From: Richard Earnshaw <Richard.Earnshaw@foss.arm.com>
To: Srinath Parvathaneni <srinath.parvathaneni@arm.com>,
newlib@sourceware.org
Cc: Richard Earnshaw <Richard.Earnshaw@arm.com>, nd <nd@arm.com>
Subject: Re: [PATCH v2][Newlib] arm: Restrict processor mode change when in hypervisor mode.
Date: Thu, 2 Mar 2023 13:05:22 +0000 [thread overview]
Message-ID: <409759de-41a3-2f52-e7d3-f74582f59efe@foss.arm.com> (raw)
In-Reply-To: <33476d31-2d9d-3aee-cd60-7f70e256e3dd@arm.com>
On 23/02/2023 17:10, Srinath Parvathaneni wrote:
> Hi All,
>
> In _stack_init function of crt0.S file, when the current mode is not
> user mode,
> all the processor modes are parsed and the corresponding stack limit are
> set for
> these modes for all A-profile and R-profile CPU's. But when the current
> processor
> mode is hypervisor mode, changing to any other mode using CPSR will
> result in an
> illegal instruction as per Arm-arm and simulator throws undefined
> instruction
> exception.
The reference to a simulator here is confusing. You might have found
this on one, but it's a reflection of the way the architecture is
specified and not specific to running under simulation.
> This patch prevent the change of hypervisor mode to any other mode in
> _stack_init
> function in crt0.S files.
>
> Regression tested on arm-none-eabi target for newlib and newlib-nano and
> found
> no regressions.
>
> Ok for newlib master?
>
> Regards,
> Srinath.
>
> libgloss/ChangeLog:
>
> 2023-02-23 Srinath Parvathaneni <srinath.parvathaneni@arm.com>
>
> * arm/crt0.S (_stack_init): Add check for hypervisor mode.
>
> newlib/ChangeLog:
>
> 2023-02-23 Srinath Parvathaneni <srinath.parvathaneni@arm.com>
>
> * libc/sys/arm/crt0.S (_stack_init): Add check for hypervisor
> mode.
- /* Test mode bits - in User of all are 0. */
- tst r4, #(CPSR_M_MASK)
- /* "eq" means r4 AND #0x0F is 0. */
+ mov r3, sp
+ ands r1, r4, #(CPSR_M_MASK)
+ beq .Lskip_cpu_modes
+ cmp r1, #(CPSR_M_HYP)
You don't mention anywhere why you've moved the instruction that copies
SP into R3 before the user-mode check. I think it's probably right, but
I think really that's a separate issue that deserves a separate patch
(even though it's pretty trivial).
So please can you resend as two patches, the first fixing the SP->r3
copy and the second for the hypervisor mode issue.
R.
prev parent reply other threads:[~2023-03-02 13:05 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-23 17:10 Srinath Parvathaneni
2023-03-02 13:05 ` Richard Earnshaw [this message]
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