selftests/mm: use sys_pkey helpers consistently

sys_pkey_alloc, sys_pkey_free and sys_mprotect_pkey are currently used in
protections_keys.c, while pkey_sighandler_tests.c calls the libc wrappers
directly (e.g.  pkey_mprotect()).  This is probably ok when using glibc
(those symbols appeared a while ago), but Musl does not currently provide
them.  The logging in the helpers from pkey-helpers.h can also come in
handy.

Make things more consistent by using the sys_pkey helpers in
pkey_sighandler_tests.c too.  To that end their implementation is moved to
a common .c file (pkey_util.c).  This also enables calling
is_pkeys_supported() outside of protections_keys.c, since it relies on
sys_pkey_{alloc,free}.

[kevin.brodsky@arm.com: fix dependency on pkey_util.c]
  Link: https://lkml.kernel.org/r/20241216092849.2140850-1-kevin.brodsky@arm.com
Link: https://lkml.kernel.org/r/20241209095019.1732120-12-kevin.brodsky@arm.com
Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Aruna Ramakrishna <aruna.ramakrishna@oracle.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Joey Gouly <joey.gouly@arm.com>
Cc: Keith Lucas <keith.lucas@oracle.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

tools/testing/selftests/mm/Makefile

@@ -158,11 +158,15 @@ $(TEST_GEN_FILES): vm_util.c thp_settings.c
 
 $(OUTPUT)/uffd-stress: uffd-common.c
 $(OUTPUT)/uffd-unit-tests: uffd-common.c
+$(OUTPUT)/protection_keys: pkey_util.c
+$(OUTPUT)/pkey_sighandler_tests: pkey_util.c
 
 ifeq ($(ARCH),x86_64)
 BINARIES_32 := $(patsubst %,$(OUTPUT)/%,$(BINARIES_32))
 BINARIES_64 := $(patsubst %,$(OUTPUT)/%,$(BINARIES_64))
 
+$(BINARIES_32) $(BINARIES_64): pkey_util.c
+
 define gen-target-rule-32
 $(1) $(1)_32: $(OUTPUT)/$(1)_32
 .PHONY: $(1) $(1)_32

tools/testing/selftests/mm/pkey-helpers.h

@@ -89,6 +89,8 @@ extern void abort_hooks(void);
 
 int sys_pkey_alloc(unsigned long flags, unsigned long init_val);
 int sys_pkey_free(unsigned long pkey);
+int sys_mprotect_pkey(void *ptr, size_t size, unsigned long orig_prot,
+		unsigned long pkey);
 
 /* For functions called from protection_keys.c only */
 noinline int read_ptr(int *ptr);

tools/testing/selftests/mm/pkey_sighandler_tests.c

@@ -311,8 +311,8 @@ static void test_sigsegv_handler_with_different_pkey_for_stack(void)
 	__write_pkey_reg(pkey_reg);
 
 	/* Protect the new stack with MPK 1 */
-	pkey = pkey_alloc(0, 0);
+	pkey = sys_pkey_alloc(0, 0);
-	pkey_mprotect(stack, STACK_SIZE, PROT_READ | PROT_WRITE, pkey);
+	sys_mprotect_pkey(stack, STACK_SIZE, PROT_READ | PROT_WRITE, pkey);
 
 	/* Set up alternate signal stack that will use the default MPK */
 	sigstack.ss_sp = mmap(0, STACK_SIZE, PROT_READ | PROT_WRITE | PROT_EXEC,
@@ -484,8 +484,8 @@ static void test_pkru_sigreturn(void)
 	__write_pkey_reg(pkey_reg);
 
 	/* Protect the stack with MPK 2 */
-	pkey = pkey_alloc(0, 0);
+	pkey = sys_pkey_alloc(0, 0);
-	pkey_mprotect(stack, STACK_SIZE, PROT_READ | PROT_WRITE, pkey);
+	sys_mprotect_pkey(stack, STACK_SIZE, PROT_READ | PROT_WRITE, pkey);
 
