[PATCH] uml: fix static binary segfault

When UML is built as a static binary, it segfaults when run.  The reason is
that a memory hole that is present in dynamic binaries isn't there in static
binaries, and it contains essential stuff.

This fix removes the code which maps some anonymous memory into that hole and
cleans up some related code.

Signed-off-by: Jeff Dike <jdike@addtoit.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/arch/um/include/skas/mode_kern_skas.h b/arch/um/include/skas/mode_kern_skas.h
index 651350adfe036aa4fca66cd3b52da779fbf202df..9cd9c6ec9a63a35ef71278730a1d752d75c7a5bd 100644 (file)
--- a/arch/um/include/skas/mode_kern_skas.h
+++ b/arch/um/include/skas/mode_kern_skas.h
@@ -29,8 +29,7 @@ extern void flush_tlb_mm_skas(struct mm_struct *mm);
 extern void force_flush_all_skas(void);
 extern long execute_syscall_skas(void *r);
 extern void before_mem_skas(unsigned long unused);
-extern unsigned long set_task_sizes_skas(unsigned long *host_size_out,
-                                        unsigned long *task_size_out);
+extern unsigned long set_task_sizes_skas(unsigned long *task_size_out);
 extern int start_uml_skas(void);
 extern int external_pid_skas(struct task_struct *task);
 extern int thread_pid_skas(struct task_struct *task);

diff --git a/arch/um/include/tt/mode_kern_tt.h b/arch/um/include/tt/mode_kern_tt.h
index fb2d3d76685adfd5d529cd25c6b24f54747be48b..a4fc63057195aaa3e0ec3260ae44e5832da7ad98 100644 (file)
--- a/arch/um/include/tt/mode_kern_tt.h
+++ b/arch/um/include/tt/mode_kern_tt.h
@@ -30,8 +30,7 @@ extern void flush_tlb_mm_tt(struct mm_struct *mm);
 extern void force_flush_all_tt(void);
 extern long execute_syscall_tt(void *r);
 extern void before_mem_tt(unsigned long brk_start);
-extern unsigned long set_task_sizes_tt(unsigned long *host_size_out,
-                                      unsigned long *task_size_out);
+extern unsigned long set_task_sizes_tt(unsigned long *task_size_out);
 extern int start_uml_tt(void);
 extern int external_pid_tt(struct task_struct *task);
 extern int thread_pid_tt(struct task_struct *task);

diff --git a/arch/um/kernel/mem.c b/arch/um/kernel/mem.c
index 44e41a35f000cd667c737d856d1f48af0f6bf200..61280167c560dd63411c105663f93519b5818817 100644 (file)
--- a/arch/um/kernel/mem.c
+++ b/arch/um/kernel/mem.c
@@ -24,8 +24,6 @@
 #include "init.h"
 #include "kern_constants.h"
 
-extern char __binary_start;
-
 /* Changed during early boot */
 unsigned long *empty_zero_page = NULL;
 unsigned long *empty_bad_page = NULL;
@@ -65,8 +63,6 @@ static void setup_highmem(unsigned long highmem_start,
 
 void mem_init(void)
 {
-       unsigned long start;
-
        max_low_pfn = (high_physmem - uml_physmem) >> PAGE_SHIFT;
 
         /* clear the zero-page */
@@ -81,13 +77,6 @@ void mem_init(void)
        free_bootmem(__pa(brk_end), uml_reserved - brk_end);
        uml_reserved = brk_end;
 
-       /* Fill in any hole at the start of the binary */
-       start = (unsigned long) &__binary_start & PAGE_MASK;
-       if(uml_physmem != start){
-               map_memory(uml_physmem, __pa(uml_physmem), start - uml_physmem,
-                          1, 1, 0);
-       }
-
        /* this will put all low memory onto the freelists */
        totalram_pages = free_all_bootmem();
        totalhigh_pages = highmem >> PAGE_SHIFT;

diff --git a/arch/um/kernel/physmem.c b/arch/um/kernel/physmem.c
index 166cb09cae4cf9f05079d84ea88ef5f7770551e4..abafa64b8727ecef4e0b35f04fbcae7d7551662a 100644 (file)
--- a/arch/um/kernel/physmem.c
+++ b/arch/um/kernel/physmem.c
@@ -317,7 +317,7 @@ void map_memory(unsigned long virt, unsigned long phys, unsigned long len,
        }
 }
 
-extern int __syscall_stub_start, __binary_start;
+extern int __syscall_stub_start;
 
 void setup_physmem(unsigned long start, unsigned long reserve_end,
                   unsigned long len, unsigned long long highmem)

diff --git a/arch/um/kernel/skas/mem.c b/arch/um/kernel/skas/mem.c
index 7e5b8f165cf29ccfb58d71682f73bee6535269bd..27bbf54b1e52a1b84fff2fd11f866582a95bb685 100644 (file)
--- a/arch/um/kernel/skas/mem.c
+++ b/arch/um/kernel/skas/mem.c
@@ -9,20 +9,19 @@
 #include "mem_user.h"
 #include "skas.h"
 
