This pull request contains the following changes for UML:

- Make stub data pages configurable
 - Make it harder to mix user and kernel code by accident
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Merge tag 'uml-for-linus-6.4-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/uml/linux

Pull uml updates from Richard Weinberger:

 - Make stub data pages configurable

 - Make it harder to mix user and kernel code by accident

* tag 'uml-for-linus-6.4-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/uml/linux:
  um: make stub data pages size tweakable
  um: prevent user code in modules
  um: further clean up user_syms
  um: don't export printf()
  um: hostfs: define our own API boundary
  um: add __weak for exported functions

arch/um/include/shared/as-layout.h

@@ -23,7 +23,8 @@
 #define STUB_START stub_start
 #define STUB_CODE STUB_START
 #define STUB_DATA (STUB_CODE + UM_KERN_PAGE_SIZE)
-#define STUB_END (STUB_DATA + UM_KERN_PAGE_SIZE)
+#define STUB_DATA_PAGES 1 /* must be a power of two */
+#define STUB_END (STUB_DATA + STUB_DATA_PAGES * UM_KERN_PAGE_SIZE)
 
 #ifndef __ASSEMBLY__
 

arch/um/kernel/skas/clone.c

@@ -24,11 +24,12 @@
 void __attribute__ ((__section__ (".__syscall_stub")))
 stub_clone_handler(void)
 {
-	struct stub_data *data = get_stub_page();
+	struct stub_data *data = get_stub_data();
 	long err;
 
 	err = stub_syscall2(__NR_clone, CLONE_PARENT | CLONE_FILES | SIGCHLD,
-			    (unsigned long)data + UM_KERN_PAGE_SIZE / 2);
+			    (unsigned long)data +
+				STUB_DATA_PAGES * UM_KERN_PAGE_SIZE / 2);
 	if (err) {
 		data->parent_err = err;
 		goto done;

arch/um/kernel/skas/mmu.c

@@ -21,7 +21,7 @@ int init_new_context(struct task_struct *task, struct mm_struct *mm)
 	unsigned long stack = 0;
 	int ret = -ENOMEM;
 
-	stack = get_zeroed_page(GFP_KERNEL);
+	stack = __get_free_pages(GFP_KERNEL | __GFP_ZERO, ilog2(STUB_DATA_PAGES));
 	if (stack == 0)
 		goto out;
 
@@ -52,7 +52,7 @@ int init_new_context(struct task_struct *task, struct mm_struct *mm)
 
  out_free:
 	if (to_mm->id.stack != 0)
-		free_page(to_mm->id.stack);
+		free_pages(to_mm->id.stack, ilog2(STUB_DATA_PAGES));
  out:
 	return ret;
 }
@@ -74,6 +74,6 @@ void destroy_context(struct mm_struct *mm)
 	}
 	os_kill_ptraced_process(mmu->id.u.pid, 1);
 
-	free_page(mmu->id.stack);
+	free_pages(mmu->id.stack, ilog2(STUB_DATA_PAGES));
 	free_ldt(mmu);
 }

arch/um/kernel/um_arch.c

@@ -326,9 +326,13 @@ int __init linux_main(int argc, char **argv)
 		add_arg(DEFAULT_COMMAND_LINE_CONSOLE);
 
 	host_task_size = os_get_top_address();
-	/* reserve two pages for the stubs */
+	/* reserve a few pages for the stubs (taking care of data alignment) */
-	host_task_size -= 2 * PAGE_SIZE;
+	/* align the data portion */
-	stub_start = host_task_size;
+	BUILD_BUG_ON(!is_power_of_2(STUB_DATA_PAGES));
+	stub_start = (host_task_size - 1) & ~(STUB_DATA_PAGES * PAGE_SIZE - 1);
+	/* another page for the code portion */
+	stub_start -= PAGE_SIZE;
+	host_task_size = stub_start;
 
