From: Richard Henderson <richard.henderson@linaro.org>
To: Peter Maydell <peter.maydell@linaro.org>
Cc: qemu-devel@nongnu.org, imp@bsdimp.com, Laurent@vivier.eu
Subject: Re: [PATCH v6 02/16] linux-user/host/ppc64: Use r11 for signal_pending address
Date: Mon, 29 Nov 2021 15:30:03 +0100 [thread overview]
Message-ID: <72a69c85-8a99-bf06-8baf-f6dbf8f49ada@linaro.org> (raw)
In-Reply-To: <CAFEAcA-x6Q_mXbFLzr=7ALGkqijj=gM5DRu_TRMAkFSm8XiZGQ@mail.gmail.com>
On 11/29/21 12:01 PM, Peter Maydell wrote:
> On Tue, 23 Nov 2021 at 17:40, Richard Henderson
> <richard.henderson@linaro.org> wrote:
>>
>> We don't need a register that can live across the syscall;
>> we only need a register that can live until the syscall.
>
> What about the case where:
> * we execute the sc instruction (r11 trashed)
> * the syscall is one that from the host kernel point of
> view is restartable
> * the kernel arranges to restart the syscall by rewinding the
> PC to point to the start of the 'sc' instruction
> * our rewind_if_in_safe_syscall() rewinds PC further to
> point at safe_syscall_start
> * we want to use r11 again, but it was trashed in step 1
> ?
>
> Put another way, this patch is effectively a revert of
> commit 5d9f3ea081721, which was a fix to an observed bug.
Whoops. I forgot about that (a mere 3 years ago).
r~
next prev parent reply other threads:[~2021-11-29 14:37 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-23 17:37 [PATCH for-7.0 v6 00/16] linux-user: simplify safe signal handling Richard Henderson
2021-11-23 17:37 ` [PATCH v6 01/16] linux-user: Untabify all safe-syscall.inc.S Richard Henderson
2021-11-25 10:17 ` Warner Losh
2021-11-23 17:37 ` [PATCH v6 02/16] linux-user/host/ppc64: Use r11 for signal_pending address Richard Henderson
2021-11-29 11:01 ` Peter Maydell
2021-11-29 14:30 ` Richard Henderson [this message]
2021-11-23 17:37 ` [PATCH v6 03/16] linux-user: Move syscall error detection into safe_syscall_base Richard Henderson
2021-11-25 10:25 ` Warner Losh
2021-11-23 17:37 ` [PATCH v6 04/16] linux-user/host/mips: Add safe-syscall.inc.S Richard Henderson
2021-11-25 10:22 ` Warner Losh
2021-11-29 16:40 ` Peter Maydell
2021-11-29 16:51 ` Richard Henderson
2021-11-23 17:37 ` [PATCH v6 05/16] linux-user/host/sparc64: " Richard Henderson
2021-11-23 17:37 ` [PATCH v6 06/16] linux-user: Remove HAVE_SAFE_SYSCALL and hostdep.h Richard Henderson
2021-11-23 17:37 ` [PATCH v6 07/16] linux-user: Rename TARGET_ERESTARTSYS to QEMU_ERESTARTSYS Richard Henderson
2021-11-23 17:37 ` [PATCH v6 08/16] bsd-user: " Richard Henderson
2021-11-23 17:37 ` [PATCH v6 09/16] linux-user: Rename TARGET_QEMU_ESIGRETURN to QEMU_ESIGRETURN Richard Henderson
2021-11-23 17:37 ` [PATCH v6 10/16] linux-user: Create special-errno.h Richard Henderson
2021-11-23 17:37 ` [PATCH v6 11/16] bsd-user: " Richard Henderson
2021-11-23 17:37 ` [PATCH v6 12/16] common-user: Move safe-syscall.* from linux-user Richard Henderson
2021-11-23 17:37 ` [PATCH v6 13/16] common-user: Adjust system call return on FreeBSD Richard Henderson
2021-11-23 17:37 ` [PATCH v6 14/16] linux-user: Move thunk.c from top-level Richard Henderson
2021-11-23 17:37 ` [PATCH v6 15/16] meson: Move linux_user_ss to linux-user/ Richard Henderson
2021-11-23 17:37 ` [PATCH v6 16/16] meson: Move bsd_user_ss to bsd-user/ Richard Henderson
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