vmcore: check if vmcore objects satify mmap()'s page-size boundary requirement

If there's some vmcore object that doesn't satisfy page-size boundary
requirement, remap_pfn_range() fails to remap it to user-space.

Objects that possibly don't satisfy the requirement are ELF note segments
only.  The memory chunks corresponding to PT_LOAD entries are guaranteed
to satisfy page-size boundary requirement by the copy from old memory to
buffer in 2nd kernel done in later patch.

This patch doesn't copy each note segment into the 2nd kernel since they
amount to so large in total if there are multiple CPUs.  For example,
current maximum number of CPUs in x86_64 is 5120, where note segments
exceed 1MB with NT_PRSTATUS only.

Signed-off-by: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>
Cc: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
index 2a0f8850c05a23dec9650cd8aed800600d31e421..0077a9a880ce81dc593aa1daf6c7350f210cf87f 100644 (file)
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -38,6 +38,8 @@ static u64 vmcore_size;
 
 static struct proc_dir_entry *proc_vmcore = NULL;
 
+static bool support_mmap_vmcore;
+
 /*
  * Returns > 0 for RAM pages, 0 for non-RAM pages, < 0 on error
  * The called function has to take care of module refcounting.
@@ -911,6 +913,7 @@ static int __init parse_crash_elf_headers(void)
 static int __init vmcore_init(void)
 {
        int rc = 0;
+       struct vmcore *m;
 
        /* If elfcorehdr= has been passed in cmdline, then capture the dump.*/
        if (!(is_vmcore_usable()))
@@ -921,6 +924,25 @@ static int __init vmcore_init(void)
                return rc;
        }
 
+       /* If some object doesn't satisfy PAGE_SIZE boundary
+        * requirement, mmap_vmcore() is not exported to
+        * user-space. */
+       support_mmap_vmcore = true;
+       list_for_each_entry(m, &vmcore_list, list) {
+               u64 paddr;
+
+               if (m->flag & MEM_TYPE_CURRENT_KERNEL)
+                       paddr = (u64)__pa(m->buf);
+               else
+                       paddr = m->paddr;
+
+               if ((m->offset & ~PAGE_MASK) || (paddr & ~PAGE_MASK)
+                   || (m->size & ~PAGE_MASK)) {
+                       support_mmap_vmcore = false;
+                       break;
+               }
+       }
+
        proc_vmcore = proc_create("vmcore", S_IRUSR, NULL, &proc_vmcore_operations);
        if (proc_vmcore)
                proc_vmcore->size = vmcore_size;