Messages in this thread | | | From | Uros Bizjak <> | Date | Thu, 12 Oct 2023 22:59:37 +0200 | Subject | Re: [PATCH v2 0/4] Introduce %rip-relative addressing to PER_CPU_VAR macro |
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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/
Uros.
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