 	/*
 	 * TASK_SIZE needs to be PGDIR_SIZE aligned or else exit_mmap craps

arch/um/os-Linux/skas/process.c

@@ -262,7 +262,7 @@ static int userspace_tramp(void *stack)
 	if (stack != NULL) {
 		fd = phys_mapping(uml_to_phys(stack), &offset);
 		addr = mmap((void *) STUB_DATA,
-			    UM_KERN_PAGE_SIZE, PROT_READ | PROT_WRITE,
+			    STUB_DATA_PAGES * UM_KERN_PAGE_SIZE, PROT_READ | PROT_WRITE,
 			    MAP_FIXED | MAP_SHARED, fd, offset);
 		if (addr == MAP_FAILED) {
 			printk(UM_KERN_ERR "mapping segfault stack at 0x%lx failed, errno = %d\n",
@@ -277,7 +277,7 @@ static int userspace_tramp(void *stack)
 				  (unsigned long) stub_segv_handler -
 				  (unsigned long) __syscall_stub_start;
 
-		set_sigstack((void *) STUB_DATA, UM_KERN_PAGE_SIZE);
+		set_sigstack((void *) STUB_DATA, STUB_DATA_PAGES * UM_KERN_PAGE_SIZE);
 		sigemptyset(&sa.sa_mask);
 		sa.sa_flags = SA_ONSTACK | SA_NODEFER | SA_SIGINFO;
 		sa.sa_sigaction = (void *) v;
@@ -515,7 +515,7 @@ static int __init init_thread_regs(void)
 	thread_regs[REGS_IP_INDEX] = STUB_CODE +
 				(unsigned long) stub_clone_handler -
 				(unsigned long) __syscall_stub_start;
-	thread_regs[REGS_SP_INDEX] = STUB_DATA + UM_KERN_PAGE_SIZE -
+	thread_regs[REGS_SP_INDEX] = STUB_DATA + STUB_DATA_PAGES * UM_KERN_PAGE_SIZE -
 		sizeof(void *);
 #ifdef __SIGNAL_FRAMESIZE
 	thread_regs[REGS_SP_INDEX] -= __SIGNAL_FRAMESIZE;

arch/um/os-Linux/user_syms.c

@@ -3,112 +3,40 @@
 #include <linux/types.h>
 #include <linux/module.h>
 
-/* Some of this are builtin function (some are not but could in the future),
+/*
- * so I *must* declare good prototypes for them and then EXPORT them.
+ * This file exports some critical string functions and compiler
- * The kernel code uses the macro defined by include/linux/string.h,
+ * built-in functions (where calls are emitted by the compiler
- * so I undef macros; the userspace code does not include that and I
+ * itself that we cannot avoid even in kernel code) to modules.
- * add an EXPORT for the glibc one.
+ *
+ * "_user.c" code that previously used exports here such as hostfs
+ * really should be considered part of the 'hypervisor' and define
+ * its own API boundary like hostfs does now; don't add exports to
+ * this file for such cases.
  */
 
-#undef strlen
-#undef strstr
-#undef memcpy
-#undef memset
-
-extern size_t strlen(const char *);
-extern void *memmove(void *, const void *, size_t);
-extern void *memset(void *, int, size_t);
-extern int printf(const char *, ...);
-
 /* If it's not defined, the export is included in lib/string.c.*/
 #ifdef __HAVE_ARCH_STRSTR
+#undef strstr
 EXPORT_SYMBOL(strstr);
 #endif
 
 #ifndef __x86_64__
+#undef memcpy
 extern void *memcpy(void *, const void *, size_t);
 EXPORT_SYMBOL(memcpy);
+extern void *memmove(void *, const void *, size_t);
 EXPORT_SYMBOL(memmove);
+#undef memset
+extern void *memset(void *, int, size_t);
 EXPORT_SYMBOL(memset);
 #endif
 