 	/* Set up alternate signal stack that will use the default MPK */
 	sigstack.ss_sp = mmap(0, STACK_SIZE, PROT_READ | PROT_WRITE | PROT_EXEC,

tools/testing/selftests/mm/pkey_util.c

@@ -0,0 +1,40 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <sys/syscall.h>
+#include <unistd.h>
+
+#include "pkey-helpers.h"
+
+int sys_pkey_alloc(unsigned long flags, unsigned long init_val)
+{
+	int ret = syscall(SYS_pkey_alloc, flags, init_val);
+	dprintf1("%s(flags=%lx, init_val=%lx) syscall ret: %d errno: %d\n",
+			__func__, flags, init_val, ret, errno);
+	return ret;
+}
+
+int sys_pkey_free(unsigned long pkey)
+{
+	int ret = syscall(SYS_pkey_free, pkey);
+	dprintf1("%s(pkey=%ld) syscall ret: %d\n", __func__, pkey, ret);
+	return ret;
+}
+
+int sys_mprotect_pkey(void *ptr, size_t size, unsigned long orig_prot,
+		unsigned long pkey)
+{
+	int sret;
+
+	dprintf2("%s(0x%p, %zx, prot=%lx, pkey=%lx)\n", __func__,
+			ptr, size, orig_prot, pkey);
+
+	errno = 0;
+	sret = syscall(__NR_pkey_mprotect, ptr, size, orig_prot, pkey);
+	if (errno) {
+		dprintf2("SYS_mprotect_key sret: %d\n", sret);
+		dprintf2("SYS_mprotect_key prot: 0x%lx\n", orig_prot);
+		dprintf2("SYS_mprotect_key failed, errno: %d\n", errno);
+		if (DEBUG_LEVEL >= 2)
+			perror("SYS_mprotect_pkey");
+	}
+	return sret;
+}

tools/testing/selftests/mm/protection_keys.c

@@ -460,34 +460,6 @@ static pid_t fork_lazy_child(void)
 	return forkret;
 }
 
-int sys_mprotect_pkey(void *ptr, size_t size, unsigned long orig_prot,
-		unsigned long pkey)
-{
-	int sret;
-
-	dprintf2("%s(0x%p, %zx, prot=%lx, pkey=%lx)\n", __func__,
-			ptr, size, orig_prot, pkey);
-
-	errno = 0;
-	sret = syscall(__NR_pkey_mprotect, ptr, size, orig_prot, pkey);
-	if (errno) {
-		dprintf2("SYS_mprotect_key sret: %d\n", sret);
-		dprintf2("SYS_mprotect_key prot: 0x%lx\n", orig_prot);
-		dprintf2("SYS_mprotect_key failed, errno: %d\n", errno);
-		if (DEBUG_LEVEL >= 2)
-			perror("SYS_mprotect_pkey");
-	}
-	return sret;
-}
-
-int sys_pkey_alloc(unsigned long flags, unsigned long init_val)
-{
-	int ret = syscall(SYS_pkey_alloc, flags, init_val);
-	dprintf1("%s(flags=%lx, init_val=%lx) syscall ret: %d errno: %d\n",
-			__func__, flags, init_val, ret, errno);
-	return ret;
-}
-
 static int alloc_pkey(void)
 {
 	int ret;
@@ -534,13 +506,6 @@ static int alloc_pkey(void)
 	return ret;
 }
 
-int sys_pkey_free(unsigned long pkey)
-{
-	int ret = syscall(SYS_pkey_free, pkey);
-	dprintf1("%s(pkey=%ld) syscall ret: %d\n", __func__, pkey, ret);
-	return ret;
-}
-
 /*
  * I had a bug where pkey bits could be set by mprotect() but
  * not cleared.  This ensures we get lots of random bit sets