vdso: Introduce vdso pie-engine

It's quite minimal at moment and provides only two helpers

 - vdso_redirect_calls, to patch vdso area redirectling
   calls to some new place.

 - vdso_fill_symtable, to parse vma area as vdso library
   and fill symbols table with offsets and names.

Because these routines will be needed in both regular criu
code and restorer code -- we compile it in pie format.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

Makefile

@@ -146,6 +146,10 @@ PROGRAM-BUILTINS	+= pie/util-net.o
 PROGRAM-BUILTINS	+= protobuf/built-in.o
 PROGRAM-BUILTINS	+= built-in.o
 
+$(ARCH_DIR)/vdso-pie.o: pie
+	$(Q) $(MAKE) $(build)=pie $(ARCH_DIR)/vdso-pie.o
+PROGRAM-BUILTINS	+= $(ARCH_DIR)/vdso-pie.o
+
 $(PROGRAM): $(SYSCALL-LIB) $(ARCH-LIB) $(PROGRAM-BUILTINS)
 	$(E) "  LINK    " $@
 	$(Q) $(CC) $(CFLAGS) $^ $(LIBS) -o $@

arch/arm/include/asm/vdso.h

+#ifndef __CR_ASM_VDSO_H__
+#define __CR_ASM_VDSO_H__
+
+#include <sys/types.h>
+
+struct vdso_symtable;
+
+extern int vdso_redirect_calls(void *base_to, void *base_from, struct vdso_symtable *to, struct vdso_symtable *from);
+extern int vdso_fill_symtable(char *mem, size_t size,struct vdso_symtable *t);
+
+#endif /* __CR_ASM_VDSO_H__ */

arch/arm/vdso-pie.c

+#include <stdlib.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <string.h>
+#include <elf.h>
+#include <fcntl.h>
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+
+#include "asm/string.h"
+#include "asm/types.h"
+
+#include "compiler.h"
+#include "crtools.h"
+#include "vdso.h"
+#include "log.h"
+
+#ifdef LOG_PREFIX
+# undef LOG_PREFIX
+#endif
+#define LOG_PREFIX "vdso: "
+
+int vdso_redirect_calls(void *base_to, void *base_from,
+			struct vdso_symtable *to,
+			struct vdso_symtable *from)
+{
+	return 0;
+}
+
+int vdso_fill_symtable(char *mem, size_t size, struct vdso_symtable *t)
+{
+	return 0;
+}

arch/x86/include/asm/vdso.h

+#ifndef __CR_ASM_VDSO_H__
+#define __CR_ASM_VDSO_H__
+
+#include <sys/types.h>
+
+struct vdso_symtable;
+
+extern int vdso_redirect_calls(void *base_to, void *base_from, struct vdso_symtable *to, struct vdso_symtable *from);
+extern int vdso_fill_symtable(char *mem, size_t size,struct vdso_symtable *t);
+
+#endif /* __CR_ASM_VDSO_H__ */

