Messages in this thread | | | Date | Thu, 12 Oct 2023 14:08:00 -0700 | Subject | Re: [PATCH v2 0/4] Introduce %rip-relative addressing to PER_CPU_VAR macro | From | "H. Peter Anvin" <> |
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On 10/12/23 13:59, Uros Bizjak wrote: > On Thu, Oct 12, 2023 at 10:53 PM Dave Hansen <dave.hansen@intel.com> wrote: >> >> On 10/12/23 13:12, Uros Bizjak wrote: >>> The last patch introduces (%rip) suffix and uses it for x86_64 target, >>> resulting in a small code size decrease: text data bss dec hex filename >>> 25510677 4386685 808388 30705750 1d48856 vmlinux-new.o 25510629 4386685 >>> 808388 30705702 1d48826 vmlinux-old.o >> >> I feel like I'm missing some of the motivation here. >> >> 50 bytes is great and all, but it isn't without the cost of changing >> some rules and introducing potential PER_CPU_ARG() vs. PER_CPU_VAR() >> confusion. >> >> Are there some other side benefits? What else does this enable? > > These changes are necessary to build the kernel as Position > Independent Executable (PIE) on x86_64 [1]. And since I was working in > percpu area I thought that it was worth implementing them. > > [1] https://lore.kernel.org/lkml/cover.1682673542.git.houwenlong.hwl@antgroup.com/ >
Are you PIC-adjusting the percpu variables as well?
-hpa
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