-EXPORT_SYMBOL(printf);
-
-/* Here, instead, I can provide a fake prototype. Yes, someone cares: genksyms.
- * However, the modules will use the CRC defined *here*, no matter if it is
- * good; so the versions of these symbols will always match
- */
-#define EXPORT_SYMBOL_PROTO(sym)       \
-	int sym(void);                  \
-	EXPORT_SYMBOL(sym);
-
-extern void readdir64(void) __attribute__((weak));
-EXPORT_SYMBOL(readdir64);
-extern void truncate64(void) __attribute__((weak));
-EXPORT_SYMBOL(truncate64);
-
 #ifdef CONFIG_ARCH_REUSE_HOST_VSYSCALL_AREA
+/* needed for __access_ok() */
 EXPORT_SYMBOL(vsyscall_ehdr);
 EXPORT_SYMBOL(vsyscall_end);
 #endif
 
-EXPORT_SYMBOL_PROTO(__errno_location);
-
-EXPORT_SYMBOL_PROTO(access);
-EXPORT_SYMBOL_PROTO(open);
-EXPORT_SYMBOL_PROTO(open64);
-EXPORT_SYMBOL_PROTO(close);
-EXPORT_SYMBOL_PROTO(read);
-EXPORT_SYMBOL_PROTO(write);
-EXPORT_SYMBOL_PROTO(dup2);
-EXPORT_SYMBOL_PROTO(__xstat);
-EXPORT_SYMBOL_PROTO(__lxstat);
-EXPORT_SYMBOL_PROTO(__lxstat64);
-EXPORT_SYMBOL_PROTO(__fxstat64);
-EXPORT_SYMBOL_PROTO(lseek);
-EXPORT_SYMBOL_PROTO(lseek64);
-EXPORT_SYMBOL_PROTO(chown);
-EXPORT_SYMBOL_PROTO(fchown);
-EXPORT_SYMBOL_PROTO(truncate);
-EXPORT_SYMBOL_PROTO(ftruncate64);
-EXPORT_SYMBOL_PROTO(utime);
-EXPORT_SYMBOL_PROTO(utimes);
-EXPORT_SYMBOL_PROTO(futimes);
-EXPORT_SYMBOL_PROTO(chmod);
-EXPORT_SYMBOL_PROTO(fchmod);
-EXPORT_SYMBOL_PROTO(rename);
-EXPORT_SYMBOL_PROTO(__xmknod);
-
-EXPORT_SYMBOL_PROTO(symlink);
-EXPORT_SYMBOL_PROTO(link);
-EXPORT_SYMBOL_PROTO(unlink);
-EXPORT_SYMBOL_PROTO(readlink);
-
-EXPORT_SYMBOL_PROTO(mkdir);
-EXPORT_SYMBOL_PROTO(rmdir);
-EXPORT_SYMBOL_PROTO(opendir);
-EXPORT_SYMBOL_PROTO(readdir);
-EXPORT_SYMBOL_PROTO(closedir);
-EXPORT_SYMBOL_PROTO(seekdir);
-EXPORT_SYMBOL_PROTO(telldir);
-
-EXPORT_SYMBOL_PROTO(ioctl);
-
-EXPORT_SYMBOL_PROTO(pread64);
-EXPORT_SYMBOL_PROTO(pwrite64);
-
-EXPORT_SYMBOL_PROTO(statfs);
-EXPORT_SYMBOL_PROTO(statfs64);
-
-EXPORT_SYMBOL_PROTO(getuid);
-
-EXPORT_SYMBOL_PROTO(fsync);
-EXPORT_SYMBOL_PROTO(fdatasync);
-
-EXPORT_SYMBOL_PROTO(lstat64);
-EXPORT_SYMBOL_PROTO(fstat64);
-EXPORT_SYMBOL_PROTO(mknod);
-
 /* Export symbols used by GCC for the stack protector. */
 extern void __stack_smash_handler(void *) __attribute__((weak));
 EXPORT_SYMBOL(__stack_smash_handler);
@@ -117,6 +45,6 @@ extern long __guard __attribute__((weak));
 EXPORT_SYMBOL(__guard);
 
