This file contains the needed initializations to support sysenter.
+ */
+
+#include <linux/init.h>
+#include <linux/smp.h>
+#include <linux/thread_info.h>
+#include <linux/sched.h>
+#include <linux/gfp.h>
+#include <linux/string.h>
+#include <linux/elf.h>
+#include <linux/mm.h>
+#include <linux/err.h>
+#include <linux/module.h>
+
+#include <asm/cpufeature.h>
+#include <asm/msr.h>
+#include <asm/pgtable.h>
+#include <asm/unistd.h>
+#include <asm/elf.h>
+#include <asm/tlbflush.h>
+#include <asm/vdso.h>
+
+enum {
+	VDSO_DISABLED = 0,
+	VDSO_ENABLED = 1,
+	VDSO_COMPAT = 2,
+};
+
+#ifdef CONFIG_COMPAT_VDSO
+#define VDSO_DEFAULT	VDSO_COMPAT
+#else
+#define VDSO_DEFAULT	VDSO_ENABLED
+#endif
+
+/*
+ * Should the kernel map a VDSO page into processes and pass its
+ * address down to glibc upon exec()?
+ */
+unsigned int __read_mostly vdso_enabled = VDSO_DEFAULT;
+
+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);
+
+extern asmlinkage void sysenter_entry(void);
+
+static __init void reloc_symtab(Elf32_Ehdr *ehdr,
+				unsigned offset, unsigned size)
+{
+	Elf32_Sym *sym = (void *)ehdr + offset;
+	unsigned nsym = size / sizeof(*sym);
+	unsigned i;
+
+	for(i = 0; i < nsym; i++, sym++) {
+		if (sym->st_shndx == SHN_UNDEF ||
+		    sym->st_shndx == SHN_ABS)
+			continue;  /* skip */
+
+		if (sym->st_shndx > SHN_LORESERVE) {
+			printk(KERN_INFO "VDSO: unexpected st_shndx %x\n",
+			       sym->st_shndx);
+			continue;
+		}
+
+		switch(ELF_ST_TYPE(sym->st_info)) {
+		case STT_OBJECT:
+		case STT_FUNC:
+		case STT_SECTION:
+		case STT_FILE:
+			sym->st_value += VDSO_HIGH_BASE;
+		}
+	}
+}
+
+static __init void reloc_dyn(Elf32_Ehdr *ehdr, unsigned offset)
+{
+	Elf32_Dyn *dyn = (void *)ehdr + offset;
+
+	for(; dyn->d_tag != DT_NULL; dyn++)
+		switch(dyn->d_tag) {
+		case DT_PLTGOT:
+		case DT_HASH:
+		case DT_STRTAB:
+		case DT_SYMTAB:
+		case DT_RELA:
+		case DT_INIT:
+		case DT_FINI:
+		case DT_REL:
+		case DT_DEBUG:
+		case DT_JMPREL:
+		case DT_VERSYM:
+		case DT_VERDEF:
+		case DT_VERNEED:
+		case DT_ADDRRNGLO ... DT_ADDRRNGHI:
+			/* definitely pointers needing relocation */
+			dyn->d_un.d_ptr += VDSO_HIGH_BASE;
+			break;
+
+		case DT_ENCODING ... OLD_DT_LOOS-1:
+		case DT_LOOS ... DT_HIOS-1:
+			/* Tags above DT_ENCODING are pointers if
+			   they're even */
+			if (dyn->d_tag >= DT_ENCODING &&
+			    (dyn->d_tag & 1) == 0)
+				dyn->d_un.d_ptr += VDSO_HIGH_BASE;
+			break;
+
+		case DT_VERDEFNUM:
+		case DT_VERNEEDNUM:
+		case DT_FLAGS_1:
+		case DT_RELACOUNT:
+		case DT_RELCOUNT:
+		case DT_VALRNGLO ... DT_VALRNGHI:
+			/* definitely not pointers */
+			break;
+
+		case OLD_DT_LOOS ... DT_LOOS-1:
+		case DT_HIOS ... DT_VALRNGLO-1:
+		default:
+			if (dyn->d_tag > DT_ENCODING)
+				printk(KERN_INFO "VDSO: unexpected DT_tag %x\n",
+				       dyn->d_tag);
+			break;
+		}
+}
+
+static __init void relocate_vdso(Elf32_Ehdr *ehdr)
+{
+	Elf32_Phdr *phdr;
+	Elf32_Shdr *shdr;
+	int i;
+
+	BUG_ON(memcmp(ehdr->e_ident, ELFMAG, 4) != 0 ||
+	       !elf_check_arch(ehdr) ||
+	       ehdr->e_type != ET_DYN);
+
+	ehdr->e_entry += VDSO_HIGH_BASE;
+
+	/* rebase phdrs */
+	phdr = (void *)ehdr + ehdr->e_phoff;
+	for (i = 0; i < ehdr->e_phnum; i++) {
+		phdr[i].p_vaddr += VDSO_HIGH_BASE;
+
+		/* relocate dynamic stuff */
+		if (phdr[i].p_type == PT_DYNAMIC)
+			reloc_dyn(ehdr, phdr[i].p_offset);
+	}
+
+	/* rebase sections */
+	shdr = (void *)ehdr + ehdr->e_shoff;
+	for(i = 0; i < ehdr->e_shnum; i++) {
+		if (!(shdr[i].sh_flags & SHF_ALLOC))
+			continue;
+
+		shdr[i].sh_addr += VDSO_HIGH_BASE;
+
+		if (shdr[i].sh_type == SHT_SYMTAB ||
+		    shdr[i].sh_type == SHT_DYNSYM)
+			reloc_symtab(ehdr, shdr[i].sh_offset,
+				     shdr[i].sh_size);
+	}
+}
+
+void enable_sep_cpu(void)
+{
+	int cpu = get_cpu();
+	struct tss_struct *tss = &per_cpu(init_tss, cpu);
+
+	if (!boot_cpu_has(X86_FEATURE_SEP)) {
+		put_cpu();
+		return;
+	}
+
+	tss->x86_tss.ss1 = __KERNEL_CS;
+	tss->x86_tss.esp1 = sizeof(struct tss_struct) + (unsigned long) tss;
+	wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
+	wrmsr(MSR_IA32_SYSENTER_ESP, tss->x86_tss.esp1, 0);
+	wrmsr(MSR_IA32_SYSENTER_EIP, (unsigned long) sysenter_entry, 0);
+	put_cpu();	
+}
+
+static struct vm_area_struct gate_vma;
+
+static int __init gate_vma_init(void)
+{
+	gate_vma.vm_mm = NULL;
+	gate_vma.vm_start = FIXADDR_USER_START;
+	gate_vma.vm_end = FIXADDR_USER_END;
+	gate_vma.vm_flags = VM_READ | VM_MAYREAD | VM_EXEC | VM_MAYEXEC;
+	gate_vma.vm_page_prot = __P101;
+	/*
+	 * Make sure the vDSO gets into every core dump.
