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re PR go/60406 (recover.go: test13reflect2 test failure)

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PR go/60406
runtime: Check callers in can_recover if return address	doesn't match.

Also use __builtin_extract_return_address and tighten up the
checks in FFI code.

Fixes PR 60406.

From-SVN: r216003
This commit is contained in:
Ian Lance Taylor 2014-10-08 14:03:13 +00:00
parent 9d07d890e6
commit 19d4baed57
5 changed files with 197 additions and 78 deletions
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27
libgo/go/reflect/makefunc_ffi_c.c
View file

@ -36,21 +36,23 @@ void ffiFree(void *data)
Go callback function (passed in user_data) with the pointer to the
arguments and the results area. */
static void ffi_callback (ffi_cif *, void *, void **, void *)
__asm__ ("reflect.ffi_callback");
static void
ffi_callback (ffi_cif* cif __attribute__ ((unused)), void *results,
void **args, void *user_data)
{
Location locs[6];
Location locs[8];
int n;
int i;
const void *pc;
FuncVal *fv;
void (*f) (void *, void *);
/* This function is called from some series of FFI closure functions
called by a Go function. We want to pass the PC of the Go
function to makefunc_can_recover. Look up the stack for a
function that is definitely not an FFI function. */
called by a Go function. We want to see whether the caller of
the closure functions can recover. Look up the stack and skip
the FFI functions. */
n = runtime_callers (1, &locs[0], sizeof locs / sizeof locs[0], true);
for (i = 0; i < n; i++)
{
@ -61,28 +63,19 @@ ffi_callback (ffi_cif* cif __attribute__ ((unused)), void *results,
if (locs[i].function.len < 4)
break;
name = locs[i].function.str;
if (*name == '_')
{
if (locs[i].function.len < 5)
break;
++name;
}
if (name[0] != 'f' || name[1] != 'f' || name[2] != 'i' || name[3] != '_')
break;
}
if (i < n)
pc = (const void *) locs[i].pc;
else
pc = __builtin_return_address (0);
__go_makefunc_can_recover (pc);
__go_makefunc_ffi_can_recover (locs + i, n - i);
fv = (FuncVal *) user_data;
__go_set_closure (fv);
f = (void *) fv->fn;
f (args, results);
__go_makefunc_returning ();
if (i < n)
__go_makefunc_returning ();
}
/* Allocate an FFI closure and arrange to call ffi_callback. */

2
libgo/runtime/go-defer.c
View file

@ -80,6 +80,6 @@ __go_set_defer_retaddr (void *retaddr)
g = runtime_g ();
if (g->defer != NULL)
g->defer->__retaddr = retaddr;
g->defer->__retaddr = __builtin_extract_return_addr (retaddr);
return 0;
}

7
libgo/runtime/go-panic.h
View file

@ -38,9 +38,12 @@ extern void __go_print_string (struct String);
extern struct __go_empty_interface __go_recover (void);
extern _Bool __go_can_recover (const void *);
extern _Bool __go_can_recover (void *);
extern void __go_makefunc_can_recover (const void *retaddr);
extern void __go_makefunc_can_recover (void *retaddr);
struct Location;
extern void __go_makefunc_ffi_can_recover (struct Location *, int);
extern void __go_makefunc_returning (void);

