diff mbox series

[v14,04/10] set_memory: allow querying whether set_direct_map_*() is actually enabled

Message ID 20201203062949.5484-5-rppt@kernel.org (mailing list archive)
State New, archived
Headers show
Series mm: introduce memfd_secret system call to create "secret" memory areas | expand

Commit Message

Mike Rapoport Dec. 3, 2020, 6:29 a.m. UTC 
From: Mike Rapoport <rppt@linux.ibm.com>

On arm64, set_direct_map_*() functions may return 0 without actually
changing the linear map. This behaviour can be controlled using kernel
parameters, so we need a way to determine at runtime whether calls to
set_direct_map_invalid_noflush() and set_direct_map_default_noflush() have
any effect.

Extend set_memory API with can_set_direct_map() function that allows
checking if calling set_direct_map_*() will actually change the page table,
replace several occurrences of open coded checks in arm64 with the new
function and provide a generic stub for architectures that always modify
page tables upon calls to set_direct_map APIs.

Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
---
 arch/arm64/include/asm/Kbuild       |  1 -
 arch/arm64/include/asm/cacheflush.h |  6 ------
 arch/arm64/include/asm/set_memory.h | 17 +++++++++++++++++
 arch/arm64/kernel/machine_kexec.c   |  1 +
 arch/arm64/mm/mmu.c                 |  6 +++---
 arch/arm64/mm/pageattr.c            | 13 +++++++++----
 include/linux/set_memory.h          | 12 ++++++++++++
 7 files changed, 42 insertions(+), 14 deletions(-)
 create mode 100644 arch/arm64/include/asm/set_memory.h

Comments

Andrew Morton Dec. 3, 2020, 11:36 p.m. UTC | #1 
On Thu,  3 Dec 2020 08:29:43 +0200 Mike Rapoport <rppt@kernel.org> wrote:

> From: Mike Rapoport <rppt@linux.ibm.com>
> 
> On arm64, set_direct_map_*() functions may return 0 without actually
> changing the linear map. This behaviour can be controlled using kernel
> parameters, so we need a way to determine at runtime whether calls to
> set_direct_map_invalid_noflush() and set_direct_map_default_noflush() have
> any effect.
> 
> Extend set_memory API with can_set_direct_map() function that allows
> checking if calling set_direct_map_*() will actually change the page table,
> replace several occurrences of open coded checks in arm64 with the new
> function and provide a generic stub for architectures that always modify
> page tables upon calls to set_direct_map APIs.
> 
> ...
>
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -22,6 +22,7 @@
>  #include <linux/io.h>
>  #include <linux/mm.h>
>  #include <linux/vmalloc.h>
> +#include <linux/set_memory.h>
>  
>  #include <asm/barrier.h>
>  #include <asm/cputype.h>
> @@ -477,7 +478,7 @@ static void __init map_mem(pgd_t *pgdp)
>  	int flags = 0;
>  	u64 i;
>  
> -	if (rodata_full || debug_pagealloc_enabled())
> +	if (can_set_direct_map())
>  		flags = NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;

Changes in -next turned this into

	if (can_set_direct_map() || crash_mem_map)
Mike Rapoport Dec. 6, 2020, 11:28 a.m. UTC | #2 
On Thu, Dec 03, 2020 at 03:36:10PM -0800, Andrew Morton wrote:
> On Thu,  3 Dec 2020 08:29:43 +0200 Mike Rapoport <rppt@kernel.org> wrote:
> 
> > From: Mike Rapoport <rppt@linux.ibm.com>
> > 
> > On arm64, set_direct_map_*() functions may return 0 without actually
> > changing the linear map. This behaviour can be controlled using kernel
> > parameters, so we need a way to determine at runtime whether calls to
> > set_direct_map_invalid_noflush() and set_direct_map_default_noflush() have
> > any effect.
> > 
> > Extend set_memory API with can_set_direct_map() function that allows
> > checking if calling set_direct_map_*() will actually change the page table,
> > replace several occurrences of open coded checks in arm64 with the new
> > function and provide a generic stub for architectures that always modify
> > page tables upon calls to set_direct_map APIs.
> > 
> > ...
> >
> > --- a/arch/arm64/mm/mmu.c
> > +++ b/arch/arm64/mm/mmu.c
> > @@ -22,6 +22,7 @@
> >  #include <linux/io.h>
> >  #include <linux/mm.h>
> >  #include <linux/vmalloc.h>
> > +#include <linux/set_memory.h>
> >  
> >  #include <asm/barrier.h>
> >  #include <asm/cputype.h>
> > @@ -477,7 +478,7 @@ static void __init map_mem(pgd_t *pgdp)
> >  	int flags = 0;
> >  	u64 i;
> >  
> > -	if (rodata_full || debug_pagealloc_enabled())
> > +	if (can_set_direct_map())
> >  		flags = NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
> 
> Changes in -next turned this into
> 
> 	if (can_set_direct_map() || crash_mem_map)

