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authorSimon Horman <horms@verge.net.au>2008-10-18 20:28:29 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2008-10-20 08:52:40 -0700
commit85a0ee342e0c06c19d78fdf48307211c6cf18fcb (patch)
tree60022c0dca3c2dfc3084d1b301d349f6dcab5363
parent630bf20747e27391b20f137a5be2edb4235ca8fa (diff)
kdump: add is_vmcore_usable() and vmcore_unusable()
The usage of elfcorehdr_addr has changed recently such that being set to ELFCORE_ADDR_MAX is used by is_kdump_kernel() to indicate if the code is executing in a kernel executed as a crash kernel. However, arch/ia64/kernel/setup.c:reserve_elfcorehdr will rest elfcorehdr_addr to ELFCORE_ADDR_MAX on error, which means any subsequent calls to is_kdump_kernel() will return 0, even though they should return 1. Ok, at this point in time there are no subsequent calls, but I think its fair to say that there is ample scope for error or at the very least confusion. This patch add an extra state, ELFCORE_ADDR_ERR, which indicates that elfcorehdr_addr was passed on the command line, and thus execution is taking place in a crashdump kernel, but vmcore can't be used for some reason. This is tested for using is_vmcore_usable() and set using vmcore_unusable(). A subsequent patch makes use of this new code. To summarise, the states that elfcorehdr_addr can now be in are as follows: ELFCORE_ADDR_MAX: not a crashdump kernel ELFCORE_ADDR_ERR: crashdump kernel but vmcore is unusable any other value: crash dump kernel and vmcore is usable Signed-off-by: Simon Horman <horms@verge.net.au> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--arch/ia64/kernel/setup.c4
-rw-r--r--fs/proc/vmcore.c2
-rw-r--r--include/linux/crash_dump.h24
3 files changed, 27 insertions, 3 deletions
diff --git a/arch/ia64/kernel/setup.c b/arch/ia64/kernel/setup.c
index a0286be6c23..60286522d54 100644
--- a/arch/ia64/kernel/setup.c
+++ b/arch/ia64/kernel/setup.c
@@ -509,11 +509,11 @@ int __init reserve_elfcorehdr(unsigned long *start, unsigned long *end)
* to work properly.
*/
- if (elfcorehdr_addr >= ELFCORE_ADDR_MAX)
+ if (!is_vmcore_usable())
return -EINVAL;
if ((length = vmcore_find_descriptor_size(elfcorehdr_addr)) == 0) {
- elfcorehdr_addr = ELFCORE_ADDR_MAX;
+ vmcore_unusable();
return -EINVAL;
}
diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
index 4c65ca432d3..cd9ca67f841 100644
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -644,7 +644,7 @@ static int __init vmcore_init(void)
int rc = 0;
/* If elfcorehdr= has been passed in cmdline, then capture the dump.*/
- if (!(elfcorehdr_addr < ELFCORE_ADDR_MAX))
+ if (!(is_vmcore_usable()))
return rc;
rc = parse_crash_elf_headers();
if (rc) {
diff --git a/include/linux/crash_dump.h b/include/linux/crash_dump.h
index de027d1db74..0acf3b737e2 100644
--- a/include/linux/crash_dump.h
+++ b/include/linux/crash_dump.h
@@ -8,6 +8,7 @@
#include <linux/proc_fs.h>
#define ELFCORE_ADDR_MAX (-1ULL)
+#define ELFCORE_ADDR_ERR (-2ULL)
extern unsigned long long elfcorehdr_addr;
@@ -38,6 +39,29 @@ static inline int is_kdump_kernel(void)
{
return (elfcorehdr_addr != ELFCORE_ADDR_MAX) ? 1 : 0;
}
+
+/* is_vmcore_usable() checks if the kernel is booting after a panic and
+ * the vmcore region is usable.
+ *
+ * This makes use of the fact that due to alignment -2ULL is not
+ * a valid pointer, much in the vain of IS_ERR(), except
+ * dealing directly with an unsigned long long rather than a pointer.
+ */
+
+static inline int is_vmcore_usable(void)
+{
+ return is_kdump_kernel() && elfcorehdr_addr != ELFCORE_ADDR_ERR ? 1 : 0;
+}
+
+/* vmcore_unusable() marks the vmcore as unusable,
+ * without disturbing the logic of is_kdump_kernel()
+ */
+
+static inline void vmcore_unusable(void)
+{
+ if (is_kdump_kernel())
+ elfcorehdr_addr = ELFCORE_ADDR_ERR;
+}
#else /* !CONFIG_CRASH_DUMP */
static inline int is_kdump_kernel(void) { return 0; }
#endif /* CONFIG_CRASH_DUMP */