From: Segher Boessenkool <segher@kernel.crashing.org>
To: Nicholas Piggin <npiggin@gmail.com>
Cc: linux-kernel@vger.kernel.org, Paul Mackerras <paulus@samba.org>,
msuchanek@suse.de, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v5 20/22] powerpc/syscall: Avoid storing 'current' in another pointer
Date: Tue, 9 Feb 2021 07:50:53 -0600 [thread overview]
Message-ID: <20210209135053.GD27854@gate.crashing.org> (raw)
In-Reply-To: <1612838134.rvncv9kzls.astroid@bobo.none>
On Tue, Feb 09, 2021 at 12:36:20PM +1000, Nicholas Piggin wrote:
> What if you did this?
> +static inline struct task_struct *get_current(void)
> +{
> + register struct task_struct *task asm ("r2");
> +
> + return task;
> +}
Local register asm variables are *only* guaranteed to live in that
register as operands to an asm. See
https://gcc.gnu.org/onlinedocs/gcc/Local-Register-Variables.html#Local-Register-Variables
("The only supported use" etc.)
You can do something like
static inline struct task_struct *get_current(void)
{
register struct task_struct *task asm ("r2");
asm("" : "+r"(task));
return task;
}
which makes sure that "task" actually is in r2 at the point of that asm.
Segher
next prev parent reply other threads:[~2021-02-09 14:01 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-08 15:10 [PATCH v5 00/22] powerpc/32: Implement C syscall entry/exit Christophe Leroy
2021-02-08 15:10 ` [PATCH v5 01/22] powerpc/32s: Add missing call to kuep_lock on syscall entry Christophe Leroy
2021-02-08 15:10 ` [PATCH v5 02/22] powerpc/32: Always enable data translation " Christophe Leroy
2021-02-08 15:10 ` [PATCH v5 03/22] powerpc/32: On syscall entry, enable instruction translation at the same time as data Christophe Leroy
2021-02-08 15:10 ` [PATCH v5 04/22] powerpc/32: Reorder instructions to avoid using CTR in syscall entry Christophe Leroy
2021-02-08 15:10 ` [PATCH v5 05/22] powerpc/irq: Add helper to set regs->softe Christophe Leroy
2021-02-09 1:11 ` Nicholas Piggin
2021-02-09 5:57 ` Christophe Leroy
2021-02-09 7:47 ` Nicholas Piggin
2021-02-09 6:18 ` Christophe Leroy
2021-02-09 7:49 ` Nicholas Piggin
2021-03-05 8:54 ` Christophe Leroy
2021-03-08 8:47 ` Nicholas Piggin
2021-02-08 15:10 ` [PATCH v5 06/22] powerpc/irq: Rework helpers that manipulate MSR[EE/RI] Christophe Leroy
2021-02-09 1:14 ` Nicholas Piggin
2021-02-08 15:10 ` [PATCH v5 07/22] powerpc/irq: Add stub irq_soft_mask_return() for PPC32 Christophe Leroy
2021-02-09 1:19 ` Nicholas Piggin
2021-02-08 15:10 ` [PATCH v5 08/22] powerpc/syscall: Rename syscall_64.c into interrupt.c Christophe Leroy
2021-02-09 1:19 ` Nicholas Piggin
2021-02-08 15:10 ` [PATCH v5 09/22] powerpc/syscall: Make interrupt.c buildable on PPC32 Christophe Leroy
2021-02-09 1:27 ` Nicholas Piggin
2021-02-09 6:02 ` Christophe Leroy
2021-02-09 7:50 ` Nicholas Piggin
2021-02-08 15:10 ` [PATCH v5 10/22] powerpc/syscall: Use is_compat_task() Christophe Leroy
2021-02-09 1:29 ` Nicholas Piggin
2021-02-08 15:10 ` [PATCH v5 11/22] powerpc/syscall: Save r3 in regs->orig_r3 Christophe Leroy
2021-02-09 1:29 ` Nicholas Piggin
2021-02-08 15:10 ` [PATCH v5 12/22] powerpc/syscall: Change condition to check MSR_RI Christophe Leroy
2021-02-09 1:36 ` Nicholas Piggin
2021-02-08 15:10 ` [PATCH v5 13/22] powerpc/32: Always save non volatile GPRs at syscall entry Christophe Leroy
2021-02-08 15:10 ` [PATCH v5 14/22] powerpc/syscall: implement system call entry/exit logic in C for PPC32 Christophe Leroy
2021-02-08 15:10 ` [PATCH v5 15/22] powerpc/32: Remove verification of MSR_PR on syscall in the ASM entry Christophe Leroy
2021-02-08 15:10 ` [PATCH v5 16/22] powerpc/syscall: Avoid stack frame in likely part of system_call_exception() Christophe Leroy
2021-02-09 1:55 ` Nicholas Piggin
2021-02-09 16:13 ` Christophe Leroy
2021-02-10 1:56 ` Nicholas Piggin
2021-02-08 15:10 ` [PATCH v5 17/22] powerpc/syscall: Do not check unsupported scv vector on PPC32 Christophe Leroy
2021-02-09 2:00 ` Nicholas Piggin
2021-02-09 6:13 ` Christophe Leroy
2021-02-09 7:56 ` Nicholas Piggin
2021-02-08 15:10 ` [PATCH v5 18/22] powerpc/syscall: Remove FULL_REGS verification in system_call_exception Christophe Leroy
2021-02-09 2:02 ` Nicholas Piggin
2021-02-09 14:31 ` Christophe Leroy
2021-02-10 1:57 ` Nicholas Piggin
2021-02-08 15:10 ` [PATCH v5 19/22] powerpc/syscall: Optimise checks in beginning of system_call_exception() Christophe Leroy
2021-02-09 2:06 ` Nicholas Piggin
2021-02-09 14:32 ` Christophe Leroy
2021-02-08 15:10 ` [PATCH v5 20/22] powerpc/syscall: Avoid storing 'current' in another pointer Christophe Leroy
2021-02-09 2:36 ` Nicholas Piggin
2021-02-09 13:50 ` Segher Boessenkool [this message]
2021-02-09 14:31 ` David Laight
2021-02-09 17:03 ` Christophe Leroy
2021-02-09 17:16 ` David Laight
2021-02-10 2:00 ` Nicholas Piggin
2021-02-10 8:45 ` Christophe Leroy
2021-02-08 15:10 ` [PATCH v5 21/22] powerpc/32: Remove the counter in global_dbcr0 Christophe Leroy
2021-02-08 15:10 ` [PATCH v5 22/22] powerpc/32: Handle bookE debugging in C in syscall entry/exit Christophe Leroy
2021-02-09 1:03 ` [PATCH v5 00/22] powerpc/32: Implement C " Nicholas Piggin
2021-02-12 0:19 ` Michael Ellerman
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