Re: PING^1 [PATCH] testsuite: 'b' instruction can't do long enough jumps

[Torbjorn SVENSSON <torbjorn.svensson@foss.st.com>]

Hi Christophe!

On 2022-09-28 13:55, Christophe Lyon wrote:
> Hi!
> 
> 
> On 9/28/22 11:17, Torbjorn SVENSSON via Gcc-patches wrote:
>> Hi,
>>
>> Ping: 
>> https://gcc.gnu.org/pipermail/gcc-patches/2022-September/601829.html
>>
>> Kind regards,
>> Torbjörn
>>
>> On 2022-09-19 18:30, Torbjörn SVENSSON wrote:
>>> After moving the testglue in commit 9d503515cee, the jump to exit and
>>> abort is too far for the 'b' instruction on Cortex-M0. As most of the
> I am not sure I understand why that commit changed the distance between 
> 'exit' and the branch instruction?

The change was that the gcc_tg.o (the DejaGNU testglue.c object file) is 
now put last on the command line. In the previous versions of GCC, it 
was put before the ldflags flag etc, so now the code is placed in a way 
that the distance might be too big.

This could also be related to that we in ST are using QEMU in system 
mode and not user mode and as a result, our test environment is slightly 
larger and might perhaps be placed in between the code for the test case 
and the testglue.

>>> C code would generate a 'bl' instruction instead of a 'b'
>>> instruction, lets do the same for the inline assembler.
>>>
>>> The error seen without this patch:
>>>
>>> /tmp/cccCRiCl.o: in function `main':
>>> stack-protector-1.c:(.text+0x4e): relocation truncated to fit: 
>>> R_ARM_THM_JUMP11 against symbol `__wrap_exit' defined in .text 
>>> section in gcc_tg.o
>>> stack-protector-1.c:(.text+0x50): relocation truncated to fit: 
>>> R_ARM_THM_JUMP11 against symbol `__wrap_abort' defined in .text 
>>> section in gcc_tg.o
>>> collect2: error: ld returned 1 exit status
>>>
> Anyway the change seems sensible to me, I suppose it's not worth adding 
> support in the linker to insert long branch stubs for these relocations.

If a simple 'bl' instead of 'b' is enough, I think that this trivial 
change is the right one as the test case is supposed to test the stack 
protection, not branching, right?

Kind regards,
Torbjörn

> 
> Christophe
> 
>>> gcc/testsuite/ChangeLog:
>>>
>>>          * gcc/testsuite/gcc.target/arm/stack-protector-1.c: Use 'bl'
>>>     instead of 'b' instruction.
>>>     * gcc/testsuite/gcc.target/arm/stack-protector-3.c: Likewise.
>>>
>>> Co-Authored-By: Yvan ROUX  <yvan.roux@foss.st.com>
>>> Signed-off-by: Torbjörn SVENSSON  <torbjorn.svensson@foss.st.com>
>>> ---
>>>   gcc/testsuite/gcc.target/arm/stack-protector-1.c | 4 ++--
>>>   gcc/testsuite/gcc.target/arm/stack-protector-3.c | 2 +-
>>>   2 files changed, 3 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/gcc/testsuite/gcc.target/arm/stack-protector-1.c 
>>> b/gcc/testsuite/gcc.target/arm/stack-protector-1.c
>>> index 8d28b0a847c..3f0ffc9c3f3 100644
>>> --- a/gcc/testsuite/gcc.target/arm/stack-protector-1.c
>>> +++ b/gcc/testsuite/gcc.target/arm/stack-protector-1.c
>>> @@ -56,8 +56,8 @@ asm (
>>>   "    ldr    r1, [sp, #4]\n"
>>>       CHECK (r1)
>>>   "    mov    r0, #0\n"
>>> -"    b    exit\n"
>>> +"    bl    exit\n"
>>>   "1:\n"
>>> -"    b    abort\n"
>>> +"    bl    abort\n"
>>>   "    .size    main, .-main"
>>>   );
>>> diff --git a/gcc/testsuite/gcc.target/arm/stack-protector-3.c 
>>> b/gcc/testsuite/gcc.target/arm/stack-protector-3.c
>>> index b8f77fa2309..2f710529b8f 100644
>>> --- a/gcc/testsuite/gcc.target/arm/stack-protector-3.c
>>> +++ b/gcc/testsuite/gcc.target/arm/stack-protector-3.c
>>> @@ -26,7 +26,7 @@ asm (
>>>   "    .type    __stack_chk_fail, %function\n"
>>>   "__stack_chk_fail:\n"
>>>   "    movs    r0, #0\n"
>>> -"    b    exit\n"
>>> +"    bl    exit\n"
>>>   "    .size    __stack_chk_fail, .-__stack_chk_fail"
>>>   );