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Fix an UB in layout tests #2055

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Fix an UB in layout tests #2055

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58d19c0
Fix an UB in layout tests
Apostoln May 15, 2021
9dd8b98
Replace zeroed buffer + mem::transmute with mem::zeroed
Apostoln May 17, 2021
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28 changes: 25 additions & 3 deletions src/codegen/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2084,8 +2084,12 @@ impl CodeGenerator for CompInfo {
.count() >
1;


// The offset of #[repr(C)] union is always 0, don't need to recheck it.
let is_not_packed_union = is_union && !packed;

let should_skip_field_offset_checks =
is_opaque || too_many_base_vtables;
is_opaque || too_many_base_vtables || is_not_packed_union;

let check_field_offset = if should_skip_field_offset_checks
{
Expand All @@ -2105,8 +2109,26 @@ impl CodeGenerator for CompInfo {

Some(quote! {
assert_eq!(
unsafe {
&(*(::#prefix::ptr::null::<#canonical_ident>())).#field_name as *const _ as usize
{
// Create an instance of #canonical_ident struct from zero bit pattern
const STRUCT_SIZE: usize = std::mem::size_of::<#canonical_ident>();
let buffer = [0u8; STRUCT_SIZE];
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This is not guaranteed to be aligned right? I think using std::mem::zeroed should be better.

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Thanks, fixed

Though, I don't catch why there is a wrong alignment. AFAIU, In case of mem::zeroed the padding bytes are not zeroed but the total behavior is the same.

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No, let's say you have a struct with an u32 member. The compiler would make sure that that is aligned appropriately, but if you use a flat array of u8s then it's not.

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@emilio
Ok, thank you. Replaced it with mem::zeroed

let struct_instance = unsafe {
// It's safe since #canonical_ident struct allows zero bit pattern
std::mem::transmute::<[u8; STRUCT_SIZE], #canonical_ident>(buffer)
};
// Get the pointers to the struct and its field
let struct_ptr = &struct_instance as *const #canonical_ident;
let field_ptr = std::ptr::addr_of!(struct_instance.#field_name);

// Get the offset of the field
let struct_address = struct_ptr as usize;
let field_address = field_ptr as usize;

//Do not call the destructor
std::mem::forget(struct_instance);

