kernel

cd kernel
git clone https://android.googlesource.com/kernel/goldfish

cd goldfish
git branch -r
git checkout origin/android-goldfish-4.4-dev -b android-goldfish-4.4-dev

#指定编译的内核类型
export ARCH=x86
#指定的gcc编译器的前缀, 就是下面PATH中的x86_64-linux-android-4.9的前缀
export CROSS_COMPILE=x86_64-linux-android-
export REAL_CROSS_COMPILE=x86_64-linux-android-
#这里android_root要写是android根目录的绝对地址例如: ~/google/android-9.0
PATH=$PATH:/home/zhenghuan/Android/Source/android-9.0.0_r3/prebuilts/gcc/linux-x86/x86/x86_64-linux-android-4.9/bin
#编译的配置,在arch/x86/configs目录下,
make x86_64_ranchu_defconfig
#编译内核命令
make -j16

~/Android/Source/android-9.0.0_r3$ emulator -show-kernel -kernel /home/zhenghuan/Android/Source/kernel/goldfish/arch/x86/boot/bzImage -qemu -s

CONFIG_DEBUG_KERNEL=y 打开这个选项后，vmlinux 才有符号
CONFIG_DEBUG_INFO=y
CONFIG_FRAME_POINTER=y
//开启kgdb
CONFIG_KGDB=y 
CONFIG_DEBUG_RODATA=n
CONFIG_RANDOMIZE_BASE=n

zhangjg@zjg:~/deve/open_source/android-kernel/goldfish$ git diff
diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
index 41218867a9a6..e67810313d97 100644
--- a/arch/arm/mm/Kconfig
+++ b/arch/arm/mm/Kconfig
@@ -1052,7 +1052,7 @@ config ARM_KERNMEM_PERMS
 config DEBUG_RODATA
        bool "Make kernel text and rodata read-only"
        depends on ARM_KERNMEM_PERMS
-       default y
+       default n
        help
          If this is set, kernel text and rodata will be made read-only. This
          is to help catch accidental or malicious attempts to change the
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index ad1f3bfafe75..50fa4dc68eff 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -307,7 +307,7 @@ config FIX_EARLYCON_MEM
        def_bool y
 
 config DEBUG_RODATA
-       def_bool y
+       def_bool n
 
 config PGTABLE_LEVELS
        int

(gdb) b vfs_write
Breakpoint 1 at 0xffffffff803474d8: file fs/read_write.c, line 524.
(gdb) c
Continuing.
Warning:
Cannot insert breakpoint 1.
Cannot access memory at address 0xffffffff803474d8

Serial console over KGDB NMI debugger port (SERIAL_KGDB_NMI) [N/y/?] (NEW) N
KGDB: kernel debugger (KGDB) [Y/n/?] y
KGDB: use kgdb over the serial console (KGDB_SERIAL_CONSOLE) [Y/n/m/?] (NEW) n
KGDB: internal test suite (KGDB_TESTS) [N/y/?] (NEW) N
KGDB: Allow debugging with traps in notifiers (KGDB_LOW_LEVEL_TRAP) [N/y/?] (NEW) N
KGDB_KDB: include kdb frontend for kgdb (KGDB_KDB) [N/y/?] (NEW) y
KDB: Select kdb command functions to be enabled by default (KDB_DEFAULT_ENABLE) [0x1] (NEW) 0x1
KGDB_KDB: keyboard as input device (KDB_KEYBOARD) [N/y/?] (NEW) y
KDB: continue after catastrophic errors (KDB_CONTINUE_CATASTROPHIC) [0] (NEW) 0

Kernel: arch/x86/boot/bzImage is ready  (#2)
ton在内核源码根目录生成vmlinux文件

~/Android/Source/kernel/goldfish$ export PATH=/home/zhenghuan/Android/Source/android-9.0.0_r3/prebuilts/gdb/linux-x86/bin:$PATH
~/Android/Source/kernel/goldfish$ which gdb
/home/zhenghuan/Android/Source/android-9.0.0_r3/prebuilts/gdb/linux-x86/bin/gdb

~/Android/Source/kernel/goldfish$ gdb ./vmlinux
GNU gdb (GDB) 7.11
Copyright (C) 2016 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from ./vmlinux...done.

(gdb) target remote :1234
Remote debugging using :1234
0xffffffff834345e8 in ?? ()
(gdb) bt
#0  0xffffffff834345e8 in ?? ()
#1  0xffffffff84003ec8 in ?? ()
#2  0xffffffff8340c0d9 in ?? ()
#3  0x0000000000000000 in ?? ()

#ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE
#KBUILD_CFLAGS	+= $(call cc-option,-Oz,-Os)
#else
#ifdef CONFIG_PROFILE_ALL_BRANCHES
#KBUILD_CFLAGS	+= -O2
#else
#KBUILD_CFLAGS   += -O2
#endif
#endif

KBUILD_CFLAGS   += -Og