powerpc: extend execmem_params for kprobes allocations

powerpc overrides kprobes::alloc_insn_page() to remove writable
permissions when STRICT_MODULE_RWX is on.

Add definition of EXECMEM_KRPOBES to execmem_params to allow using the
generic kprobes::alloc_insn_page() with the desired permissions.

As powerpc uses breakpoint instructions to inject kprobes, it does not
need to constrain kprobe allocations to the modules area and can use the
entire vmalloc address space.

Signed-off-by: Mike Rapoport (IBM) <rppt@kernel.org>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>

Author: rppt

arch/powerpc/kernel/kprobes.c

@@ -126,26 +126,6 @@ kprobe_opcode_t *arch_adjust_kprobe_addr(unsigned long addr, unsigned long offse
 	return (kprobe_opcode_t *)(addr + offset);
 }
 
-void *alloc_insn_page(void)
-{
-	void *page;
-
-	page = execmem_alloc(EXECMEM_KPROBES, PAGE_SIZE);
-	if (!page)
-		return NULL;
-
-	if (strict_module_rwx_enabled()) {
-		int err = set_memory_rox((unsigned long)page, 1);
-
-		if (err)
-			goto error;
-	}
-	return page;
-error:
-	execmem_free(page);
-	return NULL;
-}
-
 int arch_prepare_kprobe(struct kprobe *p)
 {
 	int ret = 0;

arch/powerpc/kernel/module.c

@@ -94,6 +94,7 @@ static struct execmem_info execmem_info __ro_after_init;
 
 struct execmem_info __init *execmem_arch_setup(void)
 {
+	pgprot_t kprobes_prot = strict_module_rwx_enabled() ? PAGE_KERNEL_ROX : PAGE_KERNEL_EXEC;
 	pgprot_t prot = strict_module_rwx_enabled() ? PAGE_KERNEL : PAGE_KERNEL_EXEC;
 	unsigned long fallback_start = 0, fallback_end = 0;
 	unsigned long start, end;
@@ -132,6 +133,12 @@ struct execmem_info __init *execmem_arch_setup(void)
 				.fallback_start	= fallback_start,
 				.fallback_end	= fallback_end,
 			},
+			[EXECMEM_KPROBES] = {
+				.start	= VMALLOC_START,
+				.end	= VMALLOC_END,
+				.pgprot	= kprobes_prot,
+				.alignment = 1,
+			},
 			[EXECMEM_MODULE_DATA] = {
 				.start	= VMALLOC_START,
 				.end	= VMALLOC_END,