* [PATCH 0/2] Fixups for LDT remap placement change @ 2018-11-30 11:57 Kirill A. Shutemov 2018-11-30 11:57 ` [PATCH 1/2] x86/mm: Fix guard hole handling Kirill A. Shutemov 2018-11-30 11:57 ` [PATCH 2/2] x86/dump_pagetables: Fix LDT remap address marker Kirill A. Shutemov 0 siblings, 2 replies; 6+ messages in thread From: Kirill A. Shutemov @ 2018-11-30 11:57 UTC (permalink / raw) To: tglx, mingo, bp, hpa, dave.hansen, luto, peterz Cc: boris.ostrovsky, jgross, bhe, x86, linux-mm, linux-kernel, Kirill A. Shutemov There's a couple fixes for the recent LDT remap placement change. The first patch fixes crash when kernel booted as Xen dom0. The second patch fixes address space markers in dump_pagetables output. It's purely cosmetic change, backporting to the stable tree is optional. Kirill A. Shutemov (2): x86/mm: Fix guard hole handling x86/dump_pagetables: Fix LDT remap address marker arch/x86/include/asm/pgtable_64_types.h | 5 +++++ arch/x86/mm/dump_pagetables.c | 15 ++++++--------- arch/x86/xen/mmu_pv.c | 11 ++++++----- 3 files changed, 17 insertions(+), 14 deletions(-) -- 2.19.2 ^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH 1/2] x86/mm: Fix guard hole handling 2018-11-30 11:57 [PATCH 0/2] Fixups for LDT remap placement change Kirill A. Shutemov @ 2018-11-30 11:57 ` Kirill A. Shutemov 2018-11-30 12:03 ` Juergen Gross 2018-11-30 11:57 ` [PATCH 2/2] x86/dump_pagetables: Fix LDT remap address marker Kirill A. Shutemov 1 sibling, 1 reply; 6+ messages in thread From: Kirill A. Shutemov @ 2018-11-30 11:57 UTC (permalink / raw) To: tglx, mingo, bp, hpa, dave.hansen, luto, peterz Cc: boris.ostrovsky, jgross, bhe, x86, linux-mm, linux-kernel, Kirill A. Shutemov There is a guard hole at the beginning of kernel address space, also used by hypervisors. It occupies 16 PGD entries. We do not state the reserved range directly, but calculate it relative to other entities: direct mapping and user space ranges. The calculation got broken by recent change in kernel memory layout: LDT remap range is now mapped before direct mapping and makes the calculation invalid. The breakage leads to crash on Xen dom0 boot[1]. State the reserved range directly. It's part of kernel ABI (hypervisors expect it to be stable) and must not depend on changes in the rest of kernel memory layout. [1] https://lists.xenproject.org/archives/html/xen-devel/2018-11/msg03313.html Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Reported-by: Hans van Kranenburg <Hans.van.Kranenburg@mendix.com> Fixes: d52888aa2753 ("x86/mm: Move LDT remap out of KASLR region on 5-level paging") --- arch/x86/include/asm/pgtable_64_types.h | 5 +++++ arch/x86/mm/dump_pagetables.c | 8 ++++---- arch/x86/xen/mmu_pv.c | 11 ++++++----- 3 files changed, 15 insertions(+), 9 deletions(-) diff --git a/arch/x86/include/asm/pgtable_64_types.h b/arch/x86/include/asm/pgtable_64_types.h index 84bd9bdc1987..13aef22cee18 100644 --- a/arch/x86/include/asm/pgtable_64_types.h +++ b/arch/x86/include/asm/pgtable_64_types.h @@ -111,6 +111,11 @@ extern unsigned int ptrs_per_p4d; */ #define MAXMEM (1UL << MAX_PHYSMEM_BITS) +#define GUARD_HOLE_PGD_ENTRY -256UL +#define GUARD_HOLE_SIZE (16UL << PGDIR_SHIFT) +#define GUARD_HOLE_BASE_ADDR (LDT_PGD_ENTRY << PGDIR_SHIFT) +#define GUARD_HOLE_END_ADDR (GUARD_HOLE_BASE_ADDR + GUARD_HOLE_SIZE) + #define LDT_PGD_ENTRY -240UL #define LDT_BASE_ADDR (LDT_PGD_ENTRY << PGDIR_SHIFT) #define LDT_END_ADDR (LDT_BASE_ADDR + PGDIR_SIZE) diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c index fc37bbd23eb8..dad153e5a427 100644 --- a/arch/x86/mm/dump_pagetables.c +++ b/arch/x86/mm/dump_pagetables.c @@ -512,11 +512,11 @@ static inline bool is_hypervisor_range(int idx) { #ifdef CONFIG_X86_64 /* - * ffff800000000000 - ffff87ffffffffff is reserved for - * the hypervisor. + * A hole in the beginning of kernel address space reserved + * for a hypervisor. */ - return (idx >= pgd_index(__PAGE_OFFSET) - 16) && - (idx < pgd_index(__PAGE_OFFSET)); + return (idx >= pgd_index(GUARD_HOLE_BASE_ADDR)) && + (idx < pgd_index(GUARD_HOLE_END_ADDR)); #else return false; #endif diff --git a/arch/x86/xen/mmu_pv.c b/arch/x86/xen/mmu_pv.c index a5d7ed125337..0f4fe206dcc2 100644 --- a/arch/x86/xen/mmu_pv.c +++ b/arch/x86/xen/mmu_pv.c @@ -648,19 +648,20 @@ static int __xen_pgd_walk(struct mm_struct *mm, pgd_t *pgd, unsigned long limit) { int i, nr, flush = 0; - unsigned hole_low, hole_high; + unsigned hole_low = 0, hole_high = 0; /* The limit is the last byte to be touched */ limit--; BUG_ON(limit >= FIXADDR_TOP); +#ifdef CONFIG_X86_64 /* * 64-bit has a great big hole in the middle of the address - * space, which contains the Xen mappings. On 32-bit these - * will end up making a zero-sized hole and so is a no-op. + * space, which contains the Xen mappings. */ - hole_low = pgd_index(USER_LIMIT); - hole_high = pgd_index(PAGE_OFFSET); + hole_low = pgd_index(GUARD_HOLE_BASE_ADDR); + hole_high = pgd_index(GUARD_HOLE_END_ADDR); +#endif nr = pgd_index(limit) + 1; for (i = 0; i < nr; i++) { -- 2.19.2 ^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH 1/2] x86/mm: Fix guard hole handling 2018-11-30 11:57 ` [PATCH 1/2] x86/mm: Fix guard hole handling Kirill A. Shutemov @ 2018-11-30 12:03 ` Juergen Gross 2018-11-30 12:11 ` Kirill A. Shutemov 0 siblings, 1 reply; 6+ messages in thread From: Juergen Gross @ 2018-11-30 12:03 UTC (permalink / raw) To: Kirill A. Shutemov, tglx, mingo, bp, hpa, dave.hansen, luto, peterz Cc: boris.ostrovsky, bhe, x86, linux-mm, linux-kernel On 30/11/2018 12:57, Kirill A. Shutemov wrote: > There is a guard hole at the beginning of kernel address space, also > used by hypervisors. It occupies 16 PGD entries. > > We do not state the reserved range directly, but calculate it relative > to other entities: direct mapping and user space ranges. > > The calculation got broken by recent change in kernel memory layout: LDT > remap range is now mapped before direct mapping and makes the calculation > invalid. > > The breakage leads to crash on Xen dom0 boot[1]. > > State the reserved range directly. It's part of kernel ABI (hypervisors > expect it to be stable) and must not depend on changes in the rest of > kernel memory layout. > > [1] https://lists.xenproject.org/archives/html/xen-devel/2018-11/msg03313.html > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> > Reported-by: