Date: Sat, 19 Jun 2021 20:55:08 UTC
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=256722 Bug ID: 256722 Summary: [PATCH] EFI boot: Fix boot freeze on some systems Product: Base System Version: CURRENT Hardware: amd64 OS: Any Status: New Severity: Affects Many People Priority: --- Component: misc Assignee: bugs@FreeBSD.org Reporter: email@example.com Created attachment 225941 --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=225941&action=edit [PATCH] efi: loader: Fix a boot freeze on some amd64 systems This is a copy of a patch from Bug 209821. I am creating a new ticket for it so that it does not get lost. Users keep reporting that when booting in UEFI mode, the boot process freezes after displaying framebuffer information. This patch fixes the problem for me and for some other people who tried it. After this patch gets mainlined, it will be easier to distinguish boot issues caused by this bug from those caused by something else. This patch fixes a bug that seems to be present on all supported FreeBSD versions. This patch addresses a problem that, immediately before the kernel is started, the amd64_tramp function calls the efi_copy_finish function to copy the kernel image from a temporary staging area in the memory to the actual memory address where the kernel expects to be run from. The problem is that the boot loader, including the efi_copy_finish function, may have been loaded by the UEFI firmware somewhere in the range where the kernel is being copied to. The efi_copy_finish function may thus overwrite its own instructions by the kernel image, causing the system to freeze. This is not a problem for the amd64_tramp trampoline itself, which is first copied to a safe memory location before it is executed. My patch does the following: - Instead of calling the efi_copy_finish function, which may be located anywhere in the memory, the copy operation is done by the trampoline itself. This is the most important part of the patch. - Adds missing return value checks. - Before the kernel is copied from the staging area, a new efi_verify_destination_type function checks that the target memory area is safe to use. If not, it only prints a warning message. (This is useful mainly for debugging purposes when a system freezes.) Because I changed the parameters of the trampoline function, I created a new amd64_tramp_inline function and kept the original amd64_tramp intact in order not to break any other existing code. However, the amd64_tramp function does not seem to be used anywhere else in the existing code, so it could be modified directly. The efi_copy_finish function is not needed anymore too. -- You are receiving this mail because: You are the assignee for the bug.