Attachment 316309 Details for Bug 162774 – Proof-of-concept patch

[patch] Proof-of-concept patch

1.patch (text/plain), 2.81 KB, created by Denys Vlasenko on 2008-09-10 12:53:06 UTC

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Creator: Denys Vlasenko

Created: 2008-09-10 12:53:06 UTC

Size: 2.81 KB

patch

obsolete

>diff -d -urpN strace.0/strace.c strace.1/strace.c
>--- strace.0/strace.c	2008-08-06 23:38:52.000000000 +0200
>+++ strace.1/strace.c	2008-09-10 14:18:32.000000000 +0200
>@@ -78,6 +78,8 @@
> #endif
> #endif
> 
>+int SIGTRAP80 = SIGTRAP;
>+
> int debug = 0, followfork = 0;
> int dtime = 0, cflag = 0, xflag = 0, qflag = 0;
> static int iflag = 0, interactive = 0, pflag_seen = 0, rflag = 0, tflag = 0;
>@@ -1541,9 +1543,9 @@ int sig;
> 				}
> 				break;
> 			}
>-			if ((error = ptrace(PTRACE_CONT, tcp->pid, (char *) 1,
>-			    WSTOPSIG(status) == SIGTRAP ?
>-			    0 : WSTOPSIG(status))) < 0) {
>+			error = ptrace(PTRACE_CONT, tcp->pid, (char *) 1,
>+				WSTOPSIG(status) == SIGTRAP80 ? 0 : WSTOPSIG(status));
>+			if (error < 0) {
> 				if (errno != ESRCH)
> 					perror("detach: ptrace(PTRACE_CONT, ...)");
> 				break;
>@@ -2400,10 +2402,52 @@ Process %d attached (waiting for parent)
> 					return -1;
> 				}
> 			}
>+			/* Ask kernel to set signo to SIGTRAP | 0x80
>+			 * on ptrace-generated SIGTRAPs */
>+//#if defined(PTRACE_SETOPTIONS) && defined(PTRACE_O_TRACESYSGOOD)
>+			if (ptrace(PTRACE_SETOPTIONS, pid, (char *) 0, (void *) PTRACE_O_TRACESYSGOOD) == 0) {
>+fprintf(stderr, "ptrace(PTRACE_SETOPTIONS, ..., PTRACE_O_TRACESYSGOOD) successful\n");
>+				SIGTRAP80 = SIGTRAP | 0x80;
>+			}
>+//#endif
> 			goto tracing;
> 		}
> 
>-		if (WSTOPSIG(status) != SIGTRAP) {
>+		/* Kernel bug (observed on 2.6.25 x86_64):
>+		 * even if we set PTRACE_O_TRACESYSGOOD option,
>+		 * after execve(), post-syscall ptrace-generated SIGTRAP
>+		 * has signo == SIGTRAP, not (SIGTRAP | 0x80)!
>+		 * Detect it by looking at siginfo.
>+		 */
>+		if (SIGTRAP80 != SIGTRAP && WSTOPSIG(status) == SIGTRAP) {
>+			siginfo_t si;
>+			ptrace(PTRACE_GETSIGINFO, pid, (void*) 0, (void*) &si);
>+//fprintf(stderr, "si_signo:%d\n" , si.si_signo);
>+//fprintf(stderr, "si_errno:%d\n" , si.si_errno);
>+//fprintf(stderr, "si_code:%d\n"  , si.si_code);
>+//fprintf(stderr, "si_pid:%d\n"   , si.si_pid);
>+//fprintf(stderr, "si_status:%d\n", si.si_status);
>+//fprintf(stderr, "si_int:%d\n"   , si.si_int);
>+//fprintf(stderr, "si_ptr:%p\n"   , si.si_ptr);
>+//fprintf(stderr, "si_band:%ld\n" , (long)si.si_band);
>+//I saw this:
>+//false SIGTRAP          real SIGTRAP
>+//si_signo:64768         si_signo:5 /*SIGTRAP*/
>+//si_errno:0             si_errno:0
>+//si_code:6558744        si_code:128 /*SI_KERNEL*/
>+//si_pid:2               si_pid:0
>+//si_status:-1117706216  si_status:-1117706216
>+//si_int:-1117706216     si_int:-1117706216
>+//si_ptr:0x7fffbd612818  si_ptr:0x7fffbd612818
>+//si_band:2              si_band:0
>+			if (si.si_signo != SIGTRAP || si.si_code != SI_KERNEL) {
>+				/* Set WSTOPSIG(status) = (SIGTRAP | 0x80) */
>+				status |= 0x8000;
>+fprintf(stderr, "bogus SIGTRAP: made it SIGTRAP80\n");
>+			}
>+		}
>+
>+		if (WSTOPSIG(status) != SIGTRAP80) {
> 			if (WSTOPSIG(status) == SIGSTOP &&
> 					(tcp->flags & TCB_SIGTRAPPED)) {
> 				/*

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Attachments on bug 162774: 316309 | 317582 | 327158