On Tue, May 22, 2007 at 11:46:11PM -0700, Roland McGrath wrote:
> Do you have a test case for PTRACE_SYSEMU that does not work right?
UML, obviously. Below is a smaller test. orig_eax is wrong, so you
can't read the system call number from the process.
With kernel-2.6.20-1.2948, it prints out a bunch of -1's. On FC5
kernels, you get more reasonable numbers.
Jeff
--
Work email - jdike at linux dot intel dot com
#include <stdlib.h>
#include <stdio.h>
#include <asm/unistd.h>
#include <sys/mman.h>
#include <sys/ptrace.h>
#include <asm/ptrace.h>
#include <sys/wait.h>
#define PTRACE_SYSEMU 31
#define PAGE_SIZE 4096
static inline long stub_syscall0(long syscall)
{
long ret;
__asm__ volatile ("int $0x80" : "=a" (ret) : "0" (syscall));
return ret;
}
static void child(void)
{
if(ptrace(PTRACE_TRACEME, 0, 0, 0) < 0){
perror("traceme");
exit(1);
}
kill(getpid(), SIGUSR1);
stub_syscall0(__NR_getpid);
}
int main(void)
{
void *stack;
unsigned long sp, regs[FRAME_SIZE];
int pid, n, status;
stack = mmap(NULL, PAGE_SIZE, PROT_READ | PROT_WRITE | PROT_EXEC,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if(stack == MAP_FAILED){
perror("mmap");
exit(1);
}
sp = (unsigned long) stack + PAGE_SIZE - sizeof(void *);
pid = fork();
if(pid < 0)
perror("fork");
else if(pid == 0){
child();
}
else {
while(1){
n = waitpid(pid, &status, WUNTRACED);
if(n < 0){
perror("waitpid");
exit(1);
}
n = ptrace(PTRACE_GETREGS, pid, 0, regs);
if(n < 0){
perror("PTRACE_GETREGS");
exit(1);
}
printf("Status 0x%x orig_eax 0x%x\n", status,
regs[ORIG_EAX]);
if(ptrace(PTRACE_SYSEMU, pid, 0, 0)){
perror("PTRACE_SYSEMU");
exit(1);
}
}
}
return 0;
}
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