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video: fbdev: uvesafb: use CONFIG_X86_PAE surround _PAGE_NX check code

PATCH In review Wang YanQing 2 participants 3 messages Mar 5, 2014 – Mar 6, 2014

Subsystems (2)
Framebuffer layer Uvesafb driver
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Wang YanQing

author
#0 lore raw

PATCH 1/1 video: fbdev: uvesafb: use CONFIG_X86_PAE surround _PAGE_NX check code

Because _PAGE_NX check will always false when we don't define CONFIG_X86_PAE for CONFIG_X86_32, so use CONFIG_X86_PAE surround the check code.

Although I believe "smart" compile will optimize out and generate the same code, but use CONFIG_X86_PAE surround check code will clear it and prohibit warning from static source code analyze tool.

[ This patch fix warning report by [email protected]
"drivers/video/fbdev/uvesafb.c:816 uvesafb_vbe_init()
warn: bitwise AND condition is false here" ]

Signed-off-by Wang YanQing <[email protected]>
---
 drivers/video/fbdev/uvesafb.c | 4 ++++
 1 file changed, 4 insertions(+)
drivers/video/fbdev/uvesafb.c +4 -0
index 509d452..102858c 100644
@@ -813,6 +813,7 @@ static int uvesafb_vbe_init(struct fb_info *info)
 	par->ypan = ypan;
 
 	if (par->pmi_setpal || par->ypan) {
+#ifdef CONFIG_X86_PAE
 		if (__supported_pte_mask & _PAGE_NX) {
 			par->pmi_setpal = par->ypan = 0;
 			printk(KERN_WARNING "uvesafb: NX protection is active, "

@@ -820,6 +821,9 @@ static int uvesafb_vbe_init(struct fb_info *info)
 		} else {
 			uvesafb_vbe_getpmi(task, par);
 		}
+#else
+		uvesafb_vbe_getpmi(task, par);
+#endif
 	}
 #else
 	/* The protected mode interface is not available on non-x86. */
Signature · 1 line
1.8.3.4.8.g69490f3.dirty
#1 lore raw
Quoted 30 lines · Wang YanQing

Because _PAGE_NX check will always false when we don't define CONFIG_X86_PAE for CONFIG_X86_32, so use CONFIG_X86_PAE surround the check code.

Although I believe "smart" compile will optimize out and generate the same code, but use CONFIG_X86_PAE surround check code will clear it and prohibit warning from static source code analyze tool.

[ This patch fix warning report by [email protected]
"drivers/video/fbdev/uvesafb.c:816 uvesafb_vbe_init()
warn: bitwise AND condition is false here" ]

Signed-off-by Wang YanQing <[email protected]>
---
 drivers/video/fbdev/uvesafb.c | 4 ++++
 1 file changed, 4 insertions(+)
drivers/video/fbdev/uvesafb.c +1 -0
index 509d452..102858c 100644
@@ -813,6 +813,7 @@ static int uvesafb_vbe_init(struct fb_info *info)
 	par->ypan = ypan;
 
 	if (par->pmi_setpal || par->ypan) {
+#ifdef CONFIG_X86_PAE
 		if (__supported_pte_mask & _PAGE_NX) {
 			par->pmi_setpal = par->ypan = 0;
 			printk(KERN_WARNING "uvesafb: NX protection is active, "

drivers/video/fbdev/uvesafb.c static int uvesafb_vbe_init(struct fb_info *info) · line 827

Quoted 7 lines
drivers/video/fbdev/uvesafb.c +3 -0
@@ -820,6 +821,9 @@ static int uvesafb_vbe_init(struct fb_info *info)
 		} else {
 			uvesafb_vbe_getpmi(task, par);
 		}
+#else
+		uvesafb_vbe_getpmi(task, par);
+#endif
 	}

I don't like this, I think this makes the code more messy, just to avoid that warning.

And it might even be buggy. For your patch to work correctly, you need to know the internals of _PAGE_NX, i.e. that when CONFIG_X86_PAE is not defined, _PAGE_NX is 0. But the driver should not depend on things like that. If _PAGE_NX is changed later, the driver will not work correctly.

Tomi

author
#2 lore raw
Quoted 8 lines · Tomi Valkeinen

I don't like this, I think this makes the code more messy, just to avoid that warning.

And it might even be buggy. For your patch to work correctly, you need to know the internals of _PAGE_NX, i.e. that when CONFIG_X86_PAE is not defined, _PAGE_NX is 0. But the driver should not depend on things like that. If _PAGE_NX is changed later, the driver will not work correctly.

Very right! Thanks.