X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=doc%2Fdebug.texi;h=75d9b242a79b12dfbb0496d4d962e538a0259d98;hb=749088412dc35dfc51035c30b86dd0b86a6954f7;hp=a192a73a9885d4931dbdcee1150cad2fbcd1dc3d;hpb=9d6ad9a479ddae9628dc2d45862f9281986c430b;p=pintos-anon

diff --git a/doc/debug.texi b/doc/debug.texi
index a192a73..75d9b24 100644
--- a/doc/debug.texi
+++ b/doc/debug.texi
@@ -7,7 +7,6 @@ introduces you to a few of them.
 @menu
 * printf::                      
 * ASSERT::                      
-* DEBUG::                       
 * UNUSED NO_RETURN NO_INLINE PRINTF_FORMAT::  
 * Backtraces::                  
 * i386-elf-gdb::                
@@ -53,31 +52,6 @@ When an assertion proves untrue, the kernel panics.  The panic message
 should help you to find the problem.  See the description of
 backtraces below for more information.
 
-@node DEBUG
-@section @code{DEBUG}
-
-The @code{DEBUG} macro, also defined in @file{<debug.h>}, is a sort of
-conditional @func{printf}.  It takes as its arguments the name of a
-``message class'' and a @func{printf}-like format string and
-arguments.  The message class is used to filter the messages that are
-actually displayed.  You select the messages to display on the Pintos
-command line using the @option{-d} option.  This allows you to easily
-turn different types of messages on and off while you debug, without
-the need to recompile.
-
-For example, suppose you want to output thread debugging messages.  To
-use a class named @code{thread}, you could invoke @code{DEBUG} like
-this:
-@example
-DEBUG(thread, "thread id: %d\n", id);
-@end example
-@noindent
-and then to start Pintos with @code{thread} messages enable you'd use
-a command line like this:
-@example
-pintos run -d thread
-@end example
-
 @node UNUSED NO_RETURN NO_INLINE PRINTF_FORMAT
 @section UNUSED, NO_RETURN, NO_INLINE, and PRINTF_FORMAT
 
@@ -198,7 +172,7 @@ 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 +195,8 @@ 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 +213,24 @@ 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 +358,18 @@ 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.