Now that relocation of the VDSO for COMPAT_VDSO users is done at runtime rather than compile time, it is possible to enable/disable compat mode at runtime. This patch allows you to enable COMPAT_VDSO mode with "vdso=2" on the kernel command line, or via sysctl. The COMPAT_VDSO config option still exists, but if enabled it just makes vdso_enabled default to VDSO_COMPAT. Signed-off-by: Jeremy Fitzhardinge Cc: Zachary Amsden Cc: "Jan Beulich" Cc: Eric W. Biederman Cc: Andi Kleen Cc: Ingo Molnar Cc: Roland McGrath --- Documentation/kernel-parameters.txt | 1 arch/i386/kernel/sysenter.c | 131 ++++++++++++++++++++++------------- include/asm-i386/page.h | 2 3 files changed, 84 insertions(+), 50 deletions(-) =================================================================== --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -1807,6 +1807,7 @@ and is between 256 and 4096 characters. [USBHID] The interval which mice are to be polled at. vdso= [IA-32,SH] + vdso=2: enable compat VDSO (default with COMPAT_VDSO) vdso=1: enable VDSO (default) vdso=0: disable VDSO mapping =================================================================== --- a/arch/i386/kernel/sysenter.c +++ b/arch/i386/kernel/sysenter.c @@ -24,11 +24,23 @@ #include #include +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 = 1; +unsigned int __read_mostly vdso_enabled = VDSO_DEFAULT; EXPORT_SYMBOL_GPL(vdso_enabled); @@ -43,7 +55,6 @@ __setup("vdso=", vdso_setup); extern asmlinkage void sysenter_entry(void); -#ifdef CONFIG_COMPAT_VDSO static __cpuinit void reloc_dyn(Elf32_Ehdr *ehdr, unsigned offset) { Elf32_Dyn *dyn = (void *)ehdr + offset; @@ -85,11 +96,6 @@ static __cpuinit void relocate_vdso(Elf3 reloc_dyn(ehdr, phdr[i].p_offset); } } -#else -static inline void relocate_vdso(Elf32_Ehdr *ehdr) -{ -} -#endif /* COMPAT_VDSO */ void enable_sep_cpu(void) { @@ -109,6 +115,25 @@ void enable_sep_cpu(void) put_cpu(); } +static struct vm_area_struct gate_vma; + +static int __cpuinit 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. @@ -117,6 +142,19 @@ extern const char vsyscall_sysenter_star 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); +} + int __cpuinit sysenter_setup(void) { void *syscall_page = (void *)get_zeroed_page(GFP_ATOMIC); @@ -125,10 +163,9 @@ int __cpuinit sysenter_setup(void) syscall_pages[0] = virt_to_page(syscall_page); -#ifdef CONFIG_COMPAT_VDSO - __set_fixmap(FIX_VDSO, __pa(syscall_page), PAGE_READONLY_EXEC); + gate_vma_init(); + printk("Compat vDSO mapped to %08lx.\n", __fix_to_virt(FIX_VDSO)); -#endif if (!boot_cpu_has(X86_FEATURE_SEP)) { vsyscall = &vsyscall_int80_start; @@ -147,7 +184,6 @@ int __cpuinit sysenter_setup(void) /* 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) { @@ -156,33 +192,44 @@ int arch_setup_additional_pages(struct l 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; - } - - /* - * 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; + + map_compat_vdso(vdso_enabled == VDSO_COMPAT); + + if (vdso_enabled == VDSO_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 = - (void *)VDSO_SYM(&SYSENTER_RETURN); -up_fail: + (void *)VDSO_SYM(&SYSENTER_RETURN); + + up_fail: up_write(&mm->mmap_sem); + return ret; } @@ -195,6 +242,8 @@ const char *arch_vma_name(struct vm_area struct vm_area_struct *get_gate_vma(struct task_struct *tsk) { + if (vdso_enabled == VDSO_COMPAT) + return &gate_vma; return NULL; } @@ -207,17 +256,3 @@ int in_gate_area_no_task(unsigned long a { return 0; } -#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/include/asm-i386/page.h +++ b/include/asm-i386/page.h @@ -143,9 +143,7 @@ extern int page_is_ram(unsigned long pag #include #include -#ifndef CONFIG_COMPAT_VDSO #define __HAVE_ARCH_GATE_AREA 1 -#endif #endif /* __KERNEL__ */ #endif /* _I386_PAGE_H */ -- - 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/