RISCV64: Add per-cpu overflow stacks support

The patch introduces per-cpu overflow stacks for RISCV64 to let
"bt" do backtrace on it and the 'help -m' command dispalys the
addresss of each per-cpu overflow stack.

TEST: a lkdtm DIRECT EXHAUST_STACK vmcore

  crash> bt
  PID: 1        TASK: ff600000000d8000  CPU: 1    COMMAND: "sh"
   #0 [ff6000001fc501c0] riscv_crash_save_regs at ffffffff8000a1dc
   #1 [ff6000001fc50320] panic at ffffffff808773ec
   #2 [ff6000001fc50380] walk_stackframe at ffffffff800056da
       PC: ffffffff80876a34  [memset+96]
       RA: ffffffff80563dc0  [recursive_loop+68]
       SP: ff2000000000fd50  CAUSE: 000000000000000f
  epc : ffffffff80876a34 ra : ffffffff80563dc0 sp : ff2000000000fd50
   gp : ffffffff81515d38 tp : 0000000000000000 t0 : ff2000000000fd58
   t1 : ff600000000d88c8 t2 : 6143203a6d74646b s0 : ff20000000010190
   s1 : 0000000000000012 a0 : ff2000000000fd58 a1 : 1212121212121212
   a2 : 0000000000000400 a3 : ff20000000010158 a4 : 0000000000000000
   a5 : 725bedba92260900 a6 : 000000000130e0f0 a7 : 0000000000000000
   s2 : ff2000000000fd58 s3 : ffffffff815170d8 s4 : ff20000000013e60
   s5 : 000000000000000e s6 : ff20000000013e60 s7 : 0000000000000000
   s8 : ff60000000861000 s9 : 00007fffc3641694 s10: 00007fffc3641690
   s11: 00005555796ed240 t3 : 0000000000010297 t4 : ffffffff80c17810
   t5 : ffffffff8195e7b8 t6 : ff20000000013b18
   status: 0000000200000120 badaddr: ff2000000000fd58
    cause: 000000000000000f orig_a0: 0000000000000000
  --- <OVERFLOW stack> ---
   #3 [ff2000000000fd50] memset at ffffffff80876a34
   #4 [ff20000000010190] recursive_loop at ffffffff80563e16
   #5 [ff200000000105d0] recursive_loop at ffffffff80563e16
   < recursive_loop ...>
   #16 [ff20000000013490] recursive_loop at ffffffff80563e16
   #17 [ff200000000138d0] recursive_loop at ffffffff80563e16
   #18 [ff20000000013d10] lkdtm_EXHAUST_STACK at ffffffff8088005e
   #19 [ff20000000013d30] lkdtm_do_action at ffffffff80563292
   #20 [ff20000000013d40] direct_entry at ffffffff80563474
   #21 [ff20000000013d70] full_proxy_write at ffffffff8032fb3a
   #22 [ff20000000013db0] vfs_write at ffffffff801d6414
   #23 [ff20000000013e60] ksys_write at ffffffff801d67b8
   #24 [ff20000000013eb0] __riscv_sys_write at ffffffff801d6832
   #25 [ff20000000013ec0] do_trap_ecall_u at ffffffff80884a20
  crash>

  crash> help -m
  <snip>
          irq_stack_size: 16384
           irq_stacks[0]: ff20000000000000
           irq_stacks[1]: ff20000000008000
          overflow_stack_size: 4096
           overflow_stacks[0]: ff6000001fa7a510
           overflow_stacks[1]: ff6000001fc4f510
  crash>

Signed-off-by: Song Shuai <[email protected]>

Author: Song Shuai

defs.h

@@ -3655,6 +3655,9 @@ typedef signed int s32;
 #define VM_L5_2M	(0x100)
 #define VM_L5_1G	(0x200)
 #define IRQ_STACKS	(0x400)
+#define OVERFLOW_STACKS     (0x800)
+
+#define RISCV64_OVERFLOW_STACK_SIZE (1 << 12)
 
