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[mono][aot] Type load checks do not fail at compile time but produce a runtime exception #91261

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merged 21 commits into from
Sep 27, 2023
Merged

[mono][aot] Type load checks do not fail at compile time but produce a runtime exception #91261

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78ce32e
Enable tests.
jandupej Aug 28, 2023
3c32b67
When AOTing, type checks do not fail compilation but create a runtime…
jandupej Aug 29, 2023
7676e00
Cleaned up type load error cleaning. TypeLoadException icall now has …
jandupej Aug 30, 2023
611888b
Removed another instance of indiscriminate exception clearing.
jandupej Aug 30, 2023
15b7aa5
Fixed build warning.
jandupej Aug 30, 2023
90aa674
Using class const instead of string const. Reverted some compile to r…
jandupej Aug 31, 2023
d4b6c9f
White space.
jandupej Aug 31, 2023
bda12b3
Fixed build warning.
jandupej Aug 31, 2023
fbd3614
Trying to fix weird AOT errors, fixed type load throw function.
jandupej Aug 31, 2023
805d6c4
Fixed build error.
jandupej Aug 31, 2023
0b50974
Special handling for classes that are NULL.
jandupej Sep 1, 2023
19c5155
Providing for a null klass when generating exception.
jandupej Sep 6, 2023
83bcc30
Removed flow control directive from macro.
jandupej Sep 6, 2023
c6fe63b
Fixed stack corruption.
jandupej Sep 6, 2023
9cb3d1a
Attempt to push the correct type onto the stack.
jandupej Sep 8, 2023
025ed7a
Fixing uninitialized ins.
jandupej Sep 8, 2023
4633336
Fixing ro_type.
jandupej Sep 8, 2023
55db3c6
Initializing ins.
jandupej Sep 8, 2023
4b35af0
Complex cases with type load failures replace method body with a throw.
jandupej Sep 20, 2023
ca7530d
Cleaning up superfluous code changes.
jandupej Sep 21, 2023
9709a89
Restored sizeof cosntant on failed types.
jandupej Sep 21, 2023
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1 change: 1 addition & 0 deletions src/mono/mono/metadata/jit-icall-reg.h
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Original file line number Diff line number Diff line change
Expand Up @@ -312,6 +312,7 @@ MONO_JIT_ICALL (mono_throw_bad_image) \
MONO_JIT_ICALL (mono_throw_not_supported) \
MONO_JIT_ICALL (mono_throw_platform_not_supported) \
MONO_JIT_ICALL (mono_throw_invalid_program) \
MONO_JIT_ICALL (mono_throw_type_load) \
MONO_JIT_ICALL (mono_trace_enter_method) \
MONO_JIT_ICALL (mono_trace_leave_method) \
MONO_JIT_ICALL (mono_trace_tail_method) \
Expand Down
16 changes: 16 additions & 0 deletions src/mono/mono/mini/jit-icalls.c
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Expand Up @@ -1688,6 +1688,22 @@ mono_throw_invalid_program (const char *msg)
mono_error_set_pending_exception (error);
}

void
mono_throw_type_load (MonoClass* klass)
{
ERROR_DECL (error);

if (G_UNLIKELY(!klass)) {
mono_error_set_generic_error (error, "System", "TypeLoadException", "");
} else {
char* klass_name = mono_type_get_full_name (klass);
mono_error_set_type_load_class (error, klass, "Attempting to load invalid type '%s'.", klass_name);
g_free (klass_name);
}

mono_error_set_pending_exception (error);
}

void
mono_dummy_jit_icall (void)
{
Expand Down
2 changes: 2 additions & 0 deletions src/mono/mono/mini/jit-icalls.h
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Expand Up @@ -234,6 +234,8 @@ ICALL_EXPORT void mono_throw_platform_not_supported (void);

ICALL_EXPORT void mono_throw_invalid_program (const char *msg);

ICALL_EXPORT void mono_throw_type_load (MonoClass* klass);

ICALL_EXPORT void mono_dummy_jit_icall (void);

ICALL_EXPORT void mono_dummy_jit_icall_val (gpointer ptr);
Expand Down
119 changes: 111 additions & 8 deletions src/mono/mono/mini/method-to-ir.c
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Expand Up @@ -167,7 +167,7 @@ mono_tailcall_print (const char *format, ...)

