01113bc1c5
GDB step cross kernel helpers only works if the kernel helpers are tail called, which is the case how it is used in glibc. See __aeabi_read_tp in sysdeps/unix/sysv/linux/arm/aeabi_read_tp.S. In __aeabi_read_tp, branch/jump to the kernel helper is the last instruction, and the next instruction address is in LR, which is in caller function. GDB can handle this correctly. For example, glibc function __GI___ctype_init calls __aeabi_read_tp 0xb6e19b30 <__GI___ctype_init+4>: ldr r3, [pc, #80] ; 0xb6e19b34 <__GI___ctype_init+8>: bl 0xb6e0a6e0 <__aeabi_read_tp> 0xb6e19b38 <__GI___ctype_init+12>: ldr r3, [pc, r3] and __aeabi_read_tp calls kernel helper, (gdb) disassemble __aeabi_read_tp 0xb6fef5d0 <+0>: mvn r0, #61440 ; 0xf000 0xb6fef5d4 <+4>: sub pc, r0, #31 once GDB or GDBserver single step instruction on 0xb6fef5d4, LR is 0xb6e19b38, which is right address of next instruction to set breakpoint on. However, if the kernel helpers are not tail-called, the LR is still the address in the caller function of kernel helper's caller, which isn't the right address of next instruction to set breakpoint on. For example, we use kernel helper in main, (gdb) disassemble main .... 0x00008624 <+32>: mov r3, #4064 ; 0xfe0^M 0x00008628 <+36>: movt r3, #65535 ; 0xffff^M 0x0000862c <+40>: blx r3 0x00008630 <+44>: ldr r3, [r11, #-8] kernel helper is called on 0x0000862c and the expected next instruction address is 0x00008630, but the LR now is the return address of main. The problem here is LR may not have the right address because when we single step the instruction, it isn't executed yet, so the LR isn't updated. This patch fix this problem by decoding instruction, if the instruction updates LR (BL and BLX), the next instruction address is PC + INSN_SIZE, otherwise, get the address of next instruction from LR. gdb: 2016-02-12 Yao Qi <yao.qi@linaro.org> * arch/arm-linux.c (arm_linux_get_next_pcs_fixup): Calculate nextpc according to instruction. gdb/testsuite: 2016-02-12 Yao Qi <yao.qi@linaro.org> * gdb.arch/arm-single-step-kernel-helper.c: New. * gdb.arch/arm-single-step-kernel-helper.exp: New.
97 lines
2.5 KiB
Text
97 lines
2.5 KiB
Text
# Copyright (C) 2016 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/>.
|
|
|
|
if { ![is_aarch32_target] } {
|
|
verbose "Skipping ${gdb_test_file_name}."
|
|
return
|
|
}
|
|
|
|
standard_testfile
|
|
|
|
if { [prepare_for_testing ${testfile}.exp ${testfile} ${srcfile} \
|
|
[list debug]] } {
|
|
return -1
|
|
}
|
|
|
|
if { ![runto_main] } {
|
|
return -1
|
|
}
|
|
|
|
# Check kernel helpers are supported or not.
|
|
|
|
set kernel_helper_supported 0
|
|
gdb_test_multiple "p *kernel_user_helper_version" \
|
|
"check kernel helper version" {
|
|
-re " = ($decimal)\r\n$gdb_prompt $" {
|
|
if { $expect_out(1,string) >= 1 } {
|
|
set kernel_helper_supported 1
|
|
}
|
|
}
|
|
}
|
|
|
|
if { !$kernel_helper_supported } {
|
|
unsupported "kernel doesn't have helpers"
|
|
return 0
|
|
}
|
|
|
|
# Get the instruction branching to kernel helper, they can be
|
|
# blx rN or bx rN.
|
|
set branch_to_kernel_helper 0
|
|
set branch_insn "bl?x\[ \t\]*r${decimal}"
|
|
set test "disassemble main"
|
|
gdb_test_multiple $test $test {
|
|
-re ".*($hex) <\\+$decimal>:\[ \t\]+$branch_insn" {
|
|
set branch_to_kernel_helper $expect_out(1,string)
|
|
exp_continue
|
|
}
|
|
-re ".*$gdb_prompt $" {
|
|
}
|
|
}
|
|
|
|
if { ![gdb_assert $branch_to_kernel_helper \
|
|
"find instruction branch to kernel helper"] } {
|
|
return
|
|
}
|
|
|
|
with_test_prefix "single-step" {
|
|
gdb_breakpoint "*${branch_to_kernel_helper}"
|
|
gdb_continue_to_breakpoint "branch to kernel helper"
|
|
gdb_test "si"
|
|
|
|
set test "bt"
|
|
gdb_test_multiple $test $test {
|
|
-re "#0 \[^\\r\\n\]*main .*\r\n$gdb_prompt $" {
|
|
# Test that the program still stops in main rather than
|
|
# somewhere else.
|
|
pass $test
|
|
}
|
|
-re "#0 0xffff0fe0 .*\r\n$gdb_prompt $" {
|
|
# AArch64 linux kernel can do hardware single step, so
|
|
# the program can stop at kernel helper.
|
|
pass $test
|
|
}
|
|
|
|
}
|
|
|
|
delete_breakpoints
|
|
}
|
|
|
|
with_test_prefix "cond-breakpoint" {
|
|
gdb_breakpoint "*${branch_to_kernel_helper} if i > 5"
|
|
gdb_continue_to_breakpoint "branch to kernel helper"
|
|
gdb_test "p i" " = 6"
|
|
|
|
delete_breakpoints
|
|
}
|