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Re: PR9743 / ARM: long branch stubs to PLT
On Thu, Feb 05, 2009 at 05:28:22PM +0100, Christophe LYON wrote:
> - I removed some interworking warnings because I don't feel very
> confortable with them. More skilled people are welcome to explain me if I
> got it wrong.
Could you expand on this?
The warning applies to pre-EABI code. The stubs won't help if you're
going to return from the called function using "mov pc".
In general - if it's not too much of a hassle - it helps to do
reformating patches separately from real changes. In this case, that
means breaking out the renaming from the rest. I won't insist, but
it sure does make it easier to see what's going on.
> -#define CHANGE_TO_ARM "__%s_change_to_arm"
> -#define BACK_FROM_ARM "__%s_back_from_arm"
Nothing else generates the CHANGE_TO_ARM naming, and you didn't delete
a test case... that means there wasn't a test case for this feature,
boo. So I can't see what effect you've had on whatever this used to
handle. Is this one of the new stubs?
(BACK_FROM_ARM was already unused...)
> diff -uN -r --exclude=CVS --exclude='*~' --exclude='.#*' binutils-cvs-ref/src/ld/testsuite/ld-arm/arm-call.d binutils-cvs/src/ld/testsuite/ld-arm/arm-call.d
> --- binutils-cvs-ref/src/ld/testsuite/ld-arm/arm-call.d 2007-05-22 19:17:53.000000000 +0200
> +++ binutils-cvs/src/ld/testsuite/ld-arm/arm-call.d 2009-02-02 15:21:10.000000000 +0100
Why'd this file change from __t1_from_arm to __t1_veneer?
Also, this whole "putting stubs at the front of .text" is going to be
a real problem. We've only just updated our internal binutils, and I
haven't had time to construct a test case yet, but I'm expecting this
to mess up interrupt vectors in our startup code. I don't suppose
it's easy to put them at the end instead?
> diff -uN -r --exclude=CVS --exclude='*~' --exclude='.#*' binutils-cvs-ref/src/ld/testsuite/ld-arm/arm-elf.exp binutils-cvs/src/ld/testsuite/ld-arm/arm-elf.exp
> --- binutils-cvs-ref/src/ld/testsuite/ld-arm/arm-elf.exp 2009-01-23 14:13:45.000000000 +0100
> +++ binutils-cvs/src/ld/testsuite/ld-arm/arm-elf.exp 2009-02-05 16:04:43.000000000 +0100
> @@ -190,10 +190,6 @@
> # Exclude non-ARM-EABI targets.
>
> if { ![istarget "arm*-*-*eabi"] } {
> - # Special variants of these tests, as no farcall stub is generated
> - # for a non-ARM-EABI target
> - run_dump_test "thumb2-bl-as-thumb1-bad-noeabi"
> - run_dump_test "thumb2-bl-bad-noeabi"
> return
> }
Why? Did you remove the non-EABI support?
> - {"ARM-Thumb farcall with BLX (PIC veneer)" "-Ttext 0x1000 --section-start .foo=0x2001014 --pic-veneer" "-march=armv5t" {farcall-arm-thumb.s}
> + {"ARM-Thumb farcall with BLX (PIC veneer)" "-Ttext 0x1000 --section-start .foo=0x2002014 --pic-veneer" "-march=armv5t" {farcall-arm-thumb.s}
So that's why the addresses in the test all changed; could you explain
why you made this change?
In general, I'm going to ask about any change to an existing
testcase's output. Yes, I'm that picky.
> diff -uN -r --exclude=CVS --exclude='*~' --exclude='.#*' binutils-cvs-ref/src/ld/testsuite/ld-arm/farcall-arm-thumb-pic-veneer.d binutils-cvs/src/ld/testsuite/ld-arm/farcall-arm-thumb-pic-veneer.d
> --- binutils-cvs-ref/src/ld/testsuite/ld-arm/farcall-arm-thumb-pic-veneer.d 2008-06-25 16:28:48.000000000 +0200
> +++ binutils-cvs/src/ld/testsuite/ld-arm/farcall-arm-thumb-pic-veneer.d 2009-02-02 15:40:05.000000000 +0100
> @@ -3,10 +3,10 @@
> Disassembly of section .text:
>
> 00001000 <__bar_from_arm>:
> - 1000: e59fc000 ldr ip, \[pc, #0\] ; 1008 <__bar_from_arm\+0x8>
> - 1004: e08ff00c add pc, pc, ip
> - 1008: 0200000d .word 0x0200000d
> - 100c: 00000000 .word 0x00000000
> + 1000: e59fc004 ldr ip, \[pc, #4\] ; 100c <__bar_from_arm\+0xc>
> + 1004: e08cc00f add ip, ip, pc
> + 1008: e12fff1c bx ip
> + 100c: 02000009 .word 0x02000009
Why the switch from a v5 stub to a v4t stub?
--
Daniel Jacobowitz
CodeSourcery