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Subject[RFC PATCH] lib/ioremap: Avoid triggering BUG_ON when end is not PAGE_ALIGN
Date
Zhou reported a bug on Hisilicon arm64 D06 platform with 64KB page size:

[ 2.470908] kernel BUG at lib/ioremap.c:72!
[ 2.475079] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
[ 2.480551] Modules linked in:
[ 2.483594] CPU: 1 PID: 1 Comm: swapper/0 Not tainted 4.16.0-rc7-00062-g0b41260-dirty #23
[ 2.491756] Hardware name: Huawei D06/D06, BIOS Hisilicon D06 UEFI Nemo 2.0 RC0 - B120 03/23/2018
[ 2.500614] pstate: 80c00009 (Nzcv daif +PAN +UAO)
[ 2.505395] pc : ioremap_page_range+0x268/0x36c
[ 2.509912] lr : pci_remap_iospace+0xe4/0x100
[...]
[ 2.603733] Call trace:
[ 2.606168] ioremap_page_range+0x268/0x36c
[ 2.610337] pci_remap_iospace+0xe4/0x100
[ 2.614334] acpi_pci_probe_root_resources+0x1d4/0x214
[ 2.619460] pci_acpi_root_prepare_resources+0x18/0xa8
[ 2.624585] acpi_pci_root_create+0x98/0x214
[ 2.628843] pci_acpi_scan_root+0x124/0x20c
[ 2.633013] acpi_pci_root_add+0x224/0x494
[ 2.637096] acpi_bus_attach+0xf8/0x200
[ 2.640918] acpi_bus_attach+0x98/0x200
[ 2.644740] acpi_bus_attach+0x98/0x200
[ 2.648562] acpi_bus_scan+0x48/0x9c
[ 2.652125] acpi_scan_init+0x104/0x268
[ 2.655948] acpi_init+0x308/0x374
[ 2.659337] do_one_initcall+0x48/0x14c
[ 2.663160] kernel_init_freeable+0x19c/0x250
[ 2.667504] kernel_init+0x10/0x100
[ 2.670979] ret_from_fork+0x10/0x18

The cause is the size of PCI IO resource is 32KB, which is 4K aligned but
not 64KB aligned, so when do ioremap_pte_range(), its incoming end is not
PAGE_ALIGN on 64KB page size system, but ioremap_pte_range increase the
addr by PAGE_SIZE, which makes addr != end until trigger BUG_ON.

This patch introduces pte_addr_end(addr, end) to resolve this problem, just
as what pmd_addr_end do. When end is not PAGE_ALIGN, it will return end
instead of addr + PAGE_SIZE, therefore ioremap_pte_range() can break out
when real end is coming.

Reported-by: Zhou Wang <wangzhou1@hisilicon.com>
Tested-by: Xiaojun Tan <tanxiaojun@huawei.com>
Signed-off-by: Yisheng Xie <xieyisheng1@huawei.com>
---
include/asm-generic/pgtable.h | 7 +++++++
lib/ioremap.c | 5 ++++-
2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index bfbb44a..7d5ee84 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -478,6 +478,13 @@ static inline pgprot_t pgprot_modify(pgprot_t oldprot, pgprot_t newprot)
})
#endif

+#ifndef pte_addr_end
+#define pte_addr_end(addr, end) \
+({ unsigned long __boundary = ((addr) + PAGE_SIZE) & PAGE_MASK; \
+ (__boundary - 1 < (end) - 1) ? __boundary : (end); \
+})
+#endif
+
/*
* When walking page tables, we usually want to skip any p?d_none entries;
* and any p?d_bad entries - reporting the error before resetting to none.
diff --git a/lib/ioremap.c b/lib/ioremap.c
index 54e5bba..82c8502 100644
--- a/lib/ioremap.c
+++ b/lib/ioremap.c
@@ -63,16 +63,19 @@ static int ioremap_pte_range(pmd_t *pmd, unsigned long addr,
{
pte_t *pte;
u64 pfn;
+ unsigned long next;

pfn = phys_addr >> PAGE_SHIFT;
pte = pte_alloc_kernel(pmd, addr);
if (!pte)
return -ENOMEM;
do {
+ next = pte_addr_end(addr, end);
+
BUG_ON(!pte_none(*pte));
set_pte_at(&init_mm, addr, pte, pfn_pte(pfn, prot));
pfn++;
- } while (pte++, addr += PAGE_SIZE, addr != end);
+ } while (pte++, addr = next, addr != end);
return 0;
}

--
1.7.12.4
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