x86/debug: Extend the lower bound of crash kernel low reservations

The following change in 2013:

  0212f9159694 ("x86: Add Crash kernel low reservation")

... introduced reserve_crashkernel_low(). This function is used to
reserve crash kernel memory either if crashkernel=size,low is given
on the command line or if the region reserved by reserve_crashkernel
is entirely above 4G.

reserve_crashkernel_low() tries to find a block of 'low_size' bytes.
But there seems to be no good reason to restrict the lower bound
of the range to 'low_size'.

Make memblock_find_in_range() search from the start of memory.

Signed-off-by: Jiri Bohac <[email protected]>
Cc: Eric Biederman <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Yinghai Lu <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

1 files changed, 1 insertions, 1 deletions

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 0b4d3c686b1e..848d0489ad00 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -503,7 +503,7 @@ static int __init reserve_crashkernel_low(void)
 			return 0;
 	}
 
-	low_base = memblock_find_in_range(low_size, 1ULL << 32, low_size, CRASH_ALIGN);
+	low_base = memblock_find_in_range(0, 1ULL << 32, low_size, CRASH_ALIGN);
 	if (!low_base) {
 		pr_err("Cannot reserve %ldMB crashkernel low memory, please try smaller size.\n",
 		       (unsigned long)(low_size >> 20));