checkasm: Generalize crash handling

This replaces the riscv specific handling from
7212466e73 (which essentially is
reverted), with a different implementation of the same (plus a bit
more), based on the corresponding feature in dav1d's checkasm,
supporting both Unix and Windows.

See in particular the dav1d commits
0b6ee30eab2400e4f85b735ad29a68a842c34e21,
0421f787ea592fd2cc74c887f20b8dc31393788b,
8501a4b20135f93a4c3b426468e2240e872949c5 and
d23e87f7aee26ddcf5f7a2e185112031477599a7, authored by Henrik Gramner.

The overall approach compared to the existing implementation for
riscv is the same; set up a signal handler, store the state with
sigsetjmp, jump out of the crashing function with siglongjmp.

The main difference is in what happens when the signal handler
is invoked. In the previous implementation, it would resume from
right before calling the crashing function, and then skip that call
based on the setjmp return value.

In the imported implementation from dav1d, we return to right before
the check_func() call, which will skip testing the current function
(as the pointer is the same as it was before).

Other differences are:
- Support for other signal handling mechanisms (Windows
  AddVectoredExceptionHandler)
- Using RtlCaptureContext/RtlRestoreContext instead of setjmp/longjmp
  on Windows with SEH
- Only catching signals once per function - if more than one
  signal is delivered before signal handling is reenabled, any
  signal is handled as it would without our handler
- Not using an arch specific signal handler written in assembly

Signed-off-by: Martin Storsjö <martin@martin.st>

tests/checkasm/checkasm.c

@@ -42,6 +42,11 @@
 #include <io.h>
 #endif
 
+#if defined(_WIN32) && !defined(SIGBUS)
+/* non-standard, use the same value as mingw-w64 */
+#define SIGBUS 10
+#endif
+
 #if HAVE_SETCONSOLETEXTATTRIBUTE && HAVE_GETSTDHANDLE
 #include <windows.h>
 #define COLOR_RED    FOREGROUND_RED
@@ -329,6 +334,7 @@ static struct {
     const char *cpu_flag_name;
     const char *test_name;
     int verbose;
+    volatile sig_atomic_t catch_signals;
 } state;
 
 /* PRNG state */
@@ -630,6 +636,61 @@ static CheckasmFunc *get_func(CheckasmFunc **root, const char *name)
     return f;
 }
 
+checkasm_context checkasm_context_buf;
+
+/* Crash handling: attempt to catch crashes and handle them
+ * gracefully instead of just aborting abruptly. */
+#ifdef _WIN32
+#if WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_DESKTOP)
+static LONG NTAPI signal_handler(EXCEPTION_POINTERS *e) {
+    int s;
+
+    if (!state.catch_signals)
+        return EXCEPTION_CONTINUE_SEARCH;
+
+    switch (e->ExceptionRecord->ExceptionCode) {
+    case EXCEPTION_FLT_DIVIDE_BY_ZERO:
+    case EXCEPTION_INT_DIVIDE_BY_ZERO:
+        s = SIGFPE;
+        break;
+    case EXCEPTION_ILLEGAL_INSTRUCTION:
+    case EXCEPTION_PRIV_INSTRUCTION:
+        s = SIGILL;
+        break;
+    case EXCEPTION_ACCESS_VIOLATION:
+    case EXCEPTION_ARRAY_BOUNDS_EXCEEDED:
+    case EXCEPTION_DATATYPE_MISALIGNMENT:
+    case EXCEPTION_STACK_OVERFLOW:
+        s = SIGSEGV;
+        break;
+    case EXCEPTION_IN_PAGE_ERROR:
+        s = SIGBUS;
+        break;
+    default:
+        return EXCEPTION_CONTINUE_SEARCH;
+    }
+    state.catch_signals = 0;
+    checkasm_load_context(s);
+    return EXCEPTION_CONTINUE_EXECUTION; /* never reached, but shuts up gcc */
+}
+#endif
+#else
+static void signal_handler(int s);
+
+static const struct sigaction signal_handler_act = {
+    .sa_handler = signal_handler,
+    .sa_flags = SA_RESETHAND,
+};
+
+static void signal_handler(int s) {
+    if (state.catch_signals) {
+        state.catch_signals = 0;
+        sigaction(s, &signal_handler_act, NULL);
+        checkasm_load_context(s);
+    }
+}
+#endif
+
 /* Perform tests and benchmarks for the specified cpu flag if supported by the host */
 static void check_cpu_flag(const char *name, int flag)
 {
@@ -740,18 +801,20 @@ int main(int argc, char *argv[])
     unsigned int seed = av_get_random_seed();
     int i, ret = 0;
 
