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Message-ID:
<DS7PR12MB57650AE34ABCCB41BA6123A3CB762@DS7PR12MB5765.namprd12.prod.outlook.com>
Date: Sun, 21 Jan 2024 15:48:55 -0800
From: Fangrui Song <i@...kray.me>
To: musl@...ts.openwall.com, Tatsuyuki Ishi <ishitatsuyuki@...il.com>
Subject: Re: Draft riscv64 TLSDESC implementation
On Sun, Jan 21, 2024 at 2:28 PM Rich Felker <dalias@...c.org> wrote:
>
> On Tue, Aug 22, 2023 at 01:38:21PM -0400, Rich Felker wrote:
> > The psABI work is not finalized, but based on the current status of
> > https://github.com/riscv-non-isa/riscv-elf-psabi-doc/pull/373, I think
> > the attached is a valid (but untested) implementation of TLSDESC for
> > riscv64. Actually activating it requires also adding the relocation
> > type macro to riscv64/reloc.h.
> >
> > If any rv folks could look it over and make sure I haven't made any
> > stupid asm errors or missed any obvious optimizations, that would help
> > to quickly get this merged when the psABI is finalized.
> >
> > Rich
>
> > .text
> > .global __tlsdesc_static
> > .hidden __tlsdesc_static
> > .type __tlsdesc_static,%function
> > __tlsdesc_static:
> > ld a0,8(a0)
> > jr t0
> >
> > .global __tlsdesc_dynamic
> > .hidden __tlsdesc_dynamic
> > .type __tlsdesc_dynamic,%function
> > __tlsdesc_dynamic:
> > add sp,sp,-8
> > sd t1,(sp)
> > sd t2,8(sp)
> >
> > ld t2,-8(tp) # t2=dtv
> >
> > ld a0,8(a0) # a0=&{modidx,off}
> > ld t1,8(a0) # t1=off
> > ld a0,(a0) # a0=modidx
> > sll a0,a0,3 # a0=8*modidx
> >
> > add a0,a0,t2 # a0=dtv+8*modidx
> > ld a0,(a0) # a0=dtv[modidx]
> > add a0,a0,t1 # a0=dtv[modidx]+off
> > sub a0,a0,tp # a0=dtv[modidx]+off-tp
> >
> > ld t1,(sp)
> > ld t2,8(sp)
> > add sp,sp,8
> > jr t0
>
> Any feedback on this? Offhand, it looks like adjusting sp by 8 is
> wrong and that should be 16. Anything else? Does anyone have recent
> enough tooling to test this?
Tatsuyuki, do you have links to the latest version of
gcc/binutils/glibc patches?
Downloading patches from these mailing lists is probably a large
hurdle for many users, so having the relevant repositories online may
help.
mold has implemented RISC-V TLSDESC.
On the LLVM side, I have reviewed
https://github.com/llvm/llvm-project/pull/66915 and am waiting for it
to land, before I can check the lld status.
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