5 files changed, 69 insertions, 12 deletions

diff --git a/src/pkg/runtime/linux/386/sys.s b/src/pkg/runtime/linux/386/sys.s
index 868a0d901..e8b423324 100644
--- a/src/pkg/runtime/linux/386/sys.s
+++ b/src/pkg/runtime/linux/386/sys.s
@@ -47,6 +47,14 @@ TEXT runtime·setitimer(SB),7,$0-24
 	INT	$0x80
 	RET
 
+TEXT runtime·mincore(SB),7,$0-24
+	MOVL	$218, AX			// syscall - mincore
+	MOVL	4(SP), BX
+	MOVL	8(SP), CX
+	MOVL	12(SP), DX
+	INT	$0x80
+	RET
+
 TEXT runtime·gettime(SB), 7, $32
 	MOVL	$78, AX			// syscall - gettimeofday
 	LEAL	8(SP), BX
diff --git a/src/pkg/runtime/linux/amd64/sys.s b/src/pkg/runtime/linux/amd64/sys.s
index eadd30005..66fdab208 100644
--- a/src/pkg/runtime/linux/amd64/sys.s
+++ b/src/pkg/runtime/linux/amd64/sys.s
@@ -53,6 +53,14 @@ TEXT runtime·setitimer(SB),7,$0-24
 	SYSCALL
 	RET
 
+TEXT runtime·mincore(SB),7,$0-24
+	MOVQ	8(SP), DI
+	MOVQ	16(SP), SI
+	MOVQ	24(SP), DX
+	MOVL	$27, AX			// syscall entry
+	SYSCALL
+	RET
+
 TEXT runtime·gettime(SB), 7, $32
 	LEAQ	8(SP), DI
 	MOVQ	$0, SI
diff --git a/src/pkg/runtime/linux/arm/sys.s b/src/pkg/runtime/linux/arm/sys.s
index 2b5365bd8..ab5349822 100644
--- a/src/pkg/runtime/linux/arm/sys.s
+++ b/src/pkg/runtime/linux/arm/sys.s
@@ -26,6 +26,7 @@
 #define SYS_exit_group (SYS_BASE + 248)
 #define SYS_munmap (SYS_BASE + 91)
 #define SYS_setitimer (SYS_BASE + 104)
+#define SYS_mincore (SYS_BASE + 219)
 #define SYS_gettid (SYS_BASE + 224)
 #define SYS_tkill (SYS_BASE + 238)
 
@@ -91,6 +92,14 @@ TEXT runtime·setitimer(SB),7,$0
 	SWI	$0
 	RET
 
+TEXT runtime·mincore(SB),7,$0
+	MOVW	0(FP), R0
+	MOVW	4(FP), R1
+	MOVW	8(FP), R2
+	MOVW	$SYS_mincore, R7
+	SWI	$0
+	RET
+
 TEXT runtime·gettime(SB),7,$32
 	/* dummy version - return 0,0 */
 	MOVW	$0, R1
diff --git a/src/pkg/runtime/linux/mem.c b/src/pkg/runtime/linux/mem.c
index ce1a8aa70..38ca7e4a0 100644
--- a/src/pkg/runtime/linux/mem.c
+++ b/src/pkg/runtime/linux/mem.c
@@ -3,6 +3,30 @@
 #include "os.h"
 #include "malloc.h"
 
+enum
+{
+	ENOMEM = 12,
+};
+
+static int32
+addrspace_free(void *v, uintptr n)
+{
+	uintptr page_size = 4096;
+	uintptr off;
+	int8 one_byte;
+
+	for(off = 0; off < n; off += page_size) {
+		int32 errval = runtime·mincore((int8 *)v + off, page_size, (void *)&one_byte);
+		// errval is 0 if success, or -(error_code) if error.
+		if (errval == 0 || errval != -ENOMEM)
+			return 0;
+	}
+	USED(v);
+	USED(n);
+	return 1;
+}
+
+
 void*
 runtime·SysAlloc(uintptr n)
 {
@@ -39,20 +63,21 @@ runtime·SysFree(void *v, uintptr n)
 void*
 runtime·SysReserve(void *v, uintptr n)
 {
+	void *p;
+
 	// On 64-bit, people with ulimit -v set complain if we reserve too
 	// much address space.  Instead, assume that the reservation is okay
 	// and check the assumption in SysMap.
 	if(sizeof(void*) == 8)
 		return v;
 	
-	return runtime·mmap(v, n, PROT_NONE, MAP_ANON|MAP_PRIVATE, -1, 0);
+	p = runtime·mmap(v, n, PROT_NONE, MAP_ANON|MAP_PRIVATE, -1, 0);
+	if(p < (void*)4096) {
+		return nil;
+	}
+	return p;
 }
 
-enum
-{
-	ENOMEM = 12,
-};
-
 void
 runtime·SysMap(void *v, uintptr n)
 {
@@ -63,6 +88,13 @@ runtime·SysMap(void *v, uintptr n)
 	// On 64-bit, we don't actually have v reserved, so tread carefully.
 	if(sizeof(void*) == 8) {
 		p = runtime·mmap(v, n, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_ANON|MAP_PRIVATE, -1, 0);
+		if(p != v && addrspace_free(v, n)) {
+			// On some systems, mmap ignores v without
+			// MAP_FIXED, so retry if the address space is free.
+			p = runtime·mmap(v, n, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_ANON|MAP_FIXED|MAP_PRIVATE, -1, 0);
+		}
+		if(p == (void*)ENOMEM)
+			runtime·throw("runtime: out of memory");
 		if(p != v) {
 			runtime·printf("runtime: address space conflict: map(%p) = %p\n", v, p);
 			runtime·throw("runtime: address space conflict");
@@ -71,7 +103,7 @@ runtime·SysMap(void *v, uintptr n)
 	}
 
 	p = runtime·mmap(v, n, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_ANON|MAP_FIXED|MAP_PRIVATE, -1, 0);
-	if(p == (void*)-ENOMEM)
+	if(p == (void*)ENOMEM)
 		runtime·throw("runtime: out of memory");
 	if(p != v)
 		runtime·throw("runtime: cannot map pages in arena address space");
diff --git a/src/pkg/runtime/linux/thread.c b/src/pkg/runtime/linux/thread.c
index 7166b0ef2..7c7ca7b4e 100644
--- a/src/pkg/runtime/linux/thread.c
+++ b/src/pkg/runtime/linux/thread.c
@@ -116,7 +116,7 @@ again:
 	//
 	// We only really care that (v&1) == 1 (the lock is held),
 	// and in fact there is a futex variant that could
-	// accomodate that check, but let's not get carried away.)
+	// accommodate that check, but let's not get carried away.)
 	futexsleep(&l->key, v+2);
 
 	// We're awake: remove ourselves from the count.
@@ -252,10 +252,10 @@ runtime·newosproc(M *m, G *g, void *stk, void (*fn)(void))
 			stk, m, g, fn, runtime·clone, m->id, m->tls[0], &m);
 	}
 
-	ret = runtime·clone(flags, stk, m, g, fn);
-
-	if(ret < 0)
-		*(int32*)123 = 123;
+	if((ret = runtime·clone(flags, stk, m, g, fn)) < 0) {
+		runtime·printf("runtime: failed to create new OS thread (have %d already; errno=%d)\n", runtime·mcount(), -ret);
+		runtime·throw("runtime.newosproc");
+	}
 }
 
 void