Hans van Kranenburg <Hans.van.Kranenburg@mendix.com> > Fixes: d52888aa2753 ("x86/mm: Move LDT remap out of KASLR region on 5-level paging") > --- > arch/x86/include/asm/pgtable_64_types.h | 5 +++++ > arch/x86/mm/dump_pagetables.c | 8 ++++---- > arch/x86/xen/mmu_pv.c | 11 ++++++----- > 3 files changed, 15 insertions(+), 9 deletions(-) > > diff --git a/arch/x86/include/asm/pgtable_64_types.h b/arch/x86/include/asm/pgtable_64_types.h > index 84bd9bdc1987..13aef22cee18 100644 > --- a/arch/x86/include/asm/pgtable_64_types.h > +++ b/arch/x86/include/asm/pgtable_64_types.h > @@ -111,6 +111,11 @@ extern unsigned int ptrs_per_p4d; > */ > #define MAXMEM (1UL << MAX_PHYSMEM_BITS) > > +#define GUARD_HOLE_PGD_ENTRY -256UL > +#define GUARD_HOLE_SIZE (16UL << PGDIR_SHIFT) > +#define GUARD_HOLE_BASE_ADDR (LDT_PGD_ENTRY << PGDIR_SHIFT) s/LDT_PGD_ENTRY/GUARD_HOLE_PGD_ENTRY/ Juergen ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH 1/2] x86/mm: Fix guard hole handling 2018-11-30 12:03 ` Juergen Gross @ 2018-11-30 12:11 ` Kirill A. Shutemov 2018-11-30 12:19 ` Juergen Gross 0 siblings, 1 reply; 6+ messages in thread From: Kirill A. Shutemov @ 2018-11-30 12:11 UTC (permalink / raw) To: Juergen Gross Cc: tglx, mingo, bp, hpa, dave.hansen, luto, peterz, boris.ostrovsky, bhe, x86, linux-mm, linux-kernel On Fri, Nov 30, 2018 at 12:03:33PM +0000, Juergen Gross wrote: > On 30/11/2018 12:57, Kirill A. Shutemov wrote: > > There is a guard hole at the beginning of kernel address space, also > > used by hypervisors. It occupies 16 PGD entries. > > > > We do not state the reserved range directly, but calculate it relative > > to other entities: direct mapping and user space ranges. > > > > The calculation got broken by recent change in kernel memory layout: LDT > > remap range is now mapped before direct mapping and makes the calculation > > invalid. > > > > The breakage leads to crash on Xen dom0 boot[1]. > > > > State the reserved range directly. It's part of kernel ABI (hypervisors > > expect it to be stable) and must not depend on changes in the rest of > > kernel memory layout. > > > > [1] https://lists.xenproject.org/archives/html/xen-devel/2018-11/msg03313.html > > > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> > > Reported-by: Hans van Kranenburg <Hans.van.Kranenburg@mendix.com> > > Fixes: d52888aa2753 ("x86/mm: Move LDT remap out of KASLR region on 5-level paging") > > --- > > arch/x86/include/asm/pgtable_64_types.h | 5 +++++ > > arch/x86/mm/dump_pagetables.c | 8 ++++---- > > arch/x86/xen/mmu_pv.c | 11 ++++++----- > > 3 files changed, 15 insertions(+), 9 deletions(-) > > > > diff --git a/arch/x86/include/asm/pgtable_64_types.h b/arch/x86/include/asm/pgtable_64_types.h > > index 84bd9bdc1987..13aef22cee18 100644 > > --- a/arch/x86/include/asm/pgtable_64_types.h > > +++ b/arch/x86/include/asm/pgtable_64_types.h > > @@ -111,6 +111,11 @@ extern unsigned int ptrs_per_p4d; > > */ > > #define MAXMEM (1UL << MAX_PHYSMEM_BITS) > > > > +#define GUARD_HOLE_PGD_ENTRY -256UL > > +#define GUARD_HOLE_SIZE (16UL << PGDIR_SHIFT) > > +#define GUARD_HOLE_BASE_ADDR (LDT_PGD_ENTRY << PGDIR_SHIFT) > > s/LDT_PGD_ENTRY/GUARD_HOLE_PGD_ENTRY/ Ughh.. >From 4308d560cc2874a9f596512bcb4c601b2450653d Mon Sep 17 00:00:00 2001 From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Date: Fri, 30 Nov 2018 14:29:42 +0300 Subject: [PATCH 1/2] x86/mm: Fix guard hole handling There is a guard hole at the beginning of kernel address space, also used by hypervisors. It occupies 16 PGD entries. We do not state the reserved range directly, but calculate it relative to other entities: direct mapping and user space ranges. The calculation got broken by recent change in kernel memory layout: LDT remap range is now mapped before direct mapping and makes the calculation invalid. The breakage leads to crash on Xen dom0 boot[1]. State the reserved range directly. It's part of kernel ABI (hypervisors expect it to be stable) and must not depend on changes in the rest of kernel memory layout. [1] https://lists.xenproject.org/archives/html/xen-devel/2018-11/msg03313.html Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Reported-by: Hans van Kranenburg <Hans.van.Kranenburg@mendix.com> Fixes: d52888aa2753 ("x86/mm: Move LDT remap out of KASLR region on 5-level paging") Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> --- arch/x86/include/asm/pgtable_64_types.h | 5 +++++ arch/x86/mm/dump_pagetables.c | 8 ++++---- arch/x86/xen/mmu_pv.c | 11 ++++++----- 3 files changed, 15 insertions(+), 9 deletions(-) diff --git a/arch/x86/include/asm/pgtable_64_types.h b/arch/x86/include/asm/pgtable_64_types.h index 84bd9bdc1987..ff96fbab97b5 100644 --- a/arch/x86/include/asm/pgtable_64_types.h +++ b/arch/x86/include/asm/pgtable_64_types.h @@ -111,6 +111,11 @@ extern unsigned int ptrs_per_p4d; */ #define MAXMEM (1UL << MAX_PHYSMEM_BITS) +#define GUARD_HOLE_PGD_ENTRY -256UL +#define GUARD_HOLE_SIZE (16UL << PGDIR_SHIFT) +#define GUARD_HOLE_BASE_ADDR (GUARD_HOLE_ENTRY << PGDIR_SHIFT) +#define GUARD_HOLE_END_ADDR (GUARD_HOLE_BASE_ADDR + GUARD_HOLE_SIZE) + #define LDT_PGD_ENTRY -240UL #define LDT_BASE_ADDR (LDT_PGD_ENTRY << PGDIR_SHIFT) #define LDT_END_ADDR (LDT_BASE_ADDR + PGDIR_SIZE) diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c index fc37bbd23eb8..dad153e5a427 100644 --- a/arch/x86/mm/dump_pagetables.c +++ b/arch/x86/mm/dump_pagetables.c @@ -512,11 +512,11 @@ static inline bool is_hypervisor_range(int idx) { #ifdef CONFIG_X86_64 /* - * ffff800000000000 - ffff87ffffffffff is reserved for - * the hypervisor. + * A hole in the beginning of kernel address space reserved + * for a hypervisor. */ - return (idx >= pgd_index(__PAGE_OFFSET) - 16) && - (idx < pgd_index(__PAGE_OFFSET)); + return (idx >= pgd_index(GUARD_HOLE_BASE_ADDR)) && + (idx < pgd_index(GUARD_HOLE_END_ADDR)); #else return false; #endif diff --git a/arch/x86/xen/mmu_pv.c b/arch/x86/xen/mmu_pv.c index a5d7ed125337..0f4fe206dcc2 100644 --- a/arch/x86/xen/mmu_pv.c +++ b/arch/x86/xen/mmu_pv.c @@ -648,19 +648,20 @@ static int __xen_pgd_walk(struct mm_struct *mm, pgd_t *pgd, unsigned long limit) { int i, nr, flush = 0; - unsigned hole_low, hole_high; + unsigned hole_low = 0, hole_high = 0; /* The limit is the last byte to be touched */ limit--; BUG_ON(limit >= FIXADDR_TOP); +#ifdef CONFIG_X86_64 /* * 64-bit has