[PATCH RFC] arm64/vmalloc: use module region only for module_alloc() if CONFIG_RANDOMIZE_BASE is set

[Liu Shixin]

After I add a 10GB pmem device, I got the following error message when
insert module:

 insmod: vmalloc error: size 16384, vm_struct allocation failed,
 mode:0xcc0(GFP_KERNEL), nodemask=(null),cpuset=/,mems_allowed=0

If CONFIG_RANDOMIZE_BASE is set, the module region can be located in the
vmalloc region entirely. Although module_alloc() can fall back to a 2GB
window if ARM64_MODULE_PLTS is set, the module region is still easily
exhausted because the module region is located at bottom of vmalloc region
and the vmalloc region is allocated from bottom to top.

Skip module region if not calling from module_alloc().

Signed-off-by: Liu Shixin <liushixin2 at huawei.com>
---
 arch/arm64/include/asm/vmalloc.h | 26 ++++++++++++++++++++++++++
 include/linux/vmalloc.h          |  9 +++++++++
 mm/vmalloc.c                     |  4 ++++
 3 files changed, 39 insertions(+)

diff --git a/arch/arm64/include/asm/vmalloc.h b/arch/arm64/include/asm/vmalloc.h
index 38fafffe699f..4feff546b11b 100644
--- a/arch/arm64/include/asm/vmalloc.h
+++ b/arch/arm64/include/asm/vmalloc.h
@@ -31,4 +31,30 @@ static inline pgprot_t arch_vmap_pgprot_tagged(pgprot_t prot)
 	return pgprot_tagged(prot);
 }
 
+#ifdef CONFIG_RANDOMIZE_BASE
+extern u64 module_alloc_base;
+#define arch_vmap_skip_module_region arch_vmap_skip_module_region
+static inline void arch_vmap_skip_module_region(unsigned long *addr,
+						unsigned long vstart,
+						unsigned long size,
+						unsigned long align)
+{
+	u64 module_alloc_end = module_alloc_base + MODULES_VSIZE;
+
+	if (vstart == module_alloc_base)
+		return;
+
+	if (IS_ENABLED(CONFIG_KASAN_GENERIC) ||
+	    IS_ENABLED(CONFIG_KASAN_SW_TAGS))
+		/* don't exceed the static module region - see module_alloc() */
+		module_alloc_end = MODULES_END;
+
+	if ((module_alloc_base >= *addr + size) ||
+	    (module_alloc_end <= *addr))
+		return;
+
+	*addr = ALIGN(module_alloc_end, align);
+}
+#endif
+
 #endif /* _ASM_ARM64_VMALLOC_H */
diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
index 096d48aa3437..55ef97325b84 100644
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h
@@ -122,6 +122,15 @@ static inline pgprot_t arch_vmap_pgprot_tagged(pgprot_t prot)
 }
 #endif
 
+#ifndef arch_vmap_skip_module_region
+static inline void arch_vmap_skip_module_region(unsigned long *addr,
+						unsigned long vstart,
+						unsigned long size,
+						unsigned long align)
+{
+}
+#endif
+
 /*
  *	Highlevel APIs for driver use
  */
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index ca71de7c9d77..c840d673052e 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1236,6 +1236,8 @@ is_within_this_va(struct vmap_area *va, unsigned long size,
 	else
 		nva_start_addr = ALIGN(vstart, align);
 
+	arch_vmap_skip_module_region(&nva_start_addr, vstart, size, align);
+
 	/* Can be overflowed due to big size or alignment. */
 	if (nva_start_addr + size < nva_start_addr ||
 			nva_start_addr < vstart)
@@ -1523,6 +1525,8 @@ __alloc_vmap_area(struct rb_root *root, struct list_head *head,
 	else
 		nva_start_addr = ALIGN(vstart, align);
 
+	arch_vmap_skip_module_region(&nva_start_addr, vstart, size, align);
+
 	/* Check the "vend" restriction. */
 	if (nva_start_addr + size > vend)
 		return vend;
-- 
2.25.1