Xtensa updates for v5.9:

- add syscall audit support
 - add seccomp filter support
 - clean up make rules under arch/xtensa/boot
 - fix state management for exclusive access opcodes
 - fix build with PMU enabled
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Merge tag 'xtensa-20200805' of git://github.com/jcmvbkbc/linux-xtensa

Pull Xtensa updates from Max Filippov:

 - add syscall audit support

 - add seccomp filter support

 - clean up make rules under arch/xtensa/boot

 - fix state management for exclusive access opcodes

 - fix build with PMU enabled

* tag 'xtensa-20200805' of git://github.com/jcmvbkbc/linux-xtensa:
  xtensa: add missing exclusive access state management
  xtensa: fix xtensa_pmu_setup prototype
  xtensa: add boot subdirectories build artifacts to 'targets'
  xtensa: add uImage and xipImage to targets
  xtensa: move vmlinux.bin[.gz] to boot subdirectory
  xtensa: initialize_mmu.h: fix a duplicated word
  selftests/seccomp: add xtensa support
  xtensa: add seccomp support
  xtensa: expose syscall through user_pt_regs
  xtensa: add audit support

Documentation/features/seccomp/seccomp-filter/arch-support.txt

@@ -29,5 +29,5 @@
     |       sparc: | TODO |
     |          um: |  ok  |
     |         x86: |  ok  |
-    |      xtensa: | TODO |
+    |      xtensa: |  ok  |
     -----------------------

arch/xtensa/Kconfig

@@ -21,8 +21,10 @@ config XTENSA
 	select GENERIC_PCI_IOMAP
 	select GENERIC_SCHED_CLOCK
 	select GENERIC_STRNCPY_FROM_USER if KASAN
+	select HAVE_ARCH_AUDITSYSCALL
 	select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL
 	select HAVE_ARCH_KASAN if MMU && !XIP_KERNEL
+	select HAVE_ARCH_SECCOMP_FILTER
 	select HAVE_ARCH_TRACEHOOK
 	select HAVE_DEBUG_KMEMLEAK
 	select HAVE_DMA_CONTIGUOUS
@@ -215,6 +217,20 @@ config HOTPLUG_CPU
 
 	  Say N if you want to disable CPU hotplug.
 
+config SECCOMP
+	bool
+	prompt "Enable seccomp to safely compute untrusted bytecode"
+	help
+	  This kernel feature is useful for number crunching applications
+	  that may need to compute untrusted bytecode during their
+	  execution. By using pipes or other transports made available to
+	  the process as file descriptors supporting the read/write
+	  syscalls, it's possible to isolate those applications in
+	  their own address space using seccomp. Once seccomp is
+	  enabled via prctl(PR_SET_SECCOMP), it cannot be disabled
+	  and the task is only allowed to execute a few safe syscalls
+	  defined by each seccomp mode.
+
 config FAST_SYSCALL_XTENSA
 	bool "Enable fast atomic syscalls"
 	default n

arch/xtensa/boot/Makefile

@@ -17,6 +17,8 @@ BIG_ENDIAN	:= $(shell echo __XTENSA_EB__ | $(CC) -E - | grep -v "\#")
 export BIG_ENDIAN
 
 subdir-y	:= lib
+targets		+= vmlinux.bin vmlinux.bin.gz
+targets		+= uImage xipImage
 
 # Subdirs for the boot loader(s)
 
@@ -35,19 +37,19 @@ boot-elf boot-redboot: $(addprefix $(obj)/,$(subdir-y))
 
 OBJCOPYFLAGS = --strip-all -R .comment -R .notes -O binary
 
-vmlinux.bin: vmlinux FORCE
+$(obj)/vmlinux.bin: vmlinux FORCE
 	$(call if_changed,objcopy)
 
-vmlinux.bin.gz: vmlinux.bin FORCE
+$(obj)/vmlinux.bin.gz: $(obj)/vmlinux.bin FORCE
 	$(call if_changed,gzip)
 
-boot-elf: vmlinux.bin
-boot-redboot: vmlinux.bin.gz
+boot-elf: $(obj)/vmlinux.bin
+boot-redboot: $(obj)/vmlinux.bin.gz
 
