Fixmap on xtensa grows upwards, i.e. bigger fixmap entry index
corresponds to a higher virtual address. This was lost in highmem
generalization resulting in the following runtime warnings:
WARNING: CPU: 0 PID: 18 at mm/highmem.c:494 kunmap_local_indexed+0x45/0x54
Modules linked in:
CPU: 0 PID: 18 Comm: kworker/u2:0 Not tainted 5.10.0-rc3-next-20201113 #1
Call Trace:
__warn+0x8f/0xc8
warn_slowpath_fmt+0x35/0x70
kunmap_local_indexed+0x45/0x54
handle_mm_fault+0x325/0xbe0
__get_user_pages.part.61+0x131/0x22c
__get_user_pages+0x44/0x60
__get_user_pages_remote+0xe8/0x290
get_user_pages_remote+0x24/0x40
get_arg_page+0x50/0x78
copy_string_kernel+0x5c/0x120
kernel_execve+0x76/0xc8
call_usermodehelper_exec_async+0xc8/0x10c
ret_from_kernel_thread+0xc/0x18
Fix it by adding __ARCH_HAS_POSITIVE_FIXMAP macro and implementing
vaddr_in_fixmap and fixmap_pte primitives differently depending on
whether it is defined or not.
Cc: Thomas Gleixner <t...@linutronix.de>
Fixes: 629ed3f7dad2 ("xtensa/mm/highmem: Switch to generic kmap atomic")
Signed-off-by: Max Filippov <jcmvb...@gmail.com>
---
arch/xtensa/include/asm/fixmap.h | 2 ++
mm/highmem.c | 29 ++++++++++++++++++++++++-----
2 files changed, 26 insertions(+), 5 deletions(-)
diff --git a/arch/xtensa/include/asm/fixmap.h b/arch/xtensa/include/asm/fixmap.h
index 92049b61c351..66787b5f13d6 100644
--- a/arch/xtensa/include/asm/fixmap.h
+++ b/arch/xtensa/include/asm/fixmap.h
@@ -51,6 +51,8 @@ enum fixed_addresses {
#define __fix_to_virt(x) (FIXADDR_START + ((x) << PAGE_SHIFT))
#define __virt_to_fix(x) (((x) - FIXADDR_START) >> PAGE_SHIFT)
+#define __ARCH_HAS_POSITIVE_FIXMAP
+
#ifndef __ASSEMBLY__
/*
* 'index to address' translation. If anyone tries to use the idx
diff --git a/mm/highmem.c b/mm/highmem.c
index 54bd233846c9..af27ed8d6a97 100644
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -434,6 +434,26 @@ static inline void kmap_high_unmap_local(unsigned long
vaddr)
#endif
}
+static inline bool vaddr_in_fixmap(unsigned long addr)
+{
+#ifdef __ARCH_HAS_POSITIVE_FIXMAP
+ return addr <= __fix_to_virt(FIX_KMAP_END) &&
+ addr >= __fix_to_virt(FIX_KMAP_BEGIN);
+#else
+ return addr >= __fix_to_virt(FIX_KMAP_END) &&
+ addr <= __fix_to_virt(FIX_KMAP_BEGIN);
+#endif
+}
+
+static pte_t *fixmap_pte(pte_t *kmap_pte, int idx)
+{
+#ifdef __ARCH_HAS_POSITIVE_FIXMAP
+ return kmap_pte + idx;
+#else
+ return kmap_pte - idx;
+#endif
+}
+
static inline int kmap_local_calc_idx(int idx)
{
return idx + KM_MAX_IDX * smp_processor_id();
@@ -457,9 +477,9 @@ void *__kmap_local_pfn_prot(unsigned long pfn, pgprot_t
prot)
preempt_disable();
idx = arch_kmap_local_map_idx(kmap_local_idx_push(), pfn);
vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
- BUG_ON(!pte_none(*(kmap_pte - idx)));
+ BUG_ON(!pte_none(*(fixmap_pte(kmap_pte, idx))));
pteval = pfn_pte(pfn, prot);
- set_pte_at(&init_mm, vaddr, kmap_pte - idx, pteval);
+ set_pte_at(&init_mm, vaddr, fixmap_pte(kmap_pte, idx), pteval);
arch_kmap_local_post_map(vaddr, pteval);
preempt_enable();
@@ -489,8 +509,7 @@ void kunmap_local_indexed(void *vaddr)
pte_t *kmap_pte = kmap_get_pte();
int idx;
- if (addr < __fix_to_virt(FIX_KMAP_END) ||
- addr > __fix_to_virt(FIX_KMAP_BEGIN)) {
+ if (!vaddr_in_fixmap(addr)) {
WARN_ON_ONCE(addr < PAGE_OFFSET);
/* Handle mappings which were obtained by kmap_high_get() */
@@ -503,7 +522,7 @@ void kunmap_local_indexed(void *vaddr)
WARN_ON_ONCE(addr != __fix_to_virt(FIX_KMAP_BEGIN + idx));
arch_kmap_local_pre_unmap(addr);
- pte_clear(&init_mm, addr, kmap_pte - idx);
+ pte_clear(&init_mm, addr, fixmap_pte(kmap_pte, idx));
arch_kmap_local_post_unmap(addr);
kmap_local_idx_pop();
preempt_enable();
--
2.20.1
