N900 v3.19-rc5 arm atags_to_fdt.c is broken

Hello,

when I boot zImage with appended DT n900 in qemu fdt_open_into() function called from file arch/arm/boot/compressed/atags_to_fdt.c (in function atags_to_fdt) always returns -FDT_ERR_NOSPACE.

It means that all ATAGS (including cmdline arguments) passed by bootloader are ignored.

On real n900 device I see that booted DT version also ignore cmdline arguments from bootloader. I cannot debug decompress code on real device, but I think it is same problem as in qemu.

Quoted 10 lines · On Friday 23 January 2015 22:39:55 Pali Roh?r wrote:

Hello,

when I boot zImage with appended DT n900 in qemu fdt_open_into() function called from file arch/arm/boot/compressed/atags_to_fdt.c (in function atags_to_fdt) always returns -FDT_ERR_NOSPACE.

It means that all ATAGS (including cmdline arguments) passed by bootloader are ignored.

Quoted 4 lines

On real n900 device I see that booted DT version also ignore cmdline arguments from bootloader. I cannot debug decompress code on real device, but I think it is same problem as in qemu.

Looks like this quick patch is fixing above problem:

arch/arm/boot/compressed/head.S +2 -2

index 68be901..4a7d75b 100644
@@ -268,7 +268,7 @@ restart:	adr	r0, LC0
 		 * area.  No GOT fixup has occurred yet, but none of the
 		 * code we're about to call uses any global variable.
 		*/
-		add	sp, sp, #0x10000
+		add	sp, sp, #0x20000
 		stmfd	sp!, {r0-r3, ip, lr}
 		mov	r0, r8
 		mov	r1, r6

@@ -289,7 +289,7 @@ restart:	adr	r0, LC0
 		bleq	atags_to_fdt
 
 		ldmfd	sp!, {r0-r3, ip, lr}
-		sub	sp, sp, #0x10000
+		sub	sp, sp, #0x20000
 #endif
 
 		mov	r8, r6			@ use the appended device tree

Quoted 16 lines · Pali Roh?r

Quoted 14 lines · On Friday 23 January 2015 22:39:55 Pali Roh?r wrote:

Hello,

when I boot zImage with appended DT n900 in qemu fdt_open_into() function called from file arch/arm/boot/compressed/atags_to_fdt.c (in function atags_to_fdt) always returns -FDT_ERR_NOSPACE.

It means that all ATAGS (including cmdline arguments) passed by bootloader are ignored.

On real n900 device I see that booted DT version also ignore cmdline arguments from bootloader. I cannot debug decompress code on real device, but I think it is same problem as in qemu.

Quoted 1 line

Looks like this quick patch is fixing above problem:

So... something overruns stack, and bigger stack fixes it...?

Pavel

arch/arm/boot/compressed/head.S restart: adr r0, LC0 · line 269

Quoted 8 lines

(quoted diff) +0 -0

b/arch/arm/boot/compressed/head.S index 68be901..4a7d75b 100644

arch/arm/boot/compressed/head.S +0 -0

@@ -268,7 +268,7 @@ restart:	adr	r0, LC0
 
 		 * area.  No GOT fixup has occurred yet, but none of 

Quoted 23 lines

arch/arm/boot/compressed/head.S +1 -1

 		 * code we're about to call uses any global variable.
 
 		*/
 
-		add	sp, sp, #0x10000
+		add	sp, sp, #0x20000

arch/arm/boot/compressed/head.S +1 -1

 		stmfd	sp!, {r0-r3, ip, lr}
 		mov	r0, r8
 		mov	r1, r6

@@ -289,7 +289,7 @@ restart:	adr	r0, LC0
 
 		bleq	atags_to_fdt
 
 		ldmfd	sp!, {r0-r3, ip, lr}
 
-		sub	sp, sp, #0x10000
+		sub	sp, sp, #0x20000
 

#endif

mov r8, r6 @ use the appended device tree

Quoted 7 lines · On Friday 23 January 2015 22:39:55 Pali Roh?r wrote:

Hello,

when I boot zImage with appended DT n900 in qemu fdt_open_into() function called from file arch/arm/boot/compressed/atags_to_fdt.c (in function atags_to_fdt) always returns -FDT_ERR_NOSPACE.