+	 * Dumping its contents makes post-mortem fully interpretable later
+	 * without matching up the same kernel and hardware config to see
+	 * what PC values meant.
+	 */
+	gate_vma.vm_flags |= VM_ALWAYSDUMP;
+	return 0;
+}
+
+/*
+ * These symbols are defined by vsyscall.o to mark the bounds
+ * of the ELF DSO images included therein.
+ */
+extern const char vsyscall_int80_start, vsyscall_int80_end;
+extern const char vsyscall_sysenter_start, vsyscall_sysenter_end;
+static struct page *syscall_pages[1];
+
+static void map_compat_vdso(int map)
+{
+	static int vdso_mapped;
+
+	if (map == vdso_mapped)
+		return;
+
+	vdso_mapped = map;
+
+	__set_fixmap(FIX_VDSO, page_to_pfn(syscall_pages[0]) << PAGE_SHIFT,
+		     map ? PAGE_READONLY_EXEC : PAGE_NONE);
+
+	/* flush stray tlbs */
+	flush_tlb_all();
+}
+
+int __init sysenter_setup(void)
+{
+	void *syscall_page = (void *)get_zeroed_page(GFP_ATOMIC);
+	const void *vsyscall;
+	size_t vsyscall_len;
+
+	syscall_pages[0] = virt_to_page(syscall_page);
+
+	gate_vma_init();
+
+	printk("Compat vDSO mapped to %08lx.\n", __fix_to_virt(FIX_VDSO));
+
+	if (!boot_cpu_has(X86_FEATURE_SEP)) {
+		vsyscall = &vsyscall_int80_start;
+		vsyscall_len = &vsyscall_int80_end - &vsyscall_int80_start;
+	} else {
+		vsyscall = &vsyscall_sysenter_start;
+		vsyscall_len = &vsyscall_sysenter_end - &vsyscall_sysenter_start;
+	}
+
+	memcpy(syscall_page, vsyscall, vsyscall_len);
+	relocate_vdso(syscall_page);
+
+	return 0;
+}
+
+/* Setup a VMA at program startup for the vsyscall page */
+int arch_setup_additional_pages(struct linux_binprm *bprm, int exstack)
+{
+	struct mm_struct *mm = current->mm;
+	unsigned long addr;
+	int ret = 0;
+	bool compat;
+
+	down_write(&mm->mmap_sem);
+
+	/* Test compat mode once here, in case someone
+	   changes it via sysctl */
+	compat = (vdso_enabled == VDSO_COMPAT);
+
+	map_compat_vdso(compat);
+
+	if (compat)
+		addr = VDSO_HIGH_BASE;
+	else {
+		addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
+		if (IS_ERR_VALUE(addr)) {
+			ret = addr;
+			goto up_fail;
+		}
+
+		/*
+		 * MAYWRITE to allow gdb to COW and set breakpoints
+		 *
+		 * Make sure the vDSO gets into every core dump.
+		 * Dumping its contents makes post-mortem fully
+		 * interpretable later without matching up the same
+		 * kernel and hardware config to see what PC values
+		 * meant.
+		 */
+		ret = install_special_mapping(mm, addr, PAGE_SIZE,
+					      VM_READ|VM_EXEC|
+					      VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
+					      VM_ALWAYSDUMP,
+					      syscall_pages);
+
+		if (ret)
+			goto up_fail;
+	}
+
+	current->mm->context.vdso = (void *)addr;
+	current_thread_info()->sysenter_return =
+		VDSO32_SYMBOL(addr, SYSENTER_RETURN);
+
+  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 *tsk)
+{
+	struct mm_struct *mm = tsk->mm;
+
+	/* Check to see if this task was created in compat vdso mode */
+	if (mm && mm->context.vdso == (void *)VDSO_HIGH_BASE)
+		return &gate_vma;
+	return NULL;
+}
+
+int in_gate_area(struct task_struct *task, unsigned long addr)
+{
+	const struct vm_area_struct *vma = get_gate_vma(task);
+
+	return vma && addr >= vma->vm_start && addr < vma->vm_end;
+}
+
+int in_gate_area_no_task(unsigned long addr)
+{
+	return 0;
+}