#define TYPE_LOAD_ERROR(klass) do { \
cfg->exception_ptr = klass; \
LOAD_ERROR; \
LOAD_ERROR; \
} while (0)

#define CHECK_CFG_ERROR do {\
Expand Down Expand Up @@ -2303,6 +2303,18 @@ emit_not_supported_failure (MonoCompile *cfg)
mono_emit_jit_icall (cfg, mono_throw_not_supported, NULL);
}

static void
emit_type_load_failure (MonoCompile* cfg, MonoClass* klass)
{
MonoInst* iargs[1];
if (G_LIKELY (klass)) {
EMIT_NEW_CLASSCONST (cfg, iargs [0], klass);
} else {
EMIT_NEW_PCONST (cfg, iargs [0], NULL);
}
mono_emit_jit_icall (cfg, mono_throw_type_load, iargs);
}

static void
emit_invalid_program_with_msg (MonoCompile *cfg, MonoError *error_msg, MonoMethod *caller, MonoMethod *callee)
{
Expand Down Expand Up @@ -4963,6 +4975,15 @@ inline_method (MonoCompile *cfg, MonoMethod *cmethod, MonoMethodSignature *fsig,
#define CHECK_UNVERIFIABLE(cfg) if (cfg->unverifiable) UNVERIFIED
#define CHECK_TYPELOAD(klass) if (!(klass) || mono_class_has_failure (klass)) TYPE_LOAD_ERROR ((klass))

#define CLEAR_TYPELOAD_EXCEPTION(cfg) if (cfg->exception_type == MONO_EXCEPTION_TYPE_LOAD) { clear_cfg_error (cfg); cfg->exception_type = MONO_EXCEPTION_NONE; }
#define CLASS_HAS_FAILURE(klass) (!(klass) || mono_class_has_failure (klass))
#define HANDLE_TYPELOAD_ERROR(cfg,klass) do { \
if (!cfg->compile_aot) \
TYPE_LOAD_ERROR ((klass)); \
emit_type_load_failure (cfg, klass); \
CLEAR_TYPELOAD_EXCEPTION (cfg); \
} while (0)

/* offset from br.s -> br like opcodes */
#define BIG_BRANCH_OFFSET 13

Expand Down Expand Up @@ -5438,7 +5459,9 @@ emit_optimized_ldloca_ir (MonoCompile *cfg, guchar *ip, guchar *end, int local)
if ((ip = il_read_initobj (ip, end, &token)) && ip_in_bb (cfg, cfg->cbb, start + 1)) {
/* From the INITOBJ case */
klass = mini_get_class (cfg->current_method, token, cfg->generic_context);
CHECK_TYPELOAD (klass);
if (CLASS_HAS_FAILURE (klass)) {
HANDLE_TYPELOAD_ERROR (cfg, klass);
}
type = mini_get_underlying_type (m_class_get_byval_arg (klass));
emit_init_local (cfg, local, type, TRUE);
return ip;
Expand Down Expand Up @@ -6170,6 +6193,49 @@ emit_llvmonly_interp_entry (MonoCompile *cfg, MonoMethodHeader *header)
link_bblock (cfg, cfg->cbb, cfg->bb_exit);
}

static void
method_make_alwaysthrow_typeloadfailure (MonoCompile* cfg, MonoClass* klass)
{
// Get rid of all out-BBs from the entry BB. (all but init BB)
for (gint16 i = cfg->bb_entry->out_count - 1; i >= 0; i--) {
if (cfg->bb_entry->out_bb [i] != cfg->bb_init) {
mono_unlink_bblock (cfg, cfg->bb_entry, cfg->bb_entry->out_bb [i]);
mono_remove_bblock (cfg, cfg->bb_entry->out_bb [i]);
}
}

// Discard all out-BBs from the init BB.
for (gint16 i = cfg->bb_init->out_count - 1; i >= 0; i--) {
if (cfg->bb_init->out_bb [i] != cfg->bb_exit) {
mono_unlink_bblock (cfg, cfg->bb_init, cfg->bb_init->out_bb [i]);
mono_remove_bblock (cfg, cfg->bb_init->out_bb [i]);
}
}

// Maintain linked list consistency. This BB should have been added as the last,
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Is it necessary to remove dead blocks between the bb_init and bb_exit which may not have a direct link to them?

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@jandupej jandupej Sep 20, 2023 •
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Possibly not; it seems that unreachable blocks are detected (and removed) without my explicitly doing it. This is the first iteration that seems to work locally, waiting for CI. I may be able to simplify it if CI turns out favorable.

EDIT: Are you aware of any unlinked blocks that should be kept?

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This change looks good to me. I was just curious whether the unreachable blocks are detected and removed.

Is it possible to skip the bb_init and link the bb_entry with the throw block?

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I had control flow issues when generating LLVM IR without the init block (which was empty no less). I'll see if it can be done.

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An alternative is to restart the compilation, there is already a mechanism to do that if llvm fails, etc. and emit the exception without compiling the rest of the IL.

