From 3523eda2241c22e9ddaa6739a3e52cc51252f17f Mon Sep 17 00:00:00 2001
From: Rudolf Polzer <divVerent@gmail.com>
Date: Fri, 3 Jan 2025 18:28:23 -0500
Subject: [PATCH] OP_DIV_*: add division by zero checks.
Now all the OP_DIV operations emit a warning and proceed on division by
zero, instead of potentially crashing the program.
This also handles the special case of -2147483648 / -1, which also traps on
x86 and thus must be handled.
---
prvm_execprogram.h | 46 ++++++++++++++++++++++++++++++++++++++++++----
qtypes.h | 4 ++++
2 files changed, 46 insertions(+), 4 deletions(-)
diff --git a/prvm_execprogram.h b/prvm_execprogram.h
index 984db078..5a3c8e4d 100644
--- a/prvm_execprogram.h
+++ b/prvm_execprogram.h
@@ -884,21 +884,59 @@ prvm_eval_t *src;
OPC->vector[2] = (prvm_vec_t) OPB->_int * OPA->vector[2];
DISPATCH_OPCODE();
HANDLE_OPCODE(OP_DIV_VF):
+ if( OPB->_float != 0.0f )
{
float temp = 1.0f / OPB->_float;
OPC->vector[0] = temp * OPA->vector[0];
OPC->vector[1] = temp * OPA->vector[1];
OPC->vector[2] = temp * OPA->vector[2];
}
+ else
+ {
+ PRE_ERROR();
+ VM_Warning(prog, "Attempted division of '%f %f %f' by zero\n", OPA->vector[0], OPA->vector[1], OPA->vector[2]);
+ OPC->vector[0] = 0.0f;
+ OPC->vector[1] = 0.0f;
+ OPC->vector[2] = 0.0f;
+ }
DISPATCH_OPCODE();
HANDLE_OPCODE(OP_DIV_I):
- OPC->_int = OPA->_int / OPB->_int;
+ // NOTE: This also catches the second kind of division that can trap, namely, -2147483648 / -1,
+ // whose result is not representable as int32_t and raises the same CPU exception.
+ if( OPB->_int != 0 && (OPB->_int != -1 || OPA->_int != PRVM_INT_MIN) )
+ {
+ OPC->_int = OPA->_int / OPB->_int;
+ }
+ else
+ {
+ PRE_ERROR();
+ VM_Warning(prog, "Attempted division of %"PRVM_PRIi" by %"PRVM_PRIi"\n", OPA->_int, OPB->_int);
+ OPC->_int = 0;
+ }
DISPATCH_OPCODE();
HANDLE_OPCODE(OP_DIV_IF):
- OPC->_float = ((prvm_vec_t) OPA->_int) / OPB->_float;
+ if( OPB->_float != 0.0f )
+ {
+ OPC->_float = ((prvm_vec_t) OPA->_int) / OPB->_float;
+ }
+ else
+ {
+ PRE_ERROR();
+ VM_Warning(prog, "Attempted division of %"PRVM_PRIi" by zero\n", OPA->_int);
+ OPC->_float = 0;
+ }
DISPATCH_OPCODE();
HANDLE_OPCODE(OP_DIV_FI):
- OPC->_float = OPA->_float / (prvm_vec_t) OPB->_int;
+ if( OPB->_int != 0 )
+ {
+ OPC->_float = OPA->_float / (prvm_vec_t) OPB->_int;
+ }
+ else
+ {
+ PRE_ERROR();
+ VM_Warning(prog, "Attempted division of %f by zero\n", OPA->_float);
+ OPC->_float = 0;
+ }
DISPATCH_OPCODE();
HANDLE_OPCODE(OP_CONV_ITOF):
OPC->_float = OPA->_int;
@@ -1247,7 +1285,7 @@ prvm_eval_t *src;
else
{
PRE_ERROR();
- VM_Warning(prog, "Attempted division of %u by zero\n", OPA->_uint);
+ VM_Warning(prog, "Attempted division of %"PRVM_PRIu" by zero\n", OPA->_uint);
OPC->_uint = 0;
}
DISPATCH_OPCODE();
diff --git a/qtypes.h b/qtypes.h
index 7e10a4fa..653364b9 100644
--- a/qtypes.h
+++ b/qtypes.h
@@ -49,12 +49,16 @@ typedef int64_t prvm_int_t;
typedef uint64_t prvm_uint_t;
#define PRVM_PRIi PRIi64
#define PRVM_PRIu PRIu64
+#define PRVM_INT_MIN INT64_MIN
+#define PRVM_INT_MAX INT64_MAX
#else
typedef float prvm_vec_t;
typedef int32_t prvm_int_t;
typedef uint32_t prvm_uint_t;
#define PRVM_PRIi PRIi32
#define PRVM_PRIu PRIu32
+#define PRVM_INT_MIN INT32_MIN
+#define PRVM_INT_MAX INT32_MAX
#endif
typedef prvm_vec_t prvm_vec3_t[3];
--
2.39.5