| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <20250924-b4-asi-page-alloc-v1-4-2d861768041f@google.com>
Date: Wed, 24 Sep 2025 14:59:39 +0000
From: Brendan Jackman <jackmanb@...gle.com>
To: jackmanb@...gle.com, Andy Lutomirski <luto@...nel.org>,
Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, "Liam R. Howlett" <Liam.Howlett@...cle.com>,
Suren Baghdasaryan <surenb@...gle.com>, Michal Hocko <mhocko@...e.com>,
Johannes Weiner <hannes@...xchg.org>, Zi Yan <ziy@...dia.com>,
Axel Rasmussen <axelrasmussen@...gle.com>, Yuanchu Xie <yuanchu@...gle.com>,
Roman Gushchin <roman.gushchin@...ux.dev>
Cc: peterz@...radead.org, bp@...en8.de, dave.hansen@...ux.intel.com,
mingo@...hat.com, tglx@...utronix.de, akpm@...ux-foundation.org,
david@...hat.com, derkling@...gle.com, junaids@...gle.com,
linux-kernel@...r.kernel.org, linux-mm@...ck.org, reijiw@...gle.com,
rientjes@...gle.com, rppt@...nel.org, vbabka@...e.cz, x86@...nel.org,
yosry.ahmed@...ux.dev
Subject: [PATCH 04/21] x86/mm/asi: set up asi_nonsensitive_pgd
Create the initial shared pagetable to hold all the mappings that will
be shared among ASI domains.
Mirror the physmap into the ASI pagetables, but with a maximum
granularity that's guaranteed to allow changing pageblock sensitivity
without having to allocate pagetables, and with everything as
non-present.
Signed-off-by: Brendan Jackman <jackmanb@...gle.com>
---
arch/x86/include/asm/asi.h | 4 ++++
arch/x86/mm/asi.c | 19 +++++++++++++++++++
arch/x86/mm/init.c | 2 ++
arch/x86/mm/init_64.c | 25 +++++++++++++++++++++++--
include/linux/asi.h | 4 ++++
init/main.c | 1 +
6 files changed, 53 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/asi.h b/arch/x86/include/asm/asi.h
index 32a4c04c4be0f6f425c7cbcff4c58f1827a4b4c4..85062f2a23e127c736a92bb0d49e54f6fdcc2a5b 100644
--- a/arch/x86/include/asm/asi.h
+++ b/arch/x86/include/asm/asi.h
@@ -12,4 +12,8 @@ static inline bool asi_enabled_static(void)
return cpu_feature_enabled(X86_FEATURE_ASI);
}
+void asi_init(void);
+
+extern pgd_t *asi_nonsensitive_pgd;
+
#endif /* _ASM_X86_ASI_H */
diff --git a/arch/x86/mm/asi.c b/arch/x86/mm/asi.c
index 8c907f3c84f43f66e412ecbfa99e67390d31a66f..7225f6aec936eedf98cd263d791dd62263d62575 100644
--- a/arch/x86/mm/asi.c
+++ b/arch/x86/mm/asi.c
@@ -1,11 +1,20 @@
// SPDX-License-Identifier: GPL-2.0
#include <linux/asi.h>
#include <linux/init.h>
+#include <linux/memblock.h>
#include <linux/string.h>
#include <asm/cmdline.h>
#include <asm/cpufeature.h>
+#include "mm_internal.h"
+
+/*
+ * This is a bit like init_mm.pgd, it holds mappings shared among all ASI
+ * domains.
