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From: Aneesh V <aneesh@ti.com>
To: u-boot@lists.denx.de
Subject: [U-Boot] [RFC PATCH 2/4] OMAP3+: fix issues with Thumb build
Date: Thu, 09 Feb 2012 14:28:21 +0530	[thread overview]
Message-ID: <4F338AAD.8070905@ti.com> (raw)
In-Reply-To: <4F3040D0.5070808@aribaud.net>

Hi Albert,

On Tuesday 07 February 2012 02:36 AM, Albert ARIBAUD wrote:
> Le 06/02/2012 12:37, Aneesh V a ?crit :
>> When U-Boot/SPL is built using the Thumb instruction set the
>> toolchain has a potential issue with weakly linked symbols.
>> If a function has a weakly linked default implementation in C
>> and a real implementation in assembly GCC is confused about the
>> instruction set of the assembly implementation. As a result
>> the assembly function that is built in ARM is executed as
>> if it is Thumb. This results in a crash.
>>
>> We need to investigate further to see if this is a toolchain
>> issue or an issue with our usage of it. In the meanwhile, we
>> can workaround the issue by having both the weakly linked alias
>> and the real implementation in C.
>
> I would tend to NAK a patch submission where an issue is known and
> investigation is considered but is actually bypassed by a workaround.
> These tend to turn from 'temporary fix' to 'old crust' with time,
> because there is no incentive for a better solution when the quick fix
> "works, after all".

I have a solution to this problem now. The following change solves it.

diff --git a/arch/arm/cpu/armv7/omap-common/lowlevel_init.S 
b/arch/arm/cpu/armv7/omap-common/lowlevel_init.S
index 35f38ac..177af7a 100644
--- a/arch/arm/cpu/armv7/omap-common/lowlevel_init.S
+++ b/arch/arm/cpu/armv7/omap-common/lowlevel_init.S
@@ -28,6 +28,7 @@

  #include <asm/arch/omap.h>

+.type   save_boot_params, %function
  .global save_boot_params
  save_boot_params:
  	/*

Apparently having the symbol marked as %function type in the symbol
table helps ld. However, not having the %function tag doesn't prevent
ld from linking correctly to this function. It affects only ARM/Thumb
resolution. Strange!

I came to this solution from the test-code provided by Ulrich Weigand
in reply to my queries in Linaro ML [1]. I couldn't reproduce the
problem with his code, but eventually could break it when I removed
the %function.

I will continue this discussion there and to understand whether this is
a limitation with GCC.

However, hope you are fine with the above solution. I shall fix up all
assembly functions in arm.

[1] http://article.gmane.org/gmane.linux.linaro.devel/3073

br,
Aneesh

  parent reply	other threads:[~2012-02-09  8:58 UTC|newest]

