On 22/05/2022 17:50, Tom Rini wrote:
On Sun, May 22, 2022 at 04:56:08PM +0300, Alper Nebi Yasak wrote:
It looks like we should be able to change things in common/spl/spl.c to:
#if CONFIG_IS_ENABLED(BINMAN_SYMBOLS) /* See spl.h for information about this */ binman_sym_declare_optional(ulong, u_boot_any, image_pos); binman_sym_declare_optional(ulong, u_boot_any, size); #endifwhich would mark the symbol as 'weak' and turn the error into a warning on the binman side. But that is somehow being undone by LTO.
So, looking at binman_sym_declare_optional we tell the linker that it's weak and might even be unused. LTO gets very aggressive about finding things that aren't used in the resulting binary and discarding them. Typically we have the problem of a function that is used but it's hard for LTO to see it, so we give it the "used" attribute. But for something we're already saying is "unused" this would be wrong. So why do we mark things as unused here? I assume it's marked weak as it could be overridden at link time by a definition elsewhere.
I don't know, but the GCC manual says marking things 'unused' will suppress a warning if the variable is actually unused. I guess binman symbols may become unused due to some other config options being unset, and it's done for those cases?
I think the optional symbols are marked weak just to signal the python side that they are optional. If I understand it right, binman:
1. Packs an image using the finalized 'spl/u-boot-spl.bin' 2. Figures out the image-pos and size values of every entry 3. Inspects the 'spl/u-boot-spl' ELF file for declared binman symbols 4. Raises an error if any non-'weak' symbol's value is undetermined 5. Updates the u-boot-spl.bin (in memory) with the calculated values 6. Recreates the final image based on that updated bin file.