[tip:efi/urgent] x86/sysfb_efi: Fix valid BAR address range check

From: tip-bot for Wang YanQing
Date: Thu May 05 2016 - 10:04:47 EST


Commit-ID: c10fcb14c7afd6688c7b197a814358fecf244222
Gitweb: http://git.kernel.org/tip/c10fcb14c7afd6688c7b197a814358fecf244222
Author: Wang YanQing <udknight@xxxxxxxxx>
AuthorDate: Thu, 5 May 2016 14:14:21 +0100
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Thu, 5 May 2016 16:01:00 +0200

x86/sysfb_efi: Fix valid BAR address range check

The code for checking whether a BAR address range is valid will break
out of the loop when a start address of 0x0 is encountered.

This behaviour is wrong since by breaking out of the loop we may miss
the BAR that describes the EFI frame buffer in a later iteration.

Because of this bug I can't use video=efifb: boot parameter to get
efifb on my new ThinkPad E550 for my old linux system hard disk with
3.10 kernel. In 3.10, efifb is the only choice due to DRM/I915 not
supporting the GPU.

This patch also add a trivial optimization to break out after we find
the frame buffer address range without testing later BARs.

Signed-off-by: Wang YanQing <udknight@xxxxxxxxx>
[ Rewrote changelog. ]
Signed-off-by: Matt Fleming <matt@xxxxxxxxxxxxxxxxxxx>
Reviewed-by: Peter Jones <pjones@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
Cc: David Herrmann <dh.herrmann@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Tomi Valkeinen <tomi.valkeinen@xxxxxx>
Cc: linux-efi@xxxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/1462454061-21561-2-git-send-email-matt@xxxxxxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
arch/x86/kernel/sysfb_efi.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/sysfb_efi.c b/arch/x86/kernel/sysfb_efi.c
index b285d4e..5da924b 100644
--- a/arch/x86/kernel/sysfb_efi.c
+++ b/arch/x86/kernel/sysfb_efi.c
@@ -106,14 +106,24 @@ static int __init efifb_set_system(const struct dmi_system_id *id)
continue;
for (i = 0; i < DEVICE_COUNT_RESOURCE; i++) {
resource_size_t start, end;
+ unsigned long flags;
+
+ flags = pci_resource_flags(dev, i);
+ if (!(flags & IORESOURCE_MEM))
+ continue;
+
+ if (flags & IORESOURCE_UNSET)
+ continue;
+
+ if (pci_resource_len(dev, i) == 0)
+ continue;

start = pci_resource_start(dev, i);
- if (start == 0)
- break;
end = pci_resource_end(dev, i);
if (screen_info.lfb_base >= start &&
screen_info.lfb_base < end) {
found_bar = 1;
+ break;
}
}
}