diff options
| -rw-r--r-- | labs/syscall.html | 114 | ||||
| -rw-r--r-- | user/alarmtest.c | 88 |
2 files changed, 118 insertions, 84 deletions
diff --git a/labs/syscall.html b/labs/syscall.html index 662641c..2281f2e 100644 --- a/labs/syscall.html +++ b/labs/syscall.html @@ -117,72 +117,13 @@ time in xv6, determined by how often a hardware timer generates interrupts. <p> -You should put the following test program in <tt>user/alarmtest.c</tt>: +You'll find a file <tt>user/alarmtest.c</tt> in your xv6 +repository. Add it to the Makefile. It won't compile correctly +until you've added <tt>sigalarm</tt> and <tt>sigreturn</tt> +system calls (see below). -<pre> -#include "kernel/param.h" -#include "kernel/types.h" -#include "kernel/stat.h" -#include "kernel/riscv.h" -#include "user/user.h" - -void test0(); -void test1(); -void periodic(); - -int -main(int argc, char *argv[]) -{ - test0(); - test1(); - exit(); -} - -void test0() -{ - int i; - printf(1, "test0 start\n"); - sigalarm(2, periodic); - for(i = 0; i < 1000*500000; i++){ - if((i % 250000) == 0) - write(2, ".", 1); - } - sigalarm(0, 0); - printf(1, "test0 done\n"); -} - -void -periodic() -{ - printf(1, "alarm!\n"); -} - -void __attribute__ ((noinline)) foo(int i, int *j) { - if((i % 2500000) == 0) { - write(2, ".", 1); - } - *j += 1; -} - -void test1() { - int i; - int j; - - printf(1, "test1 start\n"); - j = 0; - sigalarm(2, periodic); - for(i = 0; i < 1000*500000; i++){ - foo(i, &j); - } - if(i != j) { - printf(2, "i %d should = j %d\n", i, j); - exit(); - } - printf(1, "test1 done\n"); -} -</pre> - -The program calls <tt>sigalarm(2, periodic1)</tt> in <tt>test0</tt> to +<p> +<tt>alarmtest</tt> calls <tt>sigalarm(2, periodic)</tt> in <tt>test0</tt> to ask the kernel to force a call to <tt>periodic()</tt> every 2 ticks, and then spins for a while. You can see the assembly @@ -194,24 +135,23 @@ When you've finished the lab, <pre> $ alarmtest test0 start -...................................................alarm! -.............................................................alarm! -(repeated many times) -test0 done +......................................alarm! +test0 passed test1 start ..alarm! ..alarm! ..alarm! -(repeated many times) -test1 done +.alarm! +..alarm! +..alarm! +..alarm! +..alarm! +..alarm! +..alarm! +test1 passed $ </pre> -<p> -At first, however, you'll see that alarmtest only prints periods, -and doesn't print "alarm!". - - <p>The main challenge will be to arrange that the handler is invoked when the process's alarm interval expires. You'll need to modify usertrap() in kernel/trap.c so that when a @@ -223,6 +163,9 @@ and doesn't print "alarm!". <p>Your solution will be only a few lines of code, but it may be tricky to get it right. +We'll test your code with the version of alarmtest.c in the original +repository; if you modify alarmtest.c, make sure your kernel changes +cause the original alarmtest to pass the tests. <h3>test0: invoke handler</h3> @@ -236,15 +179,18 @@ program crashes after printing "alarm!". Here are some hints: <li>You'll need to modify the Makefile to cause <tt>alarmtest.c</tt> to be compiled as an xv6 user program. -<li>The right declaration to put in <tt>user/user.h</tt> is: +<li>The right declarations to put in <tt>user/user.h</tt> are: <pre> int sigalarm(int ticks, void (*handler)()); + int sigreturn(void); </pre> <li>Update user/sys.pl (which generates user/usys.S), kernel/syscall.h, and kernel/syscall.c - to allow <tt>alarmtest</tt> to invoke the sigalarm system - call. + to allow <tt>alarmtest</tt> to invoke the sigalarm and + sigreturn system calls. + +<li>For now, your <tt>sys_sigreturn</tt> should just return zero. <li>Your <tt>sys_sigalarm()</tt> should store the alarm interval and the pointer to the handler function in new fields in the <tt>proc</tt> @@ -300,15 +246,15 @@ can continue undisturbed after the alarm. <p>Your solution is likely to require you to save and restore registers---what registers do you need to save and restore to resume the interrupted code correctly? (Hint: it will be many). - Several approaches are possible; one convenient plan is to add another - system call <tt>sigreturn</tt> that the user-space alarm handler calls when it is - done, and which restores registers and returns to the original + Several approaches are possible; for this lab you should make + the <tt>sigreturn</tt> system call + restore registers and return to the original interrupted user instruction. + The user-space alarm handler + calls sigreturn when it is done. Some hints: <ul> - <li>Add a new <tt>sigreturn</tt> system call. - <li>Have <tt>usertrap</tt> save enough state in <tt>struct proc</tt> when the timer goes off that <tt>sigreturn</tt> can correctly return to the diff --git a/user/alarmtest.c b/user/alarmtest.c new file mode 100644 index 0000000..c6da547 --- /dev/null +++ b/user/alarmtest.c @@ -0,0 +1,88 @@ +// +// test program for the alarm lab. +// you can modify this file for testing, +// but please make sure your kernel +// modifications pass the original +// versions of these tests. +// + +#include "kernel/param.h" +#include "kernel/types.h" +#include "kernel/stat.h" +#include "kernel/riscv.h" +#include "user/user.h" + +void test0(); +void test1(); +void periodic(); + +int +main(int argc, char *argv[]) +{ + test0(); + test1(); + exit(); +} + +volatile static int count; + +void +periodic() +{ + count = count + 1; + printf(1, "alarm!\n"); + sigreturn(); +} + +// tests whether the kernel calls +// the alarm handler even a single time. +void +test0() +{ + int i; + printf(1, "test0 start\n"); + count = 0; + sigalarm(2, periodic); + for(i = 0; i < 1000*500000; i++){ + if((i % 250000) == 0) + write(2, ".", 1); + if(count > 0) + break; + } + sigalarm(0, 0); + if(count > 0){ + printf(1, "test0 passed\n"); + } else { + printf(1, "test0 failed\n"); + } +} + +void __attribute__ ((noinline)) foo(int i, int *j) { + if((i % 2500000) == 0) { + write(2, ".", 1); + } + *j += 1; +} + +void +test1() +{ + int i; + int j; + + printf(1, "test1 start\n"); + count = 0; + j = 0; + sigalarm(2, periodic); + for(i = 0; i < 500000000; i++){ + if(count >= 10) + break; + foo(i, &j); + } + if(i != j || count < 10){ + // i should equal j + printf(1, "test1 failed\n"); + } else { + printf(1, "test1 passed\n"); + } +} |