From: Scott Wood <scottwood@freescale•com>
To: Yuanjie Huang <Yuanjie.Huang@windriver•com>
Cc: Benjamin Herrenschmidt <benh@kernel•crashing.org>,
Paul Mackerras <paulus@samba•org>,
Michael Ellerman <mpe@ellerman•id.au>,
<linuxppc-dev@lists•ozlabs.org>,
Paul Gortmaker <paul.gortmaker@windriver•com>
Subject: Re: powerpc/fsl_book3e: fix the relocatable bug in debug interrupt handler
Date: Fri, 7 Aug 2015 21:29:13 -0500 [thread overview]
Message-ID: <20150808022913.GA29133@home.buserror.net> (raw)
In-Reply-To: <1438930690-28046-1-git-send-email-Yuanjie.Huang@windriver.com>
[Please wrap commit messages at around 74 columns]
On Fri, Aug 07, 2015 at 02:58:10PM +0800, Yuanjie Huang wrote:
> PowerPC Book3E processor features hardware-supported single instruction
> execution, and it is used for ptrace(PTRACE_SINGLESTEP, ...). When a
> debugger loads a debuggee, it typically sets the CPU to yield debug
> interrupt on first instruction complete or branch taken. However, the
> newly-forked child process could run into instruction TLB miss
> exception handler when switched to, and causes a debug interrupt in the
> exception entry sequence. This is not expected by caller of
> ptrace(PTRACE_SINGLESTEP, ...), so the next instruction address saved
> in DSRR0 is checked against the boundary of exception entry sequence,
> to ensure the kernel only process the interrupt as a normal exception
> if the address does not fall in the exception entry sequence. Failure
> in obtaining the correct boundary leads to such debug exception handled
> as from privileged mode, and causes kernel oops.
>
> The LOAD_REG_IMMEDIATE can't be used to load the boundary addresses
> when relocatable enabled, so this patch replace them with
> LOAD_REG_ADDR_PIC. LR is backed up and restored before and after
> calling LOAD_REG_ADDR_PIC, because LOAD_REG_ADDR_PIC clobbers it.
>
> Signed-off-by: Yuanjie Huang <Yuanjie.Huang@windriver•com>
> ---
> arch/powerpc/kernel/exceptions-64e.S | 24 ++++++++++++++++++++++++
> 1 file changed, 24 insertions(+)
>
> diff --git a/arch/powerpc/kernel/exceptions-64e.S b/arch/powerpc/kernel/exceptions-64e.S
> index 3e68d1c..c475f569 100644
> --- a/arch/powerpc/kernel/exceptions-64e.S
> +++ b/arch/powerpc/kernel/exceptions-64e.S
> @@ -735,12 +735,24 @@ END_FTR_SECTION_IFSET(CPU_FTR_ALTIVEC)
> andis. r15,r14,(DBSR_IC|DBSR_BT)@h
> beq+ 1f
>
> +#ifdef CONFIG_RELOCATABLE
> + mflr r14
> + LOAD_REG_ADDR_PIC(r15,interrupt_base_book3e)
> + mtlr r14
> + cmpld cr0,r10,r15
> + blt+ cr0,1f
> + LOAD_REG_ADDR_PIC(r15,interrupt_end_book3e)
> + mtlr r14
> + cmpld cr0,r10,r15
> + bge+ cr0,1f
> +#else
CONFIG_RELOCATABLE is not supported on 64-bit book3e without applying
additional patches, such as the RFC patchset I posted recently that
contained the patch "powerpc/book3e-64: rename interrupt_end_book3e with
__end_interrupts". But if you've applied that patchset, then you
wouldn't be working with the name interrupt_base_book3e, so how are you
seeing this?
Also, why not use the RELOCATABLE version unconditionally? I don't think
this is a performance-critical path.
-Scott
next prev parent reply other threads:[~2015-08-08 2:29 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-07 6:58 [PATCH] powerpc/fsl_book3e: fix the relocatable bug in debug interrupt handler Yuanjie Huang
2015-08-08 2:29 ` Scott Wood [this message]
2015-08-10 2:23 ` Huang, Yuanjie
2015-08-10 18:57 ` Scott Wood
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