From: Jeff Dike Date: Fri, 8 Feb 2008 12:22:07 +0000 (-0800) Subject: uml: runtime host VMSPLIT detection X-Git-Tag: v2.6.25-rc1~55 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=536788fe2d28e11db6aeda74207d95d750fb761f;p=linux-2.6 uml: runtime host VMSPLIT detection Calculate TASK_SIZE at run-time by figuring out the host's VMSPLIT - this is needed on i386 if UML is to run on hosts with varying VMSPLITs without recompilation. TASK_SIZE is now defined in terms of a variable, task_size. This gets rid of an include of pgtable.h from processor.h, which can cause include loops. On i386, task_size is calculated early in boot by probing the address space in a binary search to figure out where the boundary between usable and non-usable memory is. This tries to make sure that a page that is considered to be in userspace is, or can be made, read-write. I'm concerned about a system-global VDSO page in kernel memory being hit and considered to be a userspace page. On x86_64, task_size is just the old value of CONFIG_TOP_ADDR. A bunch of config variable are gone now. CONFIG_TOP_ADDR is directly replaced by TASK_SIZE. NEST_LEVEL is gone since the relocation of the stubs makes it irrelevant. All the HOST_VMSPLIT stuff is gone. All references to these in arch/um/Makefile are also gone. I noticed and fixed a missing extern in os.h when adding os_get_task_size. Note: This has been revised to fix the 32-bit UML on 64-bit host bug that Miklos ran into. Signed-off-by: Jeff Dike Cc: Miklos Szeredi Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/arch/um/Kconfig b/arch/um/Kconfig index 99e51d059a..dba8e05f02 100644 --- a/arch/um/Kconfig +++ b/arch/um/Kconfig @@ -203,17 +203,6 @@ config NR_CPUS depends on SMP default "32" -config NEST_LEVEL - int "Nesting level" - default "0" - help - This is set to the number of layers of UMLs that this UML will be run - in. Normally, this is zero, meaning that it will run directly on the - host. Setting it to one will build a UML that can run inside a UML - that is running on the host. Generally, if you intend this UML to run - inside another UML, set CONFIG_NEST_LEVEL to one more than the host - UML. - config HIGHMEM bool "Highmem support (EXPERIMENTAL)" depends on !64BIT && EXPERIMENTAL diff --git a/arch/um/Kconfig.i386 b/arch/um/Kconfig.i386 index e75264603d..3cd8a04d66 100644 --- a/arch/um/Kconfig.i386 +++ b/arch/um/Kconfig.i386 @@ -23,43 +23,6 @@ config SEMAPHORE_SLEEPERS bool default y -choice - prompt "Host memory split" - default HOST_VMSPLIT_3G - help - This is needed when the host kernel on which you run has a non-default - (like 2G/2G) memory split, instead of the customary 3G/1G. If you did - not recompile your own kernel but use the default distro's one, you can - safely accept the "Default split" option. - - It can be enabled on recent (>=2.6.16-rc2) vanilla kernels via - CONFIG_VM_SPLIT_*, or on previous kernels with special patches (-ck - patchset by Con Kolivas, or other ones) - option names match closely the - host CONFIG_VM_SPLIT_* ones. - - A lower setting (where 1G/3G is lowest and 3G/1G is higher) will - tolerate even more "normal" host kernels, but an higher setting will be - stricter. - - So, if you do not know what to do here, say 'Default split'. - -config HOST_VMSPLIT_3G - bool "Default split (3G/1G user/kernel host split)" -config HOST_VMSPLIT_3G_OPT - bool "3G/1G user/kernel host split (for full 1G low