Thread overview: 83+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-02-06 11:37 [U-Boot] [RFC PATCH 0/4] Enable Thumb build for ARM platforms Aneesh V
2012-02-06 11:37 ` [U-Boot] [RFC PATCH 1/4] ARM: enable Thumb build Aneesh V
2012-02-06 18:45   ` Tom Rini
2012-02-07  7:43     ` Aneesh V
2012-02-06 11:37 ` [U-Boot] [RFC PATCH 2/4] OMAP3+: fix issues with " Aneesh V
2012-02-06 21:06   ` Albert ARIBAUD
2012-02-07  7:49     ` Aneesh V
2012-02-09  8:58     ` Aneesh V [this message]
2012-02-06 11:37 ` [U-Boot] [RFC PATCH 3/4] OMAP3+: Use -march=armv7-a and thereby enable Thumb-2 Aneesh V
2012-02-06 11:37 ` [U-Boot] [RFC PATCH 4/4] OMAP4: enable Thumb build Aneesh V
2012-02-06 12:26 ` [U-Boot] [RFC PATCH 0/4] Enable Thumb build for ARM platforms Aneesh V
2012-02-06 13:22   ` Aneesh V
2012-02-15 13:57 ` [U-Boot] [PATCH " Aneesh V
2012-02-15 13:57 ` [U-Boot] [PATCH 1/4] ARM: enable Thumb build Aneesh V
2012-02-15 13:57 ` [U-Boot] [PATCH 2/4] arm: add %function attribute to assembly functions Aneesh V
2012-02-17 11:09   ` Aneesh V
2012-02-18 10:13     ` Albert ARIBAUD
2012-02-18 13:24       ` Aneesh V
2012-02-18 15:04         ` Albert ARIBAUD
2012-02-18 16:34         ` Aneesh V
2012-02-18 16:48           ` Albert ARIBAUD
2012-02-20 16:08             ` Aneesh V
2012-02-23 11:06               ` Aneesh V
2012-02-17 17:13   ` Mike Frysinger
2012-02-18 11:12     ` Aneesh V
2012-02-18 11:34       ` Albert ARIBAUD
2012-02-18 22:03   ` Simon Glass
2012-02-19  7:15     ` Mike Frysinger
2012-02-20 20:07       ` Tom Rini
2012-02-20 21:53         ` Simon Glass
2012-02-21  4:19           ` Mike Frysinger
2012-02-21  4:44             ` Simon Glass
2012-02-21 14:33             ` Tom Rini
2012-02-21 15:42               ` Mike Frysinger
2012-02-21 18:03                 ` Aneesh V
2012-02-21 19:28                   ` Mike Frysinger
2012-02-21 20:01                     ` Aneesh V
2012-02-21  4:18         ` Mike Frysinger
2012-02-15 13:57 ` [U-Boot] [PATCH 3/4] armv7: Use -march=armv7-a and thereby enable Thumb-2 Aneesh V
2012-02-15 13:57 ` [U-Boot] [PATCH 4/4] OMAP4: enable Thumb build Aneesh V
2012-02-23 13:39 ` [U-Boot] [PATCH v2 1/5] arm: adapt asm/linkage.h from Linux Aneesh V
2012-02-23 14:01   ` Aneesh V
2012-02-23 13:39 ` [U-Boot] [PATCH v2 2/5] armv7: add appropriate headers for assembly functions Aneesh V
2012-02-23 13:39 ` [U-Boot] [PATCH v2 3/5] ARM: enable Thumb build Aneesh V
2012-02-23 14:57   ` Mike Frysinger
2012-02-23 17:28     ` Aneesh V
2012-02-23 17:34       ` Tom Rini
2012-02-23 17:49         ` Aneesh V
2012-02-23 17:51           ` Tom Rini
2012-02-23 18:09             ` Aneesh V
2012-02-23 18:13               ` Aneesh V
2012-02-23 18:05           ` Mike Frysinger
2012-02-23 18:04       ` Mike Frysinger
2012-02-23 18:12         ` Aneesh V
2012-02-23 13:39 ` [U-Boot] [PATCH v2 4/5] armv7: Use -march=armv7-a and thereby enable Thumb-2 Aneesh V
2012-02-23 13:39 ` [U-Boot] [PATCH v2 5/5] OMAP4: enable Thumb build Aneesh V
2012-02-23 14:06 ` [U-Boot] [PATCH v3 1/6] arm: adapt asm/linkage.h from Linux Aneesh V
2012-02-23 14:59   ` Mike Frysinger
2012-02-23 15:24     ` Tom Rini
2012-02-23 16:57       ` Mike Frysinger
2012-02-23 17:40     ` Aneesh V
2012-02-23 23:52       ` Mike Frysinger
2012-02-24 10:30         ` Aneesh V
2012-02-23 14:06 ` [U-Boot] [PATCH v3 2/6] armv7: add appropriate headers for assembly functions Aneesh V
2012-02-23 14:59   ` Mike Frysinger
2012-02-23 14:06 ` [U-Boot] [PATCH v3 3/6] ARM: enable Thumb build Aneesh V
2012-02-23 14:06 ` [U-Boot] [PATCH v3 4/6] armv7: Use -march=armv7-a and thereby enable Thumb-2 Aneesh V
2012-02-23 15:05   ` Mike Frysinger
2012-02-23 17:50     ` Aneesh V
2012-02-23 14:06 ` [U-Boot] [PATCH v3 5/6] omap4+: Avoid using __attribute__ ((__packed__)) Aneesh V
2012-02-23 14:21   ` Tom Rini
2012-02-23 14:56     ` Aneesh V
2012-02-23 15:03       ` Mike Frysinger
2012-02-23 15:03     ` Mike Frysinger
2012-02-23 15:42       ` Aneesh V
2012-02-23 14:06 ` [U-Boot] [PATCH v3 6/6] OMAP4: enable Thumb build Aneesh V
2012-03-08 17:10 ` [U-Boot] [PATCH 1/6] arm: adapt asm/linkage.h from Linux Aneesh V
2012-03-08 17:14   ` Aneesh V
2012-03-08 17:10 ` [U-Boot] [PATCH 2/6] armv7: add appropriate headers for assembly functions Aneesh V
2012-03-08 17:10 ` [U-Boot] [PATCH 3/6] ARM: enable Thumb build Aneesh V
2012-03-08 17:10 ` [U-Boot] [PATCH 4/6] armv7: Use -march=armv7-a and thereby enable Thumb-2 Aneesh V
2012-03-08 17:10 ` [U-Boot] [PATCH 5/6] omap4+: Avoid using __attribute__ ((__packed__)) Aneesh V
2012-03-08 17:10 ` [U-Boot] [PATCH 6/6] OMAP4: enable Thumb build Aneesh V

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