--safe-crash-log-file flag

base/options.jl

@@ -57,6 +57,7 @@ struct JLOptions
     strip_ir::Int8
     permalloc_pkgimg::Int8
     heap_size_hint::UInt64
+    safe_crash_log_file::Ptr{UInt8}
 end
 
 # This runs early in the sysimage != is not defined yet

src/init.c

@@ -823,6 +823,15 @@ JL_DLLEXPORT void julia_init(JL_IMAGE_SEARCH rel)
     if (jl_options.handle_signals == JL_OPTIONS_HANDLE_SIGNALS_ON)
         jl_install_default_signal_handlers();
 
+#if defined(_OS_LINUX_) && defined(_CPU_X86_64_)
+    if (jl_options.safe_crash_log_file != NULL) {
+        jl_sig_fd = open(jl_options.safe_crash_log_file, O_WRONLY | O_CREAT | O_TRUNC, 0600);
+        if (jl_sig_fd == -1) {
+            jl_error("fatal error: could not open safe crash log file for writing");
+        }
+    }
+#endif
+
     jl_gc_init();
 
     arraylist_new(&jl_linkage_blobs, 0);

src/jl_uv.c

@@ -693,8 +693,15 @@ JL_DLLEXPORT void jl_safe_printf(const char *fmt, ...)
     va_end(args);
 
     buf[999] = '\0';
-    if (write(STDERR_FILENO, buf, strlen(buf)) < 0) {
-        // nothing we can do; ignore the failure
+    if (jl_inside_signal_handler() && jl_sig_fd != 0) {
+        if (write(jl_sig_fd, buf, strlen(buf)) < 0) {
+            // nothing we can do; ignore the failure
+        }
+    }
+    else {
+        if (write(STDERR_FILENO, buf, strlen(buf)) < 0) {
+            // nothing we can do; ignore the failure
+        }
     }
 #ifdef _OS_WINDOWS_
     SetLastError(last_error);

src/jloptions.c

@@ -90,6 +90,7 @@ JL_DLLEXPORT void jl_init_options(void)
                         0, // strip-ir
                         0, // permalloc_pkgimg
                         0, // heap-size-hint
+                        NULL, // safe_crash_log_file
     };
     jl_options_initialized = 1;
 }
@@ -258,7 +259,8 @@ JL_DLLEXPORT void jl_parse_opts(int *argcp, char ***argvp)
            opt_strip_ir,
            opt_heap_size_hint,
            opt_gc_threads,
-           opt_permalloc_pkgimg
+           opt_permalloc_pkgimg,
+           opt_safe_crash_log_file,
     };
     static const char* const shortopts = "+vhqH:e:E:L:J:C:it:p:O:g:";
     static const struct option longopts[] = {
@@ -320,6 +322,7 @@ JL_DLLEXPORT void jl_parse_opts(int *argcp, char ***argvp)
         { "strip-ir",        no_argument,       0, opt_strip_ir },
         { "permalloc-pkgimg",required_argument, 0, opt_permalloc_pkgimg },
         { "heap-size-hint",  required_argument, 0, opt_heap_size_hint },
+        { "safe-crash-log-file",   required_argument, 0, opt_safe_crash_log_file },
         { 0, 0, 0, 0 }
     };
 
@@ -850,6 +853,11 @@ JL_DLLEXPORT void jl_parse_opts(int *argcp, char ***argvp)
             else
                 jl_errorf("julia: invalid argument to --permalloc-pkgimg={yes|no} (%s)", optarg);
             break;
+        case opt_safe_crash_log_file:
+            jl_options.safe_crash_log_file = strdup(optarg);
+            if (jl_options.safe_crash_log_file == NULL)
+                jl_error("julia: failed to allocate memory for --safe-crash-log-file");
+            break;
         default:
             jl_errorf("julia: unhandled option -- %c\n"
                       "This is a bug, please report it.", c);

src/jloptions.h

@@ -61,6 +61,7 @@ typedef struct {
     int8_t strip_ir;
     int8_t permalloc_pkgimg;
     uint64_t heap_size_hint;
+    const char *safe_crash_log_file;
 } jl_options_t;
 
