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Lu" Date: Sat, 16 Mar 2024 07:37:48 -0700 Message-ID: Subject: Re: [PATCH] x86-64: Stack alignment in _dl_tlsdesc_dynamic and red zone usage (bug 31501) To: Florian Weimer Cc: libc-alpha@sourceware.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Spam-Status: No, score=-3020.4 required=5.0 tests=BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_FROM,GIT_PATCH_0,RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS,TXREP,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: On Sat, Mar 16, 2024 at 7:33=E2=80=AFAM Florian Weimer = wrote: > > In sysdeps/x86_64/dl-tlsdesc-dynamic.h, the stack pointer is > realigned for some variants (notably _dl_tlsdesc_dynamic_xsavec). > This realignment does not take into account that the function has > already used part of the red zone at this point, thus clobbering > the initally saved register values located there if the stack > alignment inherited from the caller is unfortunate. > > (Note: I do not know to write a good test case for this in the existing > framework. We saw this as a random LTO plugin crash when building GCC > with -mtls-dialect=3Dgnu2. The existing tests on pass on x86_64-linux-gn= u > with this change here.) Will a different STATE_SAVE_OFFSET for TLS descriptor work? > --- > sysdeps/x86_64/dl-tlsdesc-dynamic.h | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/sysdeps/x86_64/dl-tlsdesc-dynamic.h b/sysdeps/x86_64/dl-tlsd= esc-dynamic.h > index 9f02cfc3eb..8e49e7eece 100644 > --- a/sysdeps/x86_64/dl-tlsdesc-dynamic.h > +++ b/sysdeps/x86_64/dl-tlsdesc-dynamic.h > @@ -83,6 +83,8 @@ _dl_tlsdesc_dynamic: > 2: > #if DL_RUNTIME_RESOLVE_REALIGN_STACK > movq %rbx, -24(%rsp) > + subq $24, %rsp > + cfi_adjust_cfa_offset(24) > mov %RSP_LP, %RBX_LP > cfi_def_cfa_register(%rbx) > and $-STATE_SAVE_ALIGNMENT, %RSP_LP > @@ -153,6 +155,8 @@ _dl_tlsdesc_dynamic: > #if DL_RUNTIME_RESOLVE_REALIGN_STACK > mov %RBX_LP, %RSP_LP > cfi_def_cfa_register(%rsp) > + addq $24, %rsp > + cfi_adjust_cfa_offset(-24) > movq -24(%rsp), %rbx > cfi_restore(%rbx) > #else > > base-commit: 5ebc24f785dc0dff494a93ca82a369497c3cdc68 > --=20 H.J.