Quoted 7 lines

It means that all ATAGS (including cmdline arguments) passed by bootloader are ignored.

On real n900 device I see that booted DT version also ignore cmdline arguments from bootloader. I cannot debug decompress code on real device, but I think it is same problem as in qemu.

Looks like this quick patch is fixing above problem:

arch/arm/boot/compressed/head.S +1 -1

index 68be901..4a7d75b 100644
@@ -268,7 +268,7 @@ restart:	adr	r0, LC0
 		 * area.  No GOT fixup has occurred yet, but none of the
 		 * code we're about to call uses any global variable.
 		*/
-		add	sp, sp, #0x10000
+		add	sp, sp, #0x20000
 		stmfd	sp!, {r0-r3, ip, lr}
 		mov	r0, r8
 		mov	r1, r6

Quoted 18 lines · Pali Roh?r

Quoted 7 lines · On Friday 23 January 2015 22:39:55 Pali Roh?r wrote:

Hello,

when I boot zImage with appended DT n900 in qemu fdt_open_into() function called from file arch/arm/boot/compressed/atags_to_fdt.c (in function atags_to_fdt) always returns -FDT_ERR_NOSPACE.

Quoted 7 lines

It means that all ATAGS (including cmdline arguments) passed by bootloader are ignored.

On real n900 device I see that booted DT version also ignore cmdline arguments from bootloader. I cannot debug decompress code on real device, but I think it is same problem as in qemu.

Looks like this quick patch is fixing above problem:

arch/arm/boot/compressed/head.S restart: adr r0, LC0 · line 269

Quoted 8 lines

(quoted diff) +0 -0

b/arch/arm/boot/compressed/head.S index 68be901..4a7d75b 100644

arch/arm/boot/compressed/head.S +0 -0

@@ -268,7 +268,7 @@ restart:	adr	r0, LC0
 
 		 * area.  No GOT fixup has occurred yet, but none of 

Quoted 22 lines

arch/arm/boot/compressed/head.S +1 -1

 		 * code we're about to call uses any global variable.
 
 		*/
 
-		add	sp, sp, #0x10000
+		add	sp, sp, #0x20000

arch/arm/boot/compressed/head.S +1 -1

 		stmfd	sp!, {r0-r3, ip, lr}
 		mov	r0, r8
 		mov	r1, r6

@@ -289,7 +289,7 @@ restart:	adr	r0, LC0
 
 		bleq	atags_to_fdt
 
 		ldmfd	sp!, {r0-r3, ip, lr}
 
-		sub	sp, sp, #0x10000
+		sub	sp, sp, #0x20000
 

#endif

Quoted 1 line

mov r8, r6 @ use the appended device tree

Nico, got any ideas about this one? This seems like a regression somewhere..

Regards,

Tony

Quoted 19 lines · On Monday 26 January 2015 17:14:55 Tony Lindgren wrote:

Quoted 18 lines · Pali Roh?r

Quoted 7 lines · On Friday 23 January 2015 22:39:55 Pali Roh?r wrote:

Hello,

when I boot zImage with appended DT n900 in qemu fdt_open_into() function called from file arch/arm/boot/compressed/atags_to_fdt.c (in function atags_to_fdt) always returns -FDT_ERR_NOSPACE.

Quoted 7 lines

It means that all ATAGS (including cmdline arguments) passed by bootloader are ignored.

On real n900 device I see that booted DT version also ignore cmdline arguments from bootloader. I cannot debug decompress code on real device, but I think it is same problem as in qemu.

