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From: Mark Rutland <mark.rutland@arm.com>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: "Rémi Denis-Courmont" <remi@remlab.net>,
	will@kernel.org, linux-arm-kernel@lists.infradead.org,
	james.morse@arm.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/3] arm64: reduce trampoline data alignment
Date: Mon, 23 Mar 2020 11:58:04 +0000	[thread overview]
Message-ID: <20200323115804.GA2597@C02TD0UTHF1T.local> (raw)
In-Reply-To: <20200321134056.GB3052@mbp>

On Sat, Mar 21, 2020 at 01:41:01PM +0000, Catalin Marinas wrote:
> On Thu, Mar 19, 2020 at 11:14:07AM +0200, Rémi Denis-Courmont wrote:
> > diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
> > index c36733d8cd75..ecad15443655 100644
> > --- a/arch/arm64/kernel/entry.S
> > +++ b/arch/arm64/kernel/entry.S
> > @@ -858,7 +858,7 @@ SYM_CODE_END(tramp_exit_compat)
> >  	.popsection				// .entry.tramp.text
> >  #ifdef CONFIG_RANDOMIZE_BASE
> >  	.pushsection ".rodata", "a"
> > -	.align PAGE_SHIFT
> > +	.align	4	// all .rodata must be in a single fixmap page
> >  SYM_DATA_START(__entry_tramp_data_start)
> >  	.quad	vectors
> >  SYM_DATA_END(__entry_tramp_data_start)
> > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> > index 9b08f7c7e6f0..6a0e75f48e7b 100644
> > --- a/arch/arm64/mm/mmu.c
> > +++ b/arch/arm64/mm/mmu.c
> > @@ -599,9 +599,8 @@ static int __init map_entry_trampoline(void)
> >  	if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
> >  		extern char __entry_tramp_data_start[];
> >  
> > -		__set_fixmap(FIX_ENTRY_TRAMP_DATA,
> > -			     __pa_symbol(__entry_tramp_data_start),
> > -			     PAGE_KERNEL_RO);
> > +		pa_start = __pa_symbol(__entry_tramp_data_start) & PAGE_MASK;
> > +		__set_fixmap(FIX_ENTRY_TRAMP_DATA, pa_start, PAGE_KERNEL_RO);
> >  	}
> >  
> >  	return 0;
> 
> For some reason, I haven't investigated yet, a kernel with KASAN and 64K
> pages enabled does not boot (see the attached config). It seems to lock
> up when starting user space. Bisected to this commit, reverting it fixes
> the issue.

I think the issue might be due to ADRP + ADD :lo12: using 4K offsets,
and so patch 1 isn't quite right for !4K kernels, as we're not
accounting for 4 bits of the address when we try to generate it.

I'll check that now.

Thanks,
Mark.

WARNING: multiple messages have this Message-ID (diff)
From: Mark Rutland <mark.rutland@arm.com>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: james.morse@arm.com, will@kernel.org,
	linux-arm-kernel@lists.infradead.org,
	"Rémi Denis-Courmont" <remi@remlab.net>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/3] arm64: reduce trampoline data alignment
Date: Mon, 23 Mar 2020 11:58:04 +0000	[thread overview]
Message-ID: <20200323115804.GA2597@C02TD0UTHF1T.local> (raw)
In-Reply-To: <20200321134056.GB3052@mbp>

