efi/libstub: Skip GOP with PIXEL_BLT_ONLY format

Cohen, Eugene · Ingo Molnar · commit 540f4c0e894f · 2017-04-05T09:20:18.000+02:00
The UEFI Specification permits Graphics Output Protocol (GOP) instances without direct framebuffer access. This is indicated in the Mode structure with a PixelFormat enumeration value of PIXEL_BLT_ONLY. Given that the kernel does not know how to drive a Blt() only framebuffer (which is only permitted before ExitBootServices() anyway), we should disregard such framebuffers when looking for a GOP instance that is suitable for use as the boot console. So modify the EFI GOP initialization to not use a PIXEL_BLT_ONLY instance, preventing attempts later in boot to use an invalid screen_info.lfb_base address. Signed-off-by: Eugene Cohen <eugene@hp.com> [ Moved the Blt() only check into the loop and clarified that Blt() only GOPs are unusable by the kernel. ] Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: <stable@vger.kernel.org> # v4.7+ Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Matt Fleming <matt@codeblueprint.co.uk> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: leif.lindholm@linaro.org Cc: linux-efi@vger.kernel.org Cc: lorenzo.pieralisi@arm.com Fixes: 9822504 ("efifb: Enable the efi-framebuffer platform driver ...") Link: http://lkml.kernel.org/r/20170404152744.26687-2-ard.biesheuvel@linaro.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/drivers/firmware/efi/libstub/gop.c b/drivers/firmware/efi/libstub/gop.c
@@ -149,7 +149,8 @@ setup_gop32(efi_system_table_t *sys_table_arg, struct screen_info *si,
 
 		status = __gop_query32(sys_table_arg, gop32, &info, &size,
 				       &current_fb_base);
-		if (status == EFI_SUCCESS && (!first_gop || conout_found)) {
+		if (status == EFI_SUCCESS && (!first_gop || conout_found) &&
+		    info->pixel_format != PIXEL_BLT_ONLY) {
 			/*
 			 * Systems that use the UEFI Console Splitter may
 			 * provide multiple GOP devices, not all of which are
@@ -266,7 +267,8 @@ setup_gop64(efi_system_table_t *sys_table_arg, struct screen_info *si,
 
 		status = __gop_query64(sys_table_arg, gop64, &info, &size,
 				       &current_fb_base);
-		if (status == EFI_SUCCESS && (!first_gop || conout_found)) {
+		if (status == EFI_SUCCESS && (!first_gop || conout_found) &&
+		    info->pixel_format != PIXEL_BLT_ONLY) {
 			/*
 			 * Systems that use the UEFI Console Splitter may
 			 * provide multiple GOP devices, not all of which are