Looks like this quick patch is fixing above problem:

Quoted 8 lines

arch/arm/boot/compressed/head.S restart: adr r0, LC0 · line 269

Quoted 8 lines

(quoted diff) +0 -0

b/arch/arm/boot/compressed/head.S index 68be901..4a7d75b 100644

arch/arm/boot/compressed/head.S +0 -0

@@ -268,7 +268,7 @@ restart:	adr	r0, LC0
 
 		 * area.  No GOT fixup has occurred yet, but none of 

the

Quoted 22 lines

Quoted 22 lines

arch/arm/boot/compressed/head.S +1 -1

 		 * code we're about to call uses any global variable.
 
 		*/
 
-		add	sp, sp, #0x10000
+		add	sp, sp, #0x20000

arch/arm/boot/compressed/head.S +1 -1

 		stmfd	sp!, {r0-r3, ip, lr}
 		mov	r0, r8
 		mov	r1, r6

@@ -289,7 +289,7 @@ restart:	adr	r0, LC0
 
 		bleq	atags_to_fdt
 
 		ldmfd	sp!, {r0-r3, ip, lr}
 
-		sub	sp, sp, #0x10000
+		sub	sp, sp, #0x20000
 

#endif

Quoted 8 lines

Quoted 1 line

mov r8, r6 @ use the appended device tree

Nico, got any ideas about this one? This seems like a regression somewhere..

Regards,

Tony

$ du -b arch/arm/boot/dts/omap3-n900.dtb 
70212   arch/arm/boot/dts/omap3-n900.dtb

$ echo $((0x10000))
65536

I would say, problem is because omap3-n900 binary DT is too large

Quoted 60 lines · Pali Roh?r

Quoted 19 lines · On Monday 26 January 2015 17:14:55 Tony Lindgren wrote:

Quoted 18 lines · Pali Roh?r

Quoted 7 lines · On Friday 23 January 2015 22:39:55 Pali Roh?r wrote:

Hello,

when I boot zImage with appended DT n900 in qemu fdt_open_into() function called from file arch/arm/boot/compressed/atags_to_fdt.c (in function atags_to_fdt) always returns -FDT_ERR_NOSPACE.

Quoted 7 lines

It means that all ATAGS (including cmdline arguments) passed by bootloader are ignored.

On real n900 device I see that booted DT version also ignore cmdline arguments from bootloader. I cannot debug decompress code on real device, but I think it is same problem as in qemu.

Looks like this quick patch is fixing above problem:

Quoted 8 lines

arch/arm/boot/compressed/head.S restart: adr r0, LC0 · line 269

Quoted 8 lines

(quoted diff) +0 -0

b/arch/arm/boot/compressed/head.S index 68be901..4a7d75b 100644

arch/arm/boot/compressed/head.S +0 -0

@@ -268,7 +268,7 @@ restart:	adr	r0, LC0
 
 		 * area.  No GOT fixup has occurred yet, but none of 

the

Quoted 30 lines

Quoted 22 lines

arch/arm/boot/compressed/head.S +1 -1

 		 * code we're about to call uses any global variable.
 
 		*/
 
-		add	sp, sp, #0x10000
+		add	sp, sp, #0x20000

arch/arm/boot/compressed/head.S +1 -1

 		stmfd	sp!, {r0-r3, ip, lr}
 		mov	r0, r8
 		mov	r1, r6

@@ -289,7 +289,7 @@ restart:	adr	r0, LC0
 
 		bleq	atags_to_fdt
 
 		ldmfd	sp!, {r0-r3, ip, lr}
 
-		sub	sp, sp, #0x10000
+		sub	sp, sp, #0x20000
 

#endif

Quoted 1 line

mov r8, r6 @ use the appended device tree

Nico, got any ideas about this one? This seems like a regression somewhere..

Regards,

Tony

Quoted 7 lines

$ du -b arch/arm/boot/dts/omap3-n900.dtb 
70212   arch/arm/boot/dts/omap3-n900.dtb

$ echo $((0x10000))
65536

I would say, problem is because omap3-n900 binary DT is too large

OK if that's the case, then your patch makes sense to me. It also seems we can have the temporary stack be larger than the initial stack just for atags_to_fdt.

