[U-Boot] [PATCH 1/3] ARM: relocate: fix hang when CONFIG_ARMV7_SECURE_BASE

[Peng Fan]

Hi Albert,
On Mon, Oct 19, 2015 at 08:48:56AM +0200, Albert ARIBAUD wrote:
>Hello Peng,
>
>On Mon, 19 Oct 2015 13:40:51 +0800, Peng Fan <b51431 at freescale.com>
>wrote:
>> On Tue, Oct 06, 2015 at 05:13:24PM -0500, Frank Li wrote:
>> >When added above configuration, iram fix up plus relocate offset may locate
>> >in invalidate space. Write back fix up value will cause data abort.
>> >
>> >Add address check, skip psci code.
>> >
>> >Signed-off-by: Frank Li <Frank.Li at freescale.com>
>> >---
>> > arch/arm/lib/relocate.S | 4 ++++
>> > 1 file changed, 4 insertions(+)
>> >
>> >diff --git a/arch/arm/lib/relocate.S b/arch/arm/lib/relocate.S
>> >index 475d503..6795a1b 100644
>> >--- a/arch/arm/lib/relocate.S
>> >+++ b/arch/arm/lib/relocate.S
>> >@@ -99,6 +99,10 @@ fixloop:
>> > 	cmp	r1, #23			/* relative fixup? */
>> > 	bne	fixnext
>> > 
>> >+	ldr	r1, =__image_copy_start
>> >+	cmp	r0, r1
>> >+	blo	fixnext
>> >+
>> 
>> Hi Tom, Albert,
>> 
>> This is a bug fix, please consider to apply this patch.
>
>Sorry for not spotting your patch earlier.

Not from me -:)

>
>Took me some time to understand the commit summary. Let me see if I'm
>getting this right by paraphrasing it:
>
>	If CONFIG_ARMV7_SECURE_BASE is defined and if there is
>	a fixup to the location at __image_copy_start, then U-Boot
>	will try to fix that location and since it is write-protected,
>	it will result in a data abort.

The commit msg needs to be refined.

>
>If I got this right, then this raises the following questions:
>
>1) if this location cannot be written into for relocation fixup, then
>how could it be written into for the copying which precedes relocation?
>
>2) if there is a fixup to the location, it means that either this
>location will not work properly without a fix, or the compiler emitted
>an erroneous relocation record. In either case, just ignoring the fixup
>seems like papering over the issue.
>
>Besides, this patch will prevent image base fixups on all targets, even
>those for which CONFIG_ARMV7_SECURE_BASE is not defined.

>From my understanding, U-Boot will be relocated to high address of the DRAM space,
exactly code from __image_copy_start to __image_copy_end.

Following is part of the dump of .rel.dyn section of u-boot elf.
SECURE BASE is 0x180000, uboot entry is 0x87800000.

Relocation section '.rel.dyn' at offset 0x577d4 contains 4032 entries:
 Offset     Info    Type            Sym.Value  Sym. Name
 0018410c  00000017 R_ARM_RELATIVE   
 00184154  00000017 R_ARM_RELATIVE   
 0018415c  00000017 R_ARM_RELATIVE   
 00184164  00000017 R_ARM_RELATIVE   
 0018416c  00000017 R_ARM_RELATIVE   
 00184304  00000017 R_ARM_RELATIVE   
 00184368  00000017 R_ARM_RELATIVE   
 87800020  00000017 R_ARM_RELATIVE   
 87800024  00000017 R_ARM_RELATIVE   
 87800028  00000017 R_ARM_RELATIVE   
 8780002c  00000017 R_ARM_RELATIVE

We can see that there are several relocate entries for secure code which is not
copied to high address of DRAM.

However SECURE code will not be copied to high address and should not be copied.
The code locates from __image_copy_start to __image_copy_end are copied to high
address, after copied, we need to fix variable and function reference, means
we need to fix this according to the relocation entry. The relocation entry
for SECURE code is not needed and should not to be fixed, alought they are in
the rel.dyn section.

>
>So, for now, I would NAK it.
>
>Now, assuming the answers to the two questions above do make a valid
>point that the fix above should indeed be implemented, then:
>
>> The secure code such as PSCI is not relocated, so there is no need to fix the code
>> which generate relocate entry in rel.dyn section. We should only need take
>> code from __image_copy_start to __image_copy_end into consideration.
>
>If some part of an image needs copying but not relocating,then the

part of an image not needs copying and not needs relocating.

>right solution is not to hard-code some arbitrary location as 'not
>relocatable' in the relocation routine; the right solution is to
>put in place a generic mechanism to allow the linker script to define
>which part of the image is relocatable. This can be done as follows:
>
>- in the linker script, border the non-relocatable part of the image
>  with two symbols, say 'relocatable_image_start' and '..._end', and
>  ensure that text (code) which should *not* be relocated is mapped
>  either before '..._start' or '..._end'. Not-to-be-relocated code
>  would be recognized by its text section name, e.g. '.nonreloc.text*'.

We have another fix is to add the following linker in u-boot.lds for arm
+	.rel.secure :
+	{
+		*(.rel._secure*)
+	}

Then relocation entry for secure code will not be touched.

But from my point, when doing relocation fix like the following c code:

if ((entry < __image_copy_end)  && (entry > __image_copy_start)) {
     /* fixup according relocation entry */
}

Regards,
Peng.

>
>- in the relocation routine, only fix up those locations which lie
>  between the 'relocatable_image_start' and '..._end' symbols.
>
>- in the relevant makefile(s), make the non-relocatable object files
>  use a test section name of the for defined in the first step (e.g.
>  '.nonreloc.text*').
>
>Again, this is suggested *only* if it is shown that the data abort
>cannot be avoided some other way.
>
>> Regards,
>> Peng.
>
>Amicalement,
>-- 
>Albert.

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