ARC: support shared crt1

Submitted by Vineet Gupta on June 15, 2016, 12:39 p.m.

Details

Message ID 1465994393-7925-1-git-send-email-vgupta@synopsys.com
State New
Headers show

Commit Message

Vineet Gupta June 15, 2016, 12:39 p.m.
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
---
 libc/sysdeps/linux/arc/crt1.S | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

Comments

Waldemar Brodkorb June 15, 2016, 6:34 p.m.
Hi Vineet,
Vineet Gupta wrote,

> Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
> ---
>  libc/sysdeps/linux/arc/crt1.S | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/libc/sysdeps/linux/arc/crt1.S b/libc/sysdeps/linux/arc/crt1.S
> index 95c41f888850..e38c8e81b2c0 100644
> --- a/libc/sysdeps/linux/arc/crt1.S
> +++ b/libc/sysdeps/linux/arc/crt1.S
> @@ -41,11 +41,15 @@ __start:
>  
>  	mov_s	r5, r0		; rltd_fini
>  	add_s	r2, sp, 4	; argv
> -
> +#ifdef L_Scrt1
> +	add	r0, pcl, @main@pcl
> +	add	r3, pcl, @_init@pcl
> +	add	r4, pcl, @_fini@pcl
> +#else
>  	mov_s	r0, main
>  	mov_s	r3, _init
>  	mov	r4, _fini
> -
> +#endif
>  	and	sp, sp, -8
>  	mov	r6, sp

Can you please be a little more descriptive why this patch is
useful? Will ARC support static PIE or is Scrt1.o used in other
code?

best regards
 Waldemar

Sorry, had to resend with correct sender address.
Vineet Gupta June 16, 2016, 6:38 a.m.
On Wednesday 15 June 2016 08:34 PM, Waldemar Brodkorb wrote:
> Hi Vineet,
> Vineet Gupta wrote,
>
>> Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
>> ---
>>  libc/sysdeps/linux/arc/crt1.S | 8 ++++++--
>>  1 file changed, 6 insertions(+), 2 deletions(-)
>>
>> diff --git a/libc/sysdeps/linux/arc/crt1.S b/libc/sysdeps/linux/arc/crt1.S
>> index 95c41f888850..e38c8e81b2c0 100644
>> --- a/libc/sysdeps/linux/arc/crt1.S
>> +++ b/libc/sysdeps/linux/arc/crt1.S
>> @@ -41,11 +41,15 @@ __start:
>>  
>>  	mov_s	r5, r0		; rltd_fini
>>  	add_s	r2, sp, 4	; argv
>> -
>> +#ifdef L_Scrt1
>> +	add	r0, pcl, @main@pcl
>> +	add	r3, pcl, @_init@pcl
>> +	add	r4, pcl, @_fini@pcl
>> +#else
>>  	mov_s	r0, main
>>  	mov_s	r3, _init
>>  	mov	r4, _fini
>> -
>> +#endif
>>  	and	sp, sp, -8
>>  	mov	r6, sp
> Can you please be a little more descriptive why this patch is
> useful? Will ARC support static PIE or is Scrt1.o used in other
> code?

This is for a dynamically linked PIE - can we have static linked PIE ? Current
approach of taking addresses of functions, in not position independent but still
works for the normal dynamically linked executables (non PIE) since the zero based
addresses are rightly resolved in final link. This is not true for PIE hence we
need a really position independent way (PC relative addr) to pass those function
addresses.

Do u want me to respin with beefed up changelog.

> Sorry, had to resend with correct sender address.

