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[PATCH 7/8] gdb: Conditionally run GDB script logic for dynamically or s

From: Glenn Washburn
Subject: [PATCH 7/8] gdb: Conditionally run GDB script logic for dynamically or statically positioned GRUB
Date: Sun, 13 Feb 2022 21:42:44 -0600

There are broadly two classes of targets to consider when loading symbols
for GRUB, targets that determine where to load GRUB at runtime (dynamically
positioned) and those that do not (statically positioned). For statically
poisitioned targets, symbol loading is determined at link time, so nothing
more needs to be known to load the symbols. For dynamically positioned
targets, such as EFI targets, at runtime symbols should be offset by an
amount that depends on where the runtime chose to load GRUB.

It is important to not load symbols statically for dynamic targets because
then when subsequently loading the symbols correctly one must take care to
remove the existing static symbols, otherwise there will be two sets of
symbols and GDB seems to prefer the ones loaded first (ie the static ones).

Use autoconf variables to generate a gdb_grub for a particular target, which
conditionally run startup code depending on if the target uses static or
dynamic loading. This is complicated by the fact that a subshell is used to
check the autoconf variable and shells return 0 for success, but 0 is false
in conditionals in GDB. So an inversion of the status code is needed.

Signed-off-by: Glenn Washburn <>
 grub-core/ | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/grub-core/ b/grub-core/
index f3c6faf94..4c2b8bf52 100644
--- a/grub-core/
+++ b/grub-core/
@@ -145,7 +145,23 @@ end
 set confirm off
-file kernel.exec
-target remote :1234
+# Note: On EFI and other platforms that load GRUB to an address that is
+# determined at runtime, the symbols in kernel.exec will be wrong.
+# However, we must start by loading some executable file or GDB will
+# fail.
+# If this returns success, the exit code is 0, however, GDB's "if"
+# considers 0 to be false. So invert the status code.
+shell test "@platform@" == "efi"
+set $platform_efi = ! $_shell_exitcode
+if $platform_efi
+       # Only load the executable file, not the symbols
+       exec-file kernel.exec
+       file kernel.exec
+       runtime_load_module
+target remote :1234

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