diff options
Diffstat (limited to 'arch/um/os-Linux/sys-i386')
-rw-r--r-- | arch/um/os-Linux/sys-i386/Makefile | 2 | ||||
-rw-r--r-- | arch/um/os-Linux/sys-i386/registers.c | 4 | ||||
-rw-r--r-- | arch/um/os-Linux/sys-i386/task_size.c | 120 |
3 files changed, 123 insertions, 3 deletions
diff --git a/arch/um/os-Linux/sys-i386/Makefile b/arch/um/os-Linux/sys-i386/Makefile index a841262c594..b4bc6ac4f30 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/registers.c b/arch/um/os-Linux/sys-i386/registers.c index d1997ca76e5..f74d853a0ee 100644 --- a/arch/um/os-Linux/sys-i386/registers.c +++ b/arch/um/os-Linux/sys-i386/registers.c @@ -62,10 +62,10 @@ void arch_init_registers(int pid) int err; err = ptrace(PTRACE_GETFPXREGS, pid, 0, fpx_regs); - if(!err) + if (!err) return; - if(errno != EIO) + if (errno != EIO) panic("check_ptrace : PTRACE_GETFPXREGS failed, errno = %d", errno); 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 00000000000..48d211b3d9a --- /dev/null +++ b/arch/um/os-Linux/sys-i386/task_size.c @@ -0,0 +1,120 @@ +#include <stdio.h> +#include <stdlib.h> +#include <signal.h> +#include <sys/mman.h> +#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; +} |