+#ifdef _WIN32
+#if WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_DESKTOP)
+    AddVectoredExceptionHandler(0, signal_handler);
+#endif
+#else
+    sigaction(SIGBUS,  &signal_handler_act, NULL);
+    sigaction(SIGFPE,  &signal_handler_act, NULL);
+    sigaction(SIGILL,  &signal_handler_act, NULL);
+    sigaction(SIGSEGV, &signal_handler_act, NULL);
+#endif
 #if ARCH_ARM && HAVE_ARMV5TE_EXTERNAL
     if (have_vfp(av_get_cpu_flags()) || have_neon(av_get_cpu_flags()))
         checkasm_checked_call = checkasm_checked_call_vfp;
 #endif
-#if ARCH_RISCV && HAVE_RV
-    struct sigaction act = {
-        .sa_handler = checkasm_handle_signal,
-        .sa_flags = 0,
-    };
-
-    sigaction(SIGILL, &act, NULL);
-#endif
 
     if (!tests[0].func || !cpus[0].flag) {
         fprintf(stderr, "checkasm: no tests to perform\n");
@@ -879,13 +942,22 @@ void checkasm_fail_func(const char *msg, ...)
     }
 }
 
-void checkasm_fail_signal(int signum)
-{
+void checkasm_set_signal_handler_state(int enabled) {
+    state.catch_signals = enabled;
+}
+
+int checkasm_handle_signal(int s) {
+    if (s) {
 #ifdef __GLIBC__
-    checkasm_fail_func("fatal signal %d: %s", signum, strsignal(signum));
+        checkasm_fail_func("fatal signal %d: %s", s, strsignal(s));
 #else
-    checkasm_fail_func("fatal signal %d", signum);
+        checkasm_fail_func(s == SIGFPE ? "fatal arithmetic error" :
+                           s == SIGILL ? "illegal instruction" :
+                           s == SIGBUS ? "bus error" :
+                                         "segmentation fault");
 #endif
+    }
+    return s;
 }
 
 /* Get the benchmark context of the current function */

tests/checkasm/checkasm.h

@@ -23,7 +23,6 @@
 #ifndef TESTS_CHECKASM_CHECKASM_H
 #define TESTS_CHECKASM_CHECKASM_H
 
-#include <setjmp.h>
 #include <stdint.h>
 #include "config.h"
 
@@ -43,6 +42,37 @@
 #include "libavutil/lfg.h"
 #include "libavutil/timer.h"
 
+#ifdef _WIN32
+#include <windows.h>
+#if ARCH_X86_32
+#include <setjmp.h>
+typedef jmp_buf checkasm_context;
+#define checkasm_save_context() checkasm_handle_signal(setjmp(checkasm_context_buf))
+#define checkasm_load_context(s) longjmp(checkasm_context_buf, s)
+#elif WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_DESKTOP)
+/* setjmp/longjmp on Windows on architectures using SEH (all except x86_32)
+ * will try to use SEH to unwind the stack, which doesn't work for assembly
+ * functions without unwind information. */
+typedef struct { CONTEXT c; int status; } checkasm_context;
+#define checkasm_save_context() \
+    (checkasm_context_buf.status = 0, \
+     RtlCaptureContext(&checkasm_context_buf.c), \
+     checkasm_handle_signal(checkasm_context_buf.status))
+#define checkasm_load_context(s) \
+    (checkasm_context_buf.status = s, \
+     RtlRestoreContext(&checkasm_context_buf.c, NULL))
+#else
+#define checkasm_context void*
+#define checkasm_save_context() 0
+#define checkasm_load_context() do {} while (0)
+#endif
+#else
+#include <setjmp.h>
+typedef sigjmp_buf checkasm_context;
+#define checkasm_save_context() checkasm_handle_signal(sigsetjmp(checkasm_context_buf, 1))
+#define checkasm_load_context(s) siglongjmp(checkasm_context_buf, s)
+#endif
+
 void checkasm_check_aacencdsp(void);
 void checkasm_check_aacpsdsp(void);
 void checkasm_check_ac3dsp(void);
@@ -106,9 +136,11 @@ struct CheckasmPerf;
 void *checkasm_check_func(void *func, const char *name, ...) av_printf_format(2, 3);
 int checkasm_bench_func(void);
 void checkasm_fail_func(const char *msg, ...) av_printf_format(1, 2);
-void checkasm_fail_signal(int signum);
 struct CheckasmPerf *checkasm_get_perf_context(void);
 void checkasm_report(const char *name, ...) av_printf_format(1, 2);
+void checkasm_set_signal_handler_state(int enabled);
+int checkasm_handle_signal(int s);
+extern checkasm_context checkasm_context_buf;
 