Quoted 7 lines

Quoted 7 lines

$ du -b arch/arm/boot/dts/omap3-n900.dtb 
70212   arch/arm/boot/dts/omap3-n900.dtb

$ echo $((0x10000))
65536

I would say, problem is because omap3-n900 binary DT is too large

I agree.

Quoted 3 lines

OK if that's the case, then your patch makes sense to me. It also seems we can have the temporary stack be larger than the initial stack just for atags_to_fdt.

The stack size isn't the issue, but rather its location. We need to position it away from the DT data. The DT size is known and we could use that, plus some room for the insertion of new data coming from the ATAG conversion.

Something like the following would be a more robust solution:

arch/arm/boot/compressed/head.S +13 -5

index 68be901759..89718de9dd 100644
@@ -263,16 +263,37 @@ restart:	adr	r0, LC0
 		 * OK... Let's do some funky business here.
 		 * If we do have a DTB appended to zImage, and we do have
 		 * an ATAG list around, we want the later to be translated
-		 * and folded into the former here.  To be on the safe side,
-		 * let's temporarily move  the stack away into the malloc
-		 * area.  No GOT fixup has occurred yet, but none of the
-		 * code we're about to call uses any global variable.
+		 * and folded into the former here. No GOT fixup has occurred
+		 * yet, but none of the code we're about to call uses any
+		 * global variable.
 		*/
-		add	sp, sp, #0x10000
+
+		/* Get the initial DTB size */
+		ldr	r5, [r6, #4]
+#ifndef __ARMEB__
+		/* convert to little endian */
+		eor	r1, r5, r5, ror #16
+		bic	r1, r1, #0x00ff0000
+		mov	r5, r5, ror #8
+		eor	r5, r5, r1, lsr #8
+#endif

Hi!

Quoted 53 lines

Quoted 7 lines

Quoted 7 lines

$ du -b arch/arm/boot/dts/omap3-n900.dtb 
70212   arch/arm/boot/dts/omap3-n900.dtb

$ echo $((0x10000))
65536

I would say, problem is because omap3-n900 binary DT is too large

I agree.

Quoted 3 lines

OK if that's the case, then your patch makes sense to me. It also seems we can have the temporary stack be larger than the initial stack just for atags_to_fdt.

The stack size isn't the issue, but rather its location. We need to position it away from the DT data. The DT size is known and we could use that, plus some room for the insertion of new data coming from the ATAG conversion.

Something like the following would be a more robust solution:

arch/arm/boot/compressed/head.S +18 -5

index 68be901759..89718de9dd 100644
@@ -263,16 +263,37 @@ restart:	adr	r0, LC0
 		 * OK... Let's do some funky business here.
 		 * If we do have a DTB appended to zImage, and we do have
 		 * an ATAG list around, we want the later to be translated
-		 * and folded into the former here.  To be on the safe side,
-		 * let's temporarily move  the stack away into the malloc
-		 * area.  No GOT fixup has occurred yet, but none of the
-		 * code we're about to call uses any global variable.
+		 * and folded into the former here. No GOT fixup has occurred
+		 * yet, but none of the code we're about to call uses any
+		 * global variable.
 		*/
-		add	sp, sp, #0x10000
+
+		/* Get the initial DTB size */
+		ldr	r5, [r6, #4]
+#ifndef __ARMEB__
+		/* convert to little endian */
+		eor	r1, r5, r5, ror #16
+		bic	r1, r1, #0x00ff0000
+		mov	r5, r5, ror #8
+		eor	r5, r5, r1, lsr #8
+#endif
+		/* 50% DTB growth should be good enough */
+		add	r5, r5, r5, lsr #1
+		/* preserve 64-bit alignment */
+		add	r5, r5, #7
+		bic	r5, r5, #7

arch/arm/boot/compressed/head.S restart: adr r0, LC0 · line 289

Quoted 5 lines

arch/arm/boot/compressed/head.S +5 -0

+		/* clamp to 32KB min and 1MB max */
+		movs	r1, r5, lsr #15
+		moveq	r5, #(1 << 15)
+		movs	r1, r5, lsr #20
+		movne	r5, #(1 << 20)

Dunno. Would it be easier/simpler to just use 1MB, always? Do we support machines with <16MB RAM?

