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Safer code

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Add additional compile-time assertions
Add additional comments to define limitations future maintainers should be aware of.
This commit is contained in:
Henry Gabryjelski 2019-03-13 18:27:11 -07:00
parent c51a227fd9
commit 8def8aee53
2 changed files with 164 additions and 8 deletions
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28
src/usb/uf2/ghostfat.c
View File

@ -9,6 +9,7 @@
#include "bootloader_settings.h"
#include "bootloader.h"
typedef struct {
uint8_t JumpInstruction[3];
uint8_t OEMInfo[8];
@ -59,6 +60,7 @@ struct TextFile {
#define STR0(x) #x
#define STR(x) STR0(x)
const char infoUf2File[] = //
"UF2 Bootloader " UF2_VERSION "\r\n"
"Model: " PRODUCT_NAME "\r\n"
@ -81,11 +83,20 @@ static struct TextFile const info[] = {
{.name = "INDEX HTM", .content = indexFile},
{.name = "CURRENT UF2"},
};
#define NUM_INFO (sizeof(info) / sizeof(info[0]))
// WARNING -- code presumes each non-UF2 file content fits in single sector
// Cannot programmatically statically assert .content length
// for each element above.
STATIC_ASSERT(ARRAY_SIZE2(indexFile) < 512);
#define NUM_FILES (ARRAY_SIZE2(info))
#define NUM_DIRENTRIES (NUM_FILES + 1) // Code adds volume label as first root directory entry
#define UF2_SIZE (current_flash_size() * 2)
#define UF2_SECTORS (UF2_SIZE / 512)
#define UF2_FIRST_SECTOR (NUM_INFO + 1)
#define UF2_FIRST_SECTOR (NUM_FILES + 1) // WARNING -- code presumes each non-UF2 file content fits in single sector
#define UF2_LAST_SECTOR (UF2_FIRST_SECTOR + UF2_SECTORS - 1)
#define RESERVED_SECTORS 1
@ -99,7 +110,8 @@ static struct TextFile const info[] = {
// all directory entries must fit in a single sector
// because otherwise current code overflows buffer
STATIC_ASSERT(NUM_INFO < (512 / sizeof(DirEntry)));
STATIC_ASSERT(NUM_DIRENTRIES < (512 / sizeof(DirEntry)));
// STATIC_ASSERT(NUM_DIRENTRIES < (512 / sizeof(DirEntry)) * ROOT_DIR_SECTORS);
static FAT_BootBlock const BootBlock = {
@ -193,8 +205,8 @@ void read_block(uint32_t block_no, uint8_t *data) {
sectionIdx -= SECTORS_PER_FAT;
if (sectionIdx == 0) {
data[0] = 0xf0;
for (int i = 1; i < NUM_INFO * 2 + 4; ++i) {
data[i] = 0xff;
for (int i = 1; i < NUM_FILES * 2 + 4; ++i) {
data[i] = 0xff; // WARNING -- code presumes each non-UF2 file content fits in single sector
}
}
for (int i = 0; i < 256; ++i) {
@ -209,7 +221,7 @@ void read_block(uint32_t block_no, uint8_t *data) {
DirEntry *d = (void *)data;
padded_memcpy(d->name, (char const *) BootBlock.VolumeLabel, 11);
d->attrs = 0x28;
for (int i = 0; i < NUM_INFO; ++i) {
for (int i = 0; i < NUM_FILES; ++i) {
d++;
struct TextFile const *inf = &info[i];
d->size = inf->content ? strlen(inf->content) : UF2_SIZE;
@ -219,10 +231,10 @@ void read_block(uint32_t block_no, uint8_t *data) {
}
} else {
sectionIdx -= START_CLUSTERS;
if (sectionIdx < NUM_INFO - 1) {
if (sectionIdx < NUM_FILES - 1) {
memcpy(data, info[sectionIdx].content, strlen(info[sectionIdx].content));
} else {
sectionIdx -= NUM_INFO - 1;
sectionIdx -= NUM_FILES - 1;
uint32_t addr = USER_FLASH_START + sectionIdx * 256;
if (addr < USER_FLASH_START+FLASH_SIZE) {
UF2_Block *bl = (void *)data;

