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([2601:646:c200:1ef2:d574:d341:616c:1b33]) by smtp.gmail.com with ESMTPSA id m11sm2675028pjz.44.2021.02.03.11.29.40 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 03 Feb 2021 11:29:40 -0800 (PST) Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable From: Andy Lutomirski Mime-Version: 1.0 (1.0) Subject: Re: [PATCH 07/11] x86/fault: Split the OOPS code out from no_context() Date: Wed, 3 Feb 2021 11:29:39 -0800 Message-Id: <78B808CF-16E2-4C41-B680-0AFD1428ED4A@amacapital.net> References: <20210203185517.GH13819@zn.tnic> Cc: Andy Lutomirski , x86@kernel.org, LKML , Dave Hansen , Alexei Starovoitov , Daniel Borkmann , Yonghong Song , Masami Hiramatsu , Peter Zijlstra In-Reply-To: <20210203185517.GH13819@zn.tnic> To: Borislav Petkov X-Mailer: iPhone Mail (18C66) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Feb 3, 2021, at 10:56 AM, Borislav Petkov wrote: >=20 > =EF=BB=BFOn Sun, Jan 31, 2021 at 09:24:38AM -0800, Andy Lutomirski wrote: >> Not all callers of no_context() want to run exception fixups. >> Separate the OOPS code out from the fixup code in no_context(). >>=20 >> Cc: Dave Hansen >> Cc: Peter Zijlstra >> Signed-off-by: Andy Lutomirski >> --- >> arch/x86/mm/fault.c | 116 +++++++++++++++++++++++--------------------- >> 1 file changed, 62 insertions(+), 54 deletions(-) >>=20 >> diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c >> index 1939e546beae..6f43d080e1e8 100644 >> --- a/arch/x86/mm/fault.c >> +++ b/arch/x86/mm/fault.c >> @@ -618,53 +618,20 @@ static void set_signal_archinfo(unsigned long addre= ss, >> } >>=20 >> static noinline void >> -no_context(struct pt_regs *regs, unsigned long error_code, >> - unsigned long address, int signal, int si_code) >> +page_fault_oops(struct pt_regs *regs, unsigned long error_code, >=20 > Not sure about this name - it still tries to recover: > efi_recover_from_page_fault(). >=20 That function is a lie. It tries to keep the system alive but it doesn=E2=80= =99t return if it =E2=80=9Crecovers=E2=80=9D. Maybe I should add a comment= ? > Judging by where it is called, maybe no_context_tail() or > no_context_oops() or no_context_finish_me_already()... >=20 > Yah, I haz no better idea. :-\ >=20 > ... >=20 >> @@ -739,6 +692,61 @@ no_context(struct pt_regs *regs, unsigned long error= _code, >> oops_end(flags, regs, sig); >> } >>=20 >> +static noinline void >> +no_context(struct pt_regs *regs, unsigned long error_code, >> + unsigned long address, int signal, int si_code) >> +{ >> + if (user_mode(regs)) { >> + /* >> + * This is an implicit supervisor-mode access from user >> + * mode. Bypass all the kernel-mode recovery code and just >> + * OOPS. >> + */ >> + goto oops; >=20 > Just do >=20 > return page_fault_oops(...); >=20 > here and get rid of the label. >=20 > --=20 > Regards/Gruss, > Boris. >=20 > https://people.kernel.org/tglx/notes-about-netiquette