Messages in this thread | | | From | Atish Patra <> | Date | Thu, 17 Dec 2020 00:33:28 -0800 | Subject | Re: [PATCH v3 3/5] RISC-V: Align the .init.text section |
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On Wed, Dec 16, 2020 at 10:51 PM Palmer Dabbelt <palmer@dabbelt.com> wrote: > > On Tue, 15 Dec 2020 22:02:54 PST (-0800), Palmer Dabbelt wrote: > > On Wed, 04 Nov 2020 16:04:37 PST (-0800), Atish Patra wrote: > >> In order to improve kernel text protection, we need separate .init.text/ > >> .init.data/.text in separate sections. However, RISC-V linker relaxation > >> code is not aware of any alignment between sections. As a result, it may > >> relax any RISCV_CALL relocations between sections to JAL without realizing > >> that an inter section alignment may move the address farther. That may > >> lead to a relocation truncated fit error. However, linker relaxation code > >> is aware of the individual section alignments. > >> > >> The detailed discussion on this issue can be found here. > >> https://github.com/riscv/riscv-gnu-toolchain/issues/738 > >> > >> Keep the .init.text section aligned so that linker relaxation will take > >> that as a hint while relaxing inter section calls. > >> Here are the code size changes for each section because of this change. > >> > >> section change in size (in bytes) > >> .head.text +4 > >> .text +40 > >> .init.text +6530 > >> .exit.text +84 > >> > >> The only significant increase in size happened for .init.text because > >> all intra relocations also use 2MB alignment. > >> > >> Suggested-by: Jim Wilson <jimw@sifive.com> > >> Signed-off-by: Atish Patra <atish.patra@wdc.com> > >> --- > >> arch/riscv/kernel/vmlinux.lds.S | 8 +++++++- > >> 1 file changed, 7 insertions(+), 1 deletion(-) > >> > >> diff --git a/arch/riscv/kernel/vmlinux.lds.S b/arch/riscv/kernel/vmlinux.lds.S > >> index 3ffbd6cbdb86..cacd7898ba7f 100644 > >> --- a/arch/riscv/kernel/vmlinux.lds.S > >> +++ b/arch/riscv/kernel/vmlinux.lds.S > >> @@ -30,7 +30,13 @@ SECTIONS > >> . = ALIGN(PAGE_SIZE); > >> > >> __init_begin = .; > >> - INIT_TEXT_SECTION(PAGE_SIZE) > >> + __init_text_begin = .; > >> + .init.text : AT(ADDR(.init.text) - LOAD_OFFSET) ALIGN(SECTION_ALIGN) { \ > >> + _sinittext = .; \ > >> + INIT_TEXT \ > >> + _einittext = .; \ > >> + } > >> + > >> . = ALIGN(8); > >> __soc_early_init_table : { > >> __soc_early_init_table_start = .; > > > > Not sure what's going on here (or why I wasn't catching it earlier), but this > > is breaking boot on one of my test configs. I'm not getting any Linux boot > > spew, so it's something fairly early. I'm running defconfig with > > > > CONFIG_PREEMPT=y > > CONFIG_DEBUG_PREEMPT=y > > CONFIG_PROVE_LOCKING=y > > > > It looks like that's been throwing a bunch of warnings for a while, but it did > > at least used to boot. No idea what PREEMPT would have to do with this, and > > the other two don't generally trigger issues that early in boot (or at least, > > trigger halts that early in boot). > > > > There's a bunch of other stuff that depends on this that's on for-next so I > > don't want to just drop it, but I also don't want to break something. I'm just > > running QEMU's virt board. > >
I just verified for-next on QEMU 5.2.0 for virt (RV32,64, nommu) and sifive_u as well. I will give it a try on unleashed tomorrow as well with the above configs enabled.
> > I'll take a look again tomorrow night, but if anyone has some time to look > > that'd be great! > > Looks like this breaks on QEMU 5.0.0 but works on 5.2.0.
I will take a look tomorrow to check the root cause.
I guess technically > that means could be considered a regression, but as we don't really have any > scheme for which old versions of QEMU we support it's not absolute. I'd > usually err on the side of keeping support for older platforms, but in this > case it's probably just not worth the time so I'm going to just ignore it. > > _______________________________________________ > linux-riscv mailing list > linux-riscv@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-riscv
-- Regards, Atish
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