Re: [PATCH v2 11/11] powerpc/8xx: Add support for TASK_SIZE greater than 0x80000000

From: leroy christophe
Date: Tue Apr 07 2015 - 04:16:10 EST

Le 21/03/2015 01:47, Scott Wood a Ãcrit :
On Tue, 2015-01-20 at 10:57 +0100, Christophe Leroy wrote:
By default, TASK_SIZE is set to 0x80000000 for PPC_8xx, which is most likely
sufficient for most cases. However, kernel configuration allows to set TASK_SIZE
to another value, so the 8xx shall handle it.

Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>

v2: no change

arch/powerpc/kernel/head_8xx.S | 25 +++++++++++++++++++------
1 file changed, 19 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
index ead6448..92a6456 100644
--- a/arch/powerpc/kernel/head_8xx.S
+++ b/arch/powerpc/kernel/head_8xx.S
@@ -48,6 +48,19 @@
mtspr spr, reg
+/* Macro to test if an address is a kernel address */
+#if CONFIG_TASK_SIZE <= 0x80000000
+#define IS_KERNEL(tmp, addr) \
+ andis. tmp, addr, 0x8000 /* Address >= 0x80000000 */
+#define BRANCH_UNLESS_KERNEL(label) beq label
This works if CONFIG_TASK_SIZE == 0x80000000, but what if it's less, and
you have a kernel address < 0x80000000?

You are right, I didn't realise that PAGE_OFFSET was also configurable and could be different from 0xC0000000.
andis. (which is what is always used in the current kernel) can be used if CONFIG_TASK_SIZE <= 0x80000000 AND PAGE_OFFSET >= 0x80000000.
I will resubmit the patch accordingly.


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