memory)" -config HOST_VMSPLIT_2G - bool "2G/2G user/kernel host split" -config HOST_VMSPLIT_1G - bool "1G/3G user/kernel host split" -endchoice - -config TOP_ADDR - hex - default 0xB0000000 if HOST_VMSPLIT_3G_OPT - default 0x78000000 if HOST_VMSPLIT_2G - default 0x40000000 if HOST_VMSPLIT_1G - default 0xC0000000 - config 3_LEVEL_PGTABLES bool "Three-level pagetables (EXPERIMENTAL)" default n diff --git a/arch/um/Kconfig.x86_64 b/arch/um/Kconfig.x86_64 index b438f0e142..6533b349f0 100644 --- a/arch/um/Kconfig.x86_64 +++ b/arch/um/Kconfig.x86_64 @@ -15,10 +15,6 @@ config SEMAPHORE_SLEEPERS bool default y -config TOP_ADDR - hex - default 0x7fc0000000 - config 3_LEVEL_PGTABLES bool default y diff --git a/arch/um/Makefile b/arch/um/Makefile index cb4af9bf20..dbeab15e7b 100644 --- a/arch/um/Makefile +++ b/arch/um/Makefile @@ -79,13 +79,6 @@ KERNEL_DEFINES = $(strip -Derrno=kernel_errno -Dsigprocmask=kernel_sigprocmask \ KBUILD_CFLAGS += $(KERNEL_DEFINES) KBUILD_CFLAGS += $(call cc-option,-fno-unit-at-a-time,) -# These are needed for clean and mrproper, since in that case .config is not -# included; the values here are meaningless - -CONFIG_NEST_LEVEL ?= 0 - -SIZE = ($(CONFIG_NEST_LEVEL) * 0x20000000) - PHONY += linux all: linux @@ -120,10 +113,6 @@ CFLAGS_NO_HARDENING := $(call cc-option, -fno-PIC,) $(call cc-option, -fno-pic,) CONFIG_KERNEL_STACK_ORDER ?= 2 STACK_SIZE := $(shell echo $$[ 4096 * (1 << $(CONFIG_KERNEL_STACK_ORDER)) ] ) -ifndef START - START = $(shell echo $$[ $(TOP_ADDR) - $(SIZE) ] ) -endif - CPPFLAGS_vmlinux.lds = -U$(SUBARCH) -DSTART=$(START) -DELF_ARCH=$(ELF_ARCH) \ -DELF_FORMAT="$(ELF_FORMAT)" -DKERNEL_STACK_SIZE=$(STACK_SIZE) diff --git a/arch/um/defconfig b/arch/um/defconfig index 86db2862f2..59215bc264 100644 --- a/arch/um/defconfig +++ b/arch/um/defconfig @@ -56,8 +56,6 @@ CONFIG_X86_TSC=y CONFIG_UML_X86=y # CONFIG_64BIT is not set CONFIG_SEMAPHORE_SLEEPERS=y -# CONFIG_HOST_2G_2G is not set -CONFIG_TOP_ADDR=0xc0000000 # CONFIG_3_LEVEL_PGTABLES is not set CONFIG_ARCH_HAS_SC_SIGNALS=y CONFIG_ARCH_REUSE_HOST_VSYSCALL_AREA=y @@ -81,7 +79,6 @@ CONFIG_HOSTFS=y # CONFIG_HPPFS is not set CONFIG_MCONSOLE=y CONFIG_MAGIC_SYSRQ=y -CONFIG_NEST_LEVEL=0 # CONFIG_HIGHMEM is not set CONFIG_KERNEL_STACK_ORDER=0 diff --git a/arch/um/include/as-layout.h b/arch/um/include/as-layout.h index 606bb5c7fd..cac542d8ff 100644 --- a/arch/um/include/as-layout.h +++ b/arch/um/include/as-layout.h @@ -57,6 +57,8 @@ extern unsigned long _stext, _etext, _sdata, _edata, __bss_start, _end; extern unsigned long _unprotected_end; extern unsigned long brk_start; +extern unsigned long host_task_size; + extern int linux_main(int argc, char **argv); extern void (*sig_info[])(int, struct uml_pt_regs *); diff --git a/arch/um/include/os.h b/arch/um/include/os.h index 0b6b627333..32c799e3a4 100644 --- a/arch/um/include/os.h +++ b/arch/um/include/os.h @@ -295,6 +295,9 @@ extern void maybe_sigio_broken(int fd, int read); extern int os_arch_prctl(int pid, int code, unsigned long *addr); /* tty.c */ -int get_pty(void); +extern int get_pty(void); + +/* sys-$ARCH/task_size.c */ +extern unsigned long os_get_task_size(void); #endif diff --git a/arch/um/kernel/exec.c b/arch/um/kernel/exec.c index 76a62c0cb2..f5d7f4569b 100644 --- a/arch/um/kernel/exec.c +++ b/arch/um/kernel/exec.c @@ -25,7 +25,7 @@ void flush_thread(void) ret = unmap(¤t->mm->context.id, 0, STUB_START, 0, &data); ret = ret || unmap(¤t->mm->context.id, STUB_END, - TASK_SIZE - STUB_END, 1, &data); + host_task_size - STUB_END, 1, &data); if (ret) { printk(KERN_ERR "flush_thread - clearing address space failed, " "err = %d\n", ret); diff --git a/arch/um/kernel/um_arch.c b/arch/um/kernel/um_arch.c index 468aba990d..a6c1dd1cf5 100644 --- a/arch/um/kernel/um_arch.c +++ b/arch/um/kernel/um_arch.c @@ -241,6 +241,11 @@ static struct notifier_block panic_exit_notifier = { }; /* Set during early boot */ +unsigned long task_size; +EXPORT_SYMBOL(task_size); + +unsigned long host_task_size; + unsigned long brk_start; unsigned long end_iomem; EXPORT_SYMBOL(end_iomem); @@ -267,6 +272,13 @@ int __init linux_main(int argc, char **argv) if (have_root == 0) add_arg(DEFAULT_COMMAND_LINE); + host_task_size = os_get_task_size(); + /* + * TASK_SIZE needs to be PGDIR_SIZE aligned or else exit_mmap craps + * out + */ + task_size = host_task_size & PGDIR_MASK; + /* OS sanity checks that need to happen before the kernel runs */ os_early_checks(); @@ -303,7 +315,7 @@ int __init linux_main(int argc, char **argv) highmem = 0; iomem_size = (iomem_size + PAGE_SIZE - 1) & PAGE_MASK; - max_physmem = CONFIG_TOP_ADDR - uml_physmem - iomem_size - MIN_VMALLOC; + max_physmem = TASK_SIZE - uml_physmem - iomem_size - MIN_VMALLOC; /* * Zones have to begin on a 1 << MAX_ORDER page boundary, @@ -335,7 +347,7 @@ int __init linux_main(int argc, char **argv) } virtmem_size = physmem_size; - avail = CONFIG_TOP_ADDR - start_vm; + avail = TASK_SIZE - start_vm; if (physmem_size > avail) virtmem_size = avail; end_vm = start_vm + virtmem_size; diff --git a/arch/um/os-Linux/sys-i386/Makefile b/arch/um/os-Linux/sys-i386/Makefile index a841262c59..b4bc6ac4f3 100644 --- a/arch/um/os-Linux/sys-i386/Makefile +++ b/arch/um/os-Linux/sys-i386/Makefile @@ -3,7 +3,7 @@ # Licensed under the GPL # -obj-y = registers.o signal.o tls.o +obj-y = registers.o signal.o task_size.o tls.o USER_OBJS := $(obj-y) diff --git a/arch/um/os-Linux/sys-i386/task_size.c b/arch/um/os-Linux/sys-i386/task_size.c new file mode 100644 index 0000000000..48d211b3d9 --- /dev/null +++ b/arch/um/os-Linux/sys-i386/task_size.c @@ -0,0 +1,120 @@ +#include +#include +#include +#include +#include "longjmp.h" +#include "kern_constants.h" + +static jmp_buf buf; + +static void segfault(int sig) +{ + longjmp(buf, 1); +} + +static int page_ok(unsigned long page) +{ + unsigned long *address = (unsigned long *) (page << UM_KERN_PAGE_SHIFT); + unsigned long n = ~0UL; + void *mapped = NULL; + int ok = 0; + + /* + * First see if the page is readable. If it is, it may still + * be a VDSO, so we go on to see if it's writable. If not + * then try mapping memory there. If that fails, then we're + * still in the kernel area. As a sanity check, we'll fail if + * the mmap succeeds, but gives us an address different from + * what we wanted. + */ + if (setjmp(buf) == 0) + n = *address; + else { + mapped = mmap(address, UM_KERN_PAGE_SIZE, + PROT_READ | PROT_WRITE, + MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); + if (mapped == MAP_FAILED) + return 0; + if (mapped != address) + goto out; + } + + /* + * Now, is it writeable? If so, then we're in user address + * space. If not, then try mprotecting it and try the write + * again. + */ + if (setjmp(buf) == 0) { + *address = n; + ok = 1; + goto out; + } else if (mprotect(address, UM_KERN_PAGE_SIZE, + PROT_READ | PROT_WRITE) != 0) + goto out; + + if (setjmp(buf) == 0) { + *address = n; + ok = 1; + } + + out: + if (mapped != NULL) + munmap(mapped, UM_KERN_PAGE_SIZE); + return ok; +} + +unsigned long os_get_task_size(void) +{ + struct sigaction sa, old; + unsigned long bottom = 0; + /* + * A 32-bit UML on a 64-bit host gets confused about the VDSO at + * 0xffffe000. It is mapped, is readable, can be reprotected writeable + * and written. However, exec discovers later that it can't be + * unmapped. So, just set the highest address to be checked to just + * below it. This might waste some address space on 4G/4G 32-bit + * hosts, but shouldn't hurt otherwise. + */ + unsigned long top = 0xffffd000 >> UM_KERN_PAGE_SHIFT; + unsigned long test; + + printf("Locating the top of the address space ... "); + fflush(stdout); + + /* + * We're going to be longjmping out of the signal handler, so + * SA_DEFER needs to be set. + */ + sa.sa_handler = segfault; + sigemptyset(&sa.sa_mask); + sa.sa_flags = SA_NODEFER; + sigaction(SIGSEGV, &sa, &old); + + if (!page_ok(bottom)) { + fprintf(stderr, "Address 0x%x no good?\n", + bottom << UM_KERN_PAGE_SHIFT); + exit(1); + } + + /* This could happen with a 4G/4G split */ + if (page_ok(top)) + goto out; + + do { + test = bottom + (top - bottom) / 2; + if (page_ok(test)) + bottom = test; + else + top = test; + } while (top - bottom > 1); + +out: + /* Restore the old SIGSEGV handling */ + sigaction(SIGSEGV, &old, NULL); + + top <<= UM_KERN_PAGE_SHIFT; + printf("0x%x\n", top); + fflush(stdout); + + return top; +} diff --git a/arch/um/os-Linux/sys-x86_64/Makefile b/arch/um/os-Linux/sys-x86_64/Makefile index a42a4ef02e..a44a47f8f5 100644 --- a/arch/um/os-Linux/sys-x86_64/Makefile +++ b/arch/um/os-Linux/sys-x86_64/Makefile @@ -3,7 +3,7 @@ # Licensed under the GPL # -obj-y = registers.o prctl.o signal.o +obj-y = registers.o prctl.o signal.o task_size.o USER_OBJS := $(obj-y) diff --git a/arch/um/os-Linux/sys-x86_64/task_size.c b/arch/um/os-Linux/sys-x86_64/task_size.c new file mode 100644 index 0000000000..fad6f57f8e --- /dev/null +++ b/arch/um/os-Linux/sys-x86_64/task_size.c @@ -0,0 +1,5 @@ +unsigned long os_get_task_size(unsigned long shift) +{ + /* The old value of CONFIG_TOP_ADDR */ + return 0x7fc0000000; +} diff --git a/include/asm-um/fixmap.h b/include/asm-um/fixmap.h index 89a87c18b9..9d2be52b86 100644 --- a/include/asm-um/fixmap.h +++ b/include/asm-um/fixmap.h @@ -1,6 +1,7 @@ #ifndef __UM_FIXMAP_H #define __UM_FIXMAP_H +#include #include #include #include @@ -57,7 +58,7 @@ extern void __set_fixmap (enum fixed_addresses idx, * at the top of mem.. */ -#define FIXADDR_TOP (CONFIG_TOP_ADDR - 2 * PAGE_SIZE) +#define FIXADDR_TOP (TASK_SIZE - 2 * PAGE_SIZE) #define FIXADDR_SIZE (__end_of_fixed_addresses << PAGE_SHIFT) #define FIXADDR_START (FIXADDR_TOP - FIXADDR_SIZE) diff --git a/include/asm-um/processor-generic.h b/include/asm-um/processor-generic.h index 7a1624cdaf..bed668824b 100644 --- a/include/asm-um/processor-generic.h +++ b/include/asm-um/processor-generic.h @@ -11,7 +11,6 @@ struct pt_regs; struct task_struct; #include "asm/ptrace.h" -#include "asm/pgtable.h" #include "registers.h" #include "sysdep/archsetjmp.h" @@ -92,7 +91,9 @@ static inline void mm_copy_segments(struct mm_struct *from_mm, /* * User space process size: 3GB (default). */ -#define TASK_SIZE (CONFIG_TOP_ADDR & PGDIR_MASK) +extern unsigned long task_size; + +#define TASK_SIZE (task_size) #undef STACK_TOP #undef STACK_TOP_MAX