On 04/30/2013 10:19 PM, Rusty Russell wrote: > Tom Rini <trini@xxxxxx> writes: >> On 04/28/2013 10:59 PM, Rusty Russell wrote: >>> Tom Rini <trini@xxxxxx> writes: >>> >>>> Recent gcc's may place functions into the .text.unlikely section and we >>>> need to check this section as well for section mismatches now otherwise >>>> we may have false negatives for this test. >>> >>> Hmm, I don't think it's all that recent, is it? I can find it back to >>> gcc 4.0.4: >>> >>> `-freorder-functions' >>> Reorder functions in the object file in order to improve code >>> locality. This is implemented by using special subsections >>> `.text.hot' for most frequently executed functions and >>> `.text.unlikely' for unlikely executed functions. Reordering is >>> done by the linker so object file format must support named >>> sections and linker must place them in a reasonable way. >>> >>> Also profile feedback must be available in to make this option >>> effective. See `-fprofile-arcs' for details. >>> >>> Enabled at levels `-O2', `-O3', `-Os'. >>> >>> The comment is the same in in gcc 4.7. >>> >>> So is your real issue that this section is generated with >>> -fprofile-arcs, or has something changed with gcc 4.8, or...? >> >> I've started seeing this with Linaro based 4.7 toolchains. I can go >> back through their releases and see when it starts showing up there if >> it helps. I didn't add .text.hot as I didn't have that section at all, >> fwiw. > > Weird, did you turn on CONFIG_GCOV_KERNEL? AFAICT you shouldn't see > this section without that. Nope, CONFIG_GCOV_KERNEL is off. Must be related to whatever flags the Linaro folks set as default on -O2 (at least in their 2013.03 release), after reading over one of the .o.cmd files in the build. Do you want me to re-word the commit message a bit or ? Thanks! -- Tom -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
