powerpc: Don't ignore errors from set_memory_{n}p() in __kernel_map_pages()

set_memory_p() and set_memory_np() can fail.

As mentioned in linux/mm.h:

/*
 * To support DEBUG_PAGEALLOC architecture must ensure that
 * __kernel_map_pages() never fails
 */

So panic in case set_memory_p() or set_memory_np() fail
in __kernel_map_pages().

Link: KSPP#7
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20ef75884aa6a636e8298736f3d1056b0793d3d9.1708078640.git.christophe.leroy@csgroup.eu

Author: chleroy

arch/powerpc/mm/book3s64/hash_utils.c

@@ -2172,7 +2172,7 @@ static void kernel_unmap_linear_page(unsigned long vaddr, unsigned long lmi)
 				     mmu_kernel_ssize, 0);
 }
 
-void hash__kernel_map_pages(struct page *page, int numpages, int enable)
+int hash__kernel_map_pages(struct page *page, int numpages, int enable)
 {
 	unsigned long flags, vaddr, lmi;
 	int i;
@@ -2189,6 +2189,7 @@ void hash__kernel_map_pages(struct page *page, int numpages, int enable)
 			kernel_unmap_linear_page(vaddr, lmi);
 	}
 	local_irq_restore(flags);
+	return 0;
 }
 #endif /* CONFIG_DEBUG_PAGEALLOC || CONFIG_KFENCE */
 

arch/powerpc/mm/mmu_decl.h

@@ -187,4 +187,4 @@ int create_section_mapping(unsigned long start, unsigned long end,
 			   int nid, pgprot_t prot);
 #endif
 
-void hash__kernel_map_pages(struct page *page, int numpages, int enable);
+int hash__kernel_map_pages(struct page *page, int numpages, int enable);

arch/powerpc/mm/pageattr.c

@@ -107,17 +107,21 @@ int change_memory_attr(unsigned long addr, int numpages, long action)
 #ifdef CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC
 void __kernel_map_pages(struct page *page, int numpages, int enable)
 {
+	int err;
 	unsigned long addr = (unsigned long)page_address(page);
 
 	if (PageHighMem(page))
 		return;
 
 	if (IS_ENABLED(CONFIG_PPC_BOOK3S_64) && !radix_enabled())
-		hash__kernel_map_pages(page, numpages, enable);
+		err = hash__kernel_map_pages(page, numpages, enable);
 	else if (enable)
-		set_memory_p(addr, numpages);
+		err = set_memory_p(addr, numpages);
 	else
-		set_memory_np(addr, numpages);
+		err = set_memory_np(addr, numpages);
+
+	if (err)
+		panic("%s: changing memory protections failed\n", __func__);
 }
 #endif
 #endif