a great big hole in the middle of the address - * space, which contains the Xen mappings. On 32-bit these - * will end up making a zero-sized hole and so is a no-op. + * space, which contains the Xen mappings. */ - hole_low = pgd_index(USER_LIMIT); - hole_high = pgd_index(PAGE_OFFSET); + hole_low = pgd_index(GUARD_HOLE_BASE_ADDR); + hole_high = pgd_index(GUARD_HOLE_END_ADDR); +#endif nr = pgd_index(limit) + 1; for (i = 0; i < nr; i++) { -- Kirill A. Shutemov ^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH 1/2] x86/mm: Fix guard hole handling 2018-11-30 12:11 ` Kirill A. Shutemov @ 2018-11-30 12:19 ` Juergen Gross 0 siblings, 0 replies; 6+ messages in thread From: Juergen Gross @ 2018-11-30 12:19 UTC (permalink / raw) To: Kirill A. Shutemov Cc: tglx, mingo, bp, hpa, dave.hansen, luto, peterz, boris.ostrovsky, bhe, x86, linux-mm, linux-kernel On 30/11/2018 13:11, Kirill A. Shutemov wrote: > On Fri, Nov 30, 2018 at 12:03:33PM +0000, Juergen Gross wrote: >> On 30/11/2018 12:57, Kirill A. Shutemov wrote: >>> There is a guard hole at the beginning of kernel address space, also >>> used by hypervisors. It occupies 16 PGD entries. >>> >>> We do not state the reserved range directly, but calculate it relative >>> to other entities: direct mapping and user space ranges. >>> >>> The calculation got broken by recent change in kernel memory layout: LDT >>> remap range is now mapped before direct mapping and makes the calculation >>> invalid. >>> >>> The breakage leads to crash on Xen dom0 boot[1]. >>> >>> State the reserved range directly. It's part of kernel ABI (hypervisors >>> expect it to be stable) and must not depend on changes in the rest of >>> kernel memory layout. >>> >>> [1] https://lists.xenproject.org/archives/html/xen-devel/2018-11/msg03313.html >>> >>> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> >>> Reported-by: Hans van Kranenburg <Hans.van.Kranenburg@mendix.com> >>> Fixes: d52888aa2753 ("x86/mm: Move LDT remap out of KASLR region on 5-level paging") >>> --- >>> arch/x86/include/asm/pgtable_64_types.h | 5 +++++ >>> arch/x86/mm/dump_pagetables.c | 8 ++++---- >>> arch/x86/xen/mmu_pv.c | 11 ++++++----- >>> 3 files changed, 15 insertions(+), 9 deletions(-) >>> >>> diff --git a/arch/x86/include/asm/pgtable_64_types.h b/arch/x86/include/asm/pgtable_64_types.h >>> index 84bd9bdc1987..13aef22cee18 100644 >>> --- a/arch/x86/include/asm/pgtable_64_types.h >>> +++ b/arch/x86/include/asm/pgtable_64_types.h >>> @@ -111,6 +111,11 @@ extern unsigned int ptrs_per_p4d; >>> */ >>> #define MAXMEM (1UL << MAX_PHYSMEM_BITS) >>> >>> +#define GUARD_HOLE_PGD_ENTRY -256UL >>> +#define GUARD_HOLE_SIZE (16UL << PGDIR_SHIFT) >>> +#define GUARD_HOLE_BASE_ADDR (LDT_PGD_ENTRY << PGDIR_SHIFT) >> >> s/LDT_PGD_ENTRY/GUARD_HOLE_PGD_ENTRY/ > > Ughh.. > >>>From 4308d560cc2874a9f596512bcb4c601b2450653d Mon Sep 17 00:00:00 2001 > From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> > Date: Fri, 30 Nov 2018 14:29:42 +0300 > Subject: [PATCH 1/2] x86/mm: Fix guard hole handling > > There is a guard hole at the beginning of kernel address space, also > used by hypervisors. It occupies 16 PGD entries. > > We do not state