[PATCH v7] Add support for stack-protector

[Alex Sadovsky <nable.maininbox@googlemail.com>]

Dear Joel,

> Add support for stack protector for UBOOT, SPL, and TPL
> as well as new pytest for stackprotector
>
> Signed-off-by: Joel Peshkin <joel.peshkin@broadcom.com>
> Cc: Simon Glass <sjg@chromium.org>
> Cc: Heinrich Schuchardt <xypron.glpk@gmx.de>
>
> Changes for v7:
>??? - Fix commit message
>??? - add __builtin_extract_return_addr() calls
> Changes for v6:
>??? - Fix commit message
> Changes for v5:
>??? - Rebase
> Changes for v4:
>??? - Exclude EFI from stackprotector
>??? - Cleanups of extra includes and declaration
> Changes for v3:
>??? - Move test command to cmd/
>??? - Update Kconfig names and depends
>??? - clean up default canary initialization
> Changes for v2:
>??? - Add test command and corresponding config
>??? - Fixed incorrect description in Kconfig
>??? - Add unit test
> ---
> ---

Patch changelog is not a part of commit message, it's placed below the '---' mark. I hope this guide will help you:
https://www.denx.de/wiki/view/U-Boot/Patches#Sending_updated_patch_versions

> [...]
> +DECLARE_GLOBAL_DATA_PTR;
> +
> +unsigned long __stack_chk_guard = (long)(0xfeedf00ddeadbeef & ~0L);

'long' and 'unsigned long' are slightly different types. I suggest you the following form (please, note the UL instead of L):

unsigned long __stack_chk_guard = (unsigned long)(0xfeedf00ddeadbeef & ~0UL)

Else gcc will complain like this:

> warning: unsigned conversion from ?long int? to ?long long unsigned int? changes value from ?-1? to ?18446744073709551615? [-Wsign-conversion]
> unsigned long __stack_chk_guard = (long)(0xfeedf00ddeadbeef & ~0L);
> warning: unsigned conversion from ?long int? to ?long unsigned int? changes value from ?-559038737? to ?3735928559? [-Wsign-conversion]

I hope you'll find -Wconversion compiler flag useful, it's one of the flags that often help me to spot some corner cases with potential bugs. IMHO it should be enabled by default.