On Sat, Mar 21, 2020 at 01:41:01PM +0000, Catalin Marinas wrote:
> On Thu, Mar 19, 2020 at 11:14:07AM +0200, Rémi Denis-Courmont wrote:
> > diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
> > index c36733d8cd75..ecad15443655 100644
> > --- a/arch/arm64/kernel/entry.S
> > +++ b/arch/arm64/kernel/entry.S
> > @@ -858,7 +858,7 @@ SYM_CODE_END(tramp_exit_compat)
> >  	.popsection				// .entry.tramp.text
> >  #ifdef CONFIG_RANDOMIZE_BASE
> >  	.pushsection ".rodata", "a"
> > -	.align PAGE_SHIFT
> > +	.align	4	// all .rodata must be in a single fixmap page
> >  SYM_DATA_START(__entry_tramp_data_start)
> >  	.quad	vectors
> >  SYM_DATA_END(__entry_tramp_data_start)
> > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> > index 9b08f7c7e6f0..6a0e75f48e7b 100644
> > --- a/arch/arm64/mm/mmu.c
> > +++ b/arch/arm64/mm/mmu.c
> > @@ -599,9 +599,8 @@ static int __init map_entry_trampoline(void)
> >  	if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
> >  		extern char __entry_tramp_data_start[];
> >  
> > -		__set_fixmap(FIX_ENTRY_TRAMP_DATA,
> > -			     __pa_symbol(__entry_tramp_data_start),
> > -			     PAGE_KERNEL_RO);
> > +		pa_start = __pa_symbol(__entry_tramp_data_start) & PAGE_MASK;
> > +		__set_fixmap(FIX_ENTRY_TRAMP_DATA, pa_start, PAGE_KERNEL_RO);
> >  	}
> >  
> >  	return 0;
> 
> For some reason, I haven't investigated yet, a kernel with KASAN and 64K
> pages enabled does not boot (see the attached config). It seems to lock
> up when starting user space. Bisected to this commit, reverting it fixes
> the issue.

I think the issue might be due to ADRP + ADD :lo12: using 4K offsets,
and so patch 1 isn't quite right for !4K kernels, as we're not
accounting for 4 bits of the address when we try to generate it.

I'll check that now.

Thanks,
Mark.

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linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2020-03-23 11:58 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-19  9:12 [PATCHv3 0/3] clean up KPTI / SDEI trampoline data alignment Rémi Denis-Courmont
2020-03-19  9:12 ` Rémi Denis-Courmont
2020-03-19  9:14 ` [PATCH 1/3] arm64: clean up trampoline vector loads Rémi Denis-Courmont
2020-03-19  9:14   ` Rémi Denis-Courmont
2020-03-23 12:07   ` Mark Rutland
2020-03-23 12:07     ` Mark Rutland
2020-03-23 12:08     ` Rémi Denis-Courmont
2020-03-23 12:08       ` Rémi Denis-Courmont
2020-03-23 12:14       ` Mark Rutland
2020-03-23 12:14         ` Mark Rutland
2020-03-23 19:04         ` Catalin Marinas
2020-03-23 19:04           ` Catalin Marinas
2020-03-23 20:42           ` Rémi Denis-Courmont
2020-03-23 20:42             ` Rémi Denis-Courmont
2020-03-24 10:37             ` Catalin Marinas
2020-03-24 10:37               ` Catalin Marinas
2020-03-24 10:52             ` Mark Rutland
2020-03-24 10:52               ` Mark Rutland
2020-03-24 11:23               ` Catalin Marinas
2020-03-24 11:23                 ` Catalin Marinas
2020-03-19  9:14 ` [PATCH 2/3] arm64/sdei: gather trampolines' .rodata Rémi Denis-Courmont
2020-03-19  9:14   ` Rémi Denis-Courmont
2020-03-19  9:14 ` [PATCH 3/3] arm64: reduce trampoline data alignment Rémi Denis-Courmont
2020-03-19  9:14   ` Rémi Denis-Courmont
2020-03-21 13:40   ` Catalin Marinas
2020-03-21 13:41     ` Catalin Marinas
2020-03-23 11:58     ` Mark Rutland [this message]
2020-03-23 11:58       ` Mark Rutland
2020-03-19 18:37 ` [PATCHv3 0/3] clean up KPTI / SDEI " Will Deacon
2020-03-19 18:37   ` Will Deacon
2020-03-20 16:54 ` Catalin Marinas
2020-03-20 16:54   ` Catalin Marinas
  -- strict thread matches above, loose matches on Subject: below --
2020-03-16 12:40 [PATCH 3/3] arm64: reduce " Rémi Denis-Courmont
2020-03-16 12:40 ` Rémi Denis-Courmont
2020-03-17 22:34 ` Will Deacon
2020-03-17 22:34   ` Will Deacon

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