ha, forget it, it is all correct actually :)
On 06/07/12 17:30, Alexey Kardashevskiy wrote:
> Hi!
>
> I am trying to change DSCR's value of a specific process with pid=XXX. For
> this, I attach by ptrace() to XXX, inject a piece of code which does
> mfspr/mtspr, "continue" XXX and see how it is changing. So far so good.
>
> The problem is with "continue". The XXX process does not wake up until I
> press a key (if XXX is waiting on something like scanf() or gets()) OR it
> exits from sleep() if I change it to run sleep() in a loop.
>
> Not sure if it matters but mfspr/mtspr are privileged instructions and are
> emulated by the kernel.
>
> How to wake XXX up?
>
>
>
> #include <sys/ptrace.h>
> #include <sys/types.h>
> #include <sys/wait.h>
> #include <string.h>
> #include <unistd.h>
> #include <sys/user.h>
> #include <stdio.h>
> #include <stdlib.h>
>
> void getdata(pid_t child, long addr, void *str)
> {
> unsigned long *ptr = (unsigned long *) str;
> ptr[0] = ptrace(PTRACE_PEEKDATA, child, addr, NULL);
> }
>
> void putdata(pid_t child, long addr, void *str)
> {
> unsigned long *ptr = (unsigned long *) str;
> ptrace(PTRACE_POKEDATA, child, addr, ptr[0]);
> }
>
> int main(int argc, char *argv[])
> {
> pid_t traced_process;
> struct pt_regs regs, backup_regs;
> unsigned long dscr = -1;
> /*.set_dscr:
> * 7f d1 03 a6 mtspr 17,r30
> 7d 82 10 08 twge r2,r2 <- set breakpoint */
> unsigned int insert_set[] = { 0x7fd103a6, 0x7d821008 };
> /*.get_dscr:
> 7f d1 02 a6 mfspr r30,17
> 7d 82 10 08 twge r2,r2 <- set breakpoint */
> unsigned int insert_get[] = { 0x7fd102a6, 0x7d821008 };
> char backup[8];
> int len = 8;
>
> if((argc < 2)||(sizeof(unsigned int)!=4)) {
> printf("Usage: %s <pid to be traced> [dscr value]\n", argv[0],
> argv[1]);
> exit(1);
> }
> if (argc > 2) {
> dscr = atoi(argv[2]);
> }
>
> traced_process = atoi(argv[1]);
> ptrace(PTRACE_ATTACH, traced_process, NULL, NULL);
> wait(NULL);
>
> printf("Attached to pid=%u\n", traced_process);
> ptrace(PTRACE_GETREGS, traced_process, NULL, ®s);
> backup_regs = regs;
> getdata(traced_process, regs.nip, backup);
>
> if (dscr != -1) {
> regs.gpr[30] = dscr;
> putdata(traced_process, regs.nip, insert_set);
> ptrace(PTRACE_SETREGS, traced_process, NULL, ®s);
> printf("Setting DSCR = %x to gpr0\n", regs.gpr[30]);
> } else {
> putdata(traced_process, regs.nip, insert_get);
> printf("Reading DSCR\n");
> }
>
> printf("Continued pid=%u\n", traced_process);
> ptrace(PTRACE_CONT, traced_process, NULL, SIGCONT);
>
> printf("waiting...\n");
> wait(NULL); // <---------------- HERE IS THE PROBLEM
>
> if (dscr == -1) {
> printf("DSCR has been read\n");
> ptrace(PTRACE_GETREGS, traced_process, NULL, ®s);
> printf("Reading DSCR from gpr30 = %x\n", regs.gpr[30]);
> }
>
> printf("The process stopped, Putting back the original instructions\n");
> putdata(traced_process, backup_regs.nip, backup);
> ptrace(PTRACE_SETREGS, traced_process, NULL, &backup_regs);
> printf("Letting it continue with original flow\n");
> ptrace(PTRACE_DETACH, traced_process, NULL, NULL);
>
> return 0;
> }
>
--
Alexey
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