使用vscode和qemu调试linux内核（包含汇编）

发表于 2022-04-26 更新于 2024-11-12 分类于 linux

vscode调试kernel的汇编部分有两个麻烦点

linux加载地址和链接地址不同
vscode的默认setupCommands无法正常使用

通过一段时间的摸索我找到了调试这部分代码的方法

对于加载地址问题，可以通过gdb的add-symbol-file的-o参数来解决（这要求gdb的版本较新才可以）
对于vscode的配置，后面我会列出目前摸索出的配置文件供参考

调试步骤

编译linux内核，目前我使用的是linux-5.17.4内核

为了能更好的支持c的调试，我这边尽可能的将C代码通过O0编译，对kernel做了如下修改, 并且编译去掉了CONFIG_JUMP_LABEL：

diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index 2f1de8865..27ecec930 100644
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile
@@ -213,3 +213,5 @@ define archhelp
   echo  '                  (distribution) /sbin/installkernel or'
   echo  '                  install to $$(INSTALL_PATH) and run lilo'
 endef
+
+subdir-ccflags-y = -O0
diff --git a/drivers/Makefile b/drivers/Makefile
index a110338c8..da99b36a1 100644
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -187,3 +187,5 @@ obj-$(CONFIG_GNSS)		+= gnss/
 obj-$(CONFIG_INTERCONNECT)	+= interconnect/
 obj-$(CONFIG_COUNTER)		+= counter/
 obj-$(CONFIG_MOST)		+= most/
+
+subdir-ccflags-y = -O0
diff --git a/drivers/char/tpm/Makefile b/drivers/char/tpm/Makefile
index 66d39ea6b..252f4d9d2 100644
--- a/drivers/char/tpm/Makefile
+++ b/drivers/char/tpm/Makefile
@@ -41,3 +41,5 @@ obj-$(CONFIG_TCG_XEN) += xen-tpmfront.o
 obj-$(CONFIG_TCG_CRB) += tpm_crb.o
 obj-$(CONFIG_TCG_VTPM_PROXY) += tpm_vtpm_proxy.o
 obj-$(CONFIG_TCG_FTPM_TEE) += tpm_ftpm_tee.o
+
+subdir-ccflags-y = -O1
diff --git a/drivers/net/phy/Makefile b/drivers/net/phy/Makefile
index b2728d00f..f369abb70 100644
--- a/drivers/net/phy/Makefile
+++ b/drivers/net/phy/Makefile
@@ -85,3 +85,5 @@ obj-$(CONFIG_STE10XP)		+= ste10Xp.o
 obj-$(CONFIG_TERANETICS_PHY)	+= teranetics.o
 obj-$(CONFIG_VITESSE_PHY)	+= vitesse.o
 obj-$(CONFIG_XILINX_GMII2RGMII) += xilinx_gmii2rgmii.o
+
+CFLAGS_phylink.o = -O1
diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index 472843eed..06d6edcdf 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -512,7 +512,7 @@ static inline bool lockdep_tcf_proto_is_locked(struct tcf_proto *tp)

 static inline void qdisc_cb_private_validate(const struct sk_buff *skb, int sz)
 {
-	struct qdisc_skb_cb *qcb;
+	struct qdisc_skb_cb *qcb __attribute__((unused));

 	BUILD_BUG_ON(sizeof(skb->cb) < sizeof(*qcb));
 	BUILD_BUG_ON(sizeof(qcb->data) < sz);
diff --git a/init/Makefile b/init/Makefile
index 06326e304..9a0b7f269 100644
--- a/init/Makefile
+++ b/init/Makefile
@@ -35,3 +35,5 @@ quiet_cmd_compile.h = CHK     $@

 include/generated/compile.h: FORCE
 	$(call cmd,compile.h)
+
+subdir-ccflags-y = -O0
diff --git a/kernel/Makefile b/kernel/Makefile
index a18d16973..aeaa9d6d8 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -160,3 +160,5 @@ $(obj)/kheaders_data.tar.xz: FORCE
 	$(call cmd,genikh)