Quoted 2 lines

Quoted 2 lines

I would say, problem is because omap3-n900 binary DT is too large

I agree.

Quoted 3 lines

OK if that's the case, then your patch makes sense to me. It also seems we can have the temporary stack be larger than the initial stack just for atags_to_fdt.

The stack size isn't the issue, but rather its location. We need to position it away from the DT data. The DT size is known and we could use that, plus some room for the insertion of new data coming from the ATAG conversion.

Something like the following would be a more robust solution:

arch/arm/boot/compressed/head.S +30 -9

index 68be901759..89718de9dd 100644
@@ -263,16 +263,37 @@ restart:	adr	r0, LC0
 		 * OK... Let's do some funky business here.
 		 * If we do have a DTB appended to zImage, and we do have
 		 * an ATAG list around, we want the later to be translated
-		 * and folded into the former here.  To be on the safe side,
-		 * let's temporarily move  the stack away into the malloc
-		 * area.  No GOT fixup has occurred yet, but none of the
-		 * code we're about to call uses any global variable.
+		 * and folded into the former here. No GOT fixup has occurred
+		 * yet, but none of the code we're about to call uses any
+		 * global variable.
 		*/
-		add	sp, sp, #0x10000
+
+		/* Get the initial DTB size */
+		ldr	r5, [r6, #4]
+#ifndef __ARMEB__
+		/* convert to little endian */
+		eor	r1, r5, r5, ror #16
+		bic	r1, r1, #0x00ff0000
+		mov	r5, r5, ror #8
+		eor	r5, r5, r1, lsr #8
+#endif
+		/* 50% DTB growth should be good enough */
+		add	r5, r5, r5, lsr #1
+		/* preserve 64-bit alignment */
+		add	r5, r5, #7
+		bic	r5, r5, #7
+		/* clamp to 32KB min and 1MB max */
+		movs	r1, r5, lsr #15
+		moveq	r5, #(1 << 15)
+		movs	r1, r5, lsr #20
+		movne	r5, #(1 << 20)
+
+		/* Temporarily relocate the stack past the DTB work space */
+		add	sp, sp, r5
 		stmfd	sp!, {r0-r3, ip, lr}
 		mov	r0, r8
 		mov	r1, r6
-		sub	r2, sp, r6
+		mov	r2, r5
 		bl	atags_to_fdt
 
 		/*

@@ -285,11 +306,11 @@ restart:	adr	r0, LC0
 		bic	r0, r0, #1
 		add	r0, r0, #0x100
 		mov	r1, r6
-		sub	r2, sp, r6
+		mov	r2, r5
 		bleq	atags_to_fdt
 
 		ldmfd	sp!, {r0-r3, ip, lr}
-		sub	sp, sp, #0x10000
+		sub	sp, sp, r5
 #endif
 
 		mov	r8, r6			@ use the appended device tree

@@ -306,7 +327,7 @@ restart:	adr	r0, LC0
 		subs	r1, r5, r1
 		addhi	r9, r9, r1
 
-		/* Get the dtb's size */
+		/* Get the current DTB size */
 		ldr	r5, [r6, #4]
 #ifndef __ARMEB__
 		/* convert r5 (dtb size) to little endian */

Quoted 14 lines

Quoted 2 lines

Quoted 2 lines

I would say, problem is because omap3-n900 binary DT is too large

I agree.

Quoted 3 lines

OK if that's the case, then your patch makes sense to me. It also seems we can have the temporary stack be larger than the initial stack just for atags_to_fdt.

