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Message-ID: <cda2b44b55c96f9ac69fa92e68c01084ec9495c5.1640344012.git.christophe.leroy@csgroup.eu>
Date: Fri, 24 Dec 2021 11:07:40 +0000
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Paul Mackerras <paulus@...ba.org>,
Michael Ellerman <mpe@...erman.id.au>
CC: Christophe Leroy <christophe.leroy@...roup.eu>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
Maxime Bizon <mbizon@...ebox.fr>,
"stable@...r.kernel.org" <stable@...r.kernel.org>,
Russell Currey <ruscur@...sell.cc>
Subject: [PATCH v3 2/2] powerpc: Add set_memory_{p/np}() and remove
set_memory_attr()
set_memory_attr() was implemented by commit 4d1755b6a762 ("powerpc/mm:
implement set_memory_attr()") because the set_memory_xx() couldn't
be used at that time to modify memory "on the fly" as explained it
the commit.
But set_memory_attr() uses set_pte_at() which leads to warnings when
CONFIG_DEBUG_VM is selected, because set_pte_at() is unexpected for
updating existing page table entries.
The check could be bypassed by using __set_pte_at() instead,
as it was the case before commit c988cfd38e48 ("powerpc/32:
use set_memory_attr()") but since commit 9f7853d7609d ("powerpc/mm:
Fix set_memory_*() against concurrent accesses") it is now possible
to use set_memory_xx() functions to update page table entries
"on the fly" because the update is now atomic.
For DEBUG_PAGEALLOC we need to clear and set back _PAGE_PRESENT.
Add set_memory_np() and set_memory_p() for that.
Replace all uses of set_memory_attr() by the relevant set_memory_xx()
and remove set_memory_attr().
Reported-by: Maxime Bizon <mbizon@...ebox.fr>
Fixes: c988cfd38e48 ("powerpc/32: use set_memory_attr()")
Cc: stable@...r.kernel.org
Depends-on: 9f7853d7609d ("powerpc/mm: Fix set_memory_*() against concurrent accesses")
Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
Reviewed-by: Russell Currey <ruscur@...sell.cc>
Tested-by: Maxime Bizon <mbizon@...ebox.fr>
---
v3: Use _PAGE_PRESENT directly as all platforms have the bit
v2: Add comment to SET_MEMORY_P and SET_MEMORY_NP
---
arch/powerpc/include/asm/set_memory.h | 12 ++++++++-
arch/powerpc/mm/pageattr.c | 39 +++++----------------------
arch/powerpc/mm/pgtable_32.c | 24 ++++++++---------
3 files changed, 28 insertions(+), 47 deletions(-)
diff --git a/arch/powerpc/include/asm/set_memory.h b/arch/powerpc/include/asm/set_memory.h
index b040094f7920..7ebc807aa8cc 100644
--- a/arch/powerpc/include/asm/set_memory.h
+++ b/arch/powerpc/include/asm/set_memory.h
@@ -6,6 +6,8 @@
#define SET_MEMORY_RW 1
#define SET_MEMORY_NX 2
#define SET_MEMORY_X 3
+#define SET_MEMORY_NP 4 /* Set memory non present */
+#define SET_MEMORY_P 5 /* Set memory present */
int change_memory_attr(unsigned long addr, int numpages, long action);
@@ -29,6 +31,14 @@ static inline int set_memory_x(unsigned long addr, int numpages)
return change_memory_attr(addr, numpages, SET_MEMORY_X);
}
-int set_memory_attr(unsigned long addr, int numpages, pgprot_t prot);
+static inline int set_memory_np(unsigned long addr, int numpages)
+{
+ return change_memory_attr(addr, numpages, SET_MEMORY_NP);
+}
+
+static inline int set_memory_p(unsigned long addr, int numpages)
+{
+ return change_memory_attr(addr, numpages, SET_MEMORY_P);
+}
#endif
diff --git a/arch/powerpc/mm/pageattr.c b/arch/powerpc/mm/pageattr.c
index 8812454e70ff..85753e32a4de 100644
--- a/arch/powerpc/mm/pageattr.c
+++ b/arch/powerpc/mm/pageattr.c
@@ -46,6 +46,12 @@ static int change_page_attr(pte_t *ptep, unsigned long addr, void *data)
case SET_MEMORY_X:
pte_update_delta(ptep, addr, _PAGE_KERNEL_RO, _PAGE_KERNEL_ROX);
break;
+ case SET_MEMORY_NP:
+ pte_update(&init_mm, addr, ptep, _PAGE_PRESENT, 0, 0);
+ break;
+ case SET_MEMORY_P:
+ pte_update(&init_mm, addr, ptep, 0, _PAGE_PRESENT, 0);
+ break;
default:
WARN_ON_ONCE(1);
break;
@@ -90,36 +96,3 @@ int change_memory_attr(unsigned long addr, int numpages, long action)
return apply_to_existing_page_range(&init_mm, start, size,
change_page_attr, (void *)action);
}
-
-/*
- * Set the attributes of a page:
- *
- * This function is used by PPC32 at the end of init to set final kernel memory
- * protection. It includes changing the maping of the page it is executing from
- * and data pages it is using.