 #endif

src/julia_internal.h

@@ -702,6 +702,29 @@ JL_CALLABLE(jl_f_opaque_closure_call);
 void jl_install_default_signal_handlers(void);
 void restore_signals(void);
 void jl_install_thread_signal_handler(jl_ptls_t ptls);
+extern void *signal_stack;
+extern size_t sig_stack_size;
+STATIC_INLINE int is_addr_on_sigstack(jl_ptls_t ptls, void *ptr)
+{
+    // One guard page for signal_stack.
+    return !((char*)ptr < (char*)ptls->signal_stack - jl_page_size ||
+             (char*)ptr > (char*)ptls->signal_stack + sig_stack_size);
+}
+STATIC_INLINE int jl_inside_signal_handler(void)
+{
+#if defined(_OS_LINUX_) && defined(_CPU_X86_64_)
+    // Read the stack pointer
+    size_t sp;
+    __asm__ __volatile__("movq %%rsp, %0" : "=r"(sp));
+    // Check if the stack pointer is within the signal stack
+    jl_ptls_t ptls = jl_current_task->ptls;
+    return is_addr_on_sigstack(ptls, (void*)sp);
+#else
+    return 0;
+#endif
+}
+// File-descriptor for safe logging on signal handling
+extern int jl_sig_fd;
 
 JL_DLLEXPORT jl_fptr_args_t jl_get_builtin_fptr(jl_value_t *b);
 

src/signal-handling.c

@@ -28,6 +28,10 @@ static const    uint64_t GIGA = 1000000000ULL;
 // Timers to take samples at intervals
 JL_DLLEXPORT void jl_profile_stop_timer(void);
 JL_DLLEXPORT int jl_profile_start_timer(void);
+// Signal stack
+void *signal_stack = NULL;
+// File-descriptor for safe logging on signal handling
+int jl_sig_fd;
 
 ///////////////////////
 // Utility functions //

src/signals-unix.c

@@ -38,7 +38,7 @@
 // 8M signal stack, same as default stack size and enough
 // for reasonable finalizers.
 // Should also be enough for parallel GC when we have it =)
-#define sig_stack_size (8 * 1024 * 1024)
+size_t sig_stack_size = (8 * 1024 * 1024);
 
 #include "julia_assert.h"
 
@@ -91,13 +91,6 @@ static inline __attribute__((unused)) uintptr_t jl_get_rsp_from_ctx(const void *
 #endif
 }
 
-static int is_addr_on_sigstack(jl_ptls_t ptls, void *ptr)
-{
-    // One guard page for signal_stack.
-    return !((char*)ptr < (char*)ptls->signal_stack - jl_page_size ||
-             (char*)ptr > (char*)ptls->signal_stack + sig_stack_size);
-}
-
 // Modify signal context `_ctx` so that `fptr` will execute when the signal
 // returns. `fptr` will execute on the signal stack, and must not return.
 // jl_call_in_ctx is also currently executing on that signal stack,
@@ -640,7 +633,7 @@ static void *alloc_sigstack(size_t *ssize)
 void jl_install_thread_signal_handler(jl_ptls_t ptls)
 {
     size_t ssize = sig_stack_size;
-    void *signal_stack = alloc_sigstack(&ssize);
+    signal_stack = alloc_sigstack(&ssize);
     ptls->signal_stack = signal_stack;
     stack_t ss;
     ss.ss_flags = 0;

src/signals-win.c

@@ -4,7 +4,7 @@
 // Note that this file is `#include`d by "signal-handling.c"
 #include <mmsystem.h> // hidden by LEAN_AND_MEAN
 
-#define sig_stack_size 131072 // 128k reserved for SEGV handling
+size_t sig_stack_size = 131072; // 128k reserved for SEGV handling
 
 // Copied from MINGW_FLOAT_H which may not be found due to a collision with the builtin gcc float.h
 // eventually we can probably integrate this into OpenLibm.