The stack size isn't the issue, but rather its location. We need to position it away from the DT data. The DT size is known and we could use that, plus some room for the insertion of new data coming from the ATAG conversion.

Quoted 1 line

Something like the following would be a more robust solution:

Tested-by Pavel Machek <[email protected]>

(Note, that in 3.19 dts for n900 got too big, so we are actually triggering old bugs. That means that this is a regression fix, and should go in ASAP).

Quoted 9 lines · Pavel Machek

Quoted 9 lines

Quoted 2 lines

Quoted 2 lines

I would say, problem is because omap3-n900 binary DT is too large

I agree.

Quoted 3 lines

OK if that's the case, then your patch makes sense to me. It also seems we can have the temporary stack be larger than the initial stack just for atags_to_fdt.

Quoted 7 lines

Quoted 7 lines

The stack size isn't the issue, but rather its location. We need to position it away from the DT data. The DT size is known and we could use that, plus some room for the insertion of new data coming from the ATAG conversion.

Something like the following would be a more robust

Quoted 5 lines

Tested-by Pavel Machek <[email protected]>

(Note, that in 3.19 dts for n900 got too big, so we are actually triggering old bugs. That means that this is a regression fix, and should go in ASAP).

It is queued here:
http://www.arm.linux.org.uk/developer/patches/viewpatch.php?id
=8294/1

Nicolas

Quoted 16 lines · Pavel Machek

Quoted 15 lines

Quoted 2 lines

Quoted 2 lines

I would say, problem is because omap3-n900 binary DT is too large

I agree.

Quoted 3 lines

OK if that's the case, then your patch makes sense to me. It also seems we can have the temporary stack be larger than the initial stack just for atags_to_fdt.

The stack size isn't the issue, but rather its location. We need to position it away from the DT data. The DT size is known and we could use that, plus some room for the insertion of new data coming from the ATAG conversion.

Something like the following would be a more robust solution:

Quoted 5 lines

Tested-by Pavel Machek <[email protected]>

(Note, that in 3.19 dts for n900 got too big, so we are actually triggering old bugs. That means that this is a regression fix, and should go in ASAP).

It is queued here:
http://www.arm.linux.org.uk/developer/patches/viewpatch.php?id=8294/1

Quoted 3 lines · Pavel Machek

(Note, that in 3.19 dts for n900 got too big, so we are actually triggering old bugs. That means that this is a regression fix, and should go in ASAP).

It is queued here:
http://www.arm.linux.org.uk/developer/patches/viewpatch.php?id=8294/1

Quoted 7 lines · Nicolas Pitre

Quoted 3 lines · Pavel Machek

(Note, that in 3.19 dts for n900 got too big, so we are actually triggering old bugs. That means that this is a regression fix, and should go in ASAP).

It is queued here:
http://www.arm.linux.org.uk/developer/patches/viewpatch.php?id=8294/1

Irrespective of that patch, I commented on another thread (about adding the serial number to DT):

| How about something a little more radical.
| 
| Rather than trying to squeeze various ATAGs into DT, why don't we add a
| standard ATAG to contain the DT and pass that through into the kernel.
| This is IMHO how we _should_ have done the ATAG compatibility from the
| start.
| 
| That means we could get rid of most of the libfdt in the decompressor,
| and instead resolve the differences in the kernel.

That would allow us to get rid of all the FDT compatibility code in the decompressor, and when we encounter these special ATAGs, we can deal with them in the kernel instead of having to mess around with the DT. I'd also assume (although I haven't checked) that it would be much easier to add additional DT properties in the kernel environment, rather than in the rather restrictive decompressor environment.

We'd need to be careful about how we deal with the atags vs DT. I'd suggest (as above) that we have a tag which points at the DT in physical memory, and its size, and pre-scan the atag list for that. When we find it, we kick off the DT based stuff as we would normally do, and follow it with a parse of the atags. This would cause the atags to override whatever is in the DT, which afaics is the behaviour that we actually want.

We could augment that with code to update DT too so that we can export just the DT based information to kexec'd kernels.

