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Peter Anvin" , Jens Remus Cc: "Jason A. Donenfeld" , "Peter Zijlstra (Intel)" , Theodore Ts'o , Thomas =?ISO-8859-1?Q?Wei=DFschuh?= , Xin Li , Andrew Cooper , Andy Lutomirski , Ard Biesheuvel , Borislav Petkov , Brian Gerst , Dave Hansen , Ingo Molnar , James Morse , Jarkko Sakkinen , Josh Poimboeuf , Kees Cook , Nam Cao , Oleg Nesterov , Perry Yuan , Thomas Gleixner , Thomas Huth , Uros Bizjak , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-sgx@vger.kernel.org, x86@kernel.org, Indu Bhagat , Claudiu Zissulescu-Ianculescu , Heiko Carstens , Vasily Gorbik Date: Tue, 10 Feb 2026 12:56:39 +0800 In-Reply-To: References: <20260106211856.560186-6-hpa@zytor.com> <223707e2-3231-4037-bd1f-490ddf6aeeb6@linux.ibm.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.58.3 MIME-Version: 1.0 X-Rspamd-Queue-Id: 65CD64000C X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: 9wys97dw1pkx5h6pwbk8tocmtrg8mdx5 X-HE-Tag: 1770699418-69520 X-HE-Meta: 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 1SjjwxB/ NYuyW/AoJa+o4v/kySePr60wiICraCuh+odSoa2fZMu79EUCXYCWFbLJ8IF6H4QuBHJdZEJuLpFWHnj1o7La1TUz3DfBu90PnDjf/doDqDzcc7dkxv+1YTjiChEb4xw313sHhO7j5/1vd9d9a3IPEXOrqUS31pdAsk/WQc6MmJGljLlrVCWMPd7g96vX6VL6iHC//yEGLqdBBfSIvuPLXE7UFSOwBVHQJtrPqa/BBK7wVjRUul/05ilX35QZ5djeecv3Et1rN6D5O1t70Ztg8kwTuep1ZTCdG/y6Ym1RxLPJ2BtEjtcpExEcx/csYTYQ9UigWJdd70zuq/B0SHcsCTpp+QjiSJb0XQHsMh+A+lDPC4uZ6FpZp3y6DnYZ1Z3qBurj4hyurKTi6Y/mAeecZJc+Nff8MNOkOX/WMI2kG6R4+ZPhqaudeh13/Ultu0Zbz6RW7 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, 2026-02-09 at 20:51 -0800, H. Peter Anvin wrote: > On 2026-02-09 19:11, Xi Ruoyao wrote: > > On Mon, 2026-02-02 at 19:57 -0800, H. Peter Anvin wrote: > > > That hack dates back from before the signal frame extension. It is no > > > longer necessary. > >=20 > > Unfortunately at least it seems libgcc unwinder does not handle the > > signal frame extension properly.=C2=A0 The code reads: > >=20 > > =C2=A0 fde =3D _Unwind_Find_FDE (context->ra + _Unwind_IsSignalFrame (c= ontext) - 1,=20 > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0 &context->bases); > > =C2=A0 if (fde =3D=3D NULL) > > =C2=A0=C2=A0=C2=A0 {=C2=A0=C2=A0=C2=A0=20 > > #ifdef MD_FALLBACK_FRAME_STATE_FOR > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 /* Couldn't find frame unwind info for t= his function.=C2=A0 Try a > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 target-specific fallba= ck mechanism.=C2=A0 This will necessarily > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 not provide a personal= ity routine or LSDA.=C2=A0 */ > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 return MD_FALLBACK_FRAME_STATE_FOR (cont= ext, fs);=20 > > #else > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 return _URC_END_OF_STACK; > > #endif > > =C2=A0=C2=A0=C2=A0 }=C2=A0=C2=A0=C2=A0=20 > >=20 > > =C2=A0 fs->pc =3D context->bases.func; > >=20 > > =C2=A0 cie =3D get_cie (fde); > > =C2=A0 insn =3D extract_cie_info (cie, context, fs);=20 > >=20 > > Thus, it indeed attempts to avoid subtracting 1 for a signal frame, but > > ... _Unwind_IsSignalFrame (context) actually extracts a flag in context > > which will only be raised up by extract_cie_info. > >=20 > > Or am I missing something here? > >=20 >=20 > Well, it looks like this might be a non-manifest bug on x86 *IN THIS CASE= *, But only if after the patch _Unwind_Find_FDE returns NULL here (instead of a FDE of another function). I've not verified it on x86. If glibc tests (specifically misc/tst-sigcontext-get_pc) work fine things should be fine. /* snip */ > Could you file a gcc bug on this? Will do. --=20 Xi Ruoyao