+ */
+pgd_t *asi_nonsensitive_pgd;
+
void __init asi_check_boottime_disable(void)
{
bool enabled = false;
@@ -26,3 +35,13 @@ void __init asi_check_boottime_disable(void)
if (enabled)
setup_force_cpu_cap(X86_FEATURE_ASI);
}
+
+void __init asi_init(void)
+{
+ if (!cpu_feature_enabled(X86_FEATURE_ASI))
+ return;
+
+ asi_nonsensitive_pgd = alloc_low_page();
+ if (WARN_ON(!asi_nonsensitive_pgd))
+ setup_clear_cpu_cap(X86_FEATURE_ASI);
+}
diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index b877a41fc291284eb271ebe764a52730d51da3fc..8fd34475af7ccd49d0124e13a87342d3bfef3e05 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -773,6 +773,8 @@ void __init init_mem_mapping(void)
end = max_low_pfn << PAGE_SHIFT;
#endif
+ asi_init();
+
/* the ISA range is always mapped regardless of memory holes */
init_memory_mapping(0, ISA_END_ADDRESS, PAGE_KERNEL);
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index e98e85cf15f42db669696ba8195d8fc633351b26..7e0471d46767c63ceade479ae0d1bf738f14904a 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -7,6 +7,7 @@
* Copyright (C) 2002,2003 Andi Kleen <ak@...e.de>
*/
+#include <linux/asi.h>
#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/kernel.h>
@@ -746,7 +747,8 @@ phys_pgd_init(pgd_t *pgd_page, unsigned long paddr_start, unsigned long paddr_en
{
unsigned long vaddr, vaddr_start, vaddr_end, vaddr_next, paddr_last;
- *pgd_changed = false;
+ if (pgd_changed)
+ *pgd_changed = false;
paddr_last = paddr_end;
vaddr = (unsigned long)__va(paddr_start);
@@ -780,7 +782,8 @@ phys_pgd_init(pgd_t *pgd_page, unsigned long paddr_start, unsigned long paddr_en
(pud_t *) p4d, init);
spin_unlock(&init_mm.page_table_lock);
- *pgd_changed = true;
+ if (pgd_changed)
+ *pgd_changed = true;
}
return paddr_last;
@@ -797,6 +800,24 @@ __kernel_physical_mapping_init(unsigned long paddr_start,
paddr_last = phys_pgd_init(init_mm.pgd, paddr_start, paddr_end, page_size_mask,
prot, init, &pgd_changed);
+
+ /*
+ * Set up ASI's unrestricted physmap. This needs to mapped at minimum 2M
+ * size so that regions can be mapped and unmapped at pageblock
+ * granularity without requiring allocations.
+ */
+ if (asi_nonsensitive_pgd) {
+ /*
+ * Since most memory is expected to end up sensitive, start with
+ * everything unmapped in this pagetable.
+ */
+ pgprot_t prot_np = __pgprot(pgprot_val(prot) & ~_PAGE_PRESENT);
+
+ VM_BUG_ON((PAGE_SHIFT + pageblock_order) < page_level_shift(PG_LEVEL_2M));
+ phys_pgd_init(asi_nonsensitive_pgd, paddr_start, paddr_end, 1 << PG_LEVEL_2M,
+ prot_np, init, NULL);
+ }
+
if (pgd_changed)
sync_global_pgds((unsigned long)__va(paddr_start),
(unsigned long)__va(paddr_end) - 1);
diff --git a/include/linux/asi.h b/include/linux/asi.h
index 1832feb1b14d63f05bbfa3f87dd07753338ed70b..cc4bc957274dbf92ce5bf6185a418d0a8d1b7748 100644
--- a/include/linux/asi.h
+++ b/include/linux/asi.h
@@ -11,5 +11,9 @@
static inline void asi_check_boottime_disable(void) { }
static inline bool asi_enabled_static(void) { return false; }
+#define asi_nonsensitive_pgd NULL
+
+static inline void asi_init(void) { };
+
#endif /* CONFIG_MITIGATION_ADDRESS_SPACE_ISOLATION */
#endif /* _INCLUDE_ASI_H */
diff --git a/init/main.c b/init/main.c
index 07a3116811c5d72cbab48410493b3d0f89d1f1b2..0ec230ba123613c89c4dfbede27e0441207b2f88 100644
--- a/init/main.c
+++ b/init/main.c
@@ -12,6 +12,7 @@
#define DEBUG /* Enable initcall_debug */
+#include <linux/asi.h>
#include <linux/types.h>
#include <linux/export.h>
#include <linux/extable.h>
--
2.50.1
Powered by blists - more mailing lists