 UIMAGE_LOADADDR = $(CONFIG_KERNEL_LOAD_ADDRESS)
 UIMAGE_COMPRESSION = gzip
 
-$(obj)/uImage: vmlinux.bin.gz FORCE
+$(obj)/uImage: $(obj)/vmlinux.bin.gz FORCE
 	$(call if_changed,uimage)
 	$(Q)$(kecho) '  Kernel: $@ is ready'
 

arch/xtensa/boot/boot-elf/Makefile

@@ -15,12 +15,13 @@ export CPPFLAGS_boot.lds += -P -C
 export KBUILD_AFLAGS += -mtext-section-literals
 
 boot-y		:= bootstrap.o
+targets		+= $(boot-y) boot.lds
 
 OBJS		:= $(addprefix $(obj)/,$(boot-y))
 
-$(obj)/Image.o: vmlinux.bin $(OBJS)
+$(obj)/Image.o: $(obj)/../vmlinux.bin $(OBJS)
 	$(Q)$(OBJCOPY) $(OBJCOPY_ARGS) -R .comment \
-		--add-section image=vmlinux.bin \
+		--add-section image=$< \
 		--set-section-flags image=contents,alloc,load,load,data \
 		$(OBJS) $@
 

arch/xtensa/boot/boot-redboot/Makefile

@@ -13,15 +13,16 @@ endif
 LD_ARGS	= -T $(srctree)/$(obj)/boot.ld
 
 boot-y	:= bootstrap.o
+targets	+= $(boot-y)
 
 OBJS	:= $(addprefix $(obj)/,$(boot-y))
 LIBS	:= arch/xtensa/boot/lib/lib.a arch/xtensa/lib/lib.a
 
 LIBGCC := $(shell $(CC) $(KBUILD_CFLAGS) -print-libgcc-file-name)
 
-$(obj)/zImage.o: vmlinux.bin.gz $(OBJS)
+$(obj)/zImage.o: $(obj)/../vmlinux.bin.gz $(OBJS)
 	$(Q)$(OBJCOPY) $(OBJCOPY_ARGS) -R .comment \
-		--add-section image=vmlinux.bin.gz \
+		--add-section image=$< \
 		--set-section-flags image=contents,alloc,load,load,data \
 		$(OBJS) $@
 

arch/xtensa/include/asm/Kbuild

@@ -7,4 +7,5 @@ generic-y += mcs_spinlock.h
 generic-y += param.h
 generic-y += qrwlock.h
 generic-y += qspinlock.h
+generic-y += seccomp.h
 generic-y += user.h

arch/xtensa/include/asm/initialize_mmu.h

@@ -6,7 +6,7 @@
  *      For the new V3 MMU we remap the TLB from virtual == physical
  *      to the standard Linux mapping used in earlier MMU's.
  *
- *      The the MMU we also support a new configuration register that
+ *      For the MMU we also support a new configuration register that
  *      specifies how the S32C1I instruction operates with the cache
  *      controller.
  *

arch/xtensa/include/asm/thread_info.h

@@ -55,6 +55,10 @@ struct thread_info {
 	mm_segment_t		addr_limit;	/* thread address space */
 
 	unsigned long		cpenable;
+#if XCHAL_HAVE_EXCLUSIVE
+	/* result of the most recent exclusive store */
+	unsigned long		atomctl8;
+#endif
 
 	/* Allocate storage for extra user states and coprocessor states. */
 #if XTENSA_HAVE_COPROCESSORS
@@ -111,15 +115,20 @@ static inline struct thread_info *current_thread_info(void)
 #define TIF_RESTORE_SIGMASK	6	/* restore signal mask in do_signal() */
 #define TIF_NOTIFY_RESUME	7	/* callback before returning to user */
 #define TIF_DB_DISABLED		8	/* debug trap disabled for syscall */
+#define TIF_SYSCALL_AUDIT	9	/* syscall auditing active */
+#define TIF_SECCOMP		10	/* secure computing */
 
