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add lab2 for chapter6
Signed-off-by: Wang Long <[email protected]>
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‎rlk_lab/rlk_basic/chapter_6/lab2/0001-x86-add-a-new-syscall-which-called-getpuid.patch‎

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From e4d3eb5953e8933cad1b51915c917dd7905d7078 Mon Sep 17 00:00:00 2001
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From: Wang Long <[email protected]>
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Date: Sat, 6 Jul 2019 10:06:03 +0800
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Subject: [PATCH] x86: add a new syscall which called getpuid
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This patch add a new syscall for x86, which name is getpuid.
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getpuid return the current process's pid and uid.
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its prototype is: long sys_getpuid(pid_t *pid, uid_t *uid);
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Signed-off-by: Wang Long <[email protected]>
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---
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arch/x86/entry/syscalls/syscall_64.tbl | 1 +
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include/linux/syscalls.h | 1 +
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kernel/sys.c | 14 ++++++++++++++
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3 files changed, 16 insertions(+)
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diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
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index 92ee0b437..f8afc50c9 100644
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--- a/arch/x86/entry/syscalls/syscall_64.tbl
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+++ b/arch/x86/entry/syscalls/syscall_64.tbl
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@@ -343,6 +343,7 @@
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332 common statx __x64_sys_statx
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333 common io_pgetevents __x64_sys_io_pgetevents
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334 common rseq __x64_sys_rseq
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+350 common getpuid __x64_sys_getpuid
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# don't use numbers 387 through 423, add new calls after the last
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# 'common' entry
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424 common pidfd_send_signal __x64_sys_pidfd_send_signal
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diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
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index e446806a5..8f007f00b 100644
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--- a/include/linux/syscalls.h
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+++ b/include/linux/syscalls.h
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@@ -1390,4 +1390,5 @@ static inline unsigned int ksys_personality(unsigned int personality)
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return old;
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}
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+asmlinkage long sys_getpuid(pid_t __user *pid, uid_t __user *uid);
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#endif
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diff --git a/kernel/sys.c b/kernel/sys.c
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index bdbfe8d37..d75d8654d 100644
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--- a/kernel/sys.c
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+++ b/kernel/sys.c
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@@ -2648,4 +2648,18 @@ COMPAT_SYSCALL_DEFINE1(sysinfo, struct compat_sysinfo __user *, info)
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return 0;
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}
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+
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+SYSCALL_DEFINE2(getpuid, pid_t __user *, pid, uid_t __user *, uid) {
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+ if (pid == NULL && uid == NULL)
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+ return -EINVAL;
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+
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+ if (pid != NULL)
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+ *pid = task_tgid_vnr(current);
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+
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+ if (uid != NULL)
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+ *uid = from_kuid_munged(current_user_ns(), current_uid());
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+
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+ return 0;
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+}
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+
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#endif /* CONFIG_COMPAT */
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--
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2.17.1
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‎rlk_lab/rlk_basic/chapter_6/lab2/README.md‎

