From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on inbox.vuxu.org X-Spam-Level: X-Spam-Status: No, score=-3.1 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED,RCVD_IN_MSPIKE_H3, RCVD_IN_MSPIKE_WL,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.4 Received: from second.openwall.net (second.openwall.net [193.110.157.125]) by inbox.vuxu.org (Postfix) with SMTP id 28C54213ED for ; Tue, 23 Jan 2024 14:26:30 +0100 (CET) Received: (qmail 30611 invoked by uid 550); 23 Jan 2024 13:24:22 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Reply-To: musl@lists.openwall.com Received: (qmail 30560 invoked from network); 23 Jan 2024 13:24:22 -0000 Date: Tue, 23 Jan 2024 08:26:32 -0500 From: Rich Felker To: Fangrui Song Cc: musl@lists.openwall.com, Tatsuyuki Ishi Message-ID: <20240123132631.GF4163@brightrain.aerifal.cx> References: <20230822173821.GW4163@brightrain.aerifal.cx> <20240121222831.GC4163@brightrain.aerifal.cx> <20240122000348.GD4163@brightrain.aerifal.cx> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Subject: Re: [musl] Draft riscv64 TLSDESC implementation On Tue, Jan 23, 2024 at 12:52:01AM -0800, Fangrui Song wrote: > On Sun, Jan 21, 2024 at 7:41 PM Tatsuyuki Ishi wrote: > > > > > On Jan 22, 2024, at 9:03, Rich Felker wrote: > > > > > > On Sun, Jan 21, 2024 at 03:48:55PM -0800, Fangrui Song wrote: > > >> On Sun, Jan 21, 2024 at 2:28 PM Rich Felker 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. > > > > > > To test this, drop it in src/ldso/riscv64/tlsdesc.s, and add to > > > arch/riscv64/reloc.h: > > > > > > #define REL_TLSDESC R_RISCV_TLSDESC > > > > > > or whatever the reloc name is (I don't think it's in elf.h yet so you > > > probably need to either add it there too or just hard-code the number > > > for testing). > > > > > > Updated version with the sp bugfix attached. > > > > The assembly looks fine to me. (It’s nice that musl don’t need to bother with save/restore at all since DTVs are initialized eagerly..) > > For the patches mentioned in the other thread, most tests were done with glibc’s portable testsuite (tst-elf-*). > > If musl has a similar one, you should be able to run it with my GCC / binutils fork (with either --with_tls=desc at configure time or -mtls-dialect=desc at compile time). > > > > Tatsuyuki. > > > > > Rich > > > > > > > I have verified that the patch works using a runtime test under qemu-user. > I use Paul Kirth's pending LLVM codegen/assembly patch and my pending > lld patch:) Thanks for running tests! > Compile b.c to bb.s. Replace general dynamic code sequences (e.g. > `la.tls.gd a0,tls0; call __tls_get_addr@plt`) with TLSDESC, e.g. > ``` > ..Ltlsdesc_hi0: > auipc a0, %tlsdesc_hi(tls0) > ld a1, %tlsdesc_load_lo(.Ltlsdesc_hi0)(a0) > addi a0, a0, %tlsdesc_add_lo(.Ltlsdesc_hi0) > jalr t0, 0(a1), %tlsdesc_call(.Ltlsdesc_hi0) > add a0, a0, tp > ``` Is this due to compiler not supporting generation of TLSDESC sequence yet? If so, unlike a full test with compiler support, it does not test for the TLSDESC machinery honoring all the non-clobbering requirements of the ABI. But I think we can check by hand that that part of the ABI is honored. Rich