- */
-static int set_page_attr(pte_t *ptep, unsigned long addr, void *data)
-{
- pgprot_t prot = __pgprot((unsigned long)data);
-
- spin_lock(&init_mm.page_table_lock);
-
- set_pte_at(&init_mm, addr, ptep, pte_modify(*ptep, prot));
- flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
-
- spin_unlock(&init_mm.page_table_lock);
-
- return 0;
-}
-
-int set_memory_attr(unsigned long addr, int numpages, pgprot_t prot)
-{
- unsigned long start = ALIGN_DOWN(addr, PAGE_SIZE);
- unsigned long sz = numpages * PAGE_SIZE;
-
- if (numpages <= 0)
- return 0;
-
- return apply_to_existing_page_range(&init_mm, start, sz, set_page_attr,
- (void *)pgprot_val(prot));
-}
diff --git a/arch/powerpc/mm/pgtable_32.c b/arch/powerpc/mm/pgtable_32.c
index 906e4e4328b2..f71ededdc02a 100644
--- a/arch/powerpc/mm/pgtable_32.c
+++ b/arch/powerpc/mm/pgtable_32.c
@@ -135,10 +135,12 @@ void mark_initmem_nx(void)
unsigned long numpages = PFN_UP((unsigned long)_einittext) -
PFN_DOWN((unsigned long)_sinittext);
- if (v_block_mapped((unsigned long)_sinittext))
+ if (v_block_mapped((unsigned long)_sinittext)) {
mmu_mark_initmem_nx();
- else
- set_memory_attr((unsigned long)_sinittext, numpages, PAGE_KERNEL);
+ } else {
+ set_memory_nx((unsigned long)_sinittext, numpages);
+ set_memory_rw((unsigned long)_sinittext, numpages);
+ }
}
#ifdef CONFIG_STRICT_KERNEL_RWX
@@ -152,18 +154,14 @@ void mark_rodata_ro(void)
return;
}
- numpages = PFN_UP((unsigned long)_etext) -
- PFN_DOWN((unsigned long)_stext);
-
- set_memory_attr((unsigned long)_stext, numpages, PAGE_KERNEL_ROX);
/*
- * mark .rodata as read only. Use __init_begin rather than __end_rodata
- * to cover NOTES and EXCEPTION_TABLE.
+ * mark .text and .rodata as read only. Use __init_begin rather than
+ * __end_rodata to cover NOTES and EXCEPTION_TABLE.
*/
numpages = PFN_UP((unsigned long)__init_begin) -
- PFN_DOWN((unsigned long)__start_rodata);
+ PFN_DOWN((unsigned long)_stext);
- set_memory_attr((unsigned long)__start_rodata, numpages, PAGE_KERNEL_RO);
+ set_memory_ro((unsigned long)_stext, numpages);
// mark_initmem_nx() should have already run by now
ptdump_check_wx();
@@ -179,8 +177,8 @@ void __kernel_map_pages(struct page *page, int numpages, int enable)
return;
if (enable)
- set_memory_attr(addr, numpages, PAGE_KERNEL);
+ set_memory_p(addr, numpages);
else
- set_memory_attr(addr, numpages, __pgprot(0));
+ set_memory_np(addr, numpages);
}
#endif /* CONFIG_DEBUG_PAGEALLOC */
--
2.33.1
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