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 <jdike@linux.intel.com> Cc: Miklos Szeredi <miklos@szeredi.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Jeff Dike
Linus Torvalds
parent
2f569afd9c
commit
536788fe2d
15 changed files with 153 additions and 75 deletions
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@ -203,17 +203,6 @@ config NR_CPUS
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depends on SMP
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default "32"
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config NEST_LEVEL
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int "Nesting level"
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default "0"
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help
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This is set to the number of layers of UMLs that this UML will be run
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in. Normally, this is zero, meaning that it will run directly on the
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host. Setting it to one will build a UML that can run inside a UML
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that is running on the host. Generally, if you intend this UML to run
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inside another UML, set CONFIG_NEST_LEVEL to one more than the host
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UML.
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config HIGHMEM
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bool "Highmem support (EXPERIMENTAL)"
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depends on !64BIT && EXPERIMENTAL
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@ -23,43 +23,6 @@ config SEMAPHORE_SLEEPERS
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bool
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default y
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choice
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prompt "Host memory split"
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default HOST_VMSPLIT_3G
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help
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This is needed when the host kernel on which you run has a non-default
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(like 2G/2G) memory split, instead of the customary 3G/1G. If you did
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not recompile your own kernel but use the default distro's one, you can
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safely accept the "Default split" option.
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It can be enabled on recent (>=2.6.16-rc2) vanilla kernels via
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CONFIG_VM_SPLIT_*, or on previous kernels with special patches (-ck
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patchset by Con Kolivas, or other ones) - option names match closely the
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host CONFIG_VM_SPLIT_* ones.
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A lower setting (where 1G/3G is lowest and 3G/1G is higher) will
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tolerate even more "normal" host kernels, but an higher setting will be
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stricter.
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So, if you do not know what to do here, say 'Default split'.
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config HOST_VMSPLIT_3G
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bool "Default split (3G/1G user/kernel host split)"
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config HOST_VMSPLIT_3G_OPT
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bool "3G/1G user/kernel host split (for full 1G low memory)"
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config HOST_VMSPLIT_2G
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bool "2G/2G user/kernel host split"
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config HOST_VMSPLIT_1G
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bool "1G/3G user/kernel host split"
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endchoice
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config TOP_ADDR
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hex
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default 0xB0000000 if HOST_VMSPLIT_3G_OPT
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default 0x78000000 if HOST_VMSPLIT_2G
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default 0x40000000 if HOST_VMSPLIT_1G
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default 0xC0000000
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config 3_LEVEL_PGTABLES
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bool "Three-level pagetables (EXPERIMENTAL)"
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default n
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@ -15,10 +15,6 @@ config SEMAPHORE_SLEEPERS
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bool
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default y
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config TOP_ADDR
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hex
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default 0x7fc0000000
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config 3_LEVEL_PGTABLES
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bool
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default y
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@ -79,13 +79,6 @@ KERNEL_DEFINES = $(strip -Derrno=kernel_errno -Dsigprocmask=kernel_sigprocmask \
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KBUILD_CFLAGS += $(KERNEL_DEFINES)
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KBUILD_CFLAGS += $(call cc-option,-fno-unit-at-a-time,)
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# These are needed for clean and mrproper, since in that case .config is not
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# included; the values here are meaningless
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CONFIG_NEST_LEVEL ?= 0
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SIZE = ($(CONFIG_NEST_LEVEL) * 0x20000000)
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PHONY += linux
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all: linux
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@ -120,10 +113,6 @@ CFLAGS_NO_HARDENING := $(call cc-option, -fno-PIC,) $(call cc-option, -fno-pic,)
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CONFIG_KERNEL_STACK_ORDER ?= 2
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STACK_SIZE := $(shell echo $$[ 4096 * (1 << $(CONFIG_KERNEL_STACK_ORDER)) ] )
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ifndef START
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START = $(shell echo $$[ $(TOP_ADDR) - $(SIZE) ] )
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endif
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CPPFLAGS_vmlinux.lds = -U$(SUBARCH) -DSTART=$(START) -DELF_ARCH=$(ELF_ARCH) \
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-DELF_FORMAT="$(ELF_FORMAT)" -DKERNEL_STACK_SIZE=$(STACK_SIZE)
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@ -56,8 +56,6 @@ CONFIG_X86_TSC=y
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CONFIG_UML_X86=y
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# CONFIG_64BIT is not set
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CONFIG_SEMAPHORE_SLEEPERS=y
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# CONFIG_HOST_2G_2G is not set
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CONFIG_TOP_ADDR=0xc0000000
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# CONFIG_3_LEVEL_PGTABLES is not set
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CONFIG_ARCH_HAS_SC_SIGNALS=y
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CONFIG_ARCH_REUSE_HOST_VSYSCALL_AREA=y
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@ -81,7 +79,6 @@ CONFIG_HOSTFS=y
