RISC-V Fixes for 5.13-rc4

I have a handful of RISC-V related fixes:
 
 * A fix to avoid errors when the stack tracing code is tracing itself.
 * A fix to resurrect the memtest= kernel command line argument on
   RISC-V, which was briefly enabled during the merge window before a
   refactoring disabled it.
 * A build fix and some warning cleanups.
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Merge tag 'riscv-for-linus-5.13-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux

Pull RISC-V fixes from Palmer Dabbelt:
 "A handful of RISC-V related fixes:

   - avoid errors when the stack tracing code is tracing itself.

   - resurrect the memtest= kernel command line argument on RISC-V,
     which was briefly enabled during the merge window before a
     refactoring disabled it.

   - build fix and some warning cleanups"

* tag 'riscv-for-linus-5.13-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux:
  riscv: kexec: Fix W=1 build warnings
  riscv: kprobes: Fix build error when MMU=n
  riscv: Select ARCH_USE_MEMTEST
  riscv: stacktrace: fix the riscv stacktrace when CONFIG_FRAME_POINTER enabled

arch/riscv/Kconfig

@@ -34,6 +34,7 @@ config RISCV
 	select ARCH_OPTIONAL_KERNEL_RWX if ARCH_HAS_STRICT_KERNEL_RWX
 	select ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
 	select ARCH_SUPPORTS_HUGETLBFS if MMU
+	select ARCH_USE_MEMTEST
 	select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU
 	select ARCH_WANT_FRAME_POINTERS
 	select ARCH_WANT_HUGE_PMD_SHARE if 64BIT

arch/riscv/include/asm/kexec.h

@@ -42,8 +42,8 @@ struct kimage_arch {
 	unsigned long fdt_addr;
 };
 
-const extern unsigned char riscv_kexec_relocate[];
-const extern unsigned int riscv_kexec_relocate_size;
+extern const unsigned char riscv_kexec_relocate[];
+extern const unsigned int riscv_kexec_relocate_size;
 
 typedef void (*riscv_kexec_method)(unsigned long first_ind_entry,
 				   unsigned long jump_addr,

arch/riscv/kernel/machine_kexec.c

@@ -14,8 +14,9 @@
 #include <asm/set_memory.h>	/* For set_memory_x() */
 #include <linux/compiler.h>	/* For unreachable() */
 #include <linux/cpu.h>		/* For cpu_down() */
+#include <linux/reboot.h>
 
-/**
+/*
  * kexec_image_info - Print received image details
  */
 static void
@@ -39,7 +40,7 @@ kexec_image_info(const struct kimage *image)
 	}
 }
 
-/**
+/*
  * machine_kexec_prepare - Initialize kexec
  *
  * This function is called from do_kexec_load, when the user has
@@ -100,7 +101,7 @@ machine_kexec_prepare(struct kimage *image)
 }
 
 
-/**
+/*
  * machine_kexec_cleanup - Cleanup any leftovers from
  *			   machine_kexec_prepare
  *
@@ -135,7 +136,7 @@ void machine_shutdown(void)
 #endif
 }
 
-/**
+/*
  * machine_crash_shutdown - Prepare to kexec after a kernel crash
  *
  * This function is called by crash_kexec just before machine_kexec
@@ -151,7 +152,7 @@ machine_crash_shutdown(struct pt_regs *regs)
 	pr_info("Starting crashdump kernel...\n");
 }
 
-/**
+/*
  * machine_kexec - Jump to the loaded kimage
  *
  * This function is called by kernel_kexec which is called by the

arch/riscv/kernel/probes/kprobes.c

@@ -84,6 +84,7 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
 	return 0;
 }
 
+#ifdef CONFIG_MMU
 void *alloc_insn_page(void)
 {
 	return  __vmalloc_node_range(PAGE_SIZE, 1, VMALLOC_START, VMALLOC_END,
@@ -91,6 +92,7 @@ void *alloc_insn_page(void)
 				     VM_FLUSH_RESET_PERMS, NUMA_NO_NODE,
 				     __builtin_return_address(0));
 }
+#endif
 
 /* install breakpoint in text */
 void __kprobes arch_arm_kprobe(struct kprobe *p)

arch/riscv/kernel/stacktrace.c

@@ -27,10 +27,10 @@ void notrace walk_stackframe(struct task_struct *task, struct pt_regs *regs,
 		fp = frame_pointer(regs);
 		sp = user_stack_pointer(regs);
 		pc = instruction_pointer(regs);
-	} else if (task == NULL || task == current) {
-		fp = (unsigned long)__builtin_frame_address(0);
-		sp = sp_in_global;
-		pc = (unsigned long)walk_stackframe;
+	} else if (task == current) {
+		fp = (unsigned long)__builtin_frame_address(1);
+		sp = (unsigned long)__builtin_frame_address(0);
+		pc = (unsigned long)__builtin_return_address(0);
 	} else {
 		/* task blocked in __switch_to */
 		fp = task->thread.s[0];
@@ -106,15 +106,15 @@ static bool print_trace_address(void *arg, unsigned long pc)
 	return true;
 }
 
-void dump_backtrace(struct pt_regs *regs, struct task_struct *task,
+noinline void dump_backtrace(struct pt_regs *regs, struct task_struct *task,
 		    const char *loglvl)
 {
-	pr_cont("%sCall Trace:\n", loglvl);
 	walk_stackframe(task, regs, print_trace_address, (void *)loglvl);
 }
 
 void show_stack(struct task_struct *task, unsigned long *sp, const char *loglvl)
 {
+	pr_cont("%sCall Trace:\n", loglvl);
 	dump_backtrace(NULL, task, loglvl);
 }
 
@@ -139,7 +139,7 @@ unsigned long get_wchan(struct task_struct *task)
 
 #ifdef CONFIG_STACKTRACE
 
-void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie,
+noinline void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie,
 		     struct task_struct *task, struct pt_regs *regs)
 {
 	walk_stackframe(task, regs, consume_entry, cookie);