Re: [PATCH 1/8] arm/dt: Make __vet_atags also accept a dtb image
From: Nicolas Pitre <hidden>
Date: 2011-01-18 21:26:22
Also in:
linux-arm-kernel, lkml
On Tue, 18 Jan 2011, Grant Likely wrote:
quoted hunk ↗ jump to hunk
The dtb is passed to the kernel via register r2, which is the same method that is used to pass an atags pointer. This patch modifies __vet_atags to not clear r2 when it encounters a dtb image. Signed-off-by: Grant Likely <redacted> --- arch/arm/kernel/head-common.S | 19 +++++++++++++------ arch/arm/kernel/head.S | 8 ++++---- 2 files changed, 17 insertions(+), 10 deletions(-)diff --git a/arch/arm/kernel/head-common.S b/arch/arm/kernel/head-common.S index 8f57515..d9a9105 100644 --- a/arch/arm/kernel/head-common.S +++ b/arch/arm/kernel/head-common.S@@ -14,6 +14,7 @@ #define ATAG_CORE 0x54410001 #define ATAG_CORE_SIZE ((2*4 + 3*4) >> 2) #define ATAG_CORE_SIZE_EMPTY ((2*4) >> 2) +#define OF_DT_MAGIC 0xedfe0dd0 /* 0xd00dfeed in big-endian */
ARM can be big endian too. Would be nice to make this endian independent, or at least list this limitation in the commit log.
quoted hunk ↗ jump to hunk
/* * Exception handling. Something went wrong and we can't proceed. We@@ -105,22 +106,28 @@ __lookup_machine_type_data: /* Determine validity of the r2 atags pointer. The heuristic requires * that the pointer be aligned, in the first 16k of physical RAM and - * that the ATAG_CORE marker is first and present. Future revisions + * that the ATAG_CORE marker is first and present. If CONFIG_OF_FLATTREE + * is selected, then it will also accept a dtb pointer. Future revisions * of this function may be more lenient with the physical address and * may also be able to move the ATAGS block if necessary. * * r8 = machinfo * * Returns: - * r2 either valid atags pointer, or zero + * r2 either valid atags pointer, valid dtb pointer, or zero * r5, r6 corrupted */ __vet_atags: tst r2, #0x3 @ aligned? bne 1f - ldr r5, [r2, #0] @ is first tag ATAG_CORE? - cmp r5, #ATAG_CORE_SIZE +#ifdef CONFIG_OF_FLATTREE + ldr r5, [r2, #0] @ is it a DTB? + ldr r6, =OF_DT_MAGIC + cmp r5, r6 + beq 2f +#endif + cmp r5, #ATAG_CORE_SIZE @ is first tag ATAG_CORE?
The "ldr r5 ..." is now done only within #ifdef CONFIG_OF_FLATTREE. So if CONFIG_OF_FLATTREE is undefined then r5 will contain garbage. Nicolas