 /* float compare utilities */
 int float_near_ulp(float a, float b, unsigned max_ulp);
@@ -132,7 +164,7 @@ static av_unused void *func_ref, *func_new;
 #define BENCH_RUNS 1000 /* Trade-off between accuracy and speed */
 
 /* Decide whether or not the specified function needs to be tested */
-#define check_func(func, ...) (func_ref = checkasm_check_func((func_new = func), __VA_ARGS__))
+#define check_func(func, ...) (checkasm_save_context(), func_ref = checkasm_check_func((func_new = func), __VA_ARGS__))
 
 /* Declare the function prototype. The first argument is the return value, the remaining
  * arguments are the function parameters. Naming parameters is optional. */
@@ -147,7 +179,10 @@ static av_unused void *func_ref, *func_new;
 #define report checkasm_report
 
 /* Call the reference function */
-#define call_ref(...) ((func_type *)func_ref)(__VA_ARGS__)
+#define call_ref(...)\
+    (checkasm_set_signal_handler_state(1),\
+     ((func_type *)func_ref)(__VA_ARGS__));\
+    checkasm_set_signal_handler_state(0)
 
 #if ARCH_X86 && HAVE_X86ASM
 /* Verifies that clobbered callee-saved registers are properly saved and restored
@@ -180,16 +215,21 @@ void checkasm_stack_clobber(uint64_t clobber, ...);
         ((cpu_flags) & av_get_cpu_flags()) ? (void *)checkasm_checked_call_emms : \
                                              (void *)checkasm_checked_call;
 #define CLOB (UINT64_C(0xdeadbeefdeadbeef))
-#define call_new(...) (checkasm_stack_clobber(CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,\
+#define call_new(...) (checkasm_set_signal_handler_state(1),\
+                       checkasm_stack_clobber(CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,\
                                               CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,CLOB),\
-                      checked_call(func_new, 0, 0, 0, 0, 0, __VA_ARGS__))
+                       checked_call(func_new, 0, 0, 0, 0, 0, __VA_ARGS__));\
+                      checkasm_set_signal_handler_state(0)
 #elif ARCH_X86_32
 #define declare_new(ret, ...) ret (*checked_call)(void *, __VA_ARGS__) = (void *)checkasm_checked_call;
 #define declare_new_float(ret, ...) ret (*checked_call)(void *, __VA_ARGS__) = (void *)checkasm_checked_call_float;
 #define declare_new_emms(cpu_flags, ret, ...) ret (*checked_call)(void *, __VA_ARGS__) = \
         ((cpu_flags) & av_get_cpu_flags()) ? (void *)checkasm_checked_call_emms :        \
                                              (void *)checkasm_checked_call;
-#define call_new(...) checked_call(func_new, __VA_ARGS__)
+#define call_new(...)\
+    (checkasm_set_signal_handler_state(1),\
+     checked_call(func_new, __VA_ARGS__));\
+    checkasm_set_signal_handler_state(0)
 #endif
 #elif ARCH_ARM && HAVE_ARMV5TE_EXTERNAL
 /* Use a dummy argument, to offset the real parameters by 2, not only 1.
@@ -201,7 +241,10 @@ extern void (*checkasm_checked_call)(void *func, int dummy, ...);
 #define declare_new(ret, ...) ret (*checked_call)(void *, int dummy, __VA_ARGS__, \
                                                   int, int, int, int, int, int, int, int, \
                                                   int, int, int, int, int, int, int) = (void *)checkasm_checked_call;
-#define call_new(...) checked_call(func_new, 0, __VA_ARGS__, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0, 0, 0, 0)
+#define call_new(...) \
+    (checkasm_set_signal_handler_state(1),\
+     checked_call(func_new, 0, __VA_ARGS__, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0, 0, 0, 0));\
+    checkasm_set_signal_handler_state(0)
 #elif ARCH_AARCH64 && !defined(__APPLE__)
 void checkasm_stack_clobber(uint64_t clobber, ...);
 void checkasm_checked_call(void *func, ...);
@@ -210,35 +253,39 @@ void checkasm_checked_call(void *func, ...);
                                                   int, int, int, int, int, int, int)\
                               = (void *)checkasm_checked_call;
 #define CLOB (UINT64_C(0xdeadbeefdeadbeef))
-#define call_new(...) (checkasm_stack_clobber(CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,\
+#define call_new(...) (checkasm_set_signal_handler_state(1),\
+                       checkasm_stack_clobber(CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,\
                                               CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,CLOB,CLOB),\
                       checked_call(func_new, 0, 0, 0, 0, 0, 0, 0, __VA_ARGS__,\
-                                   7, 6, 5, 4, 3, 2, 1, 0, 0, 0, 0, 0, 0, 0, 0))
+                                   7, 6, 5, 4, 3, 2, 1, 0, 0, 0, 0, 0, 0, 0, 0));\
+                     checkasm_set_signal_handler_state(0)
 #elif ARCH_RISCV
-void checkasm_set_function(void *, sigjmp_buf);
+void checkasm_set_function(void *);
 void *checkasm_get_wrapper(void);
-void checkasm_handle_signal(int signum);
 