233
libgo/runtime/go-recover.c
View file

@ -9,6 +9,36 @@
#include "go-panic.h"
#include "go-defer.h"
/* If the top of the defer stack can be recovered, then return it.
Otherwise return NULL. */
static struct __go_defer_stack *
current_defer ()
{
G *g;
struct __go_defer_stack *d;
g = runtime_g ();
d = g->defer;
if (d == NULL)
return NULL;
/* The panic which would be recovered is the one on the top of the
panic stack. We do not want to recover it if that panic was on
the top of the panic stack when this function was deferred. */
if (d->__panic == g->panic)
return NULL;
/* The deferred thunk will call _go_set_defer_retaddr. If this has
not happened, then we have not been called via defer, and we can
not recover. */
if (d->__retaddr == NULL)
return NULL;
return d;
}
/* This is called by a thunk to see if the real function should be
permitted to recover a panic value. Recovering a value is
permitted if the thunk was called directly by defer. RETADDR is
@ -16,79 +46,126 @@
__go_can_recover--this is, the thunk. */
_Bool
__go_can_recover (const void *retaddr)
__go_can_recover (void *retaddr)
{
G *g;
struct __go_defer_stack *d;
const char* ret;
const char* dret;
Location loc;
Location locs[16];
const byte *name;
intgo len;
int n;
int i;
_Bool found_ffi_callback;
g = runtime_g ();
d = g->defer;
d = current_defer ();
if (d == NULL)
return 0;
/* The panic which this function would recover is the one on the top
of the panic stack. We do not want to recover it if that panic
was on the top of the panic stack when this function was
deferred. */
if (d->__panic == g->panic)
return 0;
/* D->__RETADDR is the address of a label immediately following the
call to the thunk. We can recover a panic if that is the same as
the return address of the thunk. We permit a bit of slack in
case there is any code between the function return and the label,
such as an instruction to adjust the stack pointer. */
ret = (const char *) retaddr;
#ifdef __sparc__
/* On SPARC the address we get, from __builtin_return_address, is
the address of the call instruction. Adjust forward, also
skipping the delayed instruction following the call. */
ret += 8;
#endif
ret = (const char *) __builtin_extract_return_addr (retaddr);
dret = (const char *) d->__retaddr;
if (ret <= dret && ret + 16 >= dret)
return 1;
/* On some systems, in some cases, the return address does not work
reliably. See http://gcc.gnu.org/PR60406. If we are permitted
to call recover, the call stack will look like this:
__go_panic, __go_undefer, etc.
thunk to call deferred function (calls __go_set_defer_retaddr)
function that calls __go_can_recover (passing return address)
__go_can_recover
Calling runtime_callers will skip the thunks. So if our caller's
caller starts with __go, then we are permitted to call
recover. */
if (runtime_callers (1, &locs[0], 2, false) < 2)
return 0;
name = locs[1].function.str;
len = locs[1].function.len;
/* Although locs[1].function is a Go string, we know it is
NUL-terminated. */
if (len > 4
&& __builtin_strchr ((const char *) name, '.') == NULL
&& __builtin_strncmp ((const char *) name, "__go_", 4) == 0)
return 1;
/* If we are called from __go_makefunc_can_recover, then we need to
look one level higher. */
if (locs[0].function.len > 0
&& __builtin_strcmp ((const char *) locs[0].function.str,
"__go_makefunc_can_recover") == 0)
{
if (runtime_callers (3, &locs[0], 1, false) < 1)
return 0;
name = locs[0].function.str;
len = locs[0].function.len;
if (len > 4
&& __builtin_strchr ((const char *) name, '.') == NULL
&& __builtin_strncmp ((const char *) name, "__go_", 4) == 0)
return 1;
}
/* If the function calling recover was created by reflect.MakeFunc,
then RETADDR will be somewhere in libffi. Our caller is
permitted to recover if it was called from libffi. */
then __go_makefunc_can_recover or __go_makefunc_ffi_can_recover
will have set the __makefunc_can_recover field. */
if (!d->__makefunc_can_recover)
return 0;
if (runtime_callers (2, &loc, 1, false) < 1)
