[SeaBIOS] [PATCH] docs: Don't use an add-symbol-file offset when describing gdb debugging

Kevin O'Connor kevin at koconnor.net
Mon Aug 24 19:16:09 CET 2015

Recent versions of gdb will only add an offset to the '.text' section
of object files via the add-symbol-file command.  The SeaBIOS build
doesn't place code directly in a '.text' section, so update the
documentation to obtain the same result via an 'objcopy' call instead.

Signed-off-by: Kevin O'Connor <kevin at koconnor.net>
 docs/Debugging.md | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/docs/Debugging.md b/docs/Debugging.md
index 4aaf472..7ab5d02 100644
--- a/docs/Debugging.md
+++ b/docs/Debugging.md
@@ -86,22 +86,23 @@ bios 16bit code) or out/rom.o (to debug bios 32bit code). For example:
 `gdb out/rom16.o`
-Once in gdb, use the command "target remote localhost:1234" to have
+Once in gdb, use the command `target remote localhost:1234` to have
 gdb connect to QEMU. See the QEMU documentation for more information
 on using gdb and QEMU in this mode.
-When debugging 16bit code, also run the following commands in gdb:
+When debugging 16bit code it is necessary to load the 16bit symbols
+twice in order for gdb to properly handle break points.  To do this,
+run the following command `objcopy --adjust-vma 0xf0000 out/rom16.o
+rom16offset.o` and then run the following in gdb:
 set architecture i8086
-add-symbol-file out/rom16.o 0xf0000
+add-symbol-file rom16offset.o 0
-The second command loads the 16bit symbols a second time at an offset
-of 0xf0000, which helps gdb set and catch breakpoints correctly.
-To debug a VGA BIOS image, run "gdb out/vgarom.o" add use the gdb
-command "add-symbol-file out/vgarom.o 0xc0000" to load the 16bit VGA
+To debug a VGA BIOS image, run `gdb out/vgarom.o`, create a
+vgaromoffset.o file with offset 0xc0000, add use the gdb
+command `add-symbol-file out/vgaromoffset.o 0` to load the 16bit VGA
 BIOS symbols twice.
 If debugging the 32bit SeaBIOS initialization code with gdb, note that

More information about the SeaBIOS mailing list