the reserved range directly, but calculate it relative > to other entities: direct mapping and user space ranges. > > The calculation got broken by recent change in kernel memory layout: LDT > remap range is now mapped before direct mapping and makes the calculation > invalid. > > The breakage leads to crash on Xen dom0 boot[1]. > > State the reserved range directly. It's part of kernel ABI (hypervisors > expect it to be stable) and must not depend on changes in the rest of > kernel memory layout. > > [1] https://lists.xenproject.org/archives/html/xen-devel/2018-11/msg03313.html > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> > Reported-by: Hans van Kranenburg <Hans.van.Kranenburg@mendix.com> > Fixes: d52888aa2753 ("x86/mm: Move LDT remap out of KASLR region on 5-level paging") > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Reviewed-by: Juergen Gross <jgross@suse.com> Juergen ^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH 2/2] x86/dump_pagetables: Fix LDT remap address marker 2018-11-30 11:57 [PATCH 0/2] Fixups for LDT remap placement change Kirill A. Shutemov 2018-11-30 11:57 ` [PATCH 1/2] x86/mm: Fix guard hole handling Kirill A. Shutemov @ 2018-11-30 11:57 ` Kirill A. Shutemov 1 sibling, 0 replies; 6+ messages in thread From: Kirill A. Shutemov @ 2018-11-30 11:57 UTC (permalink / raw) To: tglx, mingo, bp, hpa, dave.hansen, luto, peterz Cc: boris.ostrovsky, jgross, bhe, x86, linux-mm, linux-kernel, Kirill A. Shutemov The LDT remap placement has been changed. It's now placed before direct mapping in the kernel virtual address space for both paging modes. Change address markers order accordingly. Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Fixes: d52888aa2753 ("x86/mm: Move LDT remap out of KASLR region on 5-level paging") --- arch/x86/mm/dump_pagetables.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c index dad153e5a427..abcb8d00b014 100644 --- a/arch/x86/mm/dump_pagetables.c +++ b/arch/x86/mm/dump_pagetables.c @@ -55,10 +55,10 @@ struct addr_marker { enum address_markers_idx { USER_SPACE_NR = 0, KERNEL_SPACE_NR, - LOW_KERNEL_NR, -#if defined(CONFIG_MODIFY_LDT_SYSCALL) && defined(CONFIG_X86_5LEVEL) +#ifdef CONFIG_MODIFY_LDT_SYSCALL LDT_NR, #endif + LOW_KERNEL_NR, VMALLOC_START_NR, VMEMMAP_START_NR, #ifdef CONFIG_KASAN @@ -66,9 +66,6 @@ enum address_markers_idx { KASAN_SHADOW_END_NR, #endif CPU_ENTRY_AREA_NR, -#if defined(CONFIG_MODIFY_LDT_SYSCALL) && !defined(CONFIG_X86_5LEVEL) - LDT_NR, -#endif #ifdef CONFIG_X86_ESPFIX64 ESPFIX_START_NR, #endif -- 2.19.2 ^ permalink raw reply related [flat|nested] 6+ messages in thread
end of thread, other threads:[~2018-11-30 12:19 UTC | newest] Thread overview: 6+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2018-11-30 11:57 [PATCH 0/2] Fixups for LDT remap placement change Kirill A. Shutemov 2018-11-30 11:57 ` [PATCH 1/2] x86/mm: Fix guard hole handling Kirill A. Shutemov 2018-11-30 12:03 ` Juergen Gross 2018-11-30 12:11 ` Kirill A. Shutemov 2018-11-30 12:19 ` Juergen Gross 2018-11-30 11:57 ` [PATCH 2/2] x86/dump_pagetables: Fix LDT remap address marker Kirill A. Shutemov
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