field_address.checked_sub(struct_address).unwrap()
},
#field_offset,
concat!("Offset of field: ", stringify!(#canonical_ident), "::", stringify!(#field_name))
Expand Down
198 changes: 120 additions & 78 deletions tests/expectations/tests/16-byte-alignment.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -43,10 +43,24 @@ fn bindgen_test_layout_rte_ipv4_tuple__bindgen_ty_1__bindgen_ty_1() {
)
);
assert_eq!(
unsafe {
&(*(::std::ptr::null::<rte_ipv4_tuple__bindgen_ty_1__bindgen_ty_1>(
)))
.dport as *const _ as usize
{
const STRUCT_SIZE: usize = std::mem::size_of::<
rte_ipv4_tuple__bindgen_ty_1__bindgen_ty_1,
>();
let buffer = [0u8; STRUCT_SIZE];
let struct_instance = unsafe {
std::mem::transmute::<
[u8; STRUCT_SIZE],
rte_ipv4_tuple__bindgen_ty_1__bindgen_ty_1,
>(buffer)
};
let struct_ptr = &struct_instance
as *const rte_ipv4_tuple__bindgen_ty_1__bindgen_ty_1;
let field_ptr = std::ptr::addr_of!(struct_instance.dport);
let struct_address = struct_ptr as usize;
let field_address = field_ptr as usize;
std::mem::forget(struct_instance);
field_address.checked_sub(struct_address).unwrap()
},
0usize,
concat!(
Expand All @@ -57,10 +71,24 @@ fn bindgen_test_layout_rte_ipv4_tuple__bindgen_ty_1__bindgen_ty_1() {
)
);
assert_eq!(
unsafe {
&(*(::std::ptr::null::<rte_ipv4_tuple__bindgen_ty_1__bindgen_ty_1>(
)))
.sport as *const _ as usize
{
const STRUCT_SIZE: usize = std::mem::size_of::<
rte_ipv4_tuple__bindgen_ty_1__bindgen_ty_1,
>();
let buffer = [0u8; STRUCT_SIZE];
let struct_instance = unsafe {
std::mem::transmute::<
[u8; STRUCT_SIZE],
rte_ipv4_tuple__bindgen_ty_1__bindgen_ty_1,
>(buffer)
};
let struct_ptr = &struct_instance
as *const rte_ipv4_tuple__bindgen_ty_1__bindgen_ty_1;
let field_ptr = std::ptr::addr_of!(struct_instance.sport);
let struct_address = struct_ptr as usize;
let field_address = field_ptr as usize;
std::mem::forget(struct_instance);
field_address.checked_sub(struct_address).unwrap()
},
2usize,
concat!(
Expand All @@ -83,19 +111,6 @@ fn bindgen_test_layout_rte_ipv4_tuple__bindgen_ty_1() {
4usize,
concat!("Alignment of ", stringify!(rte_ipv4_tuple__bindgen_ty_1))
);
assert_eq!(
unsafe {
&(*(::std::ptr::null::<rte_ipv4_tuple__bindgen_ty_1>())).sctp_tag
as *const _ as usize
},
0usize,
concat!(
"Offset of field: ",
stringify!(rte_ipv4_tuple__bindgen_ty_1),
"::",
stringify!(sctp_tag)
)
);
}
impl Default for rte_ipv4_tuple__bindgen_ty_1 {
fn default() -> Self {
Expand All @@ -119,9 +134,18 @@ fn bindgen_test_layout_rte_ipv4_tuple() {
concat!("Alignment of ", stringify!(rte_ipv4_tuple))
);
assert_eq!(
unsafe {
&(*(::std::ptr::null::<rte_ipv4_tuple>())).src_addr as *const _
as usize
{
const STRUCT_SIZE: usize = std::mem::size_of::<rte_ipv4_tuple>();
let buffer = [0u8; STRUCT_SIZE];
let struct_instance = unsafe {
std::mem::transmute::<[u8; STRUCT_SIZE], rte_ipv4_tuple>(buffer)
};
let struct_ptr = &struct_instance as *const rte_ipv4_tuple;
let field_ptr = std::ptr::addr_of!(struct_instance.src_addr);
let struct_address = struct_ptr as usize;
let field_address = field_ptr as usize;
std::mem::forget(struct_instance);
field_address.checked_sub(struct_address).unwrap()
},
0usize,
concat!(
Expand All @@ -132,9 +156,18 @@ fn bindgen_test_layout_rte_ipv4_tuple() {
)
);
assert_eq!(
unsafe {
&(*(::std::ptr::null::<rte_ipv4_tuple>())).dst_addr as *const _
as usize
{
const STRUCT_SIZE: usize = std::mem::size_of::<rte_ipv4_tuple>();
let buffer = [0u8; STRUCT_SIZE];
let struct_instance = unsafe {
std::mem::transmute::<[u8; STRUCT_SIZE], rte_ipv4_tuple>(buffer)
};
let struct_ptr = &struct_instance as *const rte_ipv4_tuple;
let field_ptr = std::ptr::addr_of!(struct_instance.dst_addr);
let struct_address = struct_ptr as usize;
let field_address = field_ptr as usize;
std::mem::forget(struct_instance);
field_address.checked_sub(struct_address).unwrap()
},
4usize,
concat!(
Expand Down Expand Up @@ -192,10 +225,24 @@ fn bindgen_test_layout_rte_ipv6_tuple__bindgen_ty_1__bindgen_ty_1() {
)
);
assert_eq!(
unsafe {
&(*(::std::ptr::null::<rte_ipv6_tuple__bindgen_ty_1__bindgen_ty_1>(
