um: merge arch/um/os-Linux/sys-{i386,x86_64}

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Richard Weinberger <richard@nod.at>

1 files changed, 150 insertions, 0 deletions

diff --git a/arch/um/os-Linux/sys-x86/task_size.c b/arch/um/os-Linux/sys-x86/task_size.c
new file mode 100644
index 000000000000..efb16c5c9bcf
--- /dev/null
+++ b/arch/um/os-Linux/sys-x86/task_size.c
@@ -0,0 +1,150 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <signal.h>
+#include <sys/mman.h>
+#include "longjmp.h"
+
+#ifdef __i386__
+
+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_top_address(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, original;
+
+        printf("Locating the bottom 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;
+        if (sigaction(SIGSEGV, &sa, &old)) {
+                perror("os_get_top_address");
+                exit(1);
+        }
+
+        /* Manually scan the address space, bottom-up, until we find
+         * the first valid page (or run out of them).
+         */
+        for (bottom = 0; bottom < top; bottom++) {
+                if (page_ok(bottom))
+                        break;
+        }
+
+        /* If we've got this far, we ran out of pages. */
+        if (bottom == top) {
+                fprintf(stderr, "Unable to determine bottom of address "
+                        "space.\n");
+                exit(1);
+        }
+
+        printf("0x%x\n", bottom << UM_KERN_PAGE_SHIFT);
+        printf("Locating the top of the address space ... ");
+        fflush(stdout);
+
+        original = bottom;
+
+        /* 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 */
+        if (sigaction(SIGSEGV, &old, NULL)) {
+                perror("os_get_top_address");
+                exit(1);
+        }
+        top <<= UM_KERN_PAGE_SHIFT;
+        printf("0x%x\n", top);
+
+        return top;
+}
+
+#else
+
+unsigned long os_get_top_address(void)
+{
+        /* The old value of CONFIG_TOP_ADDR */
+        return 0x7fc0000000;
+}
+
+#endif