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# CONFIG_HPPFS is not set
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CONFIG_MCONSOLE=y
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CONFIG_MAGIC_SYSRQ=y
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CONFIG_NEST_LEVEL=0
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# CONFIG_HIGHMEM is not set
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CONFIG_KERNEL_STACK_ORDER=0
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@ -57,6 +57,8 @@ extern unsigned long _stext, _etext, _sdata, _edata, __bss_start, _end;
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extern unsigned long _unprotected_end;
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extern unsigned long brk_start;
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extern unsigned long host_task_size;
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extern int linux_main(int argc, char **argv);
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extern void (*sig_info[])(int, struct uml_pt_regs *);
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@ -295,6 +295,9 @@ extern void maybe_sigio_broken(int fd, int read);
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extern int os_arch_prctl(int pid, int code, unsigned long *addr);
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/* tty.c */
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int get_pty(void);
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extern int get_pty(void);
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/* sys-$ARCH/task_size.c */
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extern unsigned long os_get_task_size(void);
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#endif
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@ -25,7 +25,7 @@ void flush_thread(void)
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ret = unmap(¤t->mm->context.id, 0, STUB_START, 0, &data);
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ret = ret || unmap(¤t->mm->context.id, STUB_END,
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TASK_SIZE - STUB_END, 1, &data);
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host_task_size - STUB_END, 1, &data);
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if (ret) {
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printk(KERN_ERR "flush_thread - clearing address space failed, "
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"err = %d\n", ret);
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@ -241,6 +241,11 @@ static struct notifier_block panic_exit_notifier = {
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};
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/* Set during early boot */
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unsigned long task_size;
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EXPORT_SYMBOL(task_size);
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unsigned long host_task_size;
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unsigned long brk_start;
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unsigned long end_iomem;
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EXPORT_SYMBOL(end_iomem);
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@ -267,6 +272,13 @@ int __init linux_main(int argc, char **argv)
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if (have_root == 0)
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add_arg(DEFAULT_COMMAND_LINE);
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host_task_size = os_get_task_size();
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/*
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* TASK_SIZE needs to be PGDIR_SIZE aligned or else exit_mmap craps
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* out
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*/
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task_size = host_task_size & PGDIR_MASK;
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/* OS sanity checks that need to happen before the kernel runs */
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os_early_checks();
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@ -303,7 +315,7 @@ int __init linux_main(int argc, char **argv)
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highmem = 0;
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iomem_size = (iomem_size + PAGE_SIZE - 1) & PAGE_MASK;
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max_physmem = CONFIG_TOP_ADDR - uml_physmem - iomem_size - MIN_VMALLOC;
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max_physmem = TASK_SIZE - uml_physmem - iomem_size - MIN_VMALLOC;
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/*
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* Zones have to begin on a 1 << MAX_ORDER page boundary,
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@ -335,7 +347,7 @@ int __init linux_main(int argc, char **argv)
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}
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virtmem_size = physmem_size;
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avail = CONFIG_TOP_ADDR - start_vm;
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avail = TASK_SIZE - start_vm;
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if (physmem_size > avail)
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virtmem_size = avail;
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end_vm = start_vm + virtmem_size;
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@ -3,7 +3,7 @@
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# Licensed under the GPL
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#
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obj-y = registers.o signal.o tls.o
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obj-y = registers.o signal.o task_size.o tls.o
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USER_OBJS := $(obj-y)
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120
arch/um/os-Linux/sys-i386/task_size.c
Normal file
120
arch/um/os-Linux/sys-i386/task_size.c
Normal file
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@ -0,0 +1,120 @@
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#include <stdio.h>
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#include <stdlib.h>
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#include <signal.h>
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#include <sys/mman.h>
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#include "longjmp.h"
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#include "kern_constants.h"
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static jmp_buf buf;
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static void segfault(int sig)
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{
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longjmp(buf, 1);
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}
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static int page_ok(unsigned long page)
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{
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unsigned long *address = (unsigned long *) (page << UM_KERN_PAGE_SHIFT);
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unsigned long n = ~0UL;
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void *mapped = NULL;
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int ok = 0;
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/*
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* First see if the page is readable. If it is, it may still
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* be a VDSO, so we go on to see if it's writable. If not
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* then try mapping memory there. If that fails, then we're
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* still in the kernel area. As a sanity check, we'll fail if
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* the mmap succeeds, but gives us an address different from
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* what we wanted.
