* [RFC,PATCH] arm: use param address to establish params mapping
@ 2010-04-01 2:59 Jeremy Kerr
2010-04-12 18:43 ` Russell King - ARM Linux
0 siblings, 1 reply; 2+ messages in thread
From: Jeremy Kerr @ 2010-04-01 2:59 UTC (permalink / raw)
To: linux-arm-kernel
Currently, __create_page_tables assumes that the boot params are within
the first MB of physical memory, and creates a translation from the kernel
direct mapping region based on this assumption.
Rather than guessing, use the atags/params address instead. This also
means we don't have to rely on PHYS_ADDR to create the mapping.
Signed-off-by: Jeremy Kerr <jeremy.kerr@canonical.com>
---
arch/arm/kernel/head.S | 17 ++++++++++-------
1 file changed, 10 insertions(+), 7 deletions(-)
diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S
index eb62bf9..cec9a31 100644
--- a/arch/arm/kernel/head.S
+++ b/arch/arm/kernel/head.S
@@ -208,6 +208,7 @@ ENDPROC(__turn_mmu_on)
* amount which are required to get the kernel running, which
* generally means mapping in the kernel code.
*
+ * r2 = atags
* r8 = machinfo
* r9 = cpuid
* r10 = procinfo
@@ -279,14 +280,16 @@ __create_page_tables:
#endif
/*
- * Then map first 1MB of ram in case it contains our boot params.
+ * Create mapping for boot params to kernel direct mapped region (we
+ * expect to access the params though phys_to_virt()). This is only
+ * required if the params aren't covered by the previously established
+ * direct mapping (ie, TEXT_OFFSET > 1MB, or XIP).
*/
- add r0, r4, #PAGE_OFFSET >> 18
- orr r6, r7, #(PHYS_OFFSET & 0xff000000)
- .if (PHYS_OFFSET & 0x00f00000)
- orr r6, r6, #(PHYS_OFFSET & 0x00f00000)
- .endif
- str r6, [r0]
+ lsr r0, r2, #20 @ section index
+ orr r3, r7, r0, lsl #20 @ section entry
+ add r0, r0, #(PAGE_OFFSET >> 20) @ offset to kernel virt addr
+ str r3, [r4, r0, lsl #2]
+
#ifdef CONFIG_DEBUG_LL
ldr r7, [r10, #PROCINFO_IO_MMUFLAGS] @ io_mmuflags
^ permalink raw reply related [flat|nested] 2+ messages in thread
* [RFC,PATCH] arm: use param address to establish params mapping
2010-04-01 2:59 [RFC,PATCH] arm: use param address to establish params mapping Jeremy Kerr
@ 2010-04-12 18:43 ` Russell King - ARM Linux
0 siblings, 0 replies; 2+ messages in thread
From: Russell King - ARM Linux @ 2010-04-12 18:43 UTC (permalink / raw)
To: linux-arm-kernel
On Thu, Apr 01, 2010 at 10:59:44AM +0800, Jeremy Kerr wrote:
> Currently, __create_page_tables assumes that the boot params are within
> the first MB of physical memory, and creates a translation from the kernel
> direct mapping region based on this assumption.
>
> Rather than guessing, use the atags/params address instead. This also
> means we don't have to rely on PHYS_ADDR to create the mapping.
As we still potentially have boot loaders which don't pass a valid value
in r2, can you please add some protection against random values being
passed rather than assuming that it always contains a valid value?
^ permalink raw reply [flat|nested] 2+ messages in thread
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