[PATCH 5.10 024/116] powerpc/fixmap: Fix VM debug warning on unmap

Greg Kroah-Hartman
2022-02-14T09:48:37Z

From: Christophe Leroy <christophe.leroy@csgroup.eu>

[ Upstream commit aec982603aa8cc0a21143681feb5f60ecc69d718 ]

Unmapping a fixmap entry is done by calling __set_fixmap()
with FIXMAP_PAGE_CLEAR as flags.

Today, powerpc __set_fixmap() calls map_kernel_page().

map_kernel_page() is not happy when called a second time
for the same page.

WARNING: CPU: 0 PID: 1 at arch/powerpc/mm/pgtable.c:194 set_pte_at+0xc/0x1e8
CPU: 0 PID: 1 Comm: swapper Not tainted 5.16.0-rc3-s3k-dev-01993-g350ff07feb7d-dirty #682
NIP: c0017cd4 LR: c00187f0 CTR: 00000010
REGS: e1011d50 TRAP: 0700 Not tainted (5.16.0-rc3-s3k-dev-01993-g350ff07feb7d-dirty)
MSR: 00029032 <EE,ME,IR,DR,RI> CR: 42000208 XER: 00000000

GPR00: c0165fec e1011e10 c14c0000 c0ee2550 ff800000 c0f3d000 00000000 c001686c
GPR08: 00001000 b00045a9 00000001 c0f58460 c0f50000 00000000 c0007e10 00000000
GPR16: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
GPR24: 00000000 00000000 c0ee2550 00000000 c0f57000 00000ff8 00000000 ff800000
NIP [c0017cd4] set_pte_at+0xc/0x1e8
LR [c00187f0] map_kernel_page+0x9c/0x100
Call Trace:
[e1011e10] [c0736c68] vsnprintf+0x358/0x6c8 (unreliable)
[e1011e30] [c0165fec] __set_fixmap+0x30/0x44
[e1011e40] [c0c13bdc] early_iounmap+0x11c/0x170
[e1011e70] [c0c06cb0] ioremap_legacy_serial_console+0x88/0xc0
[e1011e90] [c0c03634] do_one_initcall+0x80/0x178
[e1011ef0] [c0c0385c] kernel_init_freeable+0xb4/0x250
[e1011f20] [c0007e34] kernel_init+0x24/0x140
[e1011f30] [c0016268] ret_from_kernel_thread+0x5c/0x64
Instruction dump:
7fe3fb78 48019689 80010014 7c630034 83e1000c 5463d97e 7c0803a6 38210010
4e800020 81250000 712a0001 41820008 <0fe00000> 9421ffe0 93e1001c 48000030

Implement unmap_kernel_page() which clears an existing pte.

Reported-by: Maxime Bizon <mbizon@freebox.fr>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Tested-by: Maxime Bizon <mbizon@freebox.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/b0b752f6f6ecc60653e873f385c6f0dce4e9ab6a.1638789098.git.christophe.leroy@csgroup.eu
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/powerpc/include/asm/book3s/32/pgtable.h | 1 +
arch/powerpc/include/asm/book3s/64/pgtable.h | 2 ++
arch/powerpc/include/asm/fixmap.h | 6 ++++--
arch/powerpc/include/asm/nohash/32/pgtable.h | 1 +
arch/powerpc/include/asm/nohash/64/pgtable.h | 1 +
arch/powerpc/mm/pgtable.c | 9 +++++++++
6 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/32/pgtable.h b/arch/powerpc/include/asm/book3s/32/pgtable.h
index 523d3e6e24009..94c5c66231a8c 100644
--- a/arch/powerpc/include/asm/book3s/32/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/32/pgtable.h
@@ -142,6 +142,7 @@ static inline bool pte_user(pte_t pte)
#ifndef __ASSEMBLY__

int map_kernel_page(unsigned long va, phys_addr_t pa, pgprot_t prot);
+void unmap_kernel_page(unsigned long va);

#endif /* !__ASSEMBLY__ */

diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
index 4a3dca0271f1e..71e2c524f1eea 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
@@ -1054,6 +1054,8 @@ static inline int map_kernel_page(unsigned long ea, unsigned long pa, pgprot_t p
return hash__map_kernel_page(ea, pa, prot);
}

+void unmap_kernel_page(unsigned long va);
+
static inline int __meminit vmemmap_create_mapping(unsigned long start,
unsigned long page_size,
unsigned long phys)
diff --git a/arch/powerpc/include/asm/fixmap.h b/arch/powerpc/include/asm/fixmap.h
index 591b2f4deed53..897cc68758d44 100644
--- a/arch/powerpc/include/asm/fixmap.h
+++ b/arch/powerpc/include/asm/fixmap.h
@@ -111,8 +111,10 @@ static inline void __set_fixmap(enum fixed_addresses idx,
BUILD_BUG_ON(idx >= __end_of_fixed_addresses);
else if (WARN_ON(idx >= __end_of_fixed_addresses))
return;
-
- map_kernel_page(__fix_to_virt(idx), phys, flags);
+ if (pgprot_val(flags))
+ map_kernel_page(__fix_to_virt(idx), phys, flags);
+ else
+ unmap_kernel_page(__fix_to_virt(idx));
}

#define __early_set_fixmap __set_fixmap
diff --git a/arch/powerpc/include/asm/nohash/32/pgtable.h b/arch/powerpc/include/asm/nohash/32/pgtable.h
index 96522f7f0618a..e53cc07e6b9ec 100644
--- a/arch/powerpc/include/asm/nohash/32/pgtable.h
+++ b/arch/powerpc/include/asm/nohash/32/pgtable.h
@@ -65,6 +65,7 @@ extern int icache_44x_need_flush;
#ifndef __ASSEMBLY__

int map_kernel_page(unsigned long va, phys_addr_t pa, pgprot_t prot);
+void unmap_kernel_page(unsigned long va);

#endif /* !__ASSEMBLY__ */

diff --git a/arch/powerpc/include/asm/nohash/64/pgtable.h b/arch/powerpc/include/asm/nohash/64/pgtable.h
index 57cd3892bfe05..1eacff0fff029 100644
--- a/arch/powerpc/include/asm/nohash/64/pgtable.h
+++ b/arch/powerpc/include/asm/nohash/64/pgtable.h
@@ -311,6 +311,7 @@ static inline void __ptep_set_access_flags(struct vm_area_struct *vma,
#define __swp_entry_to_pte(x) __pte((x).val)

int map_kernel_page(unsigned long ea, unsigned long pa, pgprot_t prot);
+void unmap_kernel_page(unsigned long va);
extern int __meminit vmemmap_create_mapping(unsigned long start,
unsigned long page_size,
unsigned long phys);
diff --git a/arch/powerpc/mm/pgtable.c b/arch/powerpc/mm/pgtable.c
index 15555c95cebc7..faaf33e204de1 100644
--- a/arch/powerpc/mm/pgtable.c
+++ b/arch/powerpc/mm/pgtable.c
@@ -194,6 +194,15 @@ void set_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep,
__set_pte_at(mm, addr, ptep, pte, 0);
}

+void unmap_kernel_page(unsigned long va)
+{
+ pmd_t *pmdp = pmd_off_k(va);
+ pte_t *ptep = pte_offset_kernel(pmdp, va);
+
+ pte_clear(&init_mm, va, ptep);
+ flush_tlb_kernel_range(va, va + PAGE_SIZE);
+}
+
/*
* This is called when relaxing access to a PTE. It's also called in the page
* fault path when we don't hit any of the major fault cases, ie, a minor
--
2.34.1