gdb/testsuite/gdb.base/patch.exp

# Copyright 2022-2024 Free Software Foundation, Inc.

# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

# Test patching executables and core files, with "set write on".

standard_testfile

if {[build_executable "failed to prepare" $testfile $srcfile debug]} {
    return -1
}

# Check that we can patch an executable.

with_test_prefix "exec" {
    clean_restart

    gdb_test_no_output "set write on"

    gdb_load $binfile

    gdb_test "p extern_global" " = 1" "read original value"
    gdb_test "p extern_global = 2" " = 2" "modify value"
    gdb_test "p extern_global" " = 2" "value modified"

    clean_restart $binfile

    gdb_test "p extern_global" " = 2" "value modified persisted"
}

# Check that we can patch a core file.

# Generate a core file.
with_test_prefix "gcore" {
    clean_restart $binfile

    if {![runto_main]} {
	return
    }

    # Extract the value at PC, and add 1, letting it wrap if
    # necessary.  This is the value we will poke into memory.
    set poke_value ""
    gdb_test_multiple "p/x (*(unsigned char *) \$pc) + 1" "compute poke value" {
	-re -wrap " = ($hex)" {
	    set poke_value $expect_out(1,string)
	    pass $gdb_test_name
	}
    }
    if {$poke_value == ""} {
	return
    }

    set corefile [standard_output_file gcore.test]
    set core_supported [gdb_gcore_cmd "$corefile" "save a corefile"]
    if {!$core_supported} {
	return
    }
}

# Load it into GDB with "set write on", and change the instruction at
# PC.
with_test_prefix "load core, write on" {
    # Don't load a binary, we want to make sure we're patching the
    # core, not the executable.
    clean_restart

    gdb_test_no_output "set write on"

    set core_loaded [gdb_core_cmd "$corefile" "re-load generated corefile"]
    if { $core_loaded == -1 } {
	return
    }

    gdb_test "p/x *(unsigned char *) \$pc = $poke_value" \
	" = $poke_value" \
	"poke value"
    gdb_test "p/x *(unsigned char *) \$pc" \
	" = $poke_value" \
	"value modified"
}

# Re-load it into a new GDB session, now with "set write off", and
# confirm the value change persisted.
with_test_prefix "re-load modified core" {
    # Don't load a binary, we want to make sure we've patched the
    # core, not the executable.
    clean_restart

    set core_loaded [gdb_core_cmd "$corefile" "re-load generated corefile"]
    gdb_assert { $core_loaded != -1 } "core re-loaded"

    gdb_test "p/x *(unsigned char *) \$pc" \
	" = $poke_value" \
	"value modified persisted"
}