Hence the ATAG-to-DT compat code in the decompressor. This was meant to smooth things around the transition to DT, etc. After all, those devices with non-replaceable bootloaders where shim layers are not possible should get out of commission eventually?

Quoted 22 lines · Russell King - ARM Linux

Quoted 7 lines · Nicolas Pitre

Quoted 3 lines · Pavel Machek

(Note, that in 3.19 dts for n900 got too big, so we are actually triggering old bugs. That means that this is a regression fix, and should go in ASAP).

It is queued here:
http://www.arm.linux.org.uk/developer/patches/viewpatch.php?id=8294/1

Irrespective of that patch, I commented on another thread (about adding the serial number to DT):

| How about something a little more radical.
| 
| Rather than trying to squeeze various ATAGs into DT, why don't we add a
| standard ATAG to contain the DT and pass that through into the kernel.
| This is IMHO how we _should_ have done the ATAG compatibility from the
| start.
| 
| That means we could get rid of most of the libfdt in the decompressor,
| and instead resolve the differences in the kernel.

Quoted 6 lines

That would allow us to get rid of all the FDT compatibility code in the decompressor, and when we encounter these special ATAGs, we can deal with them in the kernel instead of having to mess around with the DT. I'd also assume (although I haven't checked) that it would be much easier to add additional DT properties in the kernel environment, rather than in the rather restrictive decompressor environment.

Well...

I was initially against any ATAG-to-DT compatibility at all. IMHO the "right" solution is to update the bootloader.

However people complained that updating the bootloader wasn't possible. I therefore suggested they go with a shim layer I termed the "impedance matcher" acting like an intermediate boot stage converting their (often unofficial and out-of-tree) ATAGs into proper DT nodes. Some people did exactly that and it works wonderfully for them. It also works wonderfully for kernel maintenance as the platform specific tweaks are kept out of the kernel tree.

Still, that wasn't good enough for some cases as the move to DT regressed some platforms that just used to work before. Concatenating a DTB to zImage was tolerable but installing an additional shim layer was too much. Hence the ATAG-to-DT compat code in the decompressor. This was meant to smooth things around the transition to DT, etc. After all, those devices with non-replaceable bootloaders where shim layers are not possible should get out of commission eventually?

Quoted 16 lines · Pavel Machek

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I would say, problem is because omap3-n900 binary DT is too large

I agree.

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OK if that's the case, then your patch makes sense to me. It also seems we can have the temporary stack be larger than the initial stack just for atags_to_fdt.

The stack size isn't the issue, but rather its location. We need to position it away from the DT data. The DT size is known and we could use that, plus some room for the insertion of new data coming from the ATAG conversion.

Something like the following would be a more robust solution:

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Tested-by Pavel Machek <[email protected]>

(Note, that in 3.19 dts for n900 got too big, so we are actually triggering old bugs. That means that this is a regression fix, and should go in ASAP).

It is queued here:
http://www.arm.linux.org.uk/developer/patches/viewpatch.php?id=8294/1

Quoted 24 lines · Nicolas Pitre

Quoted 21 lines · Pavel Machek

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I would say, problem is because omap3-n900 binary DT is too large

I agree.

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OK if that's the case, then your patch makes sense to me. It also seems we can have the temporary stack be larger than the initial stack just for atags_to_fdt.

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The stack size isn't the issue, but rather its location. We need to position it away from the DT data. The DT size is known and we could use that, plus some room for the insertion of new data coming from the ATAG conversion.

Something like the following would be a more robust solution:

Tested-by Pavel Machek <[email protected]>

(Note, that in 3.19 dts for n900 got too big, so we are actually triggering old bugs. That means that this is a regression fix, and should go in ASAP).

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It is queued here:
http://www.arm.linux.org.uk/developer/patches/viewpatch.php?id=8294/1

Hmm, but it should be on kernel.org, not in private arm trees, as it fixes a regression. Russell, you are the ARM maintainer, can you push it to Linus?