[PATCH 2/2] arm64: errata: Workaround possible Cortex-A715 [ESR|FAR]_ELx corruption
Anshuman Khandual
anshuman.khandual at arm.com
Wed Oct 26 19:39:15 PDT 2022
If a Cortex-A715 cpu sees a page mapping permissions change from executable
to non-executable, it may corrupt the ESR_ELx and FAR_ELx registers, on the
next instruction abort caused by permission fault.
Only user-space does executable to non-executable permission transition via
mprotect() system call which calls ptep_modify_prot_start() and ptep_modify
_prot_commit() helpers, while changing the page mapping. The platform code
can override these helpers via __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION.
Work around the problem via doing a break-before-make TLB invalidation, for
all executable user space mappings, that go through mprotect() system call.
This overrides ptep_modify_prot_start() and ptep_modify_prot_commit(), via
defining HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION on the platform thus giving
an opportunity to intercept user space exec mappings, and do the necessary
TLB invalidation. Similar interceptions are also implemented for HugeTLB.
Cc: Catalin Marinas <catalin.marinas at arm.com>
Cc: Will Deacon <will at kernel.org>
Cc: Jonathan Corbet <corbet at lwn.net>
Cc: Mark Rutland <mark.rutland at arm.com>
Cc: linux-arm-kernel at lists.infradead.org
Cc: linux-doc at vger.kernel.org
Cc: linux-kernel at vger.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual at arm.com>
---
Documentation/arm64/silicon-errata.rst | 2 ++
arch/arm64/Kconfig | 16 +++++++++++
arch/arm64/include/asm/hugetlb.h | 9 +++++++
arch/arm64/include/asm/pgtable.h | 24 +++++++++++++++++
arch/arm64/kernel/cpu_errata.c | 7 +++++
arch/arm64/mm/hugetlbpage.c | 37 ++++++++++++++++++++++++++
arch/arm64/tools/cpucaps | 1 +
7 files changed, 96 insertions(+)
diff --git a/Documentation/arm64/silicon-errata.rst b/Documentation/arm64/silicon-errata.rst
index 808ade4cc008..ec5f889d7681 100644
--- a/Documentation/arm64/silicon-errata.rst
+++ b/Documentation/arm64/silicon-errata.rst
@@ -120,6 +120,8 @@ stable kernels.
+----------------+-----------------+-----------------+-----------------------------+
| ARM | Cortex-A710 | #2224489 | ARM64_ERRATUM_2224489 |
+----------------+-----------------+-----------------+-----------------------------+
+| ARM | Cortex-A715 | #2645198 | ARM64_ERRATUM_2645198 |
++----------------+-----------------+-----------------+-----------------------------+
| ARM | Cortex-X2 | #2119858 | ARM64_ERRATUM_2119858 |
+----------------+-----------------+-----------------+-----------------------------+
| ARM | Cortex-X2 | #2224489 | ARM64_ERRATUM_2224489 |
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 505c8a1ccbe0..56c3381e9d94 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -964,6 +964,22 @@ config ARM64_ERRATUM_2457168
If unsure, say Y.
+config ARM64_ERRATUM_2645198
+ bool "Cortex-A715: 2645198: Workaround possible [ESR|FAR]_ELx corruption"
+ default y
+ help
+ This option adds the workaround for ARM Cortex-A715 erratum 2645198.
+
+ If a Cortex-A715 cpu sees a page mapping permissions change from executable
+ to non-executable, it may corrupt the ESR_ELx and FAR_ELx registers on the
+ next instruction abort caused by permission fault.
+
+ Only user-space does executable to non-executable permission transition via
+ mprotect() system call. Workaround the problem by doing a break-before-make
+ TLB invalidation, for all changes to executable user space mappings.
+
+ If unsure, say Y.
+
config CAVIUM_ERRATUM_22375
bool "Cavium erratum 22375, 24313"
default y
diff --git a/arch/arm64/include/asm/hugetlb.h b/arch/arm64/include/asm/hugetlb.h
index d20f5da2d76f..6a4a1ab8eb23 100644
--- a/arch/arm64/include/asm/hugetlb.h
+++ b/arch/arm64/include/asm/hugetlb.h
@@ -49,6 +49,15 @@ extern pte_t huge_ptep_get(pte_t *ptep);
void __init arm64_hugetlb_cma_reserve(void);
+#define huge_ptep_modify_prot_start huge_ptep_modify_prot_start
+extern pte_t huge_ptep_modify_prot_start(struct vm_area_struct *vma,
+ unsigned long addr, pte_t *ptep);
+
+#define huge_ptep_modify_prot_commit huge_ptep_modify_prot_commit
+extern void huge_ptep_modify_prot_commit(struct vm_area_struct *vma,
+ unsigned long addr, pte_t *ptep,
+ pte_t old_pte, pte_t new_pte);
+
#include <asm-generic/hugetlb.h>
#endif /* __ASM_HUGETLB_H */
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 71a1af42f0e8..c4c021277f20 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -1095,7 +1095,31 @@ static inline bool pud_sect_supported(void)
return PAGE_SIZE == SZ_4K;
}
+#define __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION
+static inline pte_t ptep_modify_prot_start(struct vm_area_struct *vma,
+ unsigned long addr,
+ pte_t *ptep)
+{
+ pte_t pte = ptep_get_and_clear(vma->vm_mm, addr, ptep);
+ if (IS_ENABLED(CONFIG_ARM64_WORKAROUND_2645198)) {
+ /*
+ * Break-before-make (BBM) is required for all user space mappings
+ * when the permission changes from executable to non-executable
+ * in cases where cpu is affected with errata #2645198.