)))
.dport as *const _ as usize
{
const STRUCT_SIZE: usize = std::mem::size_of::<
rte_ipv6_tuple__bindgen_ty_1__bindgen_ty_1,
>();
let buffer = [0u8; STRUCT_SIZE];
let struct_instance = unsafe {
std::mem::transmute::<
[u8; STRUCT_SIZE],
rte_ipv6_tuple__bindgen_ty_1__bindgen_ty_1,
>(buffer)
};
let struct_ptr = &struct_instance
as *const rte_ipv6_tuple__bindgen_ty_1__bindgen_ty_1;
let field_ptr = std::ptr::addr_of!(struct_instance.dport);
let struct_address = struct_ptr as usize;
let field_address = field_ptr as usize;
std::mem::forget(struct_instance);
field_address.checked_sub(struct_address).unwrap()
},
0usize,
concat!(
Expand All @@ -206,10 +253,24 @@ fn bindgen_test_layout_rte_ipv6_tuple__bindgen_ty_1__bindgen_ty_1() {
)
);
assert_eq!(
unsafe {
&(*(::std::ptr::null::<rte_ipv6_tuple__bindgen_ty_1__bindgen_ty_1>(
)))
.sport as *const _ as usize
{
const STRUCT_SIZE: usize = std::mem::size_of::<
rte_ipv6_tuple__bindgen_ty_1__bindgen_ty_1,
>();
let buffer = [0u8; STRUCT_SIZE];
let struct_instance = unsafe {
std::mem::transmute::<
[u8; STRUCT_SIZE],
rte_ipv6_tuple__bindgen_ty_1__bindgen_ty_1,
>(buffer)
};
let struct_ptr = &struct_instance
as *const rte_ipv6_tuple__bindgen_ty_1__bindgen_ty_1;
let field_ptr = std::ptr::addr_of!(struct_instance.sport);
let struct_address = struct_ptr as usize;
let field_address = field_ptr as usize;
std::mem::forget(struct_instance);
field_address.checked_sub(struct_address).unwrap()
},
2usize,
concat!(
Expand All @@ -232,19 +293,6 @@ fn bindgen_test_layout_rte_ipv6_tuple__bindgen_ty_1() {
4usize,
concat!("Alignment of ", stringify!(rte_ipv6_tuple__bindgen_ty_1))
);
assert_eq!(
unsafe {
&(*(::std::ptr::null::<rte_ipv6_tuple__bindgen_ty_1>())).sctp_tag
as *const _ as usize
},
0usize,
concat!(
"Offset of field: ",
stringify!(rte_ipv6_tuple__bindgen_ty_1),
"::",
stringify!(sctp_tag)
)
);
}
impl Default for rte_ipv6_tuple__bindgen_ty_1 {
fn default() -> Self {
Expand All @@ -268,9 +316,18 @@ fn bindgen_test_layout_rte_ipv6_tuple() {
concat!("Alignment of ", stringify!(rte_ipv6_tuple))
);
assert_eq!(
unsafe {
&(*(::std::ptr::null::<rte_ipv6_tuple>())).src_addr as *const _
as usize
{
const STRUCT_SIZE: usize = std::mem::size_of::<rte_ipv6_tuple>();
let buffer = [0u8; STRUCT_SIZE];
let struct_instance = unsafe {
std::mem::transmute::<[u8; STRUCT_SIZE], rte_ipv6_tuple>(buffer)
};
let struct_ptr = &struct_instance as *const rte_ipv6_tuple;
let field_ptr = std::ptr::addr_of!(struct_instance.src_addr);
let struct_address = struct_ptr as usize;
let field_address = field_ptr as usize;
std::mem::forget(struct_instance);
field_address.checked_sub(struct_address).unwrap()
},
0usize,
concat!(
Expand All @@ -281,9 +338,18 @@ fn bindgen_test_layout_rte_ipv6_tuple() {
)
);
assert_eq!(
unsafe {
&(*(::std::ptr::null::<rte_ipv6_tuple>())).dst_addr as *const _
as usize
{
const STRUCT_SIZE: usize = std::mem::size_of::<rte_ipv6_tuple>();
let buffer = [0u8; STRUCT_SIZE];
let struct_instance = unsafe {
std::mem::transmute::<[u8; STRUCT_SIZE], rte_ipv6_tuple>(buffer)
};
let struct_ptr = &struct_instance as *const rte_ipv6_tuple;
let field_ptr = std::ptr::addr_of!(struct_instance.dst_addr);
let struct_address = struct_ptr as usize;
let field_address = field_ptr as usize;
std::mem::forget(struct_instance);
field_address.checked_sub(struct_address).unwrap()
},
16usize,
concat!(
Expand Down Expand Up @@ -322,30 +388,6 @@ fn bindgen_test_layout_rte_thash_tuple() {
16usize,
concat!("Alignment of ", stringify!(rte_thash_tuple))
);
assert_eq!(
unsafe {
&(*(::std::ptr::null::<rte_thash_tuple>())).v4 as *const _ as usize
},
0usize,
concat!(
"Offset of field: ",
stringify!(rte_thash_tuple),
"::",
stringify!(v4)
)
);
assert_eq!(
unsafe {
&(*(::std::ptr::null::<rte_thash_tuple>())).v6 as *const _ as usize
},
0usize,
concat!(
"Offset of field: ",
stringify!(rte_thash_tuple),
"::",
stringify!(v6)
)
);
}
impl Default for rte_thash_tuple {
fn default() -> Self {
Expand Down
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