[PATCH v4 6/9] riscv: add ARCH_SUPPORTS_DEBUG_PAGEALLOC support

[Zong Li]

ARCH_SUPPORTS_DEBUG_PAGEALLOC provides a hook to map and unmap
pages for debugging purposes. Implement the __kernel_map_pages
functions to fill the poison pattern.

Signed-off-by: Zong Li <zong.li@xxxxxxxxxx>
Reviewed-by: Palmer Dabbelt <palmerdabbelt@xxxxxxxxxx>
---
 arch/riscv/Kconfig       |  3 +++
 arch/riscv/mm/pageattr.c | 13 +++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index a94d0f064d9c..1e1efc998baf 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -132,6 +132,9 @@ config ARCH_SELECT_MEMORY_MODEL
 config ARCH_WANT_GENERAL_HUGETLB
 	def_bool y
 
+config ARCH_SUPPORTS_DEBUG_PAGEALLOC
+	def_bool y
+
 config SYS_SUPPORTS_HUGETLBFS
 	def_bool y
 
diff --git a/arch/riscv/mm/pageattr.c b/arch/riscv/mm/pageattr.c
index 7be6cd67e2ef..728759eb530a 100644
--- a/arch/riscv/mm/pageattr.c
+++ b/arch/riscv/mm/pageattr.c
@@ -172,3 +172,16 @@ int set_direct_map_default_noflush(struct page *page)
 
 	return walk_page_range(&init_mm, start, end, &pageattr_ops, &masks);
 }
+
+void __kernel_map_pages(struct page *page, int numpages, int enable)
+{
+	if (!debug_pagealloc_enabled())
+		return;
+
+	if (enable)
+		__set_memory((unsigned long)page_address(page), numpages,
+			     __pgprot(_PAGE_PRESENT), __pgprot(0));
+	else
+		__set_memory((unsigned long)page_address(page), numpages,
+			     __pgprot(0), __pgprot(_PAGE_PRESENT));
+}
-- 
2.26.0