[tip:x86/urgent] x86/sysfb: Fix lfb_size calculation

From: tip-bot for David Herrmann
Date: Wed Nov 16 2016 - 07:09:59 EST


Commit-ID: f96acec8c8020807429d21324547f4b904c37177
Gitweb: http://git.kernel.org/tip/f96acec8c8020807429d21324547f4b904c37177
Author: David Herrmann <dh.herrmann@xxxxxxxxx>
AuthorDate: Tue, 15 Nov 2016 13:01:58 +0100
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Wed, 16 Nov 2016 09:38:23 +0100

x86/sysfb: Fix lfb_size calculation

The screen_info.lfb_size field is shifted by 16 bits *only* in case of
VBE. This has historical reasons since VBE advertised it similarly.
However, in case of EFI framebuffers, the size is no longer shifted. Fix
the x86 simple-framebuffer setup code to use the correct size in the
non-VBE case.

While at it, avoid variable abbreviations and rename 'len' to 'length',
and use the correct types matching the screen_info definition.

Signed-off-by: David Herrmann <dh.herrmann@xxxxxxxxx>
Acked-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Matt Fleming <matt.fleming@xxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Tom Gundersen <teg@xxxxxxx>
Link: http://lkml.kernel.org/r/20161115120158.15388-3-dh.herrmann@xxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
arch/x86/kernel/sysfb_simplefb.c | 25 +++++++++++++++++--------
1 file changed, 17 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kernel/sysfb_simplefb.c b/arch/x86/kernel/sysfb_simplefb.c
index 35b8641..85195d4 100644
--- a/arch/x86/kernel/sysfb_simplefb.c
+++ b/arch/x86/kernel/sysfb_simplefb.c
@@ -66,8 +66,8 @@ __init int create_simplefb(const struct screen_info *si,
{
struct platform_device *pd;
struct resource res;
- unsigned long len;
- u64 base;
+ u64 base, size;
+ u32 length;

/*
* If the 64BIT_BASE capability is set, ext_lfb_base will contain the
@@ -82,11 +82,20 @@ __init int create_simplefb(const struct screen_info *si,
return -EINVAL;
}

- /* don't use lfb_size as it may contain the whole VMEM instead of only
- * the part that is occupied by the framebuffer */
- len = mode->height * mode->stride;
- len = PAGE_ALIGN(len);
- if (len > (u64)si->lfb_size << 16) {
+ /*
+ * Don't use lfb_size as IORESOURCE size, since it may contain the
+ * entire VMEM, and thus require huge mappings. Use just the part we
+ * need, that is, the part where the framebuffer is located. But verify
+ * that it does not exceed the advertised VMEM.
+ * Note that in case of VBE, the lfb_size is shifted by 16 bits for
+ * historical reasons.
+ */
+ size = si->lfb_size;
+ if (si->orig_video_isVGA == VIDEO_TYPE_VLFB)
+ size <<= 16;
+ length = mode->height * mode->stride;
+ length = PAGE_ALIGN(length);
+ if (length > size) {
printk(KERN_WARNING "sysfb: VRAM smaller than advertised\n");
return -EINVAL;
}
@@ -96,7 +105,7 @@ __init int create_simplefb(const struct screen_info *si,
res.flags = IORESOURCE_MEM | IORESOURCE_BUSY;
res.name = simplefb_resname;
res.start = base;
- res.end = res.start + len - 1;
+ res.end = res.start + length - 1;
if (res.end <= res.start)
return -EINVAL;