[PATCH] x86/boot: efistub: Assign global boot_params variable

[Ard Biesheuvel <ardb@google.com>]

From: Ard Biesheuvel <ardb@kernel.org>

Now that the x86 EFI stub calls into some APIs exposed by the
decompressor (e.g., kaslr_get_random_long()), it is necessary to ensure
that the global boot_params variable is set correctly before doing so.

Note that the decompressor and the kernel proper carry conflicting
declarations for the global variable 'boot_params' so refer to it via an
alias to work around this.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 drivers/firmware/efi/libstub/x86-stub.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/firmware/efi/libstub/x86-stub.c b/drivers/firmware/efi/libstub/x86-stub.c
index 3bfc59637dd1..51407207ded5 100644
--- a/drivers/firmware/efi/libstub/x86-stub.c
+++ b/drivers/firmware/efi/libstub/x86-stub.c
@@ -812,12 +812,15 @@ void __noreturn efi_stub_entry(efi_handle_t handle,
 			       efi_system_table_t *sys_table_arg,
 			       struct boot_params *boot_params)
 {
+	extern struct boot_params *bpp asm("boot_params");
 	efi_guid_t guid = EFI_MEMORY_ATTRIBUTE_PROTOCOL_GUID;
 	struct setup_header *hdr = &boot_params->hdr;
 	const struct linux_efi_initrd *initrd = NULL;
 	unsigned long kernel_entry;
 	efi_status_t status;
 
+	bpp = boot_params;
+
 	efi_system_table = sys_table_arg;
 	/* Check if we were booted by the EFI firmware */
 	if (efi_system_table->hdr.signature != EFI_SYSTEM_TABLE_SIGNATURE)
-- 
2.42.0.655.g421f12c284-goog