Re: FAILED: patch "[PATCH] MIPS: VDSO: Match data page cache colouring when D$ aliases" failed to apply to 4.4-stable tree

["SZ Lin (林上智)" <sz.lin@moxa.com>]

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Hi,

On Sun, Sep 16, 2018 at 02:11:33PM +0200, gregkh@linuxfoundation.org wrote:
> 
> The patch below does not apply to the 4.4-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@vger.kernel.org>.

Please find attached patch 00578cd864d45 ("MIPS: VDSO: Drop gic_get_usm_range() usage")
 and apply to {4.4,4.9}-stable tree for solving this conflict.

Thanks!

SZ Lin (林上智)

> 
> thanks,
> 
> greg k-h
> 
> ------------------ original commit in Linus's tree ------------------
> 
> From 0f02cfbc3d9e413d450d8d0fd660077c23f67eff Mon Sep 17 00:00:00 2001
> From: Paul Burton <paul.burton@mips.com>
> Date: Thu, 30 Aug 2018 11:01:21 -0700
> Subject: [PATCH] MIPS: VDSO: Match data page cache colouring when D$ aliases
> 
> When a system suffers from dcache aliasing a user program may observe
> stale VDSO data from an aliased cache line. Notably this can break the
> expectation that clock_gettime(CLOCK_MONOTONIC, ...) is, as its name
> suggests, monotonic.
> 
> In order to ensure that users observe updates to the VDSO data page as
> intended, align the user mappings of the VDSO data page such that their
> cache colouring matches that of the virtual address range which the
> kernel will use to update the data page - typically its unmapped address
> within kseg0.
> 
> This ensures that we don't introduce aliasing cache lines for the VDSO
> data page, and therefore that userland will observe updates without
> requiring cache invalidation.
> 
> Signed-off-by: Paul Burton <paul.burton@mips.com>
> Reported-by: Hauke Mehrtens <hauke@hauke-m.de>
> Reported-by: Rene Nielsen <rene.nielsen@microsemi.com>
> Reported-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
> Fixes: ebb5e78cc634 ("MIPS: Initial implementation of a VDSO")
> Patchwork: https://patchwork.linux-mips.org/patch/20344/
> Tested-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
> Tested-by: Hauke Mehrtens <hauke@hauke-m.de>
> Cc: James Hogan <jhogan@kernel.org>
> Cc: linux-mips@linux-mips.org
> Cc: stable@vger.kernel.org # v4.4+
> 
> diff --git a/arch/mips/kernel/vdso.c b/arch/mips/kernel/vdso.c
> index 019035d7225c..8f845f6e5f42 100644
> --- a/arch/mips/kernel/vdso.c
> +++ b/arch/mips/kernel/vdso.c
> @@ -13,6 +13,7 @@
>  #include <linux/err.h>
>  #include <linux/init.h>
>  #include <linux/ioport.h>
> +#include <linux/kernel.h>
>  #include <linux/mm.h>
>  #include <linux/sched.h>
>  #include <linux/slab.h>
> @@ -20,6 +21,7 @@
>  
>  #include <asm/abi.h>
>  #include <asm/mips-cps.h>
> +#include <asm/page.h>
>  #include <asm/vdso.h>
>  
>  /* Kernel-provided data used by the VDSO. */
> @@ -128,12 +130,30 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
>  	vvar_size = gic_size + PAGE_SIZE;
>  	size = vvar_size + image->size;
>  
> +	/*
> +	 * Find a region that's large enough for us to perform the
> +	 * colour-matching alignment below.
> +	 */
> +	if (cpu_has_dc_aliases)
> +		size += shm_align_mask + 1;
> +
>  	base = get_unmapped_area(NULL, 0, size, 0, 0);
>  	if (IS_ERR_VALUE(base)) {
>  		ret = base;
>  		goto out;
>  	}
>  
> +	/*
> +	 * If we suffer from dcache aliasing, ensure that the VDSO data page
> +	 * mapping is coloured the same as the kernel's mapping of that memory.
> +	 * This ensures that when the kernel updates the VDSO data userland
> +	 * will observe it without requiring cache invalidations.
> +	 */
> +	if (cpu_has_dc_aliases) {
> +		base = __ALIGN_MASK(base, shm_align_mask);
> +		base += ((unsigned long)&vdso_data - gic_size) & shm_align_mask;
> +	}
> +
>  	data_addr = base + gic_size;
>  	vdso_addr = data_addr + PAGE_SIZE;
>  
> 