// ignoring the ones that held actual method code.
cfg->cbb = cfg->bb_init;

// Create a new BB that only throws, link it after the entry.
MonoBasicBlock* bb;
NEW_BBLOCK (cfg, bb);
bb->cil_code = NULL;
bb->cil_length = 0;
cfg->cbb->next_bb = bb;
cfg->cbb = bb;

emit_type_load_failure (cfg, klass);
MonoInst* ins;
MONO_INST_NEW (cfg, ins, OP_NOT_REACHED);
MONO_ADD_INS (cfg->cbb, ins);

ADD_BBLOCK (cfg, bb);
mono_link_bblock (cfg, cfg->bb_init, bb);
mono_link_bblock (cfg, bb, cfg->bb_exit);

cfg->disable_inline = TRUE;
}

typedef union _MonoOpcodeParameter {
gint32 i32;
gint64 i64;
Expand Down Expand Up @@ -9871,6 +9937,7 @@ mono_method_to_ir (MonoCompile *cfg, MonoMethod *method, MonoBasicBlock *start_b
MonoType *ftype;
MonoInst *store_val = NULL;
MonoInst *thread_ins;
ins = NULL;

is_instance = (il_op == MONO_CEE_LDFLD || il_op == MONO_CEE_LDFLDA || il_op == MONO_CEE_STFLD);
if (is_instance) {
Expand Down Expand Up @@ -9898,8 +9965,28 @@ mono_method_to_ir (MonoCompile *cfg, MonoMethod *method, MonoBasicBlock *start_b
else {
klass = NULL;
field = mono_field_from_token_checked (image, token, &klass, generic_context, cfg->error);
if (!field)
CHECK_TYPELOAD (klass);
if (!field || CLASS_HAS_FAILURE (klass)) {
HANDLE_TYPELOAD_ERROR (cfg, klass);

// Reached only in AOT. Cannot turn a token into a class. We silence the compilation error
// and generate a runtime exception.
if (cfg->error->error_code == MONO_ERROR_BAD_IMAGE)
clear_cfg_error (cfg);

// We need to push a dummy value onto the stack, respecting the intended type.
if (il_op == MONO_CEE_LDFLDA || il_op == MONO_CEE_LDSFLDA) {
// Address is expected, push a null pointer.
EMIT_NEW_PCONST (cfg, *sp, NULL);
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sp++;
} else if (il_op == MONO_CEE_LDFLD || il_op == MONO_CEE_LDSFLD) {
// An object is expected here. It may be impossible to correctly infer its type,
// we turn this entire method into a throw.
method_make_alwaysthrow_typeloadfailure (cfg, klass);
goto all_bbs_done;
}

break;
}
CHECK_CFG_ERROR;
}
if (!dont_verify && !cfg->skip_visibility && !mono_method_can_access_field (method, field))
Expand Down Expand Up @@ -10365,8 +10452,11 @@ mono_method_to_ir (MonoCompile *cfg, MonoMethod *method, MonoBasicBlock *start_b
}

if (!is_const) {
MonoInst *load;
// This can happen in case of type load error.
if (!ins)
EMIT_NEW_PCONST (cfg, ins, 0);

MonoInst *load;
EMIT_NEW_LOAD_MEMBASE_TYPE (cfg, load, field->type, ins->dreg, 0);
load->flags |= ins_flag;
*sp++ = load;
Expand Down Expand Up @@ -11853,13 +11943,20 @@ mono_method_to_ir (MonoCompile *cfg, MonoMethod *method, MonoBasicBlock *start_b
inline_costs += 100000;
break;
case MONO_CEE_INITOBJ:
--sp;
klass = mini_get_class (method, token, generic_context);
CHECK_TYPELOAD (klass);
if (CLASS_HAS_FAILURE (klass)) {
HANDLE_TYPELOAD_ERROR (cfg, klass);
inline_costs += 10;
break; // reached only in AOT
}

