On Tue, May 15, 2018 at 02:53:52PM -0700, Nadav Amit wrote: > Josh Triplett <j...@joshtriplett.org> wrote: > > > On Tue, May 15, 2018 at 07:11:08AM -0700, Nadav Amit wrote: > >> GCC considers the number of statements in inlined assembly blocks, > >> according to new-lines and semicolons, as an indication to the cost of > >> the block in time and space. This data is distorted by the kernel code, > >> which puts information in alternative sections. As a result, the > >> compiler may perform incorrect inlining and branch optimizations. > >> > >> In the case of objtool, this distortion is extreme, since anyhow the > >> annotations of objtool are discarded during linkage. > >> > >> The solution is to set an assembly macro and call it from the inlinedv > >> assembly block. As a result GCC considers the inline assembly block as > >> a single instruction. > >> > >> This patch slightly increases the kernel size. > >> > >> text data bss dec hex filename > >> 18126699 10066728 2936832 31130259 1db0293 ./vmlinux before > >> 18126824 10067268 2936832 31130924 1db052c ./vmlinux after (+665) > > > > With what kernel config? What's the text size change for an allnoconfig? > > I use my custom config and to include the drivers in the image. Other > configs were not too appropriate: defconfig does not enable paravirt and > allyesconfig is too heavy. > > There is no effect with allnoconfig on size: > > text data bss dec hex filename > 1018441 230148 1215604 2464193 2599c1 ./vmlinux > 1018441 230148 1215604 2464193 2599c1 ./vmlinux > > I think it is expected since CONFIG_STACK_VALIDATION is off. No?
Thanks for checking; fine by me then. :)