Thanks for updating!
diff mbox series

Patch

diff --git a/arch/arm64/include/asm/Kbuild b/arch/arm64/include/asm/Kbuild
index ff9cbb631212..4306136ef329 100644
--- a/arch/arm64/include/asm/Kbuild
+++ b/arch/arm64/include/asm/Kbuild
@@ -4,5 +4,4 @@  generic-y += local64.h
 generic-y += mcs_spinlock.h
 generic-y += qrwlock.h
 generic-y += qspinlock.h
-generic-y += set_memory.h
 generic-y += user.h
diff --git a/arch/arm64/include/asm/cacheflush.h b/arch/arm64/include/asm/cacheflush.h
index d3598419a284..b1bdf83a73db 100644
--- a/arch/arm64/include/asm/cacheflush.h
+++ b/arch/arm64/include/asm/cacheflush.h
@@ -136,12 +136,6 @@  static __always_inline void __flush_icache_all(void)
 	dsb(ish);
 }
 
-int set_memory_valid(unsigned long addr, int numpages, int enable);
-
-int set_direct_map_invalid_noflush(struct page *page, int numpages);
-int set_direct_map_default_noflush(struct page *page, int numpages);
-bool kernel_page_present(struct page *page);
-
 #include <asm-generic/cacheflush.h>
 
 #endif /* __ASM_CACHEFLUSH_H */
diff --git a/arch/arm64/include/asm/set_memory.h b/arch/arm64/include/asm/set_memory.h
new file mode 100644
index 000000000000..ecb6b0f449ab
--- /dev/null
+++ b/arch/arm64/include/asm/set_memory.h
@@ -0,0 +1,17 @@ 
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef _ASM_ARM64_SET_MEMORY_H
+#define _ASM_ARM64_SET_MEMORY_H
+
+#include <asm-generic/set_memory.h>
+
+bool can_set_direct_map(void);
+#define can_set_direct_map can_set_direct_map
+
+int set_memory_valid(unsigned long addr, int numpages, int enable);
+
+int set_direct_map_invalid_noflush(struct page *page, int numpages);
+int set_direct_map_default_noflush(struct page *page, int numpages);
+bool kernel_page_present(struct page *page);
+
+#endif /* _ASM_ARM64_SET_MEMORY_H */
diff --git a/arch/arm64/kernel/machine_kexec.c b/arch/arm64/kernel/machine_kexec.c
index a0b144cfaea7..0cbc50c4fa5a 100644
--- a/arch/arm64/kernel/machine_kexec.c
+++ b/arch/arm64/kernel/machine_kexec.c
@@ -11,6 +11,7 @@ 
 #include <linux/kernel.h>
 #include <linux/kexec.h>
 #include <linux/page-flags.h>
+#include <linux/set_memory.h>
 #include <linux/smp.h>
 
 #include <asm/cacheflush.h>
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 86be6d1a78ab..aa5ec08cb902 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -22,6 +22,7 @@ 
 #include <linux/io.h>
 #include <linux/mm.h>
 #include <linux/vmalloc.h>
+#include <linux/set_memory.h>
 
