Merge tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/…

…git/arm64/linux

Pull arm64 fixes from Will Deacon:
 "It's all pretty minor but the main fix is sorting out how we deal with
  return values from 32-bit system calls as audit expects error codes to
  be sign-extended to 64 bits

  Summary:

   - Fix extension/truncation of return values from 32-bit system calls

   - Fix interaction between unwinding and tracing

   - Fix spurious toolchain warning emitted during make

   - Fix Kconfig help text for RANDOMIZE_MODULE_REGION_FULL"

* tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux:
  arm64: stacktrace: avoid tracing arch_stack_walk()
  arm64: stacktrace: fix comment
  arm64: fix the doc of RANDOMIZE_MODULE_REGION_FULL
  arm64: move warning about toolchains to archprepare
  arm64: fix compat syscall return truncation

arch/arm64/Kconfig

@@ -1800,19 +1800,22 @@ config RANDOMIZE_BASE
 	  If unsure, say N.
 
 config RANDOMIZE_MODULE_REGION_FULL
-	bool "Randomize the module region over a 4 GB range"
+	bool "Randomize the module region over a 2 GB range"
 	depends on RANDOMIZE_BASE
 	default y
 	help
-	  Randomizes the location of the module region inside a 4 GB window
+	  Randomizes the location of the module region inside a 2 GB window
 	  covering the core kernel. This way, it is less likely for modules
 	  to leak information about the location of core kernel data structures
 	  but it does imply that function calls between modules and the core
 	  kernel will need to be resolved via veneers in the module PLT.
 
 	  When this option is not set, the module region will be randomized over
 	  a limited range that contains the [_stext, _etext] interval of the
-	  core kernel, so branch relocations are always in range.
+	  core kernel, so branch relocations are almost always in range unless
+	  ARM64_MODULE_PLTS is enabled and the region is exhausted. In this
+	  particular case of region exhaustion, modules might be able to fall
+	  back to a larger 2GB area.
 
 config CC_HAVE_STACKPROTECTOR_SYSREG
 	def_bool $(cc-option,-mstack-protector-guard=sysreg -mstack-protector-guard-reg=sp_el0 -mstack-protector-guard-offset=0)

arch/arm64/Makefile

@@ -21,19 +21,11 @@ LDFLAGS_vmlinux		+= -shared -Bsymbolic -z notext \
 endif
 
 ifeq ($(CONFIG_ARM64_ERRATUM_843419),y)
-  ifneq ($(CONFIG_ARM64_LD_HAS_FIX_ERRATUM_843419),y)
-$(warning ld does not support --fix-cortex-a53-843419; kernel may be susceptible to erratum)
-  else
+  ifeq ($(CONFIG_ARM64_LD_HAS_FIX_ERRATUM_843419),y)
 LDFLAGS_vmlinux	+= --fix-cortex-a53-843419
   endif
 endif
 
-ifeq ($(CONFIG_ARM64_USE_LSE_ATOMICS), y)
-  ifneq ($(CONFIG_ARM64_LSE_ATOMICS), y)
-$(warning LSE atomics not supported by binutils)
-  endif
-endif
-
 cc_has_k_constraint := $(call try-run,echo				\
 	'int main(void) {						\
 		asm volatile("and w0, w0, %w0" :: "K" (4294967295));	\
@@ -176,6 +168,17 @@ vdso_install:
 
 archprepare:
 	$(Q)$(MAKE) $(build)=arch/arm64/tools kapi
+ifeq ($(CONFIG_ARM64_ERRATUM_843419),y)
+  ifneq ($(CONFIG_ARM64_LD_HAS_FIX_ERRATUM_843419),y)
+	@echo "warning: ld does not support --fix-cortex-a53-843419; kernel may be susceptible to erratum" >&2
+  endif
+endif
+ifeq ($(CONFIG_ARM64_USE_LSE_ATOMICS),y)
+  ifneq ($(CONFIG_ARM64_LSE_ATOMICS),y)
+	@echo "warning: LSE atomics not supported by binutils" >&2
+  endif
+endif
+
 
 # We use MRPROPER_FILES and CLEAN_FILES now
 archclean:

arch/arm64/include/asm/ptrace.h

@@ -320,7 +320,17 @@ static inline unsigned long kernel_stack_pointer(struct pt_regs *regs)
 
 static inline unsigned long regs_return_value(struct pt_regs *regs)
 {
-	return regs->regs[0];
+	unsigned long val = regs->regs[0];
+
+	/*
+	 * Audit currently uses regs_return_value() instead of
+	 * syscall_get_return_value(). Apply the same sign-extension here until
+	 * audit is updated to use syscall_get_return_value().
+	 */
+	if (compat_user_mode(regs))
+		val = sign_extend64(val, 31);
+
+	return val;
 }
 
 static inline void regs_set_return_value(struct pt_regs *regs, unsigned long rc)

arch/arm64/include/asm/stacktrace.h

@@ -35,7 +35,7 @@ struct stack_info {
  * accounting information necessary for robust unwinding.
  *
  * @fp:          The fp value in the frame record (or the real fp)
- * @pc:          The fp value in the frame record (or the real lr)
+ * @pc:          The lr value in the frame record (or the real lr)
  *
  * @stacks_done: Stacks which have been entirely unwound, for which it is no
  *               longer valid to unwind to.

