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Subject[PATCH v4 9/9] riscv: add STRICT_KERNEL_RWX support
Date
The commit contains that make text section as non-writable, rodata
section as read-only, and data section as non-executable.

The init section should be changed to non-executable.

Signed-off-by: Zong Li <zong.li@sifive.com>
---
arch/riscv/Kconfig | 1 +
arch/riscv/include/asm/set_memory.h | 8 ++++++
arch/riscv/mm/init.c | 44 +++++++++++++++++++++++++++++
3 files changed, 53 insertions(+)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 1e1efc998baf..58b556167d59 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -61,6 +61,7 @@ config RISCV
select ARCH_HAS_GIGANTIC_PAGE
select ARCH_HAS_SET_DIRECT_MAP
select ARCH_HAS_SET_MEMORY
+ select ARCH_HAS_STRICT_KERNEL_RWX
select ARCH_WANT_HUGE_PMD_SHARE if 64BIT
select SPARSEMEM_STATIC if 32BIT
select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU
diff --git a/arch/riscv/include/asm/set_memory.h b/arch/riscv/include/asm/set_memory.h
index 4c5bae7ca01c..c38df4771c09 100644
--- a/arch/riscv/include/asm/set_memory.h
+++ b/arch/riscv/include/asm/set_memory.h
@@ -22,6 +22,14 @@ static inline int set_memory_x(unsigned long addr, int numpages) { return 0; }
static inline int set_memory_nx(unsigned long addr, int numpages) { return 0; }
#endif

+#ifdef CONFIG_STRICT_KERNEL_RWX
+void set_kernel_text_ro(void);
+void set_kernel_text_rw(void);
+#else
+static inline void set_kernel_text_ro(void) { }
+static inline void set_kernel_text_rw(void) { }
+#endif
+
int set_direct_map_invalid_noflush(struct page *page);
int set_direct_map_default_noflush(struct page *page);

diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index fab855963c73..b55be44ff9bd 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -12,6 +12,7 @@
#include <linux/sizes.h>
#include <linux/of_fdt.h>
#include <linux/libfdt.h>
+#include <linux/set_memory.h>

#include <asm/fixmap.h>
#include <asm/tlbflush.h>
@@ -477,6 +478,17 @@ static void __init setup_vm_final(void)
csr_write(CSR_SATP, PFN_DOWN(__pa_symbol(swapper_pg_dir)) | SATP_MODE);
local_flush_tlb_all();
}
+
+void free_initmem(void)
+{
+ unsigned long init_begin = (unsigned long)__init_begin;
+ unsigned long init_end = (unsigned long)__init_end;
+
+ /* Make the region as non-execuatble. */
+ set_memory_nx(init_begin, (init_end - init_begin) >> PAGE_SHIFT);
+ free_initmem_default(POISON_FREE_INITMEM);
+}
+
#else
asmlinkage void __init setup_vm(uintptr_t dtb_pa)
{
@@ -488,6 +500,38 @@ static inline void setup_vm_final(void)
}
#endif /* CONFIG_MMU */

+#ifdef CONFIG_STRICT_KERNEL_RWX
+void set_kernel_text_rw(void)
+{
+ unsigned long text_start = (unsigned long)_text;
+ unsigned long text_end = (unsigned long)_etext;
+
+ set_memory_rw(text_start, (text_end - text_start) >> PAGE_SHIFT);
+}
+
+void set_kernel_text_ro(void)
+{
+ unsigned long text_start = (unsigned long)_text;
+ unsigned long text_end = (unsigned long)_etext;
+
+ set_memory_ro(text_start, (text_end - text_start) >> PAGE_SHIFT);
+}
+
+void mark_rodata_ro(void)
+{
+ unsigned long text_start = (unsigned long)_text;
+ unsigned long text_end = (unsigned long)_etext;
+ unsigned long rodata_start = (unsigned long)__start_rodata;
+ unsigned long data_start = (unsigned long)_data;
+ unsigned long max_low = (unsigned long)(__va(PFN_PHYS(max_low_pfn)));
+
+ set_memory_ro(text_start, (text_end - text_start) >> PAGE_SHIFT);
+ set_memory_ro(rodata_start, (data_start - rodata_start) >> PAGE_SHIFT);
+ set_memory_nx(rodata_start, (data_start - rodata_start) >> PAGE_SHIFT);
+ set_memory_nx(data_start, (max_low - data_start) >> PAGE_SHIFT);
+}
+#endif
+
void __init paging_init(void)
{
setup_vm_final();
--
2.26.0
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