x86: Use find_e820() instead of hard coded trampoline address

Jens found the following crash/regression:

[    0.000000] found SMP MP-table at [ffff8800000fdd80] fdd80
[    0.000000] Kernel panic - not syncing: Overlapping early reservations 12-f011 MP-table mpc to 0-fff BIOS data page

and

[    0.000000] Kernel panic - not syncing: Overlapping early reservations 12-f011 MP-table mpc to 6000-7fff TRAMPOLINE

and bisected it to b24c2a9 ("x86: Move find_smp_config()
earlier and avoid bootmem usage").

It turns out the BIOS is using the first 64k for mptable,
without reserving it.

So try to find good range for the real-mode trampoline instead of
hard coding it, in case some bios tries to use that range for sth.

Reported-by: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Tested-by: Jens Axboe <jens.axboe@oracle.com>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
LKML-Reference: <4B21630A.6000308@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 10 insertions, 1 deletions

diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index d17d482a04f4..f50447d961c0 100644
--- a/arch/x86/kernel/e820.c
+++ b/arch/x86/kernel/e820.c
@@ -732,7 +732,16 @@ struct early_res {
         char overlap_ok;
 };
 static struct early_res early_res[MAX_EARLY_RES] __initdata = {
-        { 0, PAGE_SIZE, "BIOS data page" },     /* BIOS data page */
+        { 0, PAGE_SIZE, "BIOS data page", 1 },  /* BIOS data page */
+#ifdef CONFIG_X86_32
+        /*
+         * But first pinch a few for the stack/trampoline stuff
+         * FIXME: Don't need the extra page at 4K, but need to fix
+         * trampoline before removing it. (see the GDT stuff)
+         */
+        { PAGE_SIZE, PAGE_SIZE, "EX TRAMPOLINE", 1 },
+#endif
+
         {}
 };