144
src/usb/uf2/uf2.h
View File

@ -152,3 +152,147 @@ static inline void check_uf2_handover(uint8_t *buffer, uint32_t blocks_remaining
#endif
#endif
#ifndef ARRAYSIZE2_H
#define ARRAYSIZE2_H
#ifndef __has_feature
#define __has_feature(x) 0 // Compatibility with non-clang compilers.
#endif
#if __cplusplus >= 199711L
#pragma message "using Ivan J. Johnson's ARRAY_SIZE2"
// Works on older compilers, even Visual C++ 6....
// Created by Ivan J. Johnson, March 06, 2007
// See http://drdobbs.com/cpp/197800525?pgno=1
//
// Pseudocode:
// if x is not an array
// issue a compile-time error
// else
// use the traditional (non-typesafe) C99 COUNTOF expression
//
// If the argument is any of:
// object of class type, such as an std::vector
// floating-point type
// function pointer
// pointer-to-member
// then the first reinterpret_cast<> is not legal (compiler error)
//
// The type for check1 is chosen and named to help understand
// the cause of the error, because the class name is likely to
// appear in the compiler error message.
//
// If check1 succeeds, then the argument must be one of:
// an integral type
// an enumerated type
// a pointer to an object
// an array
//
// Check2 expands approximately to sizeof(check_type(x, &x)),
// where check_type is an overloaded function.
// Because this is purely a compile-time computation,
// the function is never really called or even implemented,
// but it lets the compiler apply overload resolution,
// which allows further type discrimination.
// There are three possibilities to consider:
// x is an integral type or enumerated type.
// In this case, neither of the two function overloads
// is a match, resulting in a compiler error.
// x is a pointer to an object.
// In this case, the first argument to check_type()
// is a pointer and the second one is a pointer-to-pointer.
// The best function match is the first overload of check_type,
// the one that returns an incomplete type (Is_pointer).
// However, because Is_pointer is an incomplete type,
// sizeof(Is_pointer) is not a valid expression,
// resulting in a compiler error.
// x is an array.
// In this case, the first argument to check_type()
// is an array and the second is a pointer-to-array.
// A pointer-to-array is *NOT* convertible to a
// pointer-to-pointer, so the first overload of
// check_type() is not a match.
// However, an array IS convertible to a pointer,
// and a pointer-to-array already is a pointer.
// Any pointer is convertible to a void*,
// so the second function overload is a match.
// That overload returns a complete type (Is_array).
// Because it's a complete type,
// sizeof(Is_array) is a valid expression.
// Thus, the compiler has EXCLUDED every possible type
// except arrays via compilation errors before reaching
// the third line.
// Moreover, check1 and check2 are reduced to the value zero,
// while the third line is the old type-unsafe C-style macro,
// now made entirely type-safe.
//
// Additional benefits:
// The result is itself constexpr
//
//
#define ARRAY_SIZE2(arr) ( \
0 * sizeof(reinterpret_cast<const ::Bad_arg_to_COUNTOF*>(arr)) + /*check1*/ \
0 * sizeof(::Bad_arg_to_COUNTOF::check_type((arr), &(arr))) + /*check2*/ \
sizeof(arr) / sizeof((arr)[0]) /* eval */ \
)
struct Bad_arg_to_COUNTOF {
class Is_pointer; // incomplete
class Is_array {};
template <typename T>
static Is_pointer check_type(const T*, const T* const*);
static Is_array check_type(const void*, const void*);
};
#elif __cplusplus >= 201103L || /* any compiler claiming C++11 support */ \
_MSC_VER >= 1900 || /* Visual C++ 2015 or higher */ \
__has_feature(cxx_constexpr) /* CLang versions supporting constexp */
#pragma message "C++11 version ARRAY_SIZE2"
namespace detail
{
template <typename T, std::size_t N>
constexpr std::size_t countof(T const (&)[N]) noexcept
{
return N;
}
} // namespace detail
#define ARRAY_SIZE2(arr) detail::countof(arr)
#elif _MSC_VER // Visual C++ fallback
#pragma message "using Microsoft Visual C++ intrinsic ARRAY_SIZE2"
#define ARRAY_SIZE2(arr) _countof(arr)
#elif __cplusplus >= 199711L && ( /* C++ 98 trick */ \
defined(__INTEL_COMPILER) || \
defined(__clang__) || \
(defined(__GNUC__) && ( \
(__GNUC__ > 4) || \
(__GNUC__ == 4 && __GNUC_MINOR__ >= 4) \
)))
#pragma message "C++98 version ARRAY_SIZE2"
template <typename T, std::size_t N>
char(&_ArraySizeHelperRequiresArray(T(&)[N]))[N];
#define ARRAY_SIZE2(x) sizeof(_ArraySizeHelperRequiresArray(x))
#else
#pragma message "Using type-unsafe version of ARRAY_SIZE2"
// This is the worst-case scenario macro.
// While it is valid C, it is NOT typesafe.
// For example, if the parameter arr is a pointer instead of array,
// the compiler will SILENTLY give a (likely) incorrect result.
#define ARRAY_SIZE2(arr) sizeof(arr) / sizeof(arr[0])
#endif
#endif // ARRAYSIZE2_H