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stub: Relocate kernels below 4G for EFI handover

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Old kernels can fail to boot when they are located above the 4G
boundary even if they claim to support it.

Fixes: #27472
This commit is contained in:
Jan Janssen
2023-05-01 19:08:12 +02:00
parent 6fd3ee6916
commit 669f16acf7
1 changed files with 20 additions and 8 deletions
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src/boot/efi/linux_x86.c
+20 -8
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@@ -104,8 +104,7 @@ static void linux_efi_handover(EFI_HANDLE parent, uintptr_t kernel, BootParams *
kernel += (params->hdr.setup_sects + 1) * KERNEL_SECTOR_SIZE; /* 32bit entry address. */
/* Old kernels needs this set, while newer ones seem to ignore this. Note that this gets truncated on
* above 4G boots, which is fine as long as we do not use the value to jump to kernel entry. */
/* Old kernels needs this set, while newer ones seem to ignore this. */
params->hdr.code32_start = kernel;
#ifdef __x86_64__
@@ -153,12 +152,25 @@ EFI_STATUS linux_exec_efi_handover(
bool can_4g = image_params->hdr.version >= SETUP_VERSION_2_12 &&
FLAGS_SET(image_params->hdr.xloadflags, XLF_CAN_BE_LOADED_ABOVE_4G);
if (!can_4g && POINTER_TO_PHYSICAL_ADDRESS(linux_buffer) + linux_length > UINT32_MAX)
return log_error_status(
EFI_UNSUPPORTED,
"Unified kernel image was loaded above 4G, but kernel lacks support.");
if (!can_4g && POINTER_TO_PHYSICAL_ADDRESS(initrd_buffer) + initrd_length > UINT32_MAX)
return log_error_status(EFI_UNSUPPORTED, "Initrd is above 4G, but kernel lacks support.");
/* There is no way to pass the high bits of code32_start. Newer kernels seems to handle this
* just fine, but older kernels will fail even if they otherwise have above 4G boot support. */
_cleanup_pages_ Pages linux_relocated = {};
if (POINTER_TO_PHYSICAL_ADDRESS(linux_buffer) + linux_length > UINT32_MAX) {
linux_relocated = xmalloc_pages(
AllocateMaxAddress, EfiLoaderCode, EFI_SIZE_TO_PAGES(linux_length), UINT32_MAX);
linux_buffer = memcpy(
PHYSICAL_ADDRESS_TO_POINTER(linux_relocated.addr), linux_buffer, linux_length);
}
_cleanup_pages_ Pages initrd_relocated = {};
if (!can_4g && POINTER_TO_PHYSICAL_ADDRESS(initrd_buffer) + initrd_length > UINT32_MAX) {
initrd_relocated = xmalloc_pages(
AllocateMaxAddress, EfiLoaderData, EFI_SIZE_TO_PAGES(initrd_length), UINT32_MAX);
initrd_buffer = memcpy(
PHYSICAL_ADDRESS_TO_POINTER(initrd_relocated.addr),
initrd_buffer,
initrd_length);
}
_cleanup_pages_ Pages boot_params_page = xmalloc_pages(
can_4g ? AllocateAnyPages : AllocateMaxAddress,