-unsigned long set_task_sizes_skas(unsigned long *host_size_out,
-                                 unsigned long *task_size_out)
+unsigned long set_task_sizes_skas(unsigned long *task_size_out)
 {
        /* Round up to the nearest 4M */
-       unsigned long top = ROUND_4M((unsigned long) &host_size_out);
+       unsigned long host_task_size = ROUND_4M((unsigned long)
+                                               &host_task_size);
 
 #ifdef CONFIG_HOST_TASK_SIZE
        *host_size_out = ROUND_4M(CONFIG_HOST_TASK_SIZE);
        *task_size_out = CONFIG_HOST_TASK_SIZE;
 #else
-       *host_size_out = top;
        if (!skas_needs_stub)
-               *task_size_out = top;
+               *task_size_out = host_task_size;
        else *task_size_out = CONFIG_STUB_START & PGDIR_MASK;
 #endif
-       return ((unsigned long) set_task_sizes_skas) & ~0xffffff;
+       return host_task_size;
 }

diff --git a/arch/um/kernel/tt/mem.c b/arch/um/kernel/tt/mem.c
index 4ae8c5c1e3b316697d4c9dfabe70500a23bfd7f3..84a23b14f770b308dca9b06a982dc264706af5a9 100644 (file)
--- a/arch/um/kernel/tt/mem.c
+++ b/arch/um/kernel/tt/mem.c
@@ -24,11 +24,13 @@ void before_mem_tt(unsigned long brk_start)
 #define SIZE ((CONFIG_NEST_LEVEL + CONFIG_KERNEL_HALF_GIGS) * 0x20000000)
 #define START (CONFIG_TOP_ADDR - SIZE)
 
-unsigned long set_task_sizes_tt(unsigned long *host_size_out,
-                               unsigned long *task_size_out)
+unsigned long set_task_sizes_tt(unsigned long *task_size_out)
 {
+       unsigned long host_task_size;
+
        /* Round up to the nearest 4M */
-       *host_size_out = ROUND_4M((unsigned long) &host_size_out);
+       host_task_size = ROUND_4M((unsigned long) &host_task_size);
        *task_size_out = START;
-       return START;
+
+       return host_task_size;
 }

diff --git a/arch/um/kernel/um_arch.c b/arch/um/kernel/um_arch.c
index a50a0aac8faa2e1a04d51d1b1ca4293ea0e24a29..7896cf98232df1a06c6593957e24597b8dbb7e04 100644 (file)
--- a/arch/um/kernel/um_arch.c
+++ b/arch/um/kernel/um_arch.c
@@ -330,6 +330,8 @@ EXPORT_SYMBOL(end_iomem);
 
 #define MIN_VMALLOC (32 * 1024 * 1024)
 
+extern char __binary_start;
+
 int linux_main(int argc, char **argv)
 {
        unsigned long avail, diff;
@@ -374,8 +376,9 @@ int linux_main(int argc, char **argv)
 
        printf("UML running in %s mode\n", mode);
 
-       uml_start = CHOOSE_MODE_PROC(set_task_sizes_tt, set_task_sizes_skas,
-                                    &host_task_size, &task_size);
+       uml_start = (unsigned long) &__binary_start;
+       host_task_size = CHOOSE_MODE_PROC(set_task_sizes_tt,
+                                         set_task_sizes_skas, &task_size);
 
        /*
         * Setting up handlers to 'sig_info' struct
@@ -395,7 +398,7 @@ int linux_main(int argc, char **argv)
                physmem_size += UML_ROUND_UP(brk_start) - UML_ROUND_UP(&_end);
        }
 
-       uml_physmem = uml_start;
+       uml_physmem = uml_start & PAGE_MASK;
 
        /* Reserve up to 4M after the current brk */
        uml_reserved = ROUND_4M(brk_start) + (1 << 22);

diff --git a/arch/um/kernel/uml.lds.S b/arch/um/kernel/uml.lds.S
index af11915ce0a8ca5155dad601c853b138f250277a..8eca47a6ff082f171d76777ebb46d2601c282dcf 100644 (file)
--- a/arch/um/kernel/uml.lds.S
+++ b/arch/um/kernel/uml.lds.S
@@ -7,13 +7,16 @@ jiffies = jiffies_64;
 
 SECTIONS
 {
-  /*This must contain the right address - not quite the default ELF one.*/
+  /* This must contain the right address - not quite the default ELF one.*/
   PROVIDE (__executable_start = START);
-  . = START + SIZEOF_HEADERS;
+  /* Static binaries stick stuff here, like the sigreturn trampoline,
+   * invisibly to objdump.  So, just make __binary_start equal to the very
+   * beginning of the executable, and if there are unmapped pages after this,
+   * they are forever unusable.
+   */
+  __binary_start = START;
 
-  /* Used in arch/um/kernel/mem.c. Any memory between START and __binary_start
-   * is remapped.*/
-  __binary_start = .;
+  . = START + SIZEOF_HEADERS;
 
 #ifdef MODE_TT
   .remap_data : { UNMAP_PATH (.data .bss) }