-- 
SZ Lin (林上智) <szlin@debian.org>, http://people.debian.org/~szlin

Debian Developer, debian.org.tw Administrator

4096R/ 178F 8338 B314 01E3 04FC 44BA A959 B38A 9561 F3F9

[-- Attachment #2: 0001-MIPS-VDSO-Drop-gic_get_usm_range-usage.patch --]
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>From 890151c23e16a48ad0ba05ff60633234c1934c8b Mon Sep 17 00:00:00 2001
From: Paul Burton <paul.burton@imgtec.com>
Date: Sat, 12 Aug 2017 21:36:30 -0700
Subject: [PATCH] MIPS: VDSO: Drop gic_get_usm_range() usage

commit 00578cd864d45ae4b8fa3f684f8d6f783dd8d15d upstream

We don't really need gic_get_usm_range() to abstract discovery of the
address of the GIC user-visible section now that we have access to its
base address globally.

Switch to calculating it ourselves, which will allow us to stop
requiring the irqchip driver to care about a counter exposed to userland
for use via the VDSO.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/17040/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: SZ Lin (林上智) <sz.lin@moxa.com>
---
 arch/mips/kernel/vdso.c | 15 +++++----------
 1 file changed, 5 insertions(+), 10 deletions(-)

diff --git a/arch/mips/kernel/vdso.c b/arch/mips/kernel/vdso.c
index 5649a9e429e0..1266fd56c919 100644
--- a/arch/mips/kernel/vdso.c
+++ b/arch/mips/kernel/vdso.c
@@ -13,13 +13,13 @@
 #include <linux/err.h>
 #include <linux/init.h>
 #include <linux/ioport.h>
-#include <linux/irqchip/mips-gic.h>
 #include <linux/mm.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
 #include <linux/timekeeper_internal.h>
 
 #include <asm/abi.h>
+#include <asm/mips-cps.h>
 #include <asm/vdso.h>
 
 /* Kernel-provided data used by the VDSO. */
@@ -99,9 +99,8 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 {
 	struct mips_vdso_image *image = current->thread.abi->vdso;
 	struct mm_struct *mm = current->mm;
-	unsigned long gic_size, vvar_size, size, base, data_addr, vdso_addr;
+	unsigned long gic_size, vvar_size, size, base, data_addr, vdso_addr, gic_pfn;
 	struct vm_area_struct *vma;
-	struct resource gic_res;
 	int ret;
 
 	down_write(&mm->mmap_sem);
@@ -114,7 +113,7 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 	 * only map a page even though the total area is 64K, as we only need
 	 * the counter registers at the start.
 	 */
-	gic_size = gic_present ? PAGE_SIZE : 0;
+	gic_size = mips_gic_present() ? PAGE_SIZE : 0;
 	vvar_size = gic_size + PAGE_SIZE;
 	size = vvar_size + image->size;
 
@@ -137,13 +136,9 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 
 	/* Map GIC user page. */
 	if (gic_size) {
-		ret = gic_get_usm_range(&gic_res);
-		if (ret)
-			goto out;
+		gic_pfn = virt_to_phys(mips_gic_base + MIPS_GIC_USER_OFS) >> PAGE_SHIFT;
 
-		ret = io_remap_pfn_range(vma, base,
-					 gic_res.start >> PAGE_SHIFT,
-					 gic_size,
+		ret = io_remap_pfn_range(vma, base, gic_pfn, gic_size,
 					 pgprot_noncached(PAGE_READONLY));
 		if (ret)
 			goto out;
-- 
2.19.0