From ba569a7ebe749ea925008baf2b8ff4d1e4cd6cef Mon Sep 17 00:00:00 2001
From: Samuel Thibault <samuel.thibault@ens-lyon.org>
Date: Sun, 27 Aug 2017 18:36:25 +0200
Subject: ddb: More gracefully handle address errors

* i386/i386/db_interface.h (db_read_bytes): Return boolean_t instead of
void.
* i386/i386/db_interface.c (db_user_to_kernel_address): Return -1
instead of calling db_error() if address is bogus.
(db_read_bytes): Return FALSE instead of calling db_error() if address
is bogus.
* ddb/db_access.c (db_get_task_value): Return 0 if db_read_bytes failed.
* ddb/db_examine.c (db_xcdump): Only print * if db_read_bytes failed.
---
 ddb/db_access.c          |  3 ++-
 ddb/db_examine.c         |  5 ++++-
 i386/i386/db_interface.c | 12 +++++-------
 i386/i386/db_interface.h |  2 +-
 4 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/ddb/db_access.c b/ddb/db_access.c
index 16d4d3ef..509c1ba4 100644
--- a/ddb/db_access.c
+++ b/ddb/db_access.c
@@ -72,7 +72,8 @@ db_get_task_value(
 	db_expr_t 	value;
 	int		i;
 
-	db_read_bytes(addr, size, data, task);
+	if (!db_read_bytes(addr, size, data, task))
+	    return 0;
 
 	value = 0;
 #if	BYTE_MSF
diff --git a/ddb/db_examine.c b/ddb/db_examine.c
index 836b0e89..6f94b686 100644
--- a/ddb/db_examine.c
+++ b/ddb/db_examine.c
@@ -473,7 +473,10 @@ db_xcdump(
 		if (!DB_CHECK_ACCESS(next_page_addr, sizeof(int), task))
 		    bcount = next_page_addr - addr;
 	    }
-	    db_read_bytes(addr, bcount, data, task);
+	    if (!db_read_bytes(addr, bcount, data, task)) {
+		db_printf("*\n");
+		continue;
+	    }
 	    for (i = 0; i < bcount && off != 0; i += size) {
 		if (i % 4 == 0)
 			db_printf(" ");
diff --git a/i386/i386/db_interface.c b/i386/i386/db_interface.c
index b3fac0bb..aac29395 100644
--- a/i386/i386/db_interface.c
+++ b/i386/i386/db_interface.c
@@ -446,8 +446,6 @@ db_user_to_kernel_address(
 	    }
 	    if (flag) {
 		db_printf("\nno memory is assigned to address %08x\n", addr);
-		db_error(0);
-		/* NOTREACHED */
 	    }
 	    return(-1);
 	}
@@ -459,7 +457,7 @@ db_user_to_kernel_address(
  * Read bytes from kernel address space for debugger.
  */
 
-void
+boolean_t
 db_read_bytes(
 	vm_offset_t	addr,
 	int		size,
@@ -477,17 +475,16 @@ db_read_bytes(
 	    while (--size >= 0) {
 		if (addr < VM_MIN_KERNEL_ADDRESS && task == TASK_NULL) {
 		    db_printf("\nbad address %x\n", addr);
-		    db_error(0);
-		    /* NOTREACHED */
+		    return FALSE;
 		}
 		addr++;
 		*data++ = *src++;
 	    }
-	    return;
+	    return TRUE;
 	}
 	while (size > 0) {
 	    if (db_user_to_kernel_address(task, addr, &kern_addr, 1) < 0)
-		return;
+		return FALSE;
 	    src = (char *)kern_addr;
 	    n = intel_trunc_page(addr+INTEL_PGBYTES) - addr;
 	    if (n > size)
@@ -497,6 +494,7 @@ db_read_bytes(
 	    while (--n >= 0)
 		*data++ = *src++;
 	}
+	return TRUE;
 }
 
 /*
diff --git a/i386/i386/db_interface.h b/i386/i386/db_interface.h
index 9ffb6a60..18ee3291 100644
--- a/i386/i386/db_interface.h
+++ b/i386/i386/db_interface.h
@@ -32,7 +32,7 @@ extern boolean_t kdb_trap (
 	int			code,
 	struct i386_saved_state *regs);
 
-extern void db_read_bytes (
+extern boolean_t db_read_bytes (
 	vm_offset_t	addr,
 	int		size,
 	char		*data,
-- 
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