bootx_init.c:88: undefined reference to `__stack_chk_fail_local'

[Christophe LEROY]

Le 11/01/2017 à 23:54, Segher Boessenkool a écrit :
> On Tue, Jan 10, 2017 at 07:26:15AM +0100, Christophe LEROY wrote:
>>> Maybe ppc32 is not supposed to be built with CC_STACKPROTECTOR ?
>>
>> Indeed, the latest versions of GCC don't use anymore the global variable
>> __stack_chk_guard as canary value, but a value stored at -0x7008(r2).
>> This is not compatible with the current implementation of  the kernel
>> with uses r2 as a pointeur to current task struct.
>> So until we fix it, I don't think CC_STACKPROTECTOR is usable on PPC
>> with modern versions of GCC.
>
> I still wonder what changed.  Nothing relevant has changed for ten years
> or whatever as far as I see; unless it is just the -fstack-protector-strong
> that makes it fail now.  Curious.
>

Yes, looks like it was changed from global to TLS in 2005 on powerpc. 
Indeed when I implemented STACKPROTECTOR in Kernel on ppc I 
copied/pasted it from ARM which is (still?) using the global 
__stack_chk_guard, and at first it worked quite well on my powerpc.

x86 has the following option on GCC. Couldn't we have it on powerpc too ?

-mstack-protector-guard=guard
Generate  stack  protection  code  using  canary  at
guard.   Supported  locations are ‘ global ’ for global canary or ‘ tls
’ for per-thread canary in the TLS block (the  default). This  option 
has  effect  only  when  ‘-fstack-protector’  or ‘-fstack-protector-all’ 
is specified.

Christophe