Thread (41 messages) 41 messages, 8 authors, 2020-12-09

Re: [PATCH v8 00/16] Add support for Clang LTO

From: Arnd Bergmann <arnd@kernel.org>
Date: 2020-12-08 13:55:53
Also in: linux-arch, linux-kbuild, linux-pci, lkml

On Tue, Dec 8, 2020 at 1:15 PM Arnd Bergmann [off-list ref] wrote:
On Tue, Dec 1, 2020 at 10:37 PM 'Sami Tolvanen' via Clang Built Linux [off-list ref] wrote:

- many builds complain about thousands of duplicate symbols in the kernel, e.g.
  ld.lld: error: duplicate symbol: qrtr_endpoint_post
 >>> defined in net/qrtr/qrtr.lto.o
 >>> defined in net/qrtr/qrtr.o
 ld.lld: error: duplicate symbol: init_module
 >>> defined in crypto/842.lto.o
 >>> defined in crypto/842.o
 ld.lld: error: duplicate symbol: init_module
 >>> defined in net/netfilter/nfnetlink_log.lto.o
 >>> defined in net/netfilter/nfnetlink_log.o
 ld.lld: error: duplicate symbol: vli_from_be64
 >>> defined in crypto/ecc.lto.o
 >>> defined in crypto/ecc.o
 ld.lld: error: duplicate symbol: __mod_of__plldig_clk_id_device_table
 >>> defined in drivers/clk/clk-plldig.lto.o
 >>> defined in drivers/clk/clk-plldig.o
A small update here: I see this behavior with every single module
build, including 'tinyconfig' with one module enabled, and 'defconfig'.

I tuned the randconfig setting using KCONFIG_PROBABILITY=2:2:1
now, which only enables a few symbols. With this I see faster build
times (obvioulsy), aroudn 30 seconds per kernel, and all small builds
with CONFIG_MODULES disabled so far succeed.
It appears that the problems I saw originally only happen for larger
configurations, or possibly a combination of Kconfig options that don't
happen that often on randconfig builds with low
KCONFIG_PROBABILITY.

      Arnd

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