My address was wrong ?
Waldemar Brodkorb June 16, 2016, 7:49 p.m.
Hi Vineet,
Vineet Gupta wrote,

> On Wednesday 15 June 2016 08:34 PM, Waldemar Brodkorb wrote:
> > Hi Vineet,
> > Vineet Gupta wrote,
> >
> >> Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
> >> ---
> >>  libc/sysdeps/linux/arc/crt1.S | 8 ++++++--
> >>  1 file changed, 6 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/libc/sysdeps/linux/arc/crt1.S b/libc/sysdeps/linux/arc/crt1.S
> >> index 95c41f888850..e38c8e81b2c0 100644
> >> --- a/libc/sysdeps/linux/arc/crt1.S
> >> +++ b/libc/sysdeps/linux/arc/crt1.S
> >> @@ -41,11 +41,15 @@ __start:
> >>  
> >>  	mov_s	r5, r0		; rltd_fini
> >>  	add_s	r2, sp, 4	; argv
> >> -
> >> +#ifdef L_Scrt1
> >> +	add	r0, pcl, @main@pcl
> >> +	add	r3, pcl, @_init@pcl
> >> +	add	r4, pcl, @_fini@pcl
> >> +#else
> >>  	mov_s	r0, main
> >>  	mov_s	r3, _init
> >>  	mov	r4, _fini
> >> -
> >> +#endif
> >>  	and	sp, sp, -8
> >>  	mov	r6, sp
> > Can you please be a little more descriptive why this patch is
> > useful? Will ARC support static PIE or is Scrt1.o used in other
> > code?
> 
> This is for a dynamically linked PIE - can we have static linked PIE ? Current
> approach of taking addresses of functions, in not position independent but still
> works for the normal dynamically linked executables (non PIE) since the zero based
> addresses are rightly resolved in final link. This is not true for PIE hence we
> need a really position independent way (PC relative addr) to pass those function
> addresses.

You can try static PIE with binutils 2.26 and up with
-Wl,--no-dynamic-linker, but my tests with ARM/MIPS failed.
So I am not sure if crt1.S is the problem or something else.
 
> Do u want me to respin with beefed up changelog.

Yes, please.
 
> > Sorry, had to resend with correct sender address.
> 
> My address was wrong ?

No, I use mutt and I am to lazy to configure send-hooks, so I
manually change my mail address before sending e-Mails :/

best regards
 Waldemar
Rich Felker June 17, 2016, 2:04 a.m.
On Thu, Jun 16, 2016 at 09:49:10PM +0200, Waldemar Brodkorb wrote:
> Hi Vineet,
> Vineet Gupta wrote,
> 
> > On Wednesday 15 June 2016 08:34 PM, Waldemar Brodkorb wrote:
> > > Hi Vineet,
> > > Vineet Gupta wrote,
> > >
> > >> Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
> > >> ---
> > >>  libc/sysdeps/linux/arc/crt1.S | 8 ++++++--
> > >>  1 file changed, 6 insertions(+), 2 deletions(-)
> > >>
> > >> diff --git a/libc/sysdeps/linux/arc/crt1.S b/libc/sysdeps/linux/arc/crt1.S
> > >> index 95c41f888850..e38c8e81b2c0 100644
> > >> --- a/libc/sysdeps/linux/arc/crt1.S
> > >> +++ b/libc/sysdeps/linux/arc/crt1.S
> > >> @@ -41,11 +41,15 @@ __start:
> > >>  
> > >>  	mov_s	r5, r0		; rltd_fini
> > >>  	add_s	r2, sp, 4	; argv
> > >> -
> > >> +#ifdef L_Scrt1
> > >> +	add	r0, pcl, @main@pcl
> > >> +	add	r3, pcl, @_init@pcl
> > >> +	add	r4, pcl, @_fini@pcl
> > >> +#else
> > >>  	mov_s	r0, main
> > >>  	mov_s	r3, _init
> > >>  	mov	r4, _fini
> > >> -
> > >> +#endif
> > >>  	and	sp, sp, -8
> > >>  	mov	r6, sp
> > > Can you please be a little more descriptive why this patch is
> > > useful? Will ARC support static PIE or is Scrt1.o used in other
> > > code?
> > 
> > This is for a dynamically linked PIE - can we have static linked PIE ? Current
> > approach of taking addresses of functions, in not position independent but still
> > works for the normal dynamically linked executables (non PIE) since the zero based
> > addresses are rightly resolved in final link. This is not true for PIE hence we
> > need a really position independent way (PC relative addr) to pass those function
> > addresses.
> 
> You can try static PIE with binutils 2.26 and up with
> -Wl,--no-dynamic-linker, but my tests with ARM/MIPS failed.
> So I am not sure if crt1.S is the problem or something else.