 clean-files := kheaders_data.tar.xz kheaders.md5
+
+subdir-ccflags-y = -O0
diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile
index c1a9be6a4..d4713f4e3 100644
--- a/kernel/bpf/Makefile
+++ b/kernel/bpf/Makefile
@@ -40,3 +40,5 @@ obj-$(CONFIG_BPF_PRELOAD) += preload/
 obj-$(CONFIG_BPF_SYSCALL) += relo_core.o
 $(obj)/relo_core.o: $(srctree)/tools/lib/bpf/relo_core.c FORCE
 	$(call if_changed_rule,cc_o_c)
+
+CFLAGS_core.o = -O1
diff --git a/kernel/dma/Makefile b/kernel/dma/Makefile
index 0dd65ec1d..a09453711 100644
--- a/kernel/dma/Makefile
+++ b/kernel/dma/Makefile
@@ -10,3 +10,5 @@ obj-$(CONFIG_SWIOTLB)			+= swiotlb.o
 obj-$(CONFIG_DMA_COHERENT_POOL)		+= pool.o
 obj-$(CONFIG_DMA_REMAP)			+= remap.o
 obj-$(CONFIG_DMA_MAP_BENCHMARK)		+= map_benchmark.o
+
+CFLAGS_direct.o = -O1
diff --git a/lib/Makefile b/lib/Makefile
index 300f569c6..98aa9a698 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -398,3 +398,5 @@ $(obj)/$(TEST_FORTIFY_LOG): $(addprefix $(obj)/, $(TEST_FORTIFY_LOGS)) FORCE
 ifeq ($(CONFIG_FORTIFY_SOURCE),y)
 $(obj)/string.o: $(obj)/$(TEST_FORTIFY_LOG)
 endif
+
+subdir-ccflags-y = -O0
diff --git a/lib/zstd/Makefile b/lib/zstd/Makefile
index fc45339fc..96cb0ce27 100644
--- a/lib/zstd/Makefile
+++ b/lib/zstd/Makefile
@@ -42,3 +42,5 @@ zstd_decompress-y := \
 		decompress/zstd_ddict.o \
 		decompress/zstd_decompress.o \
 		decompress/zstd_decompress_block.o \
+
+subdir-ccflags-y = -O1
diff --git a/mm/Makefile b/mm/Makefile
index 70d4309c9..c225b254c 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -132,3 +132,12 @@ obj-$(CONFIG_PAGE_REPORTING) += page_reporting.o
 obj-$(CONFIG_IO_MAPPING) += io-mapping.o
 obj-$(CONFIG_HAVE_BOOTMEM_INFO_NODE) += bootmem_info.o
 obj-$(CONFIG_GENERIC_IOREMAP) += ioremap.o
+
+subdir-ccflags-y = -O0
+CFLAGS_truncate.o = -O1
+CFLAGS_gup.o = -O1
+CFLAGS_memory.o = -O1
+CFLAGS_pagewalk.o = -O1
+CFLAGS_page_io.o = -O1
+CFLAGS_vmalloc.o = -O1
+CFLAGS_swapfile.o = -O1

将vscode的launch按如下方式进行配置

{
    "version": "0.2.0",
    "configurations": [
        {
            "name": "linux",
            "type": "cppdbg",
            "request": "launch",
            "program": "${workspaceFolder}/vmlinux",
            "args": [],
            "stopAtEntry": false,
            "cwd": "${workspaceFolder}",
            "environment": [],
            "externalConsole": false,
            "MIMode": "gdb",
            "miDebuggerPath": "/home/gngshn/.local/opt/aarch64-buildroot-linux-gnu/bin/aarch64-linux-gdb",
            "targetArchitecture": "arm64",
            "customLaunchSetupCommands": [
                {
                    "text": "add-symbol-file vmlinux"
                },
                {
                    "text": "add-symbol-file vmlinux -o -0xffff7fffc7e00000"
                },
                {
                    "text": "b _text"
                },
                {
                    "text": "target remote :1234"
                },
            ],
        }
    ]
}

使用qemu打开linux

1	qemu-system-aarch64 -M virt -cpu cortex-a53 -smp 4 -m 4G -nographic -append "console=ttyAMA0" -kernel arch/arm64/boot/Image -initrd ../rootfs.cpio.uboot -S -s

直接再vscode中按F5开始调试即可