powerpc/32: Set user/kernel boundary at TASK_SIZE instead of PAGE_OFFSET

User space stops at TASK_SIZE. At the moment, kernel space starts
at PAGE_OFFSET.

In order to use space between TASK_SIZE and PAGE_OFFSET for modules,
make TASK_SIZE the limit between user and kernel space.

Note that fault.c already considers TASK_SIZE as the boundary between
user and kernel space.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/b38b52cd8dabbb56fbd6f9219d6f3cdccbb43b44.1593428200.git.christophe.leroy@csgroup.eu

arch/powerpc/include/asm/page.h

@@ -255,8 +255,10 @@ static inline bool pfn_valid(unsigned long pfn)
  */
 #ifdef CONFIG_PPC_BOOK3E_64
 #define is_kernel_addr(x)	((x) >= 0x8000000000000000ul)
-#else
+#elif defined(CONFIG_PPC_BOOK3S_64)
 #define is_kernel_addr(x)	((x) >= PAGE_OFFSET)
+#else
+#define is_kernel_addr(x)	((x) >= TASK_SIZE)
 #endif
 
 #ifndef CONFIG_PPC_BOOK3S_64

arch/powerpc/mm/ptdump/ptdump.c

@@ -348,7 +348,11 @@ static void populate_markers(void)
 {
 	int i = 0;
 
+#ifdef CONFIG_PPC64
 	address_markers[i++].start_address = PAGE_OFFSET;
+#else
+	address_markers[i++].start_address = TASK_SIZE;
+#endif
 	address_markers[i++].start_address = VMALLOC_START;
 	address_markers[i++].start_address = VMALLOC_END;
 #ifdef CONFIG_PPC64
@@ -385,7 +389,7 @@ static int ptdump_show(struct seq_file *m, void *v)
 	struct pg_state st = {
 		.seq = m,
 		.marker = address_markers,
-		.start_address = PAGE_OFFSET,
+		.start_address = IS_ENABLED(CONFIG_PPC64) ? PAGE_OFFSET : TASK_SIZE,
 	};
 
 #ifdef CONFIG_PPC64
@@ -429,7 +433,7 @@ void ptdump_check_wx(void)
 		.seq = NULL,
 		.marker = address_markers,
 		.check_wx = true,
-		.start_address = PAGE_OFFSET,
+		.start_address = IS_ENABLED(CONFIG_PPC64) ? PAGE_OFFSET : TASK_SIZE,
 	};
 
 #ifdef CONFIG_PPC64