diff options
| -rw-r--r-- | src/libmain/Makefile.am | 2 | ||||
| -rw-r--r-- | src/libmain/shared.cc | 7 | ||||
| -rw-r--r-- | src/libmain/stack.cc | 72 |
3 files changed, 80 insertions, 1 deletions
diff --git a/src/libmain/Makefile.am b/src/libmain/Makefile.am index 6a2d7f5f58e5..75b9d83dcf73 100644 --- a/src/libmain/Makefile.am +++ b/src/libmain/Makefile.am @@ -1,6 +1,6 @@ pkglib_LTLIBRARIES = libmain.la -libmain_la_SOURCES = shared.cc +libmain_la_SOURCES = shared.cc stack.cc libmain_la_LIBADD = ../libstore/libstore.la @BDW_GC_LIBS@ diff --git a/src/libmain/shared.cc b/src/libmain/shared.cc index 4796629dc48c..ee0dccc9d11d 100644 --- a/src/libmain/shared.cc +++ b/src/libmain/shared.cc @@ -13,6 +13,7 @@ #include <sys/time.h> #include <sys/stat.h> #include <unistd.h> +#include <signal.h> #if HAVE_BOEHMGC #include <gc/gc.h> @@ -100,6 +101,9 @@ string getArg(const string & opt, } +void detectStackOverflow(); + + /* Initialize and reorder arguments, then call the actual argument processor. */ static void initAndRun(int argc, char * * argv) @@ -131,6 +135,9 @@ static void initAndRun(int argc, char * * argv) if (sigaction(SIGCHLD, &act, 0)) throw SysError("resetting SIGCHLD"); + /* Register a SIGSEGV handler to detect stack overflows. */ + detectStackOverflow(); + /* There is no privacy in the Nix system ;-) At least not for now. In particular, store objects should be readable by everybody. */ diff --git a/src/libmain/stack.cc b/src/libmain/stack.cc new file mode 100644 index 000000000000..0ea80f18e3b0 --- /dev/null +++ b/src/libmain/stack.cc @@ -0,0 +1,72 @@ +#include "config.h" + +#include "types.hh" + +#include <cstring> +#include <cstddef> +#include <cstdlib> + +#include <unistd.h> +#include <signal.h> + +namespace nix { + + +static void sigsegvHandler(int signo, siginfo_t * info, void * ctx) +{ + /* Detect stack overflows by comparing the faulting address with + the stack pointer. Unfortunately, getting the stack pointer is + not portable. */ + bool haveSP = true; + char * sp; +#if defined(__x86_64__) && defined(REG_RSP) + sp = (char *) ((ucontext *) ctx)->uc_mcontext.gregs[REG_RSP]; +#elif defined(REG_ESP) + sp = (char *) ((ucontext *) ctx)->uc_mcontext.gregs[REG_ESP]; +#else + haveSP = false; +#endif + + if (haveSP) { + ptrdiff_t diff = (char *) info->si_addr - sp; + if (diff < 0) diff = -diff; + if (diff < 4096) { + char msg[] = "error: stack overflow (possible infinite recursion)\n"; + write(2, msg, strlen(msg)); + _exit(1); // maybe abort instead? + } + } + + /* Restore default behaviour (i.e. segfault and dump core). */ + struct sigaction act; + sigfillset(&act.sa_mask); + act.sa_handler = SIG_DFL; + act.sa_flags = 0; + if (sigaction(SIGSEGV, &act, 0)) abort(); +} + + +void detectStackOverflow() +{ +#if defined(SA_SIGINFO) && defined (SA_ONSTACK) + /* Install a SIGSEGV handler to detect stack overflows. This + requires an alternative stack, otherwise the signal cannot be + delivered when we're out of stack space. */ + stack_t stack; + stack.ss_size = 4096 * 4; + stack.ss_sp = new char[stack.ss_size]; + if (!stack.ss_sp) throw Error("cannot allocate alternative stack"); + stack.ss_flags = 0; + if (sigaltstack(&stack, 0) == -1) throw SysError("cannot set alternative stack"); + + struct sigaction act; + sigfillset(&act.sa_mask); + act.sa_sigaction = sigsegvHandler; + act.sa_flags = SA_SIGINFO | SA_ONSTACK; + if (sigaction(SIGSEGV, &act, 0)) + throw SysError("resetting SIGCHLD"); +#endif +} + + +} |