* [PATCH] powerpc/64s: Fix __pte_needs_flush() false positive warning
@ 2023-03-02 22:52 Benjamin Gray
2023-03-02 23:01 ` Benjamin Gray
0 siblings, 1 reply; 2+ messages in thread
From: Benjamin Gray @ 2023-03-02 22:52 UTC (permalink / raw)
To: linuxppc-dev; +Cc: Benjamin Gray, npiggin, ruscur
Userspace PROT_NONE ptes set _PAGE_PRIVILEGED, triggering a false
positive debug assertion that __pte_flags_need_flush() is not called
on a kernel mapping.
Detect when it is a userspace PROT_NONE page by checking the required
bits of PAGE_NONE are set, and none of the RWX bits are set.
pte_protnone() is insufficient here because it always returns 0 when
CONFIG_NUMA_BALANCING=n.
Reported-by: Russell Currey <ruscur@russell.cc>
Fixes: b11931e9adc1 ("powerpc/64s: add pte_needs_flush and huge_pmd_needs_flush")
Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
---
MRE (CONFIG_DEBUG_VM must be enabled):
int main(int argc, char **argv)
{
char *buf = mmap(NULL, getpagesize(), PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS, -1, 0);
buf[0] = '1';
mprotect(buf, getpagesize(), PROT_NONE);
return 0;
}
---
arch/powerpc/include/asm/book3s/64/tlbflush.h | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/include/asm/book3s/64/tlbflush.h b/arch/powerpc/include/asm/book3s/64/tlbflush.h
index 2bbc0fcce04a..68f25977fff7 100644
--- a/arch/powerpc/include/asm/book3s/64/tlbflush.h
+++ b/arch/powerpc/include/asm/book3s/64/tlbflush.h
@@ -2,6 +2,7 @@
#ifndef _ASM_POWERPC_BOOK3S_64_TLBFLUSH_H
#define _ASM_POWERPC_BOOK3S_64_TLBFLUSH_H
+#include "asm/book3s/64/pgtable.h"
#define MMU_NO_CONTEXT ~0UL
#include <linux/mm_types.h>
@@ -148,6 +149,11 @@ static inline void flush_tlb_fix_spurious_fault(struct vm_area_struct *vma,
*/
}
+static inline bool __pte_protnone(unsigned long pte)
+{
+ return (pte & (pgprot_val(PAGE_NONE) | _PAGE_RWX)) == pgprot_val(PAGE_NONE);
+}
+
static inline bool __pte_flags_need_flush(unsigned long oldval,
unsigned long newval)
{
@@ -164,8 +170,8 @@ static inline bool __pte_flags_need_flush(unsigned long oldval,
/*
* We do not expect kernel mappings or non-PTEs or not-present PTEs.
*/
- VM_WARN_ON_ONCE(oldval & _PAGE_PRIVILEGED);
- VM_WARN_ON_ONCE(newval & _PAGE_PRIVILEGED);
+ VM_WARN_ON_ONCE(!__pte_protnone(oldval) && oldval & _PAGE_PRIVILEGED);
+ VM_WARN_ON_ONCE(!__pte_protnone(newval) && newval & _PAGE_PRIVILEGED);
VM_WARN_ON_ONCE(!(oldval & _PAGE_PTE));
VM_WARN_ON_ONCE(!(newval & _PAGE_PTE));
VM_WARN_ON_ONCE(!(oldval & _PAGE_PRESENT));
base-commit: 90dbf76e470bc4b973052a8f26ea43bae30f9aec
--
2.39.2
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] powerpc/64s: Fix __pte_needs_flush() false positive warning
2023-03-02 22:52 [PATCH] powerpc/64s: Fix __pte_needs_flush() false positive warning Benjamin Gray
@ 2023-03-02 23:01 ` Benjamin Gray
0 siblings, 0 replies; 2+ messages in thread
From: Benjamin Gray @ 2023-03-02 23:01 UTC (permalink / raw)
To: linuxppc-dev; +Cc: npiggin, ruscur
Accidentally added a bad auto-import, V2 sent
https://patchwork.ozlabs.org/project/linuxppc-dev/patch/20230302225947.81083-1-bgray@linux.ibm.com/
^ permalink raw reply [flat|nested] 2+ messages in thread
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