Re: [PATCH v3 1/10] x86/vdso32: Define PGTABLE_LEVELS to 32bit VDSO
From: Toshi Kani
Date: Mon Aug 24 2015 - 17:50:15 EST
On Thu, 2015-08-20 at 17:04 -0600, Toshi Kani wrote:
> On 8/20/2015 1:46 PM, Thomas Gleixner wrote:
> > On Wed, 5 Aug 2015, Toshi Kani wrote:
> > > In case of CONFIG_X86_64, vdso32/vclock_gettime.c fakes a 32bit
> > > kernel configuration by re-defining it to CONFIG_X86_32. However,
> > > it does not re-define CONFIG_PGTABLE_LEVELS leaving it as 4 levels.
> > > Fix it by re-defining CONFIG_PGTABLE_LEVELS to 2 as X86_PAE is not
> > > set.
> > You fail to explain WHY this is required. I have not yet spotted any
> > code in vclock_gettime.c which is affected by this.
> Sorry about that. Without this patch 01, applying patch 02 & 03 causes
> the following compile errors in vclock_gettime.c. This is because it
> includes pgtable_type.h (see blow), which now requires PUD_SHIFT and
> PMD_SHIFT defined properly. In case of X86_32, pgtable_type.h includes
> pgtable_nopud.h and pgtable-nopmd.h, which define these SHIFTs when
> CONFIG_PGTABLE_LEVEL is set to 2 (or 3 if PAE is also defined).
Attached is patch 01/10 with updated descriptions. The rest of the patchset
still applies cleanly.
Please let me know if you have any further comments.
Subject: [PATCH v3 UPDATE 1/10] x86/vdso32: Define PGTABLE_LEVELS to 32bit
In case of CONFIG_X86_64, vdso32/vclock_gettime.c fakes a 32-bit
non-PAE kernel configuration by re-defining it to CONFIG_X86_32.
However, it does not re-define CONFIG_PGTABLE_LEVELS leaving it
as 4 levels.
This mismatch leads <asm/pgtable_type.h> to NOT include <asm-generic/
pgtable-nopud.h> and <asm-generic/pgtable-nopmd.h>, which will cause
compile errors when a later patch enhances <asm/pgtable_type.h> to
use PUD_SHIFT and PMD_SHIFT. These -nopud & -nopmd headers define
these SHIFTs for the 32-bit non-PAE kernel.
Fix it by re-defining CONFIG_PGTABLE_LEVELS to 2 levels.
Signed-off-by: Toshi Kani <toshi.kani@xxxxxx>
Cc: Juergen Gross <jgross@xxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
arch/x86/entry/vdso/vdso32/vclock_gettime.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/arch/x86/entry/vdso/vdso32/vclock_gettime.c
index 175cc72..87a86e0 100644
@@ -14,11 +14,13 @@
#define CONFIG_X86_32 1
+#define CONFIG_PGTABLE_LEVELS 2
#define CONFIG_PAGE_OFFSET 0
#define CONFIG_ILLEGAL_POINTER_VALUE 0
#define CONFIG_NR_CPUS 1
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