1 //! Trap codes describing the reason for a trap.
2 
3 use core::fmt::{self, Display, Formatter};
4 use core::str::FromStr;
5 #[cfg(feature = "enable-serde")]
6 use serde::{Deserialize, Serialize};
7 
8 /// A trap code describing the reason for a trap.
9 ///
10 /// All trap instructions have an explicit trap code.
11 #[derive(Clone, Copy, PartialEq, Eq, Debug, Hash)]
12 #[cfg_attr(feature = "enable-serde", derive(Serialize, Deserialize))]
13 pub enum TrapCode {
14     /// The current stack space was exhausted.
15     ///
16     /// On some platforms, a stack overflow may also be indicated by a segmentation fault from the
17     /// stack guard page.
18     StackOverflow,
19 
20     /// A `heap_addr` instruction detected an out-of-bounds error.
21     ///
22     /// Note that not all out-of-bounds heap accesses are reported this way;
23     /// some are detected by a segmentation fault on the heap unmapped or
24     /// offset-guard pages.
25     HeapOutOfBounds,
26 
27     /// A `table_addr` instruction detected an out-of-bounds error.
28     TableOutOfBounds,
29 
30     /// Indirect call to a null table entry.
31     IndirectCallToNull,
32 
33     /// Signature mismatch on indirect call.
34     BadSignature,
35 
36     /// An integer arithmetic operation caused an overflow.
37     IntegerOverflow,
38 
39     /// An integer division by zero.
40     IntegerDivisionByZero,
41 
42     /// Failed float-to-int conversion.
43     BadConversionToInteger,
44 
45     /// Code that was supposed to have been unreachable was reached.
46     UnreachableCodeReached,
47 
48     /// Execution has potentially run too long and may be interrupted.
49     /// This trap is resumable.
50     Interrupt,
51 
52     /// A user-defined trap code.
53     User(u16),
54 }
55 
56 impl Display for TrapCode {
fmt(&self, f: &mut Formatter) -> fmt::Result57     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
58         use self::TrapCode::*;
59         let identifier = match *self {
60             StackOverflow => "stk_ovf",
61             HeapOutOfBounds => "heap_oob",
62             TableOutOfBounds => "table_oob",
63             IndirectCallToNull => "icall_null",
64             BadSignature => "bad_sig",
65             IntegerOverflow => "int_ovf",
66             IntegerDivisionByZero => "int_divz",
67             BadConversionToInteger => "bad_toint",
68             UnreachableCodeReached => "unreachable",
69             Interrupt => "interrupt",
70             User(x) => return write!(f, "user{}", x),
71         };
72         f.write_str(identifier)
73     }
74 }
75 
76 impl FromStr for TrapCode {
77     type Err = ();
78 
from_str(s: &str) -> Result<Self, Self::Err>79     fn from_str(s: &str) -> Result<Self, Self::Err> {
80         use self::TrapCode::*;
81         match s {
82             "stk_ovf" => Ok(StackOverflow),
83             "heap_oob" => Ok(HeapOutOfBounds),
84             "table_oob" => Ok(TableOutOfBounds),
85             "icall_null" => Ok(IndirectCallToNull),
86             "bad_sig" => Ok(BadSignature),
87             "int_ovf" => Ok(IntegerOverflow),
88             "int_divz" => Ok(IntegerDivisionByZero),
89             "bad_toint" => Ok(BadConversionToInteger),
90             "unreachable" => Ok(UnreachableCodeReached),
91             "interrupt" => Ok(Interrupt),
92             _ if s.starts_with("user") => s[4..].parse().map(User).map_err(|_| ()),
93             _ => Err(()),
94         }
95     }
96 }
97 
98 #[cfg(test)]
99 mod tests {
100     use super::*;
101     use alloc::string::ToString;
102 
103     // Everything but user-defined codes.
104     const CODES: [TrapCode; 10] = [
105         TrapCode::StackOverflow,
106         TrapCode::HeapOutOfBounds,
107         TrapCode::TableOutOfBounds,
108         TrapCode::IndirectCallToNull,
109         TrapCode::BadSignature,
110         TrapCode::IntegerOverflow,
111         TrapCode::IntegerDivisionByZero,
112         TrapCode::BadConversionToInteger,
113         TrapCode::UnreachableCodeReached,
114         TrapCode::Interrupt,
115     ];
116 
117     #[test]
display()118     fn display() {
119         for r in &CODES {
120             let tc = *r;
121             assert_eq!(tc.to_string().parse(), Ok(tc));
122         }
123         assert_eq!("bogus".parse::<TrapCode>(), Err(()));
124 
125         assert_eq!(TrapCode::User(17).to_string(), "user17");
126         assert_eq!("user22".parse(), Ok(TrapCode::User(22)));
127         assert_eq!("user".parse::<TrapCode>(), Err(()));
128         assert_eq!("user-1".parse::<TrapCode>(), Err(()));
129         assert_eq!("users".parse::<TrapCode>(), Err(()));
130     }
131 }
132