--sp;

if (mini_class_is_reference (klass))
MONO_EMIT_NEW_STORE_MEMBASE_IMM (cfg, OP_STORE_MEMBASE_IMM, sp [0]->dreg, 0, 0);
else
mini_emit_initobj (cfg, *sp, NULL, klass);

inline_costs += 1;
break;
case MONO_CEE_CONSTRAINED_:
Expand Down Expand Up @@ -11949,7 +12046,12 @@ mono_method_to_ir (MonoCompile *cfg, MonoMethod *method, MonoBasicBlock *start_b
EMIT_NEW_ICONST (cfg, ins, val);
} else {
klass = mini_get_class (method, token, generic_context);
CHECK_TYPELOAD (klass);
if (CLASS_HAS_FAILURE (klass)) {
HANDLE_TYPELOAD_ERROR (cfg, klass);
EMIT_NEW_ICONST(cfg, ins, 0);
*sp++ = ins;
break;
}

if (mini_is_gsharedvt_klass (klass)) {
ins = mini_emit_get_gsharedvt_info_klass (cfg, klass, MONO_RGCTX_INFO_CLASS_SIZEOF);
Expand Down Expand Up @@ -12002,6 +12104,7 @@ mono_method_to_ir (MonoCompile *cfg, MonoMethod *method, MonoBasicBlock *start_b
}
if (start_new_bblock != 1)
UNVERIFIED;
all_bbs_done:

cfg->cbb->cil_length = GPTRDIFF_TO_INT32 (ip - cfg->cbb->cil_code);
if (cfg->cbb->next_bb) {
Expand Down
1 change: 1 addition & 0 deletions src/mono/mono/mini/mini-runtime.c
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Expand Up @@ -5139,6 +5139,7 @@ register_icalls (void)
register_icall (mono_throw_not_supported, mono_icall_sig_void, FALSE);
register_icall (mono_throw_platform_not_supported, mono_icall_sig_void, FALSE);
register_icall (mono_throw_invalid_program, mono_icall_sig_void_ptr, FALSE);
register_icall (mono_throw_type_load, mono_icall_sig_void_ptr, FALSE);
register_icall_no_wrapper (mono_dummy_jit_icall, mono_icall_sig_void);
//register_icall_no_wrapper (mono_dummy_jit_icall_val, mono_icall_sig_void_ptr);
register_icall_no_wrapper (mini_init_method_rgctx, mono_icall_sig_void_ptr_ptr);
Expand Down
9 changes: 7 additions & 2 deletions src/mono/mono/mini/mini.c
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Expand Up @@ -660,7 +660,9 @@ mono_compile_create_var_for_vreg (MonoCompile *cfg, MonoType *type, int opcode,
inst->backend.is_pinvoke = 0;
inst->dreg = vreg;

if (mono_class_has_failure (inst->klass))
// In AOT, we do not set the exception so that the compilation can succeed. To indicate
// the error, an exception is thrown in run-time.
if (!cfg->compile_aot && mono_class_has_failure (inst->klass))
mono_cfg_set_exception (cfg, MONO_EXCEPTION_TYPE_LOAD);

if (cfg->compute_gc_maps) {
Expand Down Expand Up @@ -1351,7 +1353,10 @@ mono_allocate_stack_slots (MonoCompile *cfg, gboolean backward, guint32 *stack_s
size = mini_type_stack_size (t, &ialign);
align = ialign;

if (mono_class_has_failure (mono_class_from_mono_type_internal (t)))
// In AOT, we do not set the exception but allow the compilation to succeed. The error will be
// indicated in runtime by throwing an exception when an operation with the invalid object is
// attempted.
if (!cfg->compile_aot && mono_class_has_failure (mono_class_from_mono_type_internal (t)))
mono_cfg_set_exception (cfg, MONO_EXCEPTION_TYPE_LOAD);

if (mini_class_is_simd (cfg, mono_class_from_mono_type_internal (t)))
Expand Down
9 changes: 0 additions & 9 deletions src/tests/issues.targets
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Expand Up @@ -2405,15 +2405,6 @@
<ExcludeList Include="$(XunitTestBinBase)/Loader/classloader/explicitlayout/objrefandnonobjrefoverlap/case9/**">
<Issue>expected failure: overlapped structs fail at AOT compile time, not runtime</Issue>
</ExcludeList>
<ExcludeList Include = "$(XunitTestBinBase)/Loader/classloader/explicitlayout/NestedStructs/case03/**">
<Issue>expected failure: overlapped structs fail at AOT compile time, not runtime</Issue>
</ExcludeList>
<ExcludeList Include = "$(XunitTestBinBase)/Loader/classloader/explicitlayout/NestedStructs/case04/**">
<Issue>expected failure: overlapped structs fail at AOT compile time, not runtime</Issue>
</ExcludeList>
<ExcludeList Include = "$(XunitTestBinBase)/Loader/classloader/explicitlayout/NestedStructs/case05/**">
<Issue>expected failure: overlapped structs fail at AOT compile time, not runtime</Issue>
</ExcludeList>
<ExcludeList Include = "$(XunitTestBinBase)/Loader/classloader/RefFields/Validate/**">
<Issue>expected failure: unsupported type with ref field fails at AOT compile time, not runtime</Issue>
</ExcludeList>
Expand Down
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