 #define _TIF_SYSCALL_TRACE	(1<<TIF_SYSCALL_TRACE)
 #define _TIF_SIGPENDING		(1<<TIF_SIGPENDING)
 #define _TIF_NEED_RESCHED	(1<<TIF_NEED_RESCHED)
 #define _TIF_SINGLESTEP		(1<<TIF_SINGLESTEP)
 #define _TIF_SYSCALL_TRACEPOINT	(1<<TIF_SYSCALL_TRACEPOINT)
+#define _TIF_SYSCALL_AUDIT	(1<<TIF_SYSCALL_AUDIT)
+#define _TIF_SECCOMP		(1<<TIF_SECCOMP)
 
 #define _TIF_WORK_MASK		(_TIF_SYSCALL_TRACE | _TIF_SINGLESTEP | \
-				 _TIF_SYSCALL_TRACEPOINT)
+				 _TIF_SYSCALL_TRACEPOINT | \
+				 _TIF_SYSCALL_AUDIT | _TIF_SECCOMP)
 
 #define THREAD_SIZE KERNEL_STACK_SIZE
 #define THREAD_SIZE_ORDER (KERNEL_STACK_SHIFT - PAGE_SHIFT)

arch/xtensa/include/uapi/asm/ptrace.h

@@ -50,7 +50,8 @@ struct user_pt_regs {
 	__u32 windowstart;
 	__u32 windowbase;
 	__u32 threadptr;
-	__u32 reserved[7 + 48];
+	__u32 syscall;
+	__u32 reserved[6 + 48];
 	__u32 a[64];
 };
 

arch/xtensa/kernel/asm-offsets.c

@@ -93,6 +93,9 @@ int main(void)
 	DEFINE(THREAD_RA, offsetof (struct task_struct, thread.ra));
 	DEFINE(THREAD_SP, offsetof (struct task_struct, thread.sp));
 	DEFINE(THREAD_CPENABLE, offsetof (struct thread_info, cpenable));
+#if XCHAL_HAVE_EXCLUSIVE
+	DEFINE(THREAD_ATOMCTL8, offsetof (struct thread_info, atomctl8));
+#endif
 #if XTENSA_HAVE_COPROCESSORS
 	DEFINE(THREAD_XTREGS_CP0, offsetof(struct thread_info, xtregs_cp.cp0));
 	DEFINE(THREAD_XTREGS_CP1, offsetof(struct thread_info, xtregs_cp.cp1));

arch/xtensa/kernel/entry.S

@@ -374,6 +374,11 @@ common_exception:
 	s32i	a2, a1, PT_LCOUNT
 #endif
 
+#if XCHAL_HAVE_EXCLUSIVE
+	/* Clear exclusive access monitor set by interrupted code */
+	clrex
+#endif
+
 	/* It is now save to restore the EXC_TABLE_FIXUP variable. */
 
 	rsr	a2, exccause
@@ -2020,6 +2025,12 @@ ENTRY(_switch_to)
 	s32i	a3, a4, THREAD_CPENABLE
 #endif
 
+#if XCHAL_HAVE_EXCLUSIVE
+	l32i	a3, a5, THREAD_ATOMCTL8
+	getex	a3
+	s32i	a3, a4, THREAD_ATOMCTL8
+#endif
+
 	/* Flush register file. */
 
 	spill_registers_kernel

arch/xtensa/kernel/perf_event.c

@@ -399,7 +399,7 @@ static struct pmu xtensa_pmu = {
 	.read = xtensa_pmu_read,
 };
 
-static int xtensa_pmu_setup(int cpu)
+static int xtensa_pmu_setup(unsigned int cpu)
 {
 	unsigned i;
 

arch/xtensa/kernel/ptrace.c

@@ -12,6 +12,7 @@
  * Marc Gauthier<marc@tensilica.com> <marc@alumni.uwaterloo.ca>
  */
 