return 0;
/* We look up the stack, ignoring libffi functions and functions in
the reflect package, until we find reflect.makeFuncStub or
reflect.ffi_callback called by FFI functions. Then we check the
caller of that function. */
/* If we have no function name, then we weren't called by Go code.
Guess that we were called by libffi. */
if (loc.function.len == 0)
return 1;
if (loc.function.len < 4)
return 0;
name = loc.function.str;
if (*name == '_')
n = runtime_callers (2, &locs[0], sizeof locs / sizeof locs[0], false);
found_ffi_callback = 0;
for (i = 0; i < n; i++)
{
if (loc.function.len < 5)
return 0;
++name;
const byte *name;
if (locs[i].function.len == 0)
{
/* No function name means this caller isn't Go code. Assume
that this is libffi. */
continue;
}
/* Ignore functions in libffi. */
name = locs[i].function.str;
if (__builtin_strncmp ((const char *) name, "ffi_", 4) == 0)
continue;
if (found_ffi_callback)
break;
if (__builtin_strcmp ((const char *) name, "reflect.ffi_callback") == 0)
{
found_ffi_callback = 1;
continue;
}
if (__builtin_strcmp ((const char *) name, "reflect.makeFuncStub") == 0)
{
i++;
break;
}
/* Ignore other functions in the reflect package. */
if (__builtin_strncmp ((const char *) name, "reflect.", 8) == 0)
continue;
/* We should now be looking at the real caller. */
break;
}
if (name[0] == 'f' && name[1] == 'f' && name[2] == 'i' && name[3] == '_')
return 1;
/* We may also be called by reflect.makeFuncImpl.call or
reflect.ffiCall, for a function created by reflect.MakeFunc. */
if (__builtin_strstr ((const char *) name, "makeFuncImpl") != NULL
|| __builtin_strcmp ((const char *) name, "reflect.ffiCall") == 0)
return 1;
if (i < n && locs[i].function.len > 0)
{
name = locs[i].function.str;
if (__builtin_strncmp ((const char *) name, "__go_", 4) == 0)
return 1;
}
return 0;
}
@ -99,14 +176,58 @@ __go_can_recover (const void *retaddr)
real MakeFunc function is permitted to call recover. */
void
__go_makefunc_can_recover (const void *retaddr)
__go_makefunc_can_recover (void *retaddr)
{
struct __go_defer_stack *d;
d = runtime_g ()->defer;
if (d != NULL
&& !d->__makefunc_can_recover
&& __go_can_recover (retaddr))
d = current_defer ();
if (d == NULL)
return;
/* If we are already in a call stack of MakeFunc functions, there is
nothing we can usefully check here. */
if (d->__makefunc_can_recover)
return;
if (__go_can_recover (retaddr))
d->__makefunc_can_recover = 1;
}
/* This function is called when code is about to enter a function
created by the libffi version of reflect.MakeFunc. This function
is passed the names of the callers of the libffi code that called
the stub. It uses to decide whether it is permitted to call
recover, and sets d->__makefunc_can_recover so that __go_recover
can make the same decision. */
void
__go_makefunc_ffi_can_recover (struct Location *loc, int n)
{
struct __go_defer_stack *d;
const byte *name;
intgo len;
d = current_defer ();
if (d == NULL)
return;
/* If we are already in a call stack of MakeFunc functions, there is
nothing we can usefully check here. */
if (d->__makefunc_can_recover)
return;
/* LOC points to the caller of our caller. That will be a thunk.
If its caller was a runtime function, then it was called directly
by defer. */
if (n < 2)
return;
name = (loc + 1)->function.str;
len = (loc + 1)->function.len;
if (len > 4
&& __builtin_strchr ((const char *) name, '.') == NULL
&& __builtin_strncmp ((const char *) name, "__go_", 4) == 0)
d->__makefunc_can_recover = 1;
}

6
libgo/runtime/panic.c
View file

@ -49,8 +49,10 @@ runtime_freedefer(Defer *d)
}
// Run all deferred functions for the current goroutine.
// This is noinline for go_can_recover.
static void __go_rundefer (void) __attribute__ ((noinline));
static void
rundefer(void)
__go_rundefer(void)
{
G *g;
Defer *d;
@ -219,7 +221,7 @@ void runtime_Goexit (void) __asm__ (GOSYM_PREFIX "runtime.Goexit");
void
runtime_Goexit(void)
{
rundefer();
__go_rundefer();
runtime_goexit();
}