 #include <asm/barrier.h>
 #include <asm/cputype.h>
@@ -477,7 +478,7 @@  static void __init map_mem(pgd_t *pgdp)
 	int flags = 0;
 	u64 i;
 
-	if (rodata_full || debug_pagealloc_enabled())
+	if (can_set_direct_map())
 		flags = NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
 
 	/*
@@ -1453,8 +1454,7 @@  int arch_add_memory(int nid, u64 start, u64 size,
 	 * KFENCE requires linear map to be mapped at page granularity, so that
 	 * it is possible to protect/unprotect single pages in the KFENCE pool.
 	 */
-	if (rodata_full || debug_pagealloc_enabled() ||
-	    IS_ENABLED(CONFIG_KFENCE))
+	if (can_set_direct_map() || IS_ENABLED(CONFIG_KFENCE))
 		flags = NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
 
 	__create_pgd_mapping(swapper_pg_dir, start, __phys_to_virt(start),
diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
index b53ef37bf95a..d505172265b0 100644
--- a/arch/arm64/mm/pageattr.c
+++ b/arch/arm64/mm/pageattr.c
@@ -19,6 +19,11 @@  struct page_change_data {
 
 bool rodata_full __ro_after_init = IS_ENABLED(CONFIG_RODATA_FULL_DEFAULT_ENABLED);
 
+bool can_set_direct_map(void)
+{
+	return rodata_full || debug_pagealloc_enabled();
+}
+
 static int change_page_range(pte_t *ptep, unsigned long addr, void *data)
 {
 	struct page_change_data *cdata = data;
@@ -156,7 +161,7 @@  int set_direct_map_invalid_noflush(struct page *page, int numpages)
 	};
 	unsigned long size = PAGE_SIZE * numpages;
 
-	if (!debug_pagealloc_enabled() && !rodata_full)
+	if (!can_set_direct_map())
 		return 0;
 
 	return apply_to_page_range(&init_mm,
@@ -172,7 +177,7 @@  int set_direct_map_default_noflush(struct page *page, int numpages)
 	};
 	unsigned long size = PAGE_SIZE * numpages;
 
-	if (!debug_pagealloc_enabled() && !rodata_full)
+	if (!can_set_direct_map())
 		return 0;
 
 	return apply_to_page_range(&init_mm,
@@ -183,7 +188,7 @@  int set_direct_map_default_noflush(struct page *page, int numpages)
 #ifdef CONFIG_DEBUG_PAGEALLOC
 void __kernel_map_pages(struct page *page, int numpages, int enable)
 {
-	if (!debug_pagealloc_enabled() && !rodata_full)
+	if (!can_set_direct_map())
 		return;
 
 	set_memory_valid((unsigned long)page_address(page), numpages, enable);
@@ -208,7 +213,7 @@  bool kernel_page_present(struct page *page)
 	pte_t *ptep;
 	unsigned long addr = (unsigned long)page_address(page);
 
-	if (!debug_pagealloc_enabled() && !rodata_full)
+	if (!can_set_direct_map())
 		return true;
 
 	pgdp = pgd_offset_k(addr);
diff --git a/include/linux/set_memory.h b/include/linux/set_memory.h
index c650f82db813..7b4b6626032d 100644
--- a/include/linux/set_memory.h
+++ b/include/linux/set_memory.h
@@ -28,7 +28,19 @@  static inline bool kernel_page_present(struct page *page)
 {
 	return true;
 }
+#else /* CONFIG_ARCH_HAS_SET_DIRECT_MAP */
+/*
+ * Some architectures, e.g. ARM64 can disable direct map modifications at
+ * boot time. Let them overrive this query.
+ */
+#ifndef can_set_direct_map
+static inline bool can_set_direct_map(void)
+{
+	return true;
+}
+#define can_set_direct_map can_set_direct_map
 #endif
+#endif /* CONFIG_ARCH_HAS_SET_DIRECT_MAP */
 
 #ifndef set_mce_nospec
 static inline int set_mce_nospec(unsigned long pfn, bool unmap)