Fix typo.

[pintos-anon] / doc / debug.texi

diff --git a/doc/debug.texi b/doc/debug.texi
index a192a73a9885d4931dbdcee1150cad2fbcd1dc3d..961888f297be48973b9af5d56ff28af3fcef23f1 100644 (file)
--- a/doc/debug.texi
+++ b/doc/debug.texi
@@ -198,7 +198,7 @@ tree used for this example, line 405 of @file{filesys/file.c} is the
 assertion
 
 @example
-ASSERT (file_ofs >= )0;
+ASSERT (file_ofs >= 0);
 @end example
 
 @noindent
@@ -221,9 +221,8 @@ panicked, you can re-run @command{backtrace} on the user program, like
 so: (typing the command on a single line, of course):
 
 @example
-~/cs140/pintos/src/utils/backtrace grow-too-big 0xc0106eff 0xc01102fb
-0xc010dc22 0xc010cf67 0xc0102319 0xc010325a 0x804812c 0x8048a96
-0x8048ac8
+backtrace grow-too-big 0xc0106eff 0xc01102fb 0xc010dc22 0xc010cf67
+0xc0102319 0xc010325a 0x804812c 0x8048a96 0x8048ac8
 @end example
 
 The results look like this:
@@ -240,13 +239,24 @@ The results look like this:
 0x8048ac8: _start (../../src/lib/user/entry.c:9)
 @end example
 
+Here's an extra tip for anyone who read this far: @command{backtrace}
+is smart enough to strip the @code{Call stack:} header and @samp{.}
+trailer from the command line if you include them.  This can save you
+a little bit of trouble in cutting and pasting.  Thus, the following
+command prints the same output as the first one we used:
+
+@example
+backtrace kernel.o Call stack: 0xc0106eff 0xc01102fb 0xc010dc22
+0xc010cf67 0xc0102319 0xc010325a 0x804812c 0x8048a96 0x8048ac8.
+@end example
+
 @node i386-elf-gdb
 @section @command{i386-elf-gdb}
 
 You can run the Pintos kernel under the supervision of the
 @command{i386-elf-gdb} debugger.@footnote{If you're using an
 80@var{x}86 system for development, it's probably just called
-@command{addr2line}.}  There are two steps in the process.  First,
+@command{gdb}.}  There are two steps in the process.  First,
 start Pintos with the @option{--gdb} option, e.g.@: @command{pintos
 --gdb run}.  Second, in a second terminal, invoke @command{gdb} on
 @file{kernel.o}:
@@ -374,17 +384,18 @@ above, a good place to start adding @func{printf}s is
 @node Debugging Tips
 @section Tips
 
-The page allocator in @file{threads/palloc.c} clears all the bytes in
-pages to @t{0xcc} when they are freed.  Thus, if you see an attempt to
+The page allocator in @file{threads/palloc.c} and the block allocator in
+@file{threads/malloc.c} both clear all the bytes in pages and blocks to
+@t{0xcc} when they are freed.  Thus, if you see an attempt to
 dereference a pointer like @t{0xcccccccc}, or some other reference to
 @t{0xcc}, there's a good chance you're trying to reuse a page that's
-already been freed.  Also, byte @t{0xcc} is the CPU opcode for
-``invoke interrupt 3,'' so if you see an error like @code{Interrupt
-0x03 (#BP Breakpoint Exception)}, Pintos tried to execute code in a
-freed page.
-
-Similarly, the block allocator in @file{threads/malloc.c} clears all
-the bytes in freed blocks to @t{0xcd}.  The two bytes @t{0xcdcd} are
-a CPU opcode for ``invoke interrupt @t{0xcd},'' so @code{Interrupt
-0xcd (unknown)} is a good sign that you tried to execute code in a
-block freed with @func{free}.
+already been freed.  Also, byte @t{0xcc} is the CPU opcode for ``invoke
+interrupt 3,'' so if you see an error like @code{Interrupt 0x03 (#BP
+Breakpoint Exception)}, Pintos tried to execute code in a freed page or
+block.
+
+An assertion failure on the expression @code{sec_no < d->capacity}
+indicates that Pintos tried to access a file through an inode that has
+been closed and freed.  Freeing an inode clears its starting sector
+number to @t{0xcccccccc}, which is not a valid sector number for disks
+smaller than about 1.6 TB.