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Tue, 28 Sep 2021 18:36:41 -0700 (PDT) X-Google-Smtp-Source: ABdhPJwLnW/cM1Suo+FWTs6RJKI1CQo3+FE+UoEL65KNdGKxlIxeo2lntNMs+HgoTajpWesWkIg/PQ== X-Received: by 2002:ac8:4a10:: with SMTP id x16mr9383313qtq.97.1632879401228; Tue, 28 Sep 2021 18:36:41 -0700 (PDT) Received: from treble ([2600:1700:6e32:6c00::15]) by smtp.gmail.com with ESMTPSA id p19sm622628qkk.83.2021.09.28.18.36.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Sep 2021 18:36:40 -0700 (PDT) Date: Tue, 28 Sep 2021 18:36:37 -0700 From: Josh Poimboeuf To: Mark Rutland Cc: Dmitry Vyukov , syzbot , Linux ARM , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, viro@zeniv.linux.org.uk, will@kernel.org, x86@kernel.org Subject: Re: [syzbot] upstream test error: KASAN: invalid-access Read in __entry_tramp_text_end Message-ID: <20210929013637.bcarm56e4mqo3ndt@treble> References: <000000000000a3cf8605cb2a1ec0@google.com> <20210921165134.GE35846@C02TD0UTHF1T.local> <20210927170122.GA9201@C02TD0UTHF1T.local> <20210927171812.GB9201@C02TD0UTHF1T.local> <20210928103543.GF1924@C02TD0UTHF1T.local> MIME-Version: 1.0 In-Reply-To: <20210928103543.GF1924@C02TD0UTHF1T.local> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=jpoimboe@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210928_183646_213929_20531C3F X-CRM114-Status: GOOD ( 18.08 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Sep 28, 2021 at 11:35:43AM +0100, Mark Rutland wrote: > > In the other x86 thread Josh Poimboeuf suggested to use asm goto to a > > cold part of the function instead of .fixup: > > https://lore.kernel.org/lkml/20210927234543.6waods7rraxseind@treble/ > > This sounds like a more reliable solution that will cause less > > maintenance burden. Would it work for arm64 as well? > > Maybe we can use that when CC_HAS_ASM_GOTO_OUTPUT is avaiable, but in > general we can't rely on asm goto supporting output arguments (and IIRC > GCC doesn't support that at all), so we'd still have to support the > current fixup scheme. Even without CC_HAS_ASM_GOTO_OUTPUT it should still be possible to hack something together if you split the original insn asm and the extable asm into separate statements, like: diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h index 6b52182e178a..8f62469f2027 100644 --- a/arch/x86/include/asm/msr.h +++ b/arch/x86/include/asm/msr.h @@ -137,20 +139,21 @@ static inline unsigned long long native_read_msr_safe(unsigned int msr, { DECLARE_ARGS(val, low, high); - asm volatile("2: rdmsr ; xor %[err],%[err]\n" - "1:\n\t" - ".section .fixup,\"ax\"\n\t" - "3: mov %[fault],%[err]\n\t" - "xorl %%eax, %%eax\n\t" - "xorl %%edx, %%edx\n\t" - "jmp 1b\n\t" - ".previous\n\t" - _ASM_EXTABLE(2b, 3b) - : [err] "=r" (*err), EAX_EDX_RET(val, low, high) - : "c" (msr), [fault] "i" (-EIO)); + *err = 0; + asm volatile("417: rdmsr\n" + : EAX_EDX_RET(val, low, high) + : "c" (msr)); + asm_volatile_goto(_ASM_EXTABLE(417b, %l[Efault]) :::: Efault); + +done: if (tracepoint_enabled(read_msr)) do_trace_read_msr(msr, EAX_EDX_VAL(val, low, high), *err); return EAX_EDX_VAL(val, low, high); + +Efault: + *err = -EIO; + ZERO_ARGS(val, low, high); + goto done; } /* Can be uninlined because referenced by paravirt */ _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel