Re: [PATCH][v3 3/4] uClibc: redo configuration

[Khem Raj <raj.khem@gmail.com>]

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On Thu, Jul 8, 2010 at 3:16 PM, Bernhard Reutner-Fischer
<rep.dot.nop@gmail.com> wrote:
> On Thu, Jul 08, 2010 at 03:03:04PM -0700, Khem Raj wrote:
>>On Thu, Jul 8, 2010 at 2:34 PM, Phil Blundell <philb@gnu.org> wrote:
>>> On Thu, 2010-07-08 at 14:31 -0700, Khem Raj wrote:
>>>> On Thu, Jul 8, 2010 at 2:29 PM, Phil Blundell <philb@gnu.org> wrote:
>>>> > On Thu, 2010-07-08 at 14:03 -0700, Khem Raj wrote:
>>>> >> If I am not wrong you can still do interworking and not have bx (using
>>>> >> mov pc,lr)
>>>> >
>>>> > That's not an interworking instruction in ARMv4T, and I don't think it
>>>> > is in ARMv5TE either.  You might be thinking of pop {pc}, which is
>>>> > interworking in ARMv5TE, but even this is not interworking in v4t.
>>>>
>>>> tst lr, #1
>>>> moveq pc, lr
>>>> bx lr
>>>>
>>>> Thats how its done on armv4 for EABI
>>>
>>> Right, but the MOV in that case is not an interworking instruction; it's
>>> just a way to avoid executing BX when you don't actually need to switch
>>> mode, so that you can create a library which still works in an ARM-only
>>> environment.
>>>
>>> The final BX in that sequence is mandatory in order for it to actually
>>> function as an interworking return.
>>
>>right you are. yes bx is always needed for thumb interworking. So I guess
>>for uclibc we can rely on THUMB_INTERWORK distro feature if set correctly.
>
> AFAIR eabi implies thumb, thumb makes interwork possible, interwork
> imples bx but my memory could fail me on this.

eabi does not imply thumb. EABI is supported on armv4 which does not have
thumb.

>
> Can you, khem, think of a set of "thumb" and "interwork" (and
> potentially "bx" for HW that supports it, like IIRC all e.g. cortex
> onward based designs) in DISTRO_FEATURES and MACHINE_FEATURES that can
> be used generically?
>
> A first step would be to just resuse the infrastructure in this thread,
> later on we could think about some sort of combined_feature mechanism to
> properly setup arm ontop of this proposed infrastructure.

I think we need thumb_interwork distro_feature which we could use here
here is a patch that distros would need.




>
> cheers,
>

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diff --git a/conf/distro/include/sane-toolchain.inc b/conf/distro/include/sane-toolchain.inc
index 6b6b170..78591e2 100644
--- a/conf/distro/include/sane-toolchain.inc
+++ b/conf/distro/include/sane-toolchain.inc
@@ -86,7 +86,13 @@ ARM_INSTRUCTION_SET = "${PREFERRED_ARM_INSTRUCTION_SET}"
 #    but requires more instructions (140% for 70% smaller code) so may be
 #    slower.
 
-THUMB_INTERWORK = "yes"
+# armv4 does not have thumb instruction set therefore no interworking instructions
+# so if machine is based on armv4 we dont have choice.
+
+THUMB_INTERWORK_armv4 = "no"
+
+THUMB_INTERWORK ?= "yes"
+
 # "yes" "no"
 #    Whether to compile with code to allow interworking between the two
 #    instruction sets.  This allows thumb code to be executed on a primarily
diff --git a/conf/distro/minimal-uclibc.conf b/conf/distro/minimal-uclibc.conf
index 44805cf..35c77c8 100644
--- a/conf/distro/minimal-uclibc.conf
+++ b/conf/distro/minimal-uclibc.conf
@@ -44,3 +44,4 @@ DISTRO_FEATURES += "pam"
 DISTRO_FEATURES += "largefile"
 # glib-2.0 nneds ipv6 and there is no knob to control it
 DISTRO_FEATURES += "ipv4 ipv6"
+DISTRO_FEATURES_append_arm = ' ${@["thumb-interworking",""][bb.data.getVar('THUMB_INTERWORKING', d, 1) == "yes"]}'
diff --git a/conf/distro/minimal.conf b/conf/distro/minimal.conf
index e400c14..ea9f467 100644
--- a/conf/distro/minimal.conf
+++ b/conf/distro/minimal.conf
@@ -16,7 +16,7 @@ DISTRO_VERSION = "dev-snapshot-${SRCDATE}"
 DISTRO_TYPE ?= "debug"
 
 # Ensure some form of release config, so error out if someone thinks he knows better
-DISTRO_CHECK := "${@bb.data.getVar('DISTRO_VERSION',d,1) or bb.fatal('Remove this line or set a dummy DISTRO_VERSION")
+DISTRO_CHECK := "${@bb.data.getVar('DISTRO_VERSION',d,1) or bb.fatal('Remove this line or set a dummy DISTRO_VERSION')}"
 
 #############################################################################
 # FEATURE SELECTION
@@ -34,6 +34,8 @@ DISTRO_FEATURES += "eabi"
 
 DISTRO_FEATURES += "mplt"
 
+DISTRO_FEATURES_append_arm = ' ${@["thumb-interworking",""][bb.data.getVar('THUMB_INTERWORKING', d, 1) == "yes"]}'
+
 #############################################################################
 # LIBRARY NAMES
 #############################################################################