 #define VM_FLAGS	(VM_L3_4K | VM_L3_2M | VM_L3_1G | \
 			 VM_L4_4K | VM_L4_2M | VM_L4_1G | \
@@ -7061,6 +7064,9 @@ struct machine_specific {
 	struct riscv64_register *crash_task_regs;
 	ulong irq_stack_size;
 	ulong *irq_stacks;
+
+	ulong overflow_stack_size;
+	ulong *overflow_stacks;
 };
 /* from arch/riscv/include/asm/pgtable-bits.h */
 #define _PAGE_PRESENT	(machdep->machspec->_page_present)

riscv64.c

@@ -34,6 +34,7 @@ static int riscv64_kvtop(struct task_context *tc, ulong kvaddr,
 			  physaddr_t *paddr, int verbose);
 static void riscv64_cmd_mach(void);
 static void riscv64_irq_stack_init(void);
+static void riscv64_overflow_stack_init(void);
 static void riscv64_stackframe_init(void);
 static void riscv64_back_trace_cmd(struct bt_info *bt);
 static int riscv64_eframe_search(struct bt_info *bt);
@@ -59,6 +60,8 @@ static int riscv64_on_irq_stack(int , ulong);
 static int riscv64_on_process_stack(struct bt_info *, ulong );
 static void riscv64_set_process_stack(struct bt_info *);
 static void riscv64_set_irq_stack(struct bt_info *);
+static int riscv64_on_overflow_stack(int, ulong);
+static void riscv64_set_overflow_stack(struct bt_info *);
 
 #define REG_FMT 	"%016lx"
 #define SZ_2G		0x80000000
@@ -206,6 +209,8 @@ riscv64_dump_machdep_table(ulong arg)
 		fprintf(fp, "%sKSYMS_START", others++ ? "|" : "");
 	if (machdep->flags & IRQ_STACKS)
 		fprintf(fp, "%sIRQ_STACKS", others++ ? "|" : "");
+	if (machdep->flags & OVERFLOW_STACKS)
+		fprintf(fp, "%sOVERFLOW_STACKS", others++ ? "|" : "");
 	fprintf(fp, ")\n");
 
 	fprintf(fp, "             kvbase: %lx\n", machdep->kvbase);
@@ -270,6 +275,15 @@ riscv64_dump_machdep_table(ulong arg)
 		fprintf(fp, "        irq_stack_size: (unused)\n");
 		fprintf(fp, "            irq_stacks: (unused)\n");
 	}
+	if (machdep->flags & OVERFLOW_STACKS) {
+		fprintf(fp, "        overflow_stack_size: %ld\n", ms->overflow_stack_size);
+		for (i = 0; i < kt->cpus; i++)
+			fprintf(fp, "         overflow_stacks[%d]: %lx\n",
+				i, ms->overflow_stacks[i]);
+	} else {
+		fprintf(fp, "        overflow_stack_size: (unused)\n");
+		fprintf(fp, "            overflow_stacks: (unused)\n");
+	}
 }
 
 static ulong
@@ -684,6 +698,48 @@ riscv64_display_full_frame(struct bt_info *bt, struct riscv64_unwind_frame *curr
 	fprintf(fp, "\n");
 }
 
+
+/*
+ * Gather Overflow stack values.
+ */
+static void
+riscv64_overflow_stack_init(void)
+{
+	int i;
+	struct syment *sp;
+	struct gnu_request request, *req;
+	struct machine_specific *ms = machdep->machspec;
+	req = &request;
+
+	if (symbol_exists("overflow_stack") &&
+	    (sp = per_cpu_symbol_search("overflow_stack")) &&
+	    get_symbol_type("overflow_stack", NULL, req)) {
+		if (CRASHDEBUG(1)) {
+			fprintf(fp, "overflow_stack: \n");
+			fprintf(fp, "  type: %x, %s\n",
+				(int)req->typecode,
+				(req->typecode == TYPE_CODE_ARRAY) ?
+						"TYPE_CODE_ARRAY" : "other");
+			fprintf(fp, "  target_typecode: %x, %s\n",
+				(int)req->target_typecode,
+				req->target_typecode == TYPE_CODE_INT ?
+						"TYPE_CODE_INT" : "other");
+			fprintf(fp, "  target_length: %ld\n",
+						req->target_length);
+			fprintf(fp, "  length: %ld\n", req->length);
+		}
+
+		if (!(ms->overflow_stacks = (ulong *)malloc((size_t)(kt->cpus * sizeof(ulong)))))
+			error(FATAL, "cannot malloc overflow_stack addresses\n");
+
+		ms->overflow_stack_size = RISCV64_OVERFLOW_STACK_SIZE;
+		machdep->flags |= OVERFLOW_STACKS;
+
+		for (i = 0; i < kt->cpus; i++)
+			ms->overflow_stacks[i] = kt->__per_cpu_offset[i] + sp->value;
+	}
+}
+
 /*
  * Gather IRQ stack values.
  */
@@ -757,6 +813,23 @@ riscv64_on_irq_stack(int cpu, ulong stkptr)
 	return FALSE;
 }
 