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# 说明
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该实验为《奔跑吧Linux入门版》中第六章的实验2的参考代码。
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实验要求添加的系统调用不传递任何参数，一般将`pid`和`uid`直接通过`printk`输出到`dmesg`中，但是这样非常的不优雅。该参考代码添加了一个系统调用
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```c
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long getpuid(pid_t *pid, uid_t *uid);
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```
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`pid`和`uid`通过参数返回。
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为了方便进行实验，以下实验基于《奔跑吧Linux入门版》中第一章的实验室2，我们选定了最新的社区稳定版内核来修改添加系统调用，然后编译后，安装到优麒麟Linux机器上。
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# 实验步骤
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## 下载最新的社区稳定版内核
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在完成该实验时，社区最新的稳定版内核是`linux-5.1.16`，下载方法如下：
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```
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$ wget -c https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.1.16.tar.xz
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$ xz -d linux-5.1.16.tar.xz
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$ tar -xf linux-5.1.16.tar
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$ cd linux-5.1.16/
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```
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## 添加系统调用getpuid
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`0001-x86-add-a-new-syscall-which-called-getpuid.patch`是基于`linux-5.1.16`制作的patch，如果是其它版本，请参考如下该`patch`进行修改：
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```
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$ cat 0001-x86-add-a-new-syscall-which-called-getpuid.patch
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From e4d3eb5953e8933cad1b51915c917dd7905d7078 Mon Sep 17 00:00:00 2001
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From: Wang Long <[email protected]>
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Date: Sat, 6 Jul 2019 10:06:03 +0800
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Subject: [PATCH] x86: add a new syscall which called getpuid
39+
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This patch add a new syscall for x86, which name is getpuid.
41+
getpuid return the current process's pid and uid.
42+
43+
its prototype is: long sys_getpuid(pid_t *pid, uid_t *uid);
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Signed-off-by: Wang Long <[email protected]>
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---
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arch/x86/entry/syscalls/syscall_64.tbl | 1 +
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include/linux/syscalls.h | 1 +
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kernel/sys.c | 14 ++++++++++++++
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3 files changed, 16 insertions(+)
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diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
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index 92ee0b437..f8afc50c9 100644
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--- a/arch/x86/entry/syscalls/syscall_64.tbl
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+++ b/arch/x86/entry/syscalls/syscall_64.tbl
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@@ -343,6 +343,7 @@
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332 common statx __x64_sys_statx
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333 common io_pgetevents __x64_sys_io_pgetevents
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334 common rseq __x64_sys_rseq
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+350 common getpuid __x64_sys_getpuid
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# don't use numbers 387 through 423, add new calls after the last
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# 'common' entry
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424 common pidfd_send_signal __x64_sys_pidfd_send_signal
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diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
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index e446806a5..8f007f00b 100644
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--- a/include/linux/syscalls.h
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+++ b/include/linux/syscalls.h
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@@ -1390,4 +1390,5 @@ static inline unsigned int ksys_personality(unsigned int personality)
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return old;
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}
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+asmlinkage long sys_getpuid(pid_t __user *pid, uid_t __user *uid);
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#endif
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diff --git a/kernel/sys.c b/kernel/sys.c
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index bdbfe8d37..d75d8654d 100644
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--- a/kernel/sys.c
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+++ b/kernel/sys.c
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@@ -2648,4 +2648,18 @@ COMPAT_SYSCALL_DEFINE1(sysinfo, struct compat_sysinfo __user *, info)
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return 0;
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}
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+
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+SYSCALL_DEFINE2(getpuid, pid_t __user *, pid, uid_t __user *, uid) {
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+ if (pid == NULL && uid == NULL)
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+ return -EINVAL;
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+
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+ if (pid != NULL)
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+ *pid = task_tgid_vnr(current);
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+
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+ if (uid != NULL)
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+ *uid = from_kuid_munged(current_user_ns(), current_uid());
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+
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+ return 0;
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+}
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+
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#endif /* CONFIG_COMPAT */
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--
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2.17.1
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```
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## 编译
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为了方便，我们直接复制优麒麟Linux系统中自带的配置文件，我的系统上的配置文件为：`/boot/config-4.18.0-16-generic`，相关命令如下：
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```
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$ cd linux-5.1.16/
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$ cp /boot/config-4.18.0-16-generic .config
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$ make menuconfig
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$ make -j4
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```
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## 安装
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```
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$ sudo make modules_install
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$ sudo make install
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```
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安装完成后，重启电脑，用刚才编译的内核启动，登录系统。
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## 编写应用程序并编译运行
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```
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$ cd ~/runninglinuxkernel_4.0
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$ cd rlk_lab/rlk_basic/chapter_6/lab2/
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$ gcc -o test_getpuid_syscall test_getpuid_syscall.c
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$ ./test_getpuid_syscall
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call getpuid success, return pid = 1419, uid = 1000
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$ ./test_getpuid_syscall
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call getpuid success, return pid = 1420, uid = 1000
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```

‎rlk_lab/rlk_basic/chapter_6/lab2/test_getpuid_syscall.c‎

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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <errno.h>
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int main(int argc, char **argv)
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{
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long pid, uid;
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int ret;
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pid = uid = 0;
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ret = (int)syscall(350, &pid, &uid);
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if (ret != 0) {
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printf("call getpuid failed\n");
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return 1;
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}
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printf("call getpuid success, return pid = %ld, uid = %ld\n", pid, uid);
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return 0;
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}

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