Re: [PATCH v2] ARM: kprobes: test-thumb: fix for LLVM_IAS=1

From: Jian Cai <jiancai@google.com>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: Russell King <linux@armlinux.org.uk>,
	Ard Biesheuvel <ardb@kernel.org>, Arnd Bergmann <arnd@kernel.org>,
	David Spickett <david.spickett@linaro.org>,
	Stephen Hines <srhines@google.com>,
	Nathan Chancellor <nathan@kernel.org>,
	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: test-thumb: fix for LLVM_IAS=1
Date: Mon, 17 May 2021 17:02:37 -0700	[thread overview]
Message-ID: <CA+SOCLJJWU0NGbxe139qXYsE5FY44PJnkbWDG0TAGh=Movt2Rw@mail.gmail.com> (raw)
In-Reply-To: <20210329221209.1718079-1-ndesaulniers@google.com>

Thanks for the patch. It looks good to me, and I double checked  ARM
architecture reference manual for V7 and can confirm the missing
operand in these instructions is not specified as optional.

Reviewed-by: Jian Cai <jiancai@google.com>

On Mon, Mar 29, 2021 at 3:12 PM Nick Desaulniers
<ndesaulniers@google.com> wrote:
>
> There's a few instructions that GAS infers operands but Clang doesn't;
> from what I can tell the Arm ARM doesn't say these are optional.
>
> F5.1.257 TBB, TBH T1 Halfword variant
> F5.1.238 STREXD T1 variant
> F5.1.84 LDREXD T1 variant
>
> Link: https://github.com/ClangBuiltLinux/linux/issues/1309
> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
> ---
> See:
> https://lore.kernel.org/linux-arm-kernel/CAMj1kXE5uw4+zV3JVpfA2drOD5TZVMs5a_E5wrrnzjEYc=E_fA@mail.gmail.com/
> for what I'd consider V1. The previous issues with .w suffixes have been
> fixed or have fixes pending in LLVM:
> * BL+DBG:   https://reviews.llvm.org/D97236
> * ORN/ORNS: https://reviews.llvm.org/D99538
> * RSB/RSBS: https://reviews.llvm.org/D99542
> I'd have expected the Arm ARM to use curly braces to denote optional
> operands (see also "F5.1.167 RSB, RSBS (register)" for an example).
>
>  arch/arm/probes/kprobes/test-thumb.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/arch/arm/probes/kprobes/test-thumb.c b/arch/arm/probes/kprobes/test-thumb.c
> index 456c181a7bfe..4e11f0b760f8 100644
> --- a/arch/arm/probes/kprobes/test-thumb.c
> +++ b/arch/arm/probes/kprobes/test-thumb.c
> @@ -441,21 +441,21 @@ void kprobe_thumb32_test_cases(void)
>                 "3:     mvn     r0, r0  \n\t"
>                 "2:     nop             \n\t")
>
> -       TEST_RX("tbh    [pc, r",7, (9f-(1f+4))>>1,"]",
> +       TEST_RX("tbh    [pc, r",7, (9f-(1f+4))>>1,", lsl #1]",
>                 "9:                     \n\t"
>                 ".short (2f-1b-4)>>1    \n\t"
>                 ".short (3f-1b-4)>>1    \n\t"
>                 "3:     mvn     r0, r0  \n\t"
>                 "2:     nop             \n\t")
>
> -       TEST_RX("tbh    [pc, r",12, ((9f-(1f+4))>>1)+1,"]",
> +       TEST_RX("tbh    [pc, r",12, ((9f-(1f+4))>>1)+1,", lsl #1]",
>                 "9:                     \n\t"
>                 ".short (2f-1b-4)>>1    \n\t"
>                 ".short (3f-1b-4)>>1    \n\t"
>                 "3:     mvn     r0, r0  \n\t"
>                 "2:     nop             \n\t")
>
> -       TEST_RRX("tbh   [r",1,9f, ", r",14,1,"]",
> +       TEST_RRX("tbh   [r",1,9f, ", r",14,1,", lsl #1]",
>                 "9:                     \n\t"
>                 ".short (2f-1b-4)>>1    \n\t"
>                 ".short (3f-1b-4)>>1    \n\t"
> @@ -468,10 +468,10 @@ void kprobe_thumb32_test_cases(void)
>
>         TEST_UNSUPPORTED("strexb        r0, r1, [r2]")
>         TEST_UNSUPPORTED("strexh        r0, r1, [r2]")
> -       TEST_UNSUPPORTED("strexd        r0, r1, [r2]")
> +       TEST_UNSUPPORTED("strexd        r0, r1, r2, [r2]")
>         TEST_UNSUPPORTED("ldrexb        r0, [r1]")
>         TEST_UNSUPPORTED("ldrexh        r0, [r1]")
> -       TEST_UNSUPPORTED("ldrexd        r0, [r1]")
> +       TEST_UNSUPPORTED("ldrexd        r0, r1, [r1]")
>
>         TEST_GROUP("Data-processing (shifted register) and (modified immediate)")
>
> --
> 2.31.0.291.g576ba9dcdaf-goog
>