arch/x86/vdso-pie.c

+#include <stdlib.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <string.h>
+#include <elf.h>
+#include <fcntl.h>
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+
+#include "asm/string.h"
+#include "asm/types.h"
+
+#include "compiler.h"
+#include "crtools.h"
+#include "vdso.h"
+#include "log.h"
+
+#ifdef LOG_PREFIX
+# undef LOG_PREFIX
+#endif
+#define LOG_PREFIX "vdso: "
+
+typedef struct {
+	u16	movabs;
+	u64	imm64;
+	u16	jmp_rax;
+	u32	guards;
+} __packed jmp_t;
+
+int vdso_redirect_calls(void *base_to, void *base_from,
+			struct vdso_symtable *to,
+			struct vdso_symtable *from)
+{
+	jmp_t jmp = {
+		.movabs		= 0xb848,
+		.jmp_rax	= 0xe0ff,
+		.guards		= 0xcccccccc,
+	};
+	unsigned int i;
+
+	for (i = 0; i < ARRAY_SIZE(to->symbols); i++) {
+		if (vdso_symbol_empty(&from->symbols[i]))
+			continue;
+
+		pr_debug("jmp: %lx/%lx -> %lx/%lx (index %d)\n",
+			 (unsigned long)base_from, from->symbols[i].offset,
+			 (unsigned long)base_to, to->symbols[i].offset, i);
+
+		jmp.imm64 = (unsigned long)base_to + to->symbols[i].offset;
+		builtin_memcpy((void *)(base_from + from->symbols[i].offset), &jmp, sizeof(jmp));
+	}
+
+	return 0;
+}
+
+static unsigned int get_symbol_index(char *symbol, char *symbols[], size_t size)
+{
+	unsigned int i;
+
+	for (i = 0; symbol && i < size; i++) {
+		if (!builtin_strcmp(symbol, symbols[i]))
+			return i;
+	}
+
+	return VDSO_SYMBOL_MAX;
+}
+
+/* Check if pointer is out-of-bound */
+static bool __ptr_oob(void *ptr, void *start, size_t size)
+{
+	void *end = (void *)((unsigned long)start + size);
+	return ptr > end || ptr < start;
+}
+
+int vdso_fill_symtable(char *mem, size_t size, struct vdso_symtable *t)
+{
+	Elf64_Ehdr *ehdr = (void *)mem;
+	Elf64_Shdr *shdr, *shdr_strtab;
+	Elf64_Shdr *shdr_dynsym;
+	Elf64_Shdr *shdr_dynstr;
+	Elf64_Phdr *phdr;
+	Elf64_Shdr *text;
+	Elf64_Sym *sym;
+
+	char *section_names, *dynsymbol_names;
+
+	unsigned long base = VDSO_BAD_ADDR;
+	unsigned int i, j, k;
+
+	/*
+	 * Elf header bytes. For detailed
+	 * description see Elf specification.
+	 */
+	char vdso_ident[] = {
+		0x7f, 0x45, 0x4c, 0x46, 0x02, 0x01, 0x01, 0x00,
+		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	};
+
+	char *vdso_x86_symbols[VDSO_SYMBOL_MAX] = {
+		[VDSO_SYMBOL_GETTIMEOFDAY]	= VDSO_SYMBOL_GETTIMEOFDAY_NAME,
+		[VDSO_SYMBOL_GETCPU]		= VDSO_SYMBOL_GETCPU_NAME,
+		[VDSO_SYMBOL_CLOCK_GETTIME]	= VDSO_SYMBOL_CLOCK_GETTIME_NAME,
+		[VDSO_SYMBOL_TIME]		= VDSO_SYMBOL_TIME_NAME,
+	};
+
+	BUILD_BUG_ON(sizeof(vdso_ident) != sizeof(ehdr->e_ident));
+
+	pr_debug("Parsing at %lx %lx\n",
+		 (long)mem, (long)mem + (long)size);
+
+	/*
+	 * Make sure it's a file we support.
+	 */
+	if (builtin_memcmp(ehdr->e_ident, vdso_ident, sizeof(vdso_ident))) {
+		pr_debug("Elf header magic mismatch\n");
+		goto err;
+	}
+
+	/*
+	 * Figure out base virtual address.
+	 */
+	phdr = (void *)&mem[ehdr->e_phoff];
+	for (i = 0; i < ehdr->e_phnum; i++, phdr++) {
+		if (__ptr_oob(phdr, mem, size))
+			goto err;
+		if (phdr->p_type == PT_LOAD) {
+			base = phdr->p_vaddr;
+			break;
+		}
+	}
+	if (base != VDSO_BAD_ADDR) {
+		pr_debug("Base address %lx\n", base);
+	} else {
+		pr_debug("No base address found\n");
+		goto err;
+	}
+
+	/*
+	 * Where the section names lays.
+	 */
+	if (ehdr->e_shstrndx == SHN_UNDEF) {
+		pr_err("Section names are not found\n");
+		goto err;
+	}
+
+	shdr = (void *)&mem[ehdr->e_shoff];
+	shdr_strtab = &shdr[ehdr->e_shstrndx];
+	if (__ptr_oob(shdr_strtab, mem, size))
+		goto err;
+
+	section_names = (void *)&mem[shdr_strtab->sh_offset];
+	shdr_dynsym = shdr_dynstr = text = NULL;
+
+	for (i = 0; i < ehdr->e_shnum; i++, shdr++) {
+		if (__ptr_oob(shdr, mem, size))
+			goto err;
+		if (__ptr_oob(&section_names[shdr->sh_name], mem, size))
+			goto err;
+
+#if 0
+		pr_debug("section: %2d -> %s\n",
+			 i, &section_names[shdr->sh_name]);
+#endif
+
+		if (shdr->sh_type == SHT_DYNSYM &&
+		    builtin_strcmp(&section_names[shdr->sh_name],
+				   ".dynsym") == 0) {
+			shdr_dynsym = shdr;
+		} else if (shdr->sh_type == SHT_STRTAB &&
+			   builtin_strcmp(&section_names[shdr->sh_name],
+					  ".dynstr") == 0) {
+			shdr_dynstr = shdr;
+		} else if (shdr->sh_type == SHT_PROGBITS &&
+			   builtin_strcmp(&section_names[shdr->sh_name],
+					  ".text") == 0) {
+			text = shdr;
+		}
+	}
+
+	if (!shdr_dynsym || !shdr_dynstr || !text) {
+		pr_debug("No required sections found\n");
+		goto err;
+	}
+
+	dynsymbol_names = (void *)&mem[shdr_dynstr->sh_offset];
+	if (__ptr_oob(dynsymbol_names, mem, size)	||
+	    __ptr_oob(shdr_dynsym, mem, size)		||
+	    __ptr_oob(text, mem, size))
+		goto err;
+
+	/*
+	 * Walk over global symbols and choose ones we need.
+	 */
+	j = shdr_dynsym->sh_size / sizeof(*sym);
+	sym = (void *)&mem[shdr_dynsym->sh_offset];
+
+	for (i = 0; i < j; i++, sym++) {
+		if (__ptr_oob(sym, mem, size))
+			goto err;
+
+		if (ELF64_ST_BIND(sym->st_info) != STB_GLOBAL ||
+		    ELF64_ST_TYPE(sym->st_info) != STT_FUNC)
+			continue;
+
+		if (__ptr_oob(&dynsymbol_names[sym->st_name], mem, size))
+			goto err;
+
+		k = get_symbol_index(&dynsymbol_names[sym->st_name],
+				     vdso_x86_symbols,
+				     ARRAY_SIZE(vdso_x86_symbols));
+		if (k != VDSO_SYMBOL_MAX) {
+			builtin_memcpy(t->symbols[k].name, vdso_x86_symbols[k],
+				       sizeof(t->symbols[k].name));
+			t->symbols[k].offset = (unsigned long)sym->st_value - base;
+#if 0
+			pr_debug("symbol: %#-16lx %2d %s\n",
+				 t->symbols[k].offset, sym->st_shndx, t->symbols[k].name);
+#endif
+		}
+	}
+	return 0;
+err:
+	return -1;
+}

