diff mbox series

[v4,16/26] x86/boot: Reduce lower limit of physical KASLR

Message ID 672320297f9d8860ddafbfa90933f8df7b537a5d.1671098103.git.baskov@ispras.ru
State New
Headers
Series x86_64: Improvements at compressed kernel stage |

Commit Message

Evgeniy Baskov Dec. 15, 2022, 12:38 p.m. UTC 
  Set lower limit of physical KASLR to 64M.

Previously is was set to 512M when kernel is loaded higher than that.
That prevented physical KASLR from being performed on x86_32, where
upper limit is also set to 512M. The limit is pretty arbitrary, and the
most important is to set it above the ISA hole, i.e. higher than 16M.

It was not that important before, but now kernel is not getting
relocated to the lower address when booting via EFI, exposing the
KASLR failures.

Tested-by: Mario Limonciello <mario.limonciello@amd.com>
Tested-by: Peter Jones <pjones@redhat.com>
Signed-off-by: Evgeniy Baskov <baskov@ispras.ru>
---
 arch/x86/boot/compressed/kaslr.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index c0ee116c4fa2..74d1327adbba 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -852,10 +852,10 @@  void choose_random_location(unsigned long input,
 
 	/*
 	 * Low end of the randomization range should be the
-	 * smaller of 512M or the initial kernel image
+	 * smaller of 64M or the initial kernel image
 	 * location:
 	 */
-	min_addr = min(*output, 512UL << 20);
+	min_addr = min(*output, 64UL << 20);
 	/* Make sure minimum is aligned. */
 	min_addr = ALIGN(min_addr, CONFIG_PHYSICAL_ALIGN);