RISC-V Fixes for 5.12-rc8 (or 5.12)

I have a handful of fixes that I'd like to target for 5.12, regardless
 of whether there's an rc8 or not:
 
 * A fix to properly select SPARSEMEM_STATIC on rv32.
 * A handful of fixes to kprobes.
 
 I don't generally like sending stuff this late, but these all seem
 pretty safe.
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Merge tag 'riscv-for-linus-5.12-rc8' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux

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

   - a fix to properly select SPARSEMEM_STATIC on rv32

   - a few fixes to kprobes

  I don't generally like sending stuff this late, but these all seem
  pretty safe"

* tag 'riscv-for-linus-5.12-rc8' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux:
  riscv: keep interrupts disabled for BREAKPOINT exception
  riscv: kprobes/ftrace: Add recursion protection to the ftrace callback
  riscv: add do_page_fault and do_trap_break into the kprobes blacklist
  riscv: Fix spelling mistake "SPARSEMEM" to "SPARSMEM"

arch/riscv/Kconfig

@@ -153,7 +153,7 @@ config ARCH_FLATMEM_ENABLE
 config ARCH_SPARSEMEM_ENABLE
 	def_bool y
 	depends on MMU
-	select SPARSEMEM_STATIC if 32BIT && SPARSMEM
+	select SPARSEMEM_STATIC if 32BIT && SPARSEMEM
 	select SPARSEMEM_VMEMMAP_ENABLE if 64BIT
 
 config ARCH_SELECT_MEMORY_MODEL

arch/riscv/kernel/entry.S

@@ -130,6 +130,9 @@ skip_context_tracking:
 	 */
 	andi t0, s1, SR_PIE
 	beqz t0, 1f
+	/* kprobes, entered via ebreak, must have interrupts disabled. */
+	li t0, EXC_BREAKPOINT
+	beq s4, t0, 1f
 #ifdef CONFIG_TRACE_IRQFLAGS
 	call trace_hardirqs_on
 #endif

arch/riscv/kernel/probes/ftrace.c

@@ -9,10 +9,16 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
 	struct kprobe *p;
 	struct pt_regs *regs;
 	struct kprobe_ctlblk *kcb;
+	int bit;
 
+	bit = ftrace_test_recursion_trylock(ip, parent_ip);
+	if (bit < 0)
+		return;
+
+	preempt_disable_notrace();
 	p = get_kprobe((kprobe_opcode_t *)ip);
 	if (unlikely(!p) || kprobe_disabled(p))
-		return;
+		goto out;
 
 	regs = ftrace_get_regs(fregs);
 	kcb = get_kprobe_ctlblk();
@@ -45,6 +51,9 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
 		 */
 		__this_cpu_write(current_kprobe, NULL);
 	}
+out:
+	preempt_enable_notrace();
+	ftrace_test_recursion_unlock(bit);
 }
 NOKPROBE_SYMBOL(kprobe_ftrace_handler);
 

arch/riscv/kernel/traps.c

@@ -178,6 +178,7 @@ asmlinkage __visible void do_trap_break(struct pt_regs *regs)
 	else
 		die(regs, "Kernel BUG");
 }
+NOKPROBE_SYMBOL(do_trap_break);
 
 #ifdef CONFIG_GENERIC_BUG
 int is_valid_bugaddr(unsigned long pc)

arch/riscv/mm/fault.c

@@ -328,3 +328,4 @@ asmlinkage void do_page_fault(struct pt_regs *regs)
 	}
 	return;
 }
+NOKPROBE_SYMBOL(do_page_fault);