[PATCH] i386: Relocate VDSO ELF headers to match mapped location with COMPAT_VDSO
Some versions of libc can't deal with a VDSO which doesn't have its
ELF headers matching its mapped address. COMPAT_VDSO maps the VDSO at
a specific system-wide fixed address. Previously this was all done at
build time, on the grounds that the fixed VDSO address is always at
the top of the address space. However, a hypervisor may reserve some
of that address space, pushing the fixmap address down.
This patch does the adjustment dynamically at runtime, depending on
the runtime location of the VDSO fixmap.
[ Patch has been through several hands: Jan Beulich wrote the orignal
version; Zach reworked it, and Jeremy converted it to relocate phdrs
as well as sections. ]
Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Zachary Amsden <zach@vmware.com>
Cc: "Jan Beulich" <JBeulich@novell.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Andi Kleen <ak@suse.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Roland McGrath <roland@redhat.com>
diff --git a/arch/i386/kernel/sysenter.c b/arch/i386/kernel/sysenter.c
index 13ca54a..e5a9583 100644
--- a/arch/i386/kernel/sysenter.c
+++ b/arch/i386/kernel/sysenter.c
@@ -22,6 +22,7 @@
#include <asm/msr.h>
#include <asm/pgtable.h>
#include <asm/unistd.h>
+#include <asm/elf.h>
/*
* Should the kernel map a VDSO page into processes and pass its
@@ -46,6 +47,129 @@
extern asmlinkage void sysenter_entry(void);
+#ifdef CONFIG_COMPAT_VDSO
+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);
+ }
+}
+#else
+static inline void relocate_vdso(Elf32_Ehdr *ehdr)
+{
+}
+#endif /* COMPAT_VDSO */
+
void enable_sep_cpu(void)
{
int cpu = get_cpu();
@@ -75,6 +199,9 @@
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);
#ifdef CONFIG_COMPAT_VDSO
@@ -83,23 +210,23 @@
#endif
if (!boot_cpu_has(X86_FEATURE_SEP)) {
- memcpy(syscall_page,
- &vsyscall_int80_start,
- &vsyscall_int80_end - &vsyscall_int80_start);
- return 0;
+ 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_sysenter_start,
- &vsyscall_sysenter_end - &vsyscall_sysenter_start);
+ memcpy(syscall_page, vsyscall, vsyscall_len);
+ relocate_vdso(syscall_page);
return 0;
}
-#ifndef CONFIG_COMPAT_VDSO
/* Defined in vsyscall-sysenter.S */
extern void SYSENTER_RETURN;
+#ifdef __HAVE_ARCH_GATE_AREA
/* Setup a VMA at program startup for the vsyscall page */
int arch_setup_additional_pages(struct linux_binprm *bprm, int exstack)
{
@@ -159,4 +286,17 @@
{
return 0;
}
-#endif
+#else /* !__HAVE_ARCH_GATE_AREA */
+int arch_setup_additional_pages(struct linux_binprm *bprm, int exstack)
+{
+ /*
+ * If not creating userspace VMA, simply set vdso to point to
+ * fixmap page.
+ */
+ current->mm->context.vdso = (void *)VDSO_HIGH_BASE;
+ current_thread_info()->sysenter_return =
+ (void *)VDSO_SYM(&SYSENTER_RETURN);
+
+ return 0;
+}
+#endif /* __HAVE_ARCH_GATE_AREA */