 #ifdef _FORTIFY_SOURCE
-extern int __sprintf_chk(char *str, int flag, size_t strlen, const char *format);
+extern int __sprintf_chk(char *str, int flag, size_t len, const char *format);
 EXPORT_SYMBOL(__sprintf_chk);
 #endif

arch/um/scripts/Makefile.rules

@@ -4,8 +4,8 @@
 # ===========================================================================
 
 USER_SINGLE_OBJS := \
-	$(foreach f,$(patsubst %.o,%,$(obj-y) $(obj-m)),$($(f)-objs))
+	$(foreach f,$(patsubst %.o,%,$(obj-y)),$($(f)-objs))
-USER_OBJS += $(filter %_user.o,$(obj-y) $(obj-m)  $(USER_SINGLE_OBJS))
+USER_OBJS += $(filter %_user.o,$(obj-y) $(USER_SINGLE_OBJS))
 USER_OBJS := $(foreach file,$(USER_OBJS),$(obj)/$(file))
 
 $(USER_OBJS:.o=.%): \

arch/x86/um/shared/sysdep/stub_32.h

@@ -89,19 +89,19 @@ static inline void remap_stack_and_trap(void)
 		"addl %4,%%ebx ; movl %%eax, (%%ebx) ;"
 		"int $3"
 		: :
-		"g" (~(UM_KERN_PAGE_SIZE - 1)),
+		"g" (~(STUB_DATA_PAGES * UM_KERN_PAGE_SIZE - 1)),
 		"g" (STUB_MMAP_NR),
 		"g" (UML_STUB_FIELD_FD),
 		"g" (UML_STUB_FIELD_OFFSET),
 		"g" (UML_STUB_FIELD_CHILD_ERR),
-		"c" (UM_KERN_PAGE_SIZE),
+		"c" (STUB_DATA_PAGES * UM_KERN_PAGE_SIZE),
 		"d" (PROT_READ | PROT_WRITE),
 		"S" (MAP_FIXED | MAP_SHARED)
 		:
 		"memory");
 }
 
-static __always_inline void *get_stub_page(void)
+static __always_inline void *get_stub_data(void)
 {
 	unsigned long ret;
 
@@ -109,7 +109,7 @@ static __always_inline void *get_stub_page(void)
 		"movl %%esp,%0 ;"
 		"andl %1,%0"
 		: "=a" (ret)
-		: "g" (~(UM_KERN_PAGE_SIZE - 1)));
+		: "g" (~(STUB_DATA_PAGES * UM_KERN_PAGE_SIZE - 1)));
 
 	return (void *)ret;
 }

arch/x86/um/shared/sysdep/stub_64.h

@@ -98,18 +98,18 @@ static inline void remap_stack_and_trap(void)
 		"int3"
 		: :
 		"g" (STUB_MMAP_NR),
-		"g" (~(UM_KERN_PAGE_SIZE - 1)),
+		"g" (~(STUB_DATA_PAGES * UM_KERN_PAGE_SIZE - 1)),
 		"g" (MAP_FIXED | MAP_SHARED),
 		"g" (UML_STUB_FIELD_FD),
 		"g" (UML_STUB_FIELD_OFFSET),
 		"g" (UML_STUB_FIELD_CHILD_ERR),
-		"S" (UM_KERN_PAGE_SIZE),
+		"S" (STUB_DATA_PAGES * UM_KERN_PAGE_SIZE),
 		"d" (PROT_READ | PROT_WRITE)
 		:
 		__syscall_clobber, "r10", "r8", "r9");
 }
 
-static __always_inline void *get_stub_page(void)
+static __always_inline void *get_stub_data(void)
 {
 	unsigned long ret;
 
