From: Richard Henderson <richard.henderson@linaro.org>
To: Ilya Leoshkevich <iii@linux.ibm.com>,
David Hildenbrand <david@redhat.com>
Cc: Thomas Huth <thuth@redhat.com>,
qemu-s390x@nongnu.org, qemu-devel@nongnu.org,
Michael Tokarev <mjt@tls.msk.ru>
Subject: Re: [PATCH 2/4] tests/tcg/s390x: Test CLC with inaccessible second operand
Date: Tue, 31 Oct 2023 15:53:59 -0700 [thread overview]
Message-ID: <9963393c-f641-402a-94a1-86e6ef740adf@linaro.org> (raw)
In-Reply-To: <20231031053718.347100-3-iii@linux.ibm.com>
On 10/30/23 22:32, Ilya Leoshkevich wrote:
> +int main(void)
> +{
> + register unsigned long r0 asm("r0");
> + unsigned long mem = 42, rhs = 500;
> + struct sigaction act;
> + int err;
> +
> + memset(&act, 0, sizeof(act));
> + act.sa_sigaction = handle_sigsegv;
> + act.sa_flags = SA_SIGINFO;
> + err = sigaction(SIGSEGV, &act, NULL);
> + assert(err == 0);
> +
> + r0 = 100;
> + asm("algr %[r0],%[rhs]\n"
> + "clc 0(8,%[mem]),0(0)\n" /* The 2nd operand will cause a SEGV. */
> + : [r0] "+r" (r0)
> + : [mem] "r" (&mem)
> + , [rhs] "r" (rhs)
> + : "cc", "memory");
> +
You could just as easily set cc based on CHI or something to avoid hard-coding r0, or even
clobbering an output register at all.
But I guess there's little point bike shedding this too much...
r~
next prev parent reply other threads:[~2023-10-31 22:54 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-31 5:32 [PATCH 0/4] target/s390x: CC fixes Ilya Leoshkevich
2023-10-31 5:32 ` [PATCH 1/4] target/s390x: Fix CLC corrupting cc_src Ilya Leoshkevich
2023-10-31 22:49 ` Richard Henderson
2023-10-31 5:32 ` [PATCH 2/4] tests/tcg/s390x: Test CLC with inaccessible second operand Ilya Leoshkevich
2023-10-31 22:53 ` Richard Henderson [this message]
2023-11-06 9:20 ` Ilya Leoshkevich
2023-10-31 5:32 ` [PATCH 3/4] target/s390x: Fix LAALG not updating cc_src Ilya Leoshkevich
2023-10-31 22:57 ` Richard Henderson
2023-10-31 5:32 ` [PATCH 4/4] tests/tcg/s390x: Test LAALG with negative cc_src Ilya Leoshkevich
2023-10-31 8:38 ` [PATCH 0/4] target/s390x: CC fixes David Hildenbrand
2023-11-03 16:44 ` Ilya Leoshkevich
2023-11-03 17:02 ` David Hildenbrand
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