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*/
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if (setjmp(buf) == 0)
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n = *address;
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else {
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mapped = mmap(address, UM_KERN_PAGE_SIZE,
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PROT_READ | PROT_WRITE,
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MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
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if (mapped == MAP_FAILED)
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return 0;
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if (mapped != address)
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goto out;
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}
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/*
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* Now, is it writeable? If so, then we're in user address
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* space. If not, then try mprotecting it and try the write
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* again.
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*/
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if (setjmp(buf) == 0) {
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*address = n;
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ok = 1;
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goto out;
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} else if (mprotect(address, UM_KERN_PAGE_SIZE,
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PROT_READ | PROT_WRITE) != 0)
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goto out;
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if (setjmp(buf) == 0) {
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*address = n;
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ok = 1;
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}
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out:
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if (mapped != NULL)
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munmap(mapped, UM_KERN_PAGE_SIZE);
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return ok;
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}
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unsigned long os_get_task_size(void)
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{
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struct sigaction sa, old;
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unsigned long bottom = 0;
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/*
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* A 32-bit UML on a 64-bit host gets confused about the VDSO at
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* 0xffffe000. It is mapped, is readable, can be reprotected writeable
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* and written. However, exec discovers later that it can't be
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* unmapped. So, just set the highest address to be checked to just
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* below it. This might waste some address space on 4G/4G 32-bit
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* hosts, but shouldn't hurt otherwise.
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*/
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unsigned long top = 0xffffd000 >> UM_KERN_PAGE_SHIFT;
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unsigned long test;
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printf("Locating the top of the address space ... ");
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fflush(stdout);
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/*
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* We're going to be longjmping out of the signal handler, so
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* SA_DEFER needs to be set.
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*/
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sa.sa_handler = segfault;
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sigemptyset(&sa.sa_mask);
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sa.sa_flags = SA_NODEFER;
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sigaction(SIGSEGV, &sa, &old);
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if (!page_ok(bottom)) {
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fprintf(stderr, "Address 0x%x no good?\n",
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bottom << UM_KERN_PAGE_SHIFT);
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exit(1);
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}
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/* This could happen with a 4G/4G split */
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if (page_ok(top))
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goto out;
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do {
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test = bottom + (top - bottom) / 2;
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if (page_ok(test))
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bottom = test;
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else
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top = test;
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} while (top - bottom > 1);
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out:
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/* Restore the old SIGSEGV handling */
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sigaction(SIGSEGV, &old, NULL);
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top <<= UM_KERN_PAGE_SHIFT;
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printf("0x%x\n", top);
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fflush(stdout);
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return top;
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}
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@ -3,7 +3,7 @@
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# Licensed under the GPL
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#
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obj-y = registers.o prctl.o signal.o
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obj-y = registers.o prctl.o signal.o task_size.o
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USER_OBJS := $(obj-y)
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5
arch/um/os-Linux/sys-x86_64/task_size.c
Normal file
5
arch/um/os-Linux/sys-x86_64/task_size.c
Normal file
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@ -0,0 +1,5 @@
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unsigned long os_get_task_size(unsigned long shift)
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{
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/* The old value of CONFIG_TOP_ADDR */
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return 0x7fc0000000;
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}
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@ -1,6 +1,7 @@
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#ifndef __UM_FIXMAP_H
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#define __UM_FIXMAP_H
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#include <asm/processor.h>
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#include <asm/system.h>
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#include <asm/kmap_types.h>
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#include <asm/archparam.h>
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@ -57,7 +58,7 @@ extern void __set_fixmap (enum fixed_addresses idx,
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* at the top of mem..
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*/
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#define FIXADDR_TOP (CONFIG_TOP_ADDR - 2 * PAGE_SIZE)
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#define FIXADDR_TOP (TASK_SIZE - 2 * PAGE_SIZE)
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#define FIXADDR_SIZE (__end_of_fixed_addresses << PAGE_SHIFT)
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#define FIXADDR_START (FIXADDR_TOP - FIXADDR_SIZE)
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@ -11,7 +11,6 @@ struct pt_regs;
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struct task_struct;
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#include "asm/ptrace.h"
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#include "asm/pgtable.h"
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#include "registers.h"
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#include "sysdep/archsetjmp.h"
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@ -92,7 +91,9 @@ static inline void mm_copy_segments(struct mm_struct *from_mm,
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/*
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* User space process size: 3GB (default).
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*/
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#define TASK_SIZE (CONFIG_TOP_ADDR & PGDIR_MASK)
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extern unsigned long task_size;
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#define TASK_SIZE (task_size)
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#undef STACK_TOP
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#undef STACK_TOP_MAX
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