+static int
+riscv64_on_overflow_stack(int cpu, ulong stkptr)
+{
+	struct machine_specific *ms = machdep->machspec;
+	ulong * stacks = ms->overflow_stacks;
+	ulong stack_size = ms->overflow_stack_size;
+
+	if ((cpu >= kt->cpus) || (stacks == NULL) || !stack_size)
+		return FALSE;
+
+	if ((stkptr >= stacks[cpu]) &&
+	    (stkptr < (stacks[cpu] + stack_size)))
+		return TRUE;
+
+	return FALSE;
+}
+
 static int
 riscv64_on_process_stack(struct bt_info *bt, ulong stkptr)
 {
@@ -781,6 +854,16 @@ riscv64_set_irq_stack(struct bt_info *bt)
 	alter_stackbuf(bt);
 }
 
+static void
+riscv64_set_overflow_stack(struct bt_info *bt)
+{
+	struct machine_specific *ms = machdep->machspec;
+
+	bt->stackbase = ms->overflow_stacks[bt->tc->processor];
+	bt->stacktop = bt->stackbase + ms->overflow_stack_size;
+	alter_stackbuf(bt);
+}
+
 static void
 riscv64_set_process_stack(struct bt_info *bt)
 {
@@ -875,7 +958,7 @@ riscv64_back_trace_cmd(struct bt_info *bt)
 {
 	struct riscv64_unwind_frame current, previous;
 	struct stackframe curr_frame;
-	struct riscv64_register *regs, *irq_regs;
+	struct riscv64_register *regs, *irq_regs, *overflow_regs;
 	int level = 0;
 
 	if (bt->flags & BT_REGS_NOT_FOUND)
@@ -888,6 +971,11 @@ riscv64_back_trace_cmd(struct bt_info *bt)
 		bt->flags |= BT_IRQSTACK;
 	}
 
+	if (riscv64_on_overflow_stack(bt->tc->processor, bt->frameptr)) {
+		riscv64_set_overflow_stack(bt);
+		bt->flags |= BT_OVERFLOW_STACK;
+	}
+
 	current.pc = bt->instptr;
 	current.sp = bt->stkptr;
 	current.fp = bt->frameptr;
@@ -971,6 +1059,28 @@ riscv64_back_trace_cmd(struct bt_info *bt)
 			}
 		}
 
+		/*
+		 * When backtracing to handle_kernel_stack_overflow()
+		 * use pt_regs saved in overflow stack to continue
+		 */
+		if ((bt->flags & BT_OVERFLOW_STACK) &&
+		    !riscv64_on_overflow_stack(bt->tc->processor, current.fp)) {
+
+				overflow_regs = (struct riscv64_register *)
+					&bt->stackbuf[(ulong)(STACK_OFFSET_TYPE(current.sp))];
+
+				riscv64_print_exception_frame(bt, current.sp, KERNEL_MODE);
+
+				current.pc = overflow_regs->regs[RISCV64_REGS_EPC];
+				current.fp = overflow_regs->regs[RISCV64_REGS_FP];
+				current.sp = overflow_regs->regs[RISCV64_REGS_SP];
+
+				riscv64_set_process_stack(bt);
+
+				bt->flags &= ~BT_OVERFLOW_STACK;
+				fprintf(fp, "--- <OVERFLOW stack> ---\n");
+		}
+
 		if (CRASHDEBUG(8))
 			fprintf(fp, "next %d pc %#lx sp %#lx fp %lx\n",
 				level, current.pc, current.sp, current.fp);
@@ -1583,6 +1693,7 @@ riscv64_init(int when)
 		machdep->max_physmem_bits = _MAX_PHYSMEM_BITS;
 
 		riscv64_irq_stack_init();
+		riscv64_overflow_stack_init();
 		riscv64_stackframe_init();
 		riscv64_page_type_init();