Static PIE requires an rcrt1.o that's responsible for performing
self-relocation equivalent to what the dynamic linker does to itself.
Scrt1.o is for dynamic-linker PIE (and it's compatible with linking in
non-PIE code whether it's static or dynamic linked, but not necessary
in those cases).

Rich
Waldemar Brodkorb June 21, 2016, 6:56 p.m.
Hi Vineet,
Vineet Gupta wrote,

ping?
(resend with better changelog)

> On Wednesday 15 June 2016 08:34 PM, Waldemar Brodkorb wrote:
> > Hi Vineet,
> > Vineet Gupta wrote,
> >
> >> Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
> >> ---
> >>  libc/sysdeps/linux/arc/crt1.S | 8 ++++++--
> >>  1 file changed, 6 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/libc/sysdeps/linux/arc/crt1.S b/libc/sysdeps/linux/arc/crt1.S
> >> index 95c41f888850..e38c8e81b2c0 100644
> >> --- a/libc/sysdeps/linux/arc/crt1.S
> >> +++ b/libc/sysdeps/linux/arc/crt1.S
> >> @@ -41,11 +41,15 @@ __start:
> >>  
> >>  	mov_s	r5, r0		; rltd_fini
> >>  	add_s	r2, sp, 4	; argv
> >> -
> >> +#ifdef L_Scrt1
> >> +	add	r0, pcl, @main@pcl
> >> +	add	r3, pcl, @_init@pcl
> >> +	add	r4, pcl, @_fini@pcl
> >> +#else
> >>  	mov_s	r0, main
> >>  	mov_s	r3, _init
> >>  	mov	r4, _fini
> >> -
> >> +#endif
> >>  	and	sp, sp, -8
> >>  	mov	r6, sp
> > Can you please be a little more descriptive why this patch is
> > useful? Will ARC support static PIE or is Scrt1.o used in other
> > code?
> 
> This is for a dynamically linked PIE - can we have static linked PIE ? Current
> approach of taking addresses of functions, in not position independent but still
> works for the normal dynamically linked executables (non PIE) since the zero based
> addresses are rightly resolved in final link. This is not true for PIE hence we
> need a really position independent way (PC relative addr) to pass those function
> addresses.
> 
> Do u want me to respin with beefed up changelog.
> 
> > Sorry, had to resend with correct sender address.
> 
> My address was wrong ?
> 
> 
> _______________________________________________
> uClibc mailing list
> uClibc@uclibc.org
> http://lists.busybox.net/mailman/listinfo/uclibc
>

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diff --git a/libc/sysdeps/linux/arc/crt1.S b/libc/sysdeps/linux/arc/crt1.S
index 95c41f888850..e38c8e81b2c0 100644
--- a/libc/sysdeps/linux/arc/crt1.S
+++ b/libc/sysdeps/linux/arc/crt1.S
@@ -41,11 +41,15 @@  __start:
 
 	mov_s	r5, r0		; rltd_fini
 	add_s	r2, sp, 4	; argv
-
+#ifdef L_Scrt1
+	add	r0, pcl, @main@pcl
+	add	r3, pcl, @_init@pcl
+	add	r4, pcl, @_fini@pcl
+#else
 	mov_s	r0, main
 	mov_s	r3, _init
 	mov	r4, _fini
-
+#endif
 	and	sp, sp, -8
 	mov	r6, sp