[systemd-commits] src/libsystemd-bus
Lennart Poettering
lennart at kemper.freedesktop.org
Tue Apr 9 12:06:08 PDT 2013
src/libsystemd-bus/bus-message.c | 142 ++++++++++++++++++++++++++++++---------
1 file changed, 111 insertions(+), 31 deletions(-)
New commits:
commit fe1d424d29d7fd3a20ad1247db90cdf5473f522f
Author: Lennart Poettering <lennart at poettering.net>
Date: Tue Apr 9 21:03:12 2013 +0200
bus: implement message_read_ap() non-recursively
As it turns out if you pass a va_list to a function its state becomes
undefined after that function returns, and this actually does break on
x86-32.
Hence, let's reimplement message_read_ap() without the use of recursion.
Instead we now build our own stack of types in an array so that we can
decode the entire parameter list in a single stackframe.
diff --git a/src/libsystemd-bus/bus-message.c b/src/libsystemd-bus/bus-message.c
index 2d051e8..12756bf 100644
--- a/src/libsystemd-bus/bus-message.c
+++ b/src/libsystemd-bus/bus-message.c
@@ -2091,14 +2091,89 @@ int sd_bus_message_rewind(sd_bus_message *m, int complete) {
return !isempty(c->signature);
}
+typedef struct {
+ const char *types;
+ unsigned n_struct;
+ unsigned n_array;
+} TypeStack;
+
+static int type_stack_push(TypeStack *stack, unsigned max, unsigned *i, const char *types, unsigned n_struct, unsigned n_array) {
+ assert(stack);
+ assert(max > 0);
+
+ if (*i >= max)
+ return -EINVAL;
+
+ stack[*i].types = types;
+ stack[*i].n_struct = n_struct;
+ stack[*i].n_array = n_array;
+ (*i)++;
+
+ return 0;
+}
+
+static int type_stack_pop(TypeStack *stack, unsigned max, unsigned *i, const char **types, unsigned *n_struct, unsigned *n_array) {
+ assert(stack);
+ assert(max > 0);
+ assert(types);
+ assert(n_struct);
+ assert(n_array);
+
+ if (*i <= 0)
+ return 0;
+
+ (*i)--;
+ *types = stack[*i].types;
+ *n_struct = stack[*i].n_struct;
+ *n_array = stack[*i].n_array;
+
+ return 1;
+}
+
static int message_read_ap(sd_bus_message *m, const char *types, va_list ap) {
- const char *t;
+ unsigned n_array, n_struct;
+ TypeStack stack[BUS_CONTAINER_DEPTH];
+ unsigned stack_ptr = 0;
int r;
assert(m);
assert(types);
- for (t = types; *t; t++) {
+ /* Ideally, we'd just call ourselves recursively on every
+ * complex type. However, the state of a va_list that is
+ * passed to a function is undefined after that function
+ * returns. This means we need to docode the va_list linearly
+ * in a single stackframe. We hence implement our own
+ * home-grown stack in an array. */
+
+ n_array = (unsigned) -1;
+ n_struct = strlen(types);
+
+ for (;;) {
+ const char *t;
+
+ if (n_array == 0 || (n_struct == 0 && n_array == (unsigned) -1)) {
+ r = type_stack_pop(stack, ELEMENTSOF(stack), &stack_ptr, &types, &n_struct, &n_array);
+ if (r < 0)
+ return r;
+ if (r == 0)
+ break;
+
+ r = sd_bus_message_exit_container(m);
+ if (r < 0)
+ return r;
+
+ continue;
+ }
+
+ t = types;
+ if (n_array != (unsigned) -1)
+ n_array --;
+ else {
+ types ++;
+ n_struct--;
+ }
+
switch (*t) {
case SD_BUS_TYPE_BYTE:
@@ -2118,6 +2193,11 @@ static int message_read_ap(sd_bus_message *m, const char *types, va_list ap) {
p = va_arg(ap, void*);
r = sd_bus_message_read_basic(m, *t, p);
+ if (r < 0)
+ return r;
+ if (r == 0)
+ return -ENXIO;
+
break;
}
@@ -2129,29 +2209,30 @@ static int message_read_ap(sd_bus_message *m, const char *types, va_list ap) {
return r;
{
- unsigned i, n;
char s[k + 1];
-
memcpy(s, t + 1, k);
s[k] = 0;
- t += k;
r = sd_bus_message_enter_container(m, SD_BUS_TYPE_ARRAY, s);
if (r < 0)
return r;
if (r == 0)
return -ENXIO;
+ }
- n = va_arg(ap, unsigned);
- for (i = 0; i < n; i++) {
- r = message_read_ap(m, s, ap);
- if (r < 0)
- return r;
- }
-
- r = sd_bus_message_exit_container(m);
+ if (n_array == (unsigned) -1) {
+ types += k;
+ n_struct -= k;
}
+ r = type_stack_push(stack, ELEMENTSOF(stack), &stack_ptr, types, n_struct, n_array);
+ if (r < 0)
+ return r;
+
+ types = t + 1;
+ n_struct = k;
+ n_array = va_arg(ap, unsigned);
+
break;
}
@@ -2168,13 +2249,14 @@ static int message_read_ap(sd_bus_message *m, const char *types, va_list ap) {
if (r == 0)
return -ENXIO;
- r = message_read_ap(m, s, ap);
+ r = type_stack_push(stack, ELEMENTSOF(stack), &stack_ptr, types, n_struct, n_array);
if (r < 0)
return r;
- if (r == 0)
- return -ENXIO;
- r = sd_bus_message_exit_container(m);
+ types = s;
+ n_struct = strlen(s);
+ n_array = (unsigned) -1;
+
break;
}
@@ -2196,29 +2278,27 @@ static int message_read_ap(sd_bus_message *m, const char *types, va_list ap) {
return r;
if (r == 0)
return -ENXIO;
+ }
- t += k - 1;
+ if (n_array == (unsigned) -1) {
+ types += k - 1;
+ n_struct -= k - 1;
+ }
- r = message_read_ap(m, s, ap);
- if (r < 0)
- return r;
- if (r == 0)
- return -ENXIO;
+ r = type_stack_push(stack, ELEMENTSOF(stack), &stack_ptr, types, n_struct, n_array);
+ if (r < 0)
+ return r;
- r = sd_bus_message_exit_container(m);
- }
+ types = t + 1;
+ n_struct = k - 2;
+ n_array = (unsigned) -1;
break;
}
default:
- r = -EINVAL;
+ return -EINVAL;
}
-
- if (r < 0)
- return r;
- if (r == 0)
- return -ENXIO;
}
return 1;
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