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); >> #endif >> >> which 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.
