1 files changed, 147 insertions, 0 deletions
diff --git a/src/signal/__segv.c b/src/signal/__segv.c
new file mode 100644
index 00000000..7a4a2656
--- /dev/null
+++ b/src/signal/__segv.c
@@ -0,0 +1,147 @@
+#include <errno.h>
+#include <limits.h>
+#include <stdlib.h>
+#include <signal.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+
+#include "_safety.h"
+
+#ifdef _XOPEN_SOURCE
+#else
+#include "_forced/sigaction.h"
+#include "_forced/mprotect.h"
+
+#define sysconf(__n) 4096
+#define psiginfo(x, y)	fprintf(stderr, "%s (%p)\n", (char*)(y), (void*)(x))
+#define sigemptyset(x) memset(x, 0, sizeof(*x))
+#endif
+
+#include "stdlib/_jkmalloc.h"
+
+static void __jk_undef(void)
+{
+	static int printed = 0;
+	if (printed == 0) {
+		printed = 1;
+		fprintf(stderr, "Undefined Behavior: ");
+	}
+}
+
+static void __jk_error(const char *s, void *addr, struct jk_source *src)
+{
+	__jk_undef();
+
+	if (s && *s) {
+		fputs(s, stderr);
+		if (addr != NULL) {
+			fprintf(stderr, " %p", addr);
+		}
+		fputs("\n", stderr);
+	}
+
+	if (src && src->bucket && src->bucket->trace[0] != '\0') {
+		fwrite(src->bucket->trace, src->bucket->tlen, 1, stderr);
+		fputs("\n", stderr);
+	}
+
+	if (src && src->file) {
+		fprintf(stderr, "!!! %s() (%s:%ju)\n", src->func, src->file, src->line);
+	}
+
+	_Exit(JKMALLOC_EXIT_VALUE);
+}
+
+static void __jk_sigaction(int sig, siginfo_t *si, void *addr)
+{
+	__signal_h.current = 0;
+
+	(void)sig; (void)addr;
+
+	__jk_undef();
+
+	if (__dangerous[0].func) {
+		fprintf(stderr, "In call to %s, attempting to read parameter %s (%p)\n", __dangerous[0].func, __dangerous[0].param, __dangerous[0].addr);
+	}
+
+	if (__dangerous[1].func) {
+		fprintf(stderr, "In call to %s, attempting to write parameter %s (%p)\n", __dangerous[1].func, __dangerous[1].param, __dangerous[1].addr);
+	}
+
+	if (!si) {
+		__jk_error("No signal information provided", NULL, NULL);
+	}
+
+	if (si->si_addr == NULL) {
+		psiginfo(si, "NULL pointer dereference");
+		__jk_error(NULL, NULL, NULL);
+	}
+
+	struct jk_bucket *bucket = jk_pageof(si->si_addr);
+	if (mprotect(bucket, __jk_pagesize, PROT_READ) != 0) {
+		psiginfo(si, NULL);
+		__jk_error(NULL, NULL, NULL);
+	}
+
+	MAGIC_CHECK:
+	switch (bucket->magic) {
+	case JK_UNDER_MAGIC:
+		if (bucket->size == 0) {
+			psiginfo(si, "Attempt to use 0-byte allocation");
+		} else {
+			psiginfo(si, "Heap underflow detected");
+		}
+		break;
+
+	case JK_OVER_MAGIC:
+		if (bucket->size == 0) {
+			psiginfo(si, "Attempt to use 0-byte allocation");
+		} else {
+			psiginfo(si, "Heap overflow detected");
+			fprintf(stderr, "Allocation of size %zu at %p, overflow at %p (offset %zu)\n", bucket->size, (void*)bucket->start, si->si_addr, (size_t)((char*)si->si_addr - (char*)bucket->start));
+			fprintf(stderr, "Buffer begins with %4s\n", (char*)bucket->start);
+		}
+		break;
+
+	case JK_FREE_MAGIC:
+		psiginfo(si, "Use after free() detected");
+		break;
+
+	case JK_RONLY_MAGIC:
+		psiginfo(si, "Attempt to modify read-only memory detected");
+		break;
+
+	default:
+		/* try to find the actual error */
+		bucket = (void*)((char*)bucket - __jk_pagesize);
+		if (mprotect(bucket, __jk_pagesize, PROT_READ) != 0) {
+			psiginfo(si, NULL);
+			__jk_error(NULL, NULL, NULL);
+		}
+		goto MAGIC_CHECK;
+	}
+
+	struct jk_source src = { .bucket = bucket };
+	__jk_error(NULL, NULL, &src);
+}
+
+GCC_SSE_HACK
+void __segv(void)
+{
+	static int sa_set = 0;
+	if (!sa_set) {
+		struct sigaction sa = {
+			.sa_flags = SA_SIGINFO,
+			.sa_sigaction = __jk_sigaction,
+		};
+		sigemptyset(&sa.sa_mask);
+		sigaction(SIGSEGV, &sa, NULL);
+		sa_set = 1;
+	}
+}
+
+/*
+SIGNAL_SAFE(0)
+STDC(0)
+*/