From: Nick Desaulniers <ndesaulniers@google.com> To: Ard Biesheuvel <ardb@kernel.org> Cc: Russell King <linux@armlinux.org.uk>, Arnd Bergmann <arnd@arndb.de>, Nathan Chancellor <natechancellor@gmail.com>, Linux ARM <linux-arm-kernel@lists.infradead.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, clang-built-linux <clang-built-linux@googlegroups.com> Subject: Re: [PATCH v2] ARM: kprobes: rewrite test-[arm|thumb].c in UAL Date: Thu, 28 Jan 2021 16:21:55 -0800 [thread overview] Message-ID: <CAKwvOdneTwx8LwKyAA+iMELEBWBxu2nkr9dVuQ=+hgsZROu-tw@mail.gmail.com> (raw) In-Reply-To: <CAMj1kXE5uw4+zV3JVpfA2drOD5TZVMs5a_E5wrrnzjEYc=E_fA@mail.gmail.com> > On Thu, 28 Jan 2021 at 20:34, Nick Desaulniers <ndesaulniers@google.com> wrote: > > + TEST_RX("tbh [pc, r",7, (9f-(1f+4))>>1,", lsl #1]", > > > On Thu, Jan 28, 2021 at 1:03 PM Ard Biesheuvel <ardb@kernel.org> wrote: > Why is this change needed? Are the resulting opcodes equivalent? Does > GAS infer the lsl #1 but Clang doesn't? Yes; it seems if you serialize/deserialize this using GNU `as` and objdump, that's the canonical form (GNU objdump seems to print in UAL form, IIUC). I didn't see anything specifically about `tbh` in https://developer.arm.com/documentation/dui0473/c/writing-arm-assembly-language/assembly-language-changes-after-rvctv2-1?lang=en but it's what GNU objdump produces and what clang's integrated assembler accepts. > > > > #define _DATA_PROCESSING32_DNM(op,s,val) \ > > - TEST_RR(op s".w r0, r",1, VAL1,", r",2, val, "") \ > > + TEST_RR(op s" r0, r",1, VAL1,", r",2, val, "") \ > > What is wrong with these .w suffixes? Shouldn't the assembler accept > these even on instructions that only exist in a wide encoding? Yeah, I'm not sure these have anything to do with UAL. Looking at LLVM's sources and IIRC, LLVM has "InstAlias"es it uses for .w suffixes. I think I need to fix those in LLVM for a couple instructions, rather than modify these in kernel sources. I'll split off the arm-test.c and thumb-test.c into separate patches, fix LLVM, and drop the .w suffix changes to thumb-test.c. -- Thanks, ~Nick Desaulniers
WARNING: multiple messages have this Message-ID (diff)
From: Nick Desaulniers <ndesaulniers@google.com> To: Ard Biesheuvel <ardb@kernel.org> Cc: Arnd Bergmann <arnd@arndb.de>, Russell King <linux@armlinux.org.uk>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, clang-built-linux <clang-built-linux@googlegroups.com>, Nathan Chancellor <natechancellor@gmail.com>, Linux ARM <linux-arm-kernel@lists.infradead.org> Subject: Re: [PATCH v2] ARM: kprobes: rewrite test-[arm|thumb].c in UAL Date: Thu, 28 Jan 2021 16:21:55 -0800 [thread overview] Message-ID: <CAKwvOdneTwx8LwKyAA+iMELEBWBxu2nkr9dVuQ=+hgsZROu-tw@mail.gmail.com> (raw) In-Reply-To: <CAMj1kXE5uw4+zV3JVpfA2drOD5TZVMs5a_E5wrrnzjEYc=E_fA@mail.gmail.com> > On Thu, 28 Jan 2021 at 20:34, Nick Desaulniers <ndesaulniers@google.com> wrote: > > + TEST_RX("tbh [pc, r",7, (9f-(1f+4))>>1,", lsl #1]", > > > On Thu, Jan 28, 2021 at 1:03 PM Ard Biesheuvel <ardb@kernel.org> wrote: > Why is this change needed? Are the resulting opcodes equivalent? Does > GAS infer the lsl #1 but Clang doesn't? Yes; it seems if you serialize/deserialize this using GNU `as` and objdump, that's the canonical form (GNU objdump seems to print in UAL form, IIUC). I didn't see anything specifically about `tbh` in https://developer.arm.com/documentation/dui0473/c/writing-arm-assembly-language/assembly-language-changes-after-rvctv2-1?lang=en but it's what GNU objdump produces and what clang's integrated assembler accepts. > > > > #define _DATA_PROCESSING32_DNM(op,s,val) \ > > - TEST_RR(op s".w r0, r",1, VAL1,", r",2, val, "") \ > > + TEST_RR(op s" r0, r",1, VAL1,", r",2, val, "") \ > > What is wrong with these .w suffixes? Shouldn't the assembler accept > these even on instructions that only exist in a wide encoding? Yeah, I'm not sure these have anything to do with UAL. Looking at LLVM's sources and IIRC, LLVM has "InstAlias"es it uses for .w suffixes. I think I need to fix those in LLVM for a couple instructions, rather than modify these in kernel sources. I'll split off the arm-test.c and thumb-test.c into separate patches, fix LLVM, and drop the .w suffix changes to thumb-test.c. -- Thanks, ~Nick Desaulniers _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2021-01-29 0:23 UTC|newest] Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-01-28 4:43 [PATCH] ARM: kprobes: rewrite in UAL Nick Desaulniers 2021-01-28 4:43 ` Nick Desaulniers 2021-01-28 16:15 ` Arnd Bergmann 2021-01-28 16:15 ` Arnd Bergmann 2021-01-28 18:59 ` Nick Desaulniers 2021-01-28 21:23 ` Arnd Bergmann 2021-01-28 21:23 ` Arnd Bergmann 2021-01-28 19:34 ` [PATCH v2] ARM: kprobes: rewrite test-[arm|thumb].c " Nick Desaulniers 2021-01-28 21:03 ` Ard Biesheuvel 2021-01-28 21:03 ` Ard Biesheuvel 2021-01-28 22:28 ` Arnd Bergmann 2021-01-28 22:28 ` Arnd Bergmann 2021-01-28 23:30 ` Ard Biesheuvel 2021-01-28 23:30 ` Ard Biesheuvel 2021-02-13 11:01 ` Ard Biesheuvel 2021-02-13 11:01 ` Ard Biesheuvel 2021-01-29 0:21 ` Nick Desaulniers [this message] 2021-01-29 0:21 ` Nick Desaulniers 2021-01-29 9:40 ` Ard Biesheuvel 2021-01-29 18:54 ` [PATCH v3] ARM: kprobes: rewrite test-arm.c " Nick Desaulniers 2021-01-29 18:54 ` Nick Desaulniers 2021-03-29 22:08 ` [PATCH v2] ARM: kprobes: rewrite test-[arm|thumb].c " Nick Desaulniers 2021-03-29 22:08 ` Nick Desaulniers
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