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 Cc: Zachary Amsden Cc: "Jan Beulich" Cc: Eric W. Biederman Cc: Andi Kleen Cc: Ingo Molnar Cc: Roland McGrath --- arch/i386/kernel/entry.S | 4 - arch/i386/kernel/sysenter.c | 170 +++++++++++++++++++++++++++++++++++++++---- arch/i386/mm/pgtable.c | 6 - include/asm-i386/elf.h | 28 ++----- include/asm-i386/fixmap.h | 8 -- include/linux/elf.h | 17 ++++ 6 files changed, 184 insertions(+), 49 deletions(-) =================================================================== --- a/arch/i386/kernel/entry.S +++ b/arch/i386/kernel/entry.S @@ -305,16 +305,12 @@ sysenter_past_esp: pushl $(__USER_CS) CFI_ADJUST_CFA_OFFSET 4 /*CFI_REL_OFFSET cs, 0*/ -#ifndef CONFIG_COMPAT_VDSO /* * Push current_thread_info()->sysenter_return to the stack. * A tiny bit of offset fixup is necessary - 4*4 means the 4 words * pushed above; +8 corresponds to copy_thread's esp0 setting. */ pushl (TI_sysenter_return-THREAD_SIZE+8+4*4)(%esp) -#else - pushl $SYSENTER_RETURN -#endif CFI_ADJUST_CFA_OFFSET 4 CFI_REL_OFFSET eip, 0 =================================================================== --- a/arch/i386/kernel/sysenter.c +++ b/arch/i386/kernel/sysenter.c @@ -22,6 +22,7 @@ #include #include #include +#include /* * Should the kernel map a VDSO page into processes and pass its @@ -41,6 +42,129 @@ __setup("vdso=", vdso_setup); __setup("vdso=", vdso_setup); 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) { @@ -71,6 +195,9 @@ int __init sysenter_setup(void) 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 @@ -79,23 +206,23 @@ int __init sysenter_setup(void) #endif if (!boot_cpu_has(X86_FEATURE_SEP)) { - memcpy(syscall_page, - &vsyscall_int80_start, - &vsyscall_int80_end - &vsyscall_int80_start); - return 0; - } - - memcpy(syscall_page, - &vsyscall_sysenter_start, - &vsyscall_sysenter_end - &vsyscall_sysenter_start); - - return 0; -} - -#ifndef CONFIG_COMPAT_VDSO + 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; +} + /* 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) { @@ -155,4 +282,17 @@ int in_gate_area_no_task(unsigned long a { 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 */ =================================================================== --- a/arch/i386/mm/pgtable.c +++ b/arch/i386/mm/pgtable.c @@ -144,10 +144,8 @@ void set_pmd_pfn(unsigned long vaddr, un } static int fixmaps; -#ifndef CONFIG_COMPAT_VDSO unsigned long __FIXADDR_TOP = 0xfffff000; EXPORT_SYMBOL(__FIXADDR_TOP); -#endif void __set_fixmap (enum fixed_addresses idx, unsigned long phys, pgprot_t flags) { @@ -173,12 +171,8 @@ void reserve_top_address(unsigned long r BUG_ON(fixmaps > 0); printk(KERN_INFO "Reserving virtual address space above 0x%08x\n", (int)-reserve); -#ifdef CONFIG_COMPAT_VDSO - BUG_ON(reserve != 0); -#else __FIXADDR_TOP = -reserve - PAGE_SIZE; __VMALLOC_RESERVE += reserve; -#endif } pte_t *pte_alloc_one_kernel(struct mm_struct *mm, unsigned long address) =================================================================== --- a/include/asm-i386/elf.h +++ b/include/asm-i386/elf.h @@ -133,39 +133,31 @@ extern int dump_task_extended_fpu (struc #define ELF_CORE_COPY_XFPREGS(tsk, elf_xfpregs) dump_task_extended_fpu(tsk, elf_xfpregs) #define VDSO_HIGH_BASE (__fix_to_virt(FIX_VDSO)) -#define VDSO_BASE ((unsigned long)current->mm->context.vdso) - -#ifdef CONFIG_COMPAT_VDSO -# define VDSO_COMPAT_BASE VDSO_HIGH_BASE -# define VDSO_PRELINK VDSO_HIGH_BASE -#else -# define VDSO_COMPAT_BASE VDSO_BASE -# define VDSO_PRELINK 0 -#endif +#define VDSO_CURRENT_BASE ((unsigned long)current->mm->context.vdso) +#define VDSO_PRELINK 0 #define VDSO_SYM(x) \ - (VDSO_COMPAT_BASE + (unsigned long)(x) - VDSO_PRELINK) + (VDSO_CURRENT_BASE + (unsigned long)(x) - VDSO_PRELINK) #define VDSO_HIGH_EHDR ((const struct elfhdr *) VDSO_HIGH_BASE) -#define VDSO_EHDR ((const struct elfhdr *) VDSO_COMPAT_BASE) +#define VDSO_EHDR ((const struct elfhdr *) VDSO_CURRENT_BASE) extern void __kernel_vsyscall; #define VDSO_ENTRY VDSO_SYM(&__kernel_vsyscall) -#ifndef CONFIG_COMPAT_VDSO +struct linux_binprm; + #define ARCH_HAS_SETUP_ADDITIONAL_PAGES -struct linux_binprm; extern int arch_setup_additional_pages(struct linux_binprm *bprm, int executable_stack); -#endif extern unsigned int vdso_enabled; -#define ARCH_DLINFO \ -do if (vdso_enabled) { \ - NEW_AUX_ENT(AT_SYSINFO, VDSO_ENTRY); \ - NEW_AUX_ENT(AT_SYSINFO_EHDR, VDSO_COMPAT_BASE); \ +#define ARCH_DLINFO \ +do if (vdso_enabled) { \ + NEW_AUX_ENT(AT_SYSINFO, VDSO_ENTRY); \ + NEW_AUX_ENT(AT_SYSINFO_EHDR, VDSO_CURRENT_BASE); \ } while (0) #endif =================================================================== --- a/include/asm-i386/fixmap.h +++ b/include/asm-i386/fixmap.h @@ -19,13 +19,9 @@ * Leave one empty page between vmalloc'ed areas and * the start of the fixmap. */ -#ifndef CONFIG_COMPAT_VDSO extern unsigned long __FIXADDR_TOP; -#else -#define __FIXADDR_TOP 0xfffff000 -#define FIXADDR_USER_START __fix_to_virt(FIX_VDSO) -#define FIXADDR_USER_END __fix_to_virt(FIX_VDSO - 1) -#endif +#define FIXADDR_USER_START __fix_to_virt(FIX_VDSO) +#define FIXADDR_USER_END __fix_to_virt(FIX_VDSO - 1) #ifndef __ASSEMBLY__ #include =================================================================== --- a/include/linux/elf.h +++ b/include/linux/elf.h @@ -83,6 +83,23 @@ typedef __s64 Elf64_Sxword; #define DT_DEBUG 21 #define DT_TEXTREL 22 #define DT_JMPREL 23 +#define DT_ENCODING 32 +#define OLD_DT_LOOS 0x60000000 +#define DT_LOOS 0x6000000d +#define DT_HIOS 0x6ffff000 +#define DT_VALRNGLO 0x6ffffd00 +#define DT_VALRNGHI 0x6ffffdff +#define DT_ADDRRNGLO 0x6ffffe00 +#define DT_ADDRRNGHI 0x6ffffeff +#define DT_VERSYM 0x6ffffff0 +#define DT_RELACOUNT 0x6ffffff9 +#define DT_RELCOUNT 0x6ffffffa +#define DT_FLAGS_1 0x6ffffffb +#define DT_VERDEF 0x6ffffffc +#define DT_VERDEFNUM 0x6ffffffd +#define DT_VERNEED 0x6ffffffe +#define DT_VERNEEDNUM 0x6fffffff +#define OLD_DT_HIOS 0x6fffffff #define DT_LOPROC 0x70000000 #define DT_HIPROC 0x7fffffff -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/