Learning VPP: Building DPDK with debug symbols

dpdk-vpp源码解读

发布于 2023-09-05 17:56:02

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发布于 2023-09-05 17:56:02

本文内容来源于国外程序员Denys Haryachyy 个人博客，下面是基于vpp 主线master分支在Ubuntu22.04环境进行测试验证。学习如何构建DPDK的debug版本，并且能够在DPDK源代码中进行单步调试。

主要是修改了两个文件，如下：

#修改ububtu deb包编译规则,增加不去除符号文件和调试信息（strip 操作）
build/external/deb/debian/rules
#dpdk make文件打开debug开关
build/external/packages/dpdk.mk

下面是修改后的patch文件内容：

diff --git a/build/external/deb/debian/rules b/build/external/deb/debian/rules
index 901d46897..b2a079bcd 100755
--- a/build/external/deb/debian/rules
+++ b/build/external/deb/debian/rules
@@ -31,3 +31,5 @@ override_dh_install:

 override_dh_shlibdeps:
        dh_shlibdeps -l$(INSTALL_DIR)lib/
+override_dh_strip:
+       dh_strip --exclude=librte
diff --git a/build/external/packages/dpdk.mk b/build/external/packages/dpdk.mk
index 04a069bb1..302522631 100644
--- a/build/external/packages/dpdk.mk
+++ b/build/external/packages/dpdk.mk
@@ -13,7 +13,7 @@

 DPDK_PKTMBUF_HEADROOM        ?= 128
 DPDK_USE_LIBBSD              ?= n
-DPDK_DEBUG                   ?= n
+DPDK_DEBUG                   ?= y
 DPDK_TAP_PMD                 ?= n
 DPDK_FAILSAFE_PMD            ?= n
 DPDK_MACHINE                 ?= default

重新编译vpp并运行启动vpp进程。进入GDB界面下面来调试一下dpdk收包模块的流程，由于我当前环境中show hardware无法查询到网卡收发包函数的具体名称，需要通过直接打印rte_eth_devices网卡设备来查询收发包函数。

#因为当前环境show hardware未查询到rx tx函数名称。
(gdb) p rte_eth_devices[0]
$1 = {rx_pkt_burst = 0x7f26bbead580 <eth_em_recv_scattered_pkts>,
  tx_pkt_burst = 0x7f26bbeae050 <eth_em_xmit_pkts>, tx_pkt_prepare = 0x7f26bbeaf440 <eth_em_prep_pkts>,
  rx_queue_count = 0x7f26bbeafde0 <eth_em_rx_queue_count>,
  rx_descriptor_status = 0x7f26bbeafe50 <eth_em_rx_descriptor_status>,
  tx_descriptor_status = 0x7f26bbeafea0 <eth_em_tx_descriptor_status>, data = 0xac03a8d40,
  process_private = 0x0, dev_ops = 0x7f26bc93ab80 <eth_em_ops>, device = 0x5571f465ead0,
  intr_handle = 0x5571f4619840, link_intr_cbs = {tqh_first = 0x0,
    tqh_last = 0x7f26bcc55ad8 <rte_eth_devices+88>}, post_rx_burst_cbs = {0x0 <repeats 1024 times>},
  pre_tx_burst_cbs = {0x0 <repeats 1024 times>}, state = RTE_ETH_DEV_ATTACHED, security_ctx = 0x0}

通过gdb list 函数名来查询函数所在的文件，下面提示查询不到函数对应的文件

(gdb) list eth_em_recv_scattered_pkts
849    ../src-dpdk/drivers/net/e1000/em_rxtx.c: No such file or directory.

接下来我们通过set substitute-path来修改搜索源码文件的路径，再次list 函数查询可以显示函数内容。

(gdb) set substitute-path '../src-dpdk/' '/home/jinsh/workspace/vpp-master/build/external/downloads/dpdk-23.03'
(gdb) list eth_em_recv_scattered_pkts
849    }
850
851    uint16_t
852    eth_em_recv_scattered_pkts(void *rx_queue, struct rte_mbuf **rx_pkts,
853                 uint16_t nb_pkts)
854    {
855        struct em_rx_queue *rxq;
856        volatile struct e1000_rx_desc *rx_ring;
857        volatile struct e1000_rx_desc *rxdp;
858        struct em_rx_entry *sw_ring;

substitute-path的详细用法可以在下面链接学习 https://www.irya.unam.mx/computo/sites/manuales/fce12/debugger/cl/commandref/gdb_mode/cmd_set_substitu.ht

设置函数断点eth_em_recv_scattered_pkts，并运行程序。程序会中断在网卡收包函数中，之后可以进行单步调试代码。

#设置断点函数到dpdk收包函数
(gdb) b eth_em_recv_scattered_pkts
Breakpoint 1 at 0x7f26bbead580: file ../src-dpdk/drivers/net/e1000/em_rxtx.c, line 854.
(gdb) c   #运行程序
Continuing.
#gdb 停留在断点位置
Thread 1 "vpp_main" hit Breakpoint 1, eth_em_recv_scattered_pkts (rx_queue=0xac02777c0, rx_pkts=0x7f26c211b900, nb_pkts=32) at ../src-dpdk/drivers/net/e1000/em_rxtx.c:854
854    {
(gdb) list  #显示源代码程序
849    }
850
851    uint16_t
852    eth_em_recv_scattered_pkts(void *rx_queue, struct rte_mbuf **rx_pkts,
853                 uint16_t nb_pkts)
854    {
855        struct em_rx_queue *rxq;
856        volatile struct e1000_rx_desc *rx_ring;
857        volatile struct e1000_rx_desc *rxdp;
858        struct em_rx_entry *sw_ring;
(gdb) next 继续运行程序
877        rx_ring = rxq->rx_ring;
(gdb) n
878        sw_ring = rxq->sw_ring;

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原始发表：2023-07-07，如有侵权请联系 cloudcommunity@tencent.com 删除

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