 #if HAVE_RV && (__riscv_xlen == 64) && defined (__riscv_d)
 #define declare_new(ret, ...) \
-    int checked_call_signum = 0; \
-    sigjmp_buf checked_call_jb; \
     ret (*checked_call)(__VA_ARGS__) = checkasm_get_wrapper();
 #define call_new(...) \
-    (checkasm_set_function(func_new, checked_call_jb), \
-     (checked_call_signum = sigsetjmp(checked_call_jb, 1)) == 0 \
-        ? checked_call(__VA_ARGS__) \
-        : (checkasm_fail_signal(checked_call_signum), 0))
+    (checkasm_set_signal_handler_state(1),\
+     checkasm_set_function(func_new), checked_call(__VA_ARGS__));\
+    checkasm_set_signal_handler_state(0)
 #else
 #define declare_new(ret, ...)
-#define call_new(...) ((func_type *)func_new)(__VA_ARGS__)
+#define call_new(...)\
+    (checkasm_set_signal_handler_state(1),\
+     ((func_type *)func_new)(__VA_ARGS__));\
+    checkasm_set_signal_handler_state(0)
 #endif
 #else
 #define declare_new(ret, ...)
 #define declare_new_float(ret, ...)
 #define declare_new_emms(cpu_flags, ret, ...)
 /* Call the function */
-#define call_new(...) ((func_type *)func_new)(__VA_ARGS__)
+#define call_new(...)\
+    (checkasm_set_signal_handler_state(1),\
+     ((func_type *)func_new)(__VA_ARGS__));\
+    checkasm_set_signal_handler_state(0)
 #endif
 
 #ifndef declare_new_emms
@@ -285,6 +332,7 @@ typedef struct CheckasmPerf {
             uint64_t tsum = 0;\
             int ti, tcount = 0;\
             uint64_t t = 0; \
+            checkasm_set_signal_handler_state(1);\
             for (ti = 0; ti < BENCH_RUNS; ti++) {\
                 PERF_START(t);\
                 tfunc(__VA_ARGS__);\
@@ -300,6 +348,7 @@ typedef struct CheckasmPerf {
             emms_c();\
             perf->cycles += t;\
             perf->iterations++;\
+            checkasm_set_signal_handler_state(0);\
         }\
     } while (0)
 #else

tests/checkasm/riscv/checkasm.S

@@ -41,7 +41,6 @@ endconst
 
 checked_func:
         .quad   0
-        .quad   0
 
 saved_regs:
         /* Space to spill RA, SP, GP, TP, S0-S11 and FS0-FS11 */
@@ -53,7 +52,6 @@ func checkasm_set_function
         la.tls.ie t0, checked_func
         add     t0, tp, t0
         sd      a0, (t0)
-        sd      a1, 8(t0)
         ret
 endfunc
 
@@ -177,14 +175,4 @@ func checkasm_get_wrapper, v
         call    checkasm_fail_func
         j       4b
 endfunc
-
-func checkasm_handle_signal
-        mv      a1, a0
-        la.tls.ie a0, checked_func
-        add     a0, tp, a0
-        ld      a0, 8(a0)
-        beqz    a0, 8f
-        tail    siglongjmp
-8:      tail    abort /* No jump buffer to go to */
-endfunc
 #endif