include/vdso.h

+#ifndef __CR_VDSO_H__
+#define __CR_VDSO_H__
+
+#include <sys/mman.h>
+
+#include "asm/vdso.h"
+
+#define VDSO_PROT		(PROT_READ | PROT_EXEC)
+
+/*
+ * This is a minimal amount of symbols
+ * we should support at the moment.
+ */
+enum {
+	VDSO_SYMBOL_GETTIMEOFDAY,
+	VDSO_SYMBOL_GETCPU,
+	VDSO_SYMBOL_CLOCK_GETTIME,
+	VDSO_SYMBOL_TIME,
+
+	VDSO_SYMBOL_MAX
+};
+
+#define VDSO_SYMBOL_GETTIMEOFDAY_NAME	"__vdso_gettimeofday"
+#define VDSO_SYMBOL_GETCPU_NAME		"__vdso_getcpu"
+#define VDSO_SYMBOL_CLOCK_GETTIME_NAME	"__vdso_clock_gettime"
+#define VDSO_SYMBOL_TIME_NAME		"__vdso_time"
+
+#define VDSO_BAD_ADDR		(-1ul)
+
+struct vdso_symbol {
+	char		name[32];
+	unsigned long	offset;
+};
+
+#define VDSO_SYMBOL_INIT						\
+	{ .offset = VDSO_BAD_ADDR, }
+
+/* Check if symbol present in symtable */
+static inline bool vdso_symbol_empty(struct vdso_symbol *s)
+{
+	return s->offset == VDSO_BAD_ADDR && s->name[0] == '\0';
+}
+
+struct vdso_symtable {
+	unsigned long		vma_start;
+	unsigned long		vma_end;
+	struct vdso_symbol	symbols[VDSO_SYMBOL_MAX];
+};
+
+#define VDSO_SYMTABLE_INIT						\
+	{								\
+		.vma_start	= VDSO_BAD_ADDR,			\
+		.vma_end	= VDSO_BAD_ADDR,			\
+		.symbols		= {				\
+			[0 ... VDSO_SYMBOL_MAX - 1] =			\
+				(struct vdso_symbol)VDSO_SYMBOL_INIT,	\
+			},						\
+	}
+
+#define VDSO_INIT_SYMTABLE(symtable)					\
+	*(symtable) = (struct vdso_symtable)VDSO_SYMTABLE_INIT
+
+/* Size of VMA associated with vdso */
+static inline unsigned long vdso_vma_size(struct vdso_symtable *t)
+{
+	return t->vma_end - t->vma_start;
+}
+
+#endif /* __CR_VDSO_H__ */

pie/Makefile

@@ -10,6 +10,7 @@ parasite-libs-e		+= $(SYSCALL-LIB)
 
 restorer-obj-y		+= restorer.o
 restorer-obj-e		+= $(ARCH_DIR)/restorer.o
+restorer-obj-e		+= $(ARCH_DIR)/vdso-pie.o
 restorer-libs-e		+= $(SYSCALL-LIB)
 
 cflags-y		+= -DCR_NOGLIBC -fpie  -Wa,--noexecstack -fno-stack-protector