previous thread was: [edk2] OVMF networking revisited
Spliting off this gdb+qemu+ovmf debugging discussion.
Versions:
qemu-kvm 1.2.0
gdb 7.5.1
OVMF X64 built on Linux with GCC 4.6
On Tue, Apr 9, 2013 at 12:27 AM, Joe Vernaci <jvern...@gmail.com> wrote:
> ...
> The error you are seeing means gdb does not have a type for
> EFI_SYSTEM_TABLE so the file provided when you ran the command 'reload-uefi
> /path/to/GdbSyms.dll' either was not there or did not have a symbol for
> EFI_SYSTEM_TABLE. You can confirm this by running 'info types
> EFI_SYSTEM_TABLE_POINTER' after you have run 'reload-uefi ...' It should
> tell you there is nothing matching this type.
>
Here is Andrei's blog documenting GdbSyms:
http://osdevnotes.blogspot.com/2011/05/gdb-scripting-example-reloading-symbols.html
Let's get more concrete and use actual command lines:
term1: $ qemu-system-x86_64 -m 1024 -bios OVMF.fd -S -s -monitor stdio
term2: $ cd edk2/OvmfPkg
term2: $ gdb
term2: (gdb) target remote :1234
term2: (gdb) source ../../andreiw-wip/uefi/DebugPkg/Scripts/gdb_uefi.py
term2: (gdb) reload-uefi -o
../Build/AppPkg/DEBUG_GCC46/X64/AppPkg/Applications/GdbSyms/GdbSyms/DEBUG/GdbSyms.dll
term2: Python Exception <class 'gdb.error'> No type named
EFI_SYSTEM_TABLE_POINTER
term2:
As I understand his site, the above is how we're supposed to load and use
GdbSyms. I assumed that 2 years ago (when Andrei last used GdbSyms) that
no other command lines were needed and that over the last couple years only
symbol names might have changed.
An alternative approach that has provided some fruit is that I also have
.debug files in my edk2/Build directory which load into gdb. However,
since this is ROM/bootstrap code, the offsets need to be set manually.
(without using GdbSyms) I've managed to get this far using this alternate
approach:
term1: $ qemu-system-x86_64 -m 1024 -bios OVMF.fd -S -s -monitor stdio
term2: $ cd edk2/OvmfPkg
term2: $ gdb
term2: (gdb) target remote :1234
term2: (gdb) add-symbol-file ../Build/OvmfX64/DEBUG_GCC46/X64/SecMain.debug
0xfffcc2c4
term2: add symbol table from file
"../Build/OvmfX64/DEBUG_GCC46/X64/SecMain.debug" at
term2: .text_addr = 0xfffcc2c4
term2: (y or n) y
term2: Reading symbols from
/home/duanev/efi/edk2/Build/OvmfX64/DEBUG_GCC46/X64/SecMain.debug...done.
term2: (gdb)
term2: (gdb) info address FindMainFv
term2: Symbol "FindMainFv" is a function at address 0xfffcc2db.
term2: (gdb) info address EFI_SYSTEM_TABLE
term2: No symbol "EFI_SYSTEM_TABLE" in current context.
term2: (gdb) info type EFI_SYSTEM_TABLE_POINTER
term2: All types matching regular expression "EFI_SYSTEM_TABLE_POINTER":
term2: (gdb)
where 0xfffcc2c4 was determined empirically. At this point all the text
addresses line up correctly and single stepping isn't as barren a prospect,
however computing the load offset for the symbol table is I believe exactly
what Andrei managed to automate.
> His script like mine use the system table pointer which as I said above is
> only valid after DxeMain.efi is loaded. After a quick grep it looks like
> AcpiTimerLibConstructor is only called from Dxe files so this should be ok.
>
>
Ovmf appears to be "a collection" of .efi files (again each with some new
offset). SecMain.debug (aka. SecMain.efi) seems to provide all the symbols
I need for my ACPI debugging, and that includes several of the modules in
the ovmf collection, but this is all a bit kludgy. I hope there is
something I'm missing...
Also you can read the i/o ports from qemu's monitor is the 'i' command or
> from gdb with the 'monitor i' command.
>
Thanks for pointing this out. Interestingly, though, all my gdb 'monitor'
commands return blank lines with the exact count of the number of actual
lines they should have printed. :) I'll use the qemu command line for
now...
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