qemu-efi-aarch64 now implements EFI Memory Attribute Protocol. When shim detects this, it uses it to set memory attributes appropriately for the sections of the bootloader image it loads before passing control to it. After this change, fresh Ubuntu VMs began crashing on startup (bug 2036604):
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BdsDxe: loading Boot0001 "UEFI Misc Device" from PciRoot(0x0)/Pci(0x1,0x3)/Pci(0x0,0x0)
BdsDxe: starting Boot0001 "UEFI Misc Device" from PciRoot(0x0)/Pci(0x1,0x3)/Pci(0x0,0x0)
Synchronous Exception at 0x00000000BC300000
Synchronous Exception at 0x00000000BC300000
--------------------------------------
I narrowed this down to only happening when shim executes fbaa64.efi (thus the fresh VM). I found upstream shim is unaffected, so I used bisection to identify the relevant change:
From c7b305152802c8db688605654f75e1195def9fd6 Mon Sep 17 00:00:00 2001
From: Nicholas Bishop <REDACTED>
Date: Mon, 19 Dec 2022 18:56:13 -0500
Subject: [PATCH] pe: Align section size up to page size for mem attrs
Setting memory attributes is generally done at page granularity, and
this is enforced by checks in `get_mem_attrs` and
`update_mem_attrs`. But unlike the section address, the section size
isn't necessarily aligned to 4KiB. Round up the section size to fix
this.
Signed-off-by: Nicholas Bishop <email address hidden>
shim 15.7-0ubuntu1
qemu-efi-aarch64 now implements EFI Memory Attribute Protocol. When shim detects this, it uses it to set memory attributes appropriately for the sections of the bootloader image it loads before passing control to it. After this change, fresh Ubuntu VMs began crashing on startup (bug 2036604):
----- ------- ------- ------- ------- ----- 0x0)/Pci( 0x1,0x3) /Pci(0x0, 0x0) 0x0)/Pci( 0x1,0x3) /Pci(0x0, 0x0)
BdsDxe: loading Boot0001 "UEFI Misc Device" from PciRoot(
BdsDxe: starting Boot0001 "UEFI Misc Device" from PciRoot(
Synchronous Exception at 0x00000000BC300000
Synchronous Exception at 0x00000000BC300000
----- ------- ------- ------- ------- -----
I narrowed this down to only happening when shim executes fbaa64.efi (thus the fresh VM). I found upstream shim is unaffected, so I used bisection to identify the relevant change:
From c7b305152802c8d b688605654f75e1 195def9fd6 Mon Sep 17 00:00:00 2001
From: Nicholas Bishop <REDACTED>
Date: Mon, 19 Dec 2022 18:56:13 -0500
Subject: [PATCH] pe: Align section size up to page size for mem attrs
Setting memory attributes is generally done at page granularity, and mem_attrs` . But unlike the section address, the section size
this is enforced by checks in `get_mem_attrs` and
`update_
isn't necessarily aligned to 4KiB. Round up the section size to fix
this.
Signed-off-by: Nicholas Bishop <email address hidden>
Please add this patch to shim.