+ */
+ if (pte_user_exec(pte) && cpus_have_const_cap(ARM64_WORKAROUND_2645198))
+ __flush_tlb_range(vma, addr, addr + PAGE_SIZE, PAGE_SIZE, false, 3);
+ }
+ return pte;
+}
+
+static inline void ptep_modify_prot_commit(struct vm_area_struct *vma,
+ unsigned long addr,
+ pte_t *ptep, pte_t old_pte, pte_t pte)
+{
+ __set_pte_at(vma->vm_mm, addr, ptep, pte);
+}
#endif /* !__ASSEMBLY__ */
#endif /* __ASM_PGTABLE_H */
diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index 89ac00084f38..307faa2b4395 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -661,6 +661,13 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
CAP_MIDR_RANGE_LIST(trbe_write_out_of_range_cpus),
},
#endif
+#ifdef CONFIG_ARM64_ERRATUM_2645198
+ {
+ .desc = "ARM erratum 2645198",
+ .capability = ARM64_WORKAROUND_2645198,
+ ERRATA_MIDR_ALL_VERSIONS(MIDR_CORTEX_A715)
+ },
+#endif
#ifdef CONFIG_ARM64_ERRATUM_2077057
{
.desc = "ARM erratum 2077057",
diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
index 35e9a468d13e..8cdcb3a34c27 100644
--- a/arch/arm64/mm/hugetlbpage.c
+++ b/arch/arm64/mm/hugetlbpage.c
@@ -559,3 +559,40 @@ bool __init arch_hugetlb_valid_size(unsigned long size)
{
return __hugetlb_valid_size(size);
}
+
+pte_t huge_ptep_modify_prot_start(struct vm_area_struct *vma,
+ unsigned long addr, pte_t *ptep)
+{
+ pte_t pte = huge_ptep_get_and_clear(vma->vm_mm, addr, ptep);
+
+ if (IS_ENABLED(CONFIG_ARM64_WORKAROUND_2645198)) {
+ /*
+ * Break-before-make (BBM) is required for all user space mappings
+ * when the permission changes from executable to non-executable
+ * in cases where cpu is affected with errata #2645198.
+ */
+ if (pte_user_exec(pte) && cpus_have_const_cap(ARM64_WORKAROUND_2645198)) {
+ size_t pgsize = page_size(pte_page(pte));
+ int level = 3;
+
+ if (pgsize == PUD_SIZE)
+ level = 1;
+ else if ((pgsize == PMD_SIZE) || (pgsize == CONT_PMD_SIZE))
+ level = 2;
+ else if (pgsize == CONT_PTE_SIZE)
+ level = 3;
+ else
+ pr_warn("%s: unrecognized huge page size 0x%lx\n",
+ __func__, pgsize);
+ __flush_tlb_range(vma, addr, addr + pgsize, pgsize, false, level);
+ }
+ }
+ return pte;
+}
+
+void huge_ptep_modify_prot_commit(struct vm_area_struct *vma,
+ unsigned long addr, pte_t *ptep,
+ pte_t old_pte, pte_t pte)
+{
+ set_huge_pte_at(vma->vm_mm, addr, ptep, pte);
+}
diff --git a/arch/arm64/tools/cpucaps b/arch/arm64/tools/cpucaps
index f1c0347ec31a..2274d836fcfe 100644
--- a/arch/arm64/tools/cpucaps
+++ b/arch/arm64/tools/cpucaps
@@ -70,6 +70,7 @@ WORKAROUND_2038923
WORKAROUND_2064142
WORKAROUND_2077057
WORKAROUND_2457168
+WORKAROUND_2645198
WORKAROUND_2658417
WORKAROUND_TRBE_OVERWRITE_FILL_MODE
WORKAROUND_TSB_FLUSH_FAILURE
--
2.25.1
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