@@ -117,7 +117,7 @@ static __always_inline void *get_stub_page(void)
 		"movq %%rsp,%0 ;"
 		"andq %1,%0"
 		: "=a" (ret)
-		: "g" (~(UM_KERN_PAGE_SIZE - 1)));
+		: "g" (~(STUB_DATA_PAGES * UM_KERN_PAGE_SIZE - 1)));
 
 	return (void *)ret;
 }

arch/x86/um/stub_segv.c

@@ -11,7 +11,7 @@
 void __attribute__ ((__section__ (".__syscall_stub")))
 stub_segv_handler(int sig, siginfo_t *info, void *p)
 {
-	struct faultinfo *f = get_stub_page();
+	struct faultinfo *f = get_stub_data();
 	ucontext_t *uc = p;
 
 	GET_FAULTINFO_FROM_MC(*f, &uc->uc_mcontext);

fs/Makefile

@@ -123,7 +123,7 @@ obj-$(CONFIG_9P_FS)		+= 9p/
 obj-$(CONFIG_AFS_FS)		+= afs/
 obj-$(CONFIG_NILFS2_FS)		+= nilfs2/
 obj-$(CONFIG_BEFS_FS)		+= befs/
-obj-$(CONFIG_HOSTFS)		+= hostfs/
+obj-y				+= hostfs/
 obj-$(CONFIG_CACHEFILES)	+= cachefiles/
 obj-$(CONFIG_DEBUG_FS)		+= debugfs/
 obj-$(CONFIG_TRACING)		+= tracefs/

fs/hostfs/Makefile

@@ -3,9 +3,11 @@
 # Licensed under the GPL
 #
 
-hostfs-objs := hostfs_kern.o hostfs_user.o
+hostfs-objs := hostfs_kern.o
 
-obj-y :=
+hostfs-builtin-$(CONFIG_HOSTFS) += hostfs_user.o hostfs_user_exp.o
+
+obj-y := $(hostfs-builtin-y) $(hostfs-builtin-m)
 obj-$(CONFIG_HOSTFS) += hostfs.o
 
 include $(srctree)/arch/um/scripts/Makefile.rules

fs/hostfs/hostfs_user_exp.c

@@ -0,0 +1,28 @@
+#include <linux/module.h>
+#include "hostfs.h"
+
+EXPORT_SYMBOL_GPL(stat_file);
+EXPORT_SYMBOL_GPL(access_file);
+EXPORT_SYMBOL_GPL(open_file);
+EXPORT_SYMBOL_GPL(open_dir);
+EXPORT_SYMBOL_GPL(seek_dir);
+EXPORT_SYMBOL_GPL(read_dir);
+EXPORT_SYMBOL_GPL(read_file);
+EXPORT_SYMBOL_GPL(write_file);
+EXPORT_SYMBOL_GPL(lseek_file);
+EXPORT_SYMBOL_GPL(fsync_file);
+EXPORT_SYMBOL_GPL(replace_file);
+EXPORT_SYMBOL_GPL(close_file);
+EXPORT_SYMBOL_GPL(close_dir);
+EXPORT_SYMBOL_GPL(file_create);
+EXPORT_SYMBOL_GPL(set_attr);
+EXPORT_SYMBOL_GPL(make_symlink);
+EXPORT_SYMBOL_GPL(unlink_file);
+EXPORT_SYMBOL_GPL(do_mkdir);
+EXPORT_SYMBOL_GPL(hostfs_do_rmdir);
+EXPORT_SYMBOL_GPL(do_mknod);
+EXPORT_SYMBOL_GPL(link_file);
+EXPORT_SYMBOL_GPL(hostfs_do_readlink);
+EXPORT_SYMBOL_GPL(rename_file);
+EXPORT_SYMBOL_GPL(rename2_file);
+EXPORT_SYMBOL_GPL(do_statfs);