+#include <linux/audit.h>
 #include <linux/errno.h>
 #include <linux/hw_breakpoint.h>
 #include <linux/kernel.h>
@@ -21,6 +22,7 @@
 #include <linux/regset.h>
 #include <linux/sched.h>
 #include <linux/sched/task_stack.h>
+#include <linux/seccomp.h>
 #include <linux/security.h>
 #include <linux/signal.h>
 #include <linux/smp.h>
@@ -51,6 +53,7 @@ static int gpr_get(struct task_struct *target,
 		.threadptr = regs->threadptr,
 		.windowbase = regs->windowbase,
 		.windowstart = regs->windowstart,
+		.syscall = regs->syscall,
 	};
 
 	memcpy(newregs.a,
@@ -90,6 +93,9 @@ static int gpr_set(struct task_struct *target,
 	regs->sar = newregs.sar;
 	regs->threadptr = newregs.threadptr;
 
+	if (newregs.syscall)
+		regs->syscall = newregs.syscall;
+
 	if (newregs.windowbase != regs->windowbase ||
 	    newregs.windowstart != regs->windowstart) {
 		u32 rotws, wmask;
@@ -554,7 +560,8 @@ int do_syscall_trace_enter(struct pt_regs *regs)
 		return 0;
 	}
 
-	if (regs->syscall == NO_SYSCALL) {
+	if (regs->syscall == NO_SYSCALL ||
+	    secure_computing() == -1) {
 		do_syscall_trace_leave(regs);
 		return 0;
 	}
@@ -562,6 +569,9 @@ int do_syscall_trace_enter(struct pt_regs *regs)
 	if (test_thread_flag(TIF_SYSCALL_TRACEPOINT))
 		trace_sys_enter(regs, syscall_get_nr(current, regs));
 
+	audit_syscall_entry(regs->syscall, regs->areg[6],
+			    regs->areg[3], regs->areg[4],
+			    regs->areg[5]);
 	return 1;
 }
 
@@ -569,6 +579,8 @@ void do_syscall_trace_leave(struct pt_regs *regs)
 {
 	int step;
 
+	audit_syscall_exit(regs);
+
 	if (test_thread_flag(TIF_SYSCALL_TRACEPOINT))
 		trace_sys_exit(regs, regs_return_value(regs));
 

tools/testing/selftests/seccomp/seccomp_bpf.c

@@ -129,6 +129,8 @@ struct seccomp_data {
 #  define __NR_seccomp 358
 # elif defined(__s390__)
 #  define __NR_seccomp 348
+# elif defined(__xtensa__)
+#  define __NR_seccomp 337
 # else
 #  warning "seccomp syscall number unknown for this architecture"
 #  define __NR_seccomp 0xffff
@@ -1699,6 +1701,14 @@ TEST_F(TRACE_poke, getpid_runs_normally)
 # define SYSCALL_SYSCALL_NUM regs[4]
 # define SYSCALL_RET	regs[2]
 # define SYSCALL_NUM_RET_SHARE_REG
+#elif defined(__xtensa__)
+# define ARCH_REGS	struct user_pt_regs
+# define SYSCALL_NUM	syscall
+/*
+ * On xtensa syscall return value is in the register
+ * a2 of the current window which is not fixed.
+ */
+#define SYSCALL_RET(reg) a[(reg).windowbase * 4 + 2]
 #else
 # error "Do not know how to find your architecture's registers and syscalls"
 #endif
@@ -1770,7 +1780,8 @@ void change_syscall(struct __test_metadata *_metadata,
 	EXPECT_EQ(0, ret) {}
 
 #if defined(__x86_64__) || defined(__i386__) || defined(__powerpc__) || \
-	defined(__s390__) || defined(__hppa__) || defined(__riscv)
+	defined(__s390__) || defined(__hppa__) || defined(__riscv) || \
+	defined(__xtensa__)
 	{
 		regs.SYSCALL_NUM = syscall;
 	}
@@ -1813,6 +1824,9 @@ void change_syscall(struct __test_metadata *_metadata,
 	if (syscall == -1)
 #ifdef SYSCALL_NUM_RET_SHARE_REG
 		TH_LOG("Can't modify syscall return on this architecture");
+
+#elif defined(__xtensa__)
+		regs.SYSCALL_RET(regs) = result;
 #else
 		regs.SYSCALL_RET = result;
 #endif