arch/arm64/include/asm/syscall.h

@@ -29,22 +29,23 @@ static inline void syscall_rollback(struct task_struct *task,
 	regs->regs[0] = regs->orig_x0;
 }
 
-
-static inline long syscall_get_error(struct task_struct *task,
-				     struct pt_regs *regs)
+static inline long syscall_get_return_value(struct task_struct *task,
+					    struct pt_regs *regs)
 {
-	unsigned long error = regs->regs[0];
+	unsigned long val = regs->regs[0];
 
 	if (is_compat_thread(task_thread_info(task)))
-		error = sign_extend64(error, 31);
+		val = sign_extend64(val, 31);
 
-	return IS_ERR_VALUE(error) ? error : 0;
+	return val;
 }
 
-static inline long syscall_get_return_value(struct task_struct *task,
-					    struct pt_regs *regs)
+static inline long syscall_get_error(struct task_struct *task,
+				     struct pt_regs *regs)
 {
-	return regs->regs[0];
+	unsigned long error = syscall_get_return_value(task, regs);
+
+	return IS_ERR_VALUE(error) ? error : 0;
 }
 
 static inline void syscall_set_return_value(struct task_struct *task,

arch/arm64/kernel/kaslr.c

@@ -162,7 +162,9 @@ u64 __init kaslr_early_init(void)
 		 * a PAGE_SIZE multiple in the range [_etext - MODULES_VSIZE,
 		 * _stext) . This guarantees that the resulting region still
 		 * covers [_stext, _etext], and that all relative branches can
-		 * be resolved without veneers.
+		 * be resolved without veneers unless this region is exhausted
+		 * and we fall back to a larger 2GB window in module_alloc()
+		 * when ARM64_MODULE_PLTS is enabled.
 		 */
 		module_range = MODULES_VSIZE - (u64)(_etext - _stext);
 		module_alloc_base = (u64)_etext + offset - MODULES_VSIZE;

arch/arm64/kernel/ptrace.c

@@ -1862,7 +1862,7 @@ void syscall_trace_exit(struct pt_regs *regs)
 	audit_syscall_exit(regs);
 
 	if (flags & _TIF_SYSCALL_TRACEPOINT)
-		trace_sys_exit(regs, regs_return_value(regs));
+		trace_sys_exit(regs, syscall_get_return_value(current, regs));
 
 	if (flags & (_TIF_SYSCALL_TRACE | _TIF_SINGLESTEP))
 		tracehook_report_syscall(regs, PTRACE_SYSCALL_EXIT);

arch/arm64/kernel/signal.c

@@ -29,6 +29,7 @@
 #include <asm/unistd.h>
 #include <asm/fpsimd.h>
 #include <asm/ptrace.h>
+#include <asm/syscall.h>
 #include <asm/signal32.h>
 #include <asm/traps.h>
 #include <asm/vdso.h>
@@ -890,7 +891,7 @@ static void do_signal(struct pt_regs *regs)
 		     retval == -ERESTART_RESTARTBLOCK ||
 		     (retval == -ERESTARTSYS &&
 		      !(ksig.ka.sa.sa_flags & SA_RESTART)))) {
-			regs->regs[0] = -EINTR;
+			syscall_set_return_value(current, regs, -EINTR, 0);
 			regs->pc = continue_addr;
 		}
 

arch/arm64/kernel/stacktrace.c

@@ -218,7 +218,7 @@ void show_stack(struct task_struct *tsk, unsigned long *sp, const char *loglvl)
 
 #ifdef CONFIG_STACKTRACE
 
-noinline void arch_stack_walk(stack_trace_consume_fn consume_entry,
+noinline notrace void arch_stack_walk(stack_trace_consume_fn consume_entry,
 			      void *cookie, struct task_struct *task,
 			      struct pt_regs *regs)
 {

arch/arm64/kernel/syscall.c

@@ -54,10 +54,7 @@ static void invoke_syscall(struct pt_regs *regs, unsigned int scno,
 		ret = do_ni_syscall(regs, scno);
 	}
 
-	if (is_compat_task())
-		ret = lower_32_bits(ret);
-
-	regs->regs[0] = ret;
+	syscall_set_return_value(current, regs, 0, ret);
 
 	/*
 	 * Ultimately, this value will get limited by KSTACK_OFFSET_MAX(),
@@ -115,7 +112,7 @@ static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr,
 		 * syscall. do_notify_resume() will send a signal to userspace
 		 * before the syscall is restarted.
 		 */
-		regs->regs[0] = -ERESTARTNOINTR;
+		syscall_set_return_value(current, regs, -ERESTARTNOINTR, 0);
 		return;
 	}
 
@@ -136,7 +133,7 @@ static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr,
 		 * anyway.
 		 */
 		if (scno == NO_SYSCALL)
-			regs->regs[0] = -ENOSYS;
+			syscall_set_return_value(current, regs, -ENOSYS, 0);
 		scno = syscall_trace_enter(regs);
 		if (scno == NO_SYSCALL)
 			goto trace_exit;