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Improve linker scripts a little (#1275)

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* Allow for optional sections in linker scripts
  These are more useful for frameworks/toolchains.

* Check for an active mem region everywhere
  Do you like segfaults? Too bad!

* Allow the address to be floating in linker scripts
  Try and make the life of SDCC interop easier.

* Also validate alignment when floating

* Overhaul the linker script manual page
  Documenting the new features, but also restructuring the
  existing documentation to make the manual page (hopefully)
  easier to understand.
This commit is contained in:
Eldred Habert
2023-12-25 05:29:11 +01:00
committed by GitHub
parent 7b199d7550
commit ccf9dcb851
2 changed files with 248 additions and 115 deletions
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151
src/link/script.y
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@@ -37,9 +37,10 @@
static void setSectionType(SectionType type);
static void setSectionType(SectionType type, uint32_t bank);
static void setAddr(uint32_t addr);
static void makeAddrFloating(void);
static void alignTo(uint32_t alignment, uint32_t offset);
static void pad(uint32_t length);
static void placeSection(std::string const &name);
static void placeSection(std::string const &name, bool isOptional);
static yy::parser::symbol_type yylex(void);
@@ -53,21 +54,27 @@
%token newline
%token COMMA ","
%token ORG "ORG"
FLOATING "FLOATING"
INCLUDE "INCLUDE"
ALIGN "ALIGN"
DS "DS"
OPTIONAL "OPTIONAL"
%code {
static std::array keywords{
Keyword{"ORG"sv, yy::parser::make_ORG},
Keyword{"INCLUDE"sv, yy::parser::make_INCLUDE},
Keyword{"ALIGN"sv, yy::parser::make_ALIGN},
Keyword{"DS"sv, yy::parser::make_DS},
Keyword{"ORG"sv, yy::parser::make_ORG},
Keyword{"FLOATING"sv, yy::parser::make_FLOATING},
Keyword{"INCLUDE"sv, yy::parser::make_INCLUDE},
Keyword{"ALIGN"sv, yy::parser::make_ALIGN},
Keyword{"DS"sv, yy::parser::make_DS},
Keyword{"OPTIONAL"sv, yy::parser::make_OPTIONAL},
};
}
%token <std::string> string;
%token <uint32_t> number;
%token <SectionType> section_type;
%type <bool> optional;
%%
lines: %empty
@@ -82,11 +89,16 @@ line: INCLUDE string newline { includeFile(std::move($2)); } // Note: this addit
directive: section_type { setSectionType($1); }
| section_type number { setSectionType($1, $2); }
| FLOATING { makeAddrFloating(); }
| ORG number { setAddr($2); }
| ALIGN number { alignTo($2, 0); }
| ALIGN number COMMA number { alignTo($2, $4); }
| DS number { pad($2); }
| string { placeSection($1); }
| string optional { placeSection($1, $2); }
;
optional: %empty { $$ = false; }
| OPTIONAL { $$ = true; }
;
%%
@@ -318,10 +330,14 @@ try_again: // Can't use a `do {} while(0)` loop, otherwise compilers (wrongly) t
static std::array<std::vector<uint16_t>, SECTTYPE_INVALID> curAddr;
static SectionType activeType; // Index into curAddr
static uint32_t activeBankIdx; // Index into curAddr[activeType]
static bool isPcFloating;
static uint16_t floatingAlignMask;
static uint16_t floatingAlignOffset;
static void setActiveTypeAndIdx(SectionType type, uint32_t idx) {
activeType = type;
activeBankIdx = idx;
isPcFloating = false;
if (curAddr[activeType].size() <= activeBankIdx) {
curAddr[activeType].resize(activeBankIdx + 1, sectionTypeInfo[type].startAddr);
}
@@ -344,11 +360,11 @@ static void setSectionType(SectionType type, uint32_t bank) {
auto const &typeInfo = sectionTypeInfo[type];
if (bank < typeInfo.firstBank) {
scriptError(context, "%s bank %" PRIu32 " doesn't exist, the minimum is %" PRIu32,
scriptError(context, "%s bank %" PRIu32 " doesn't exist (the minimum is %" PRIu32 ")",
typeInfo.name.c_str(), bank, typeInfo.firstBank);
bank = typeInfo.firstBank;
} else if (bank > typeInfo.lastBank) {
scriptError(context, "%s bank %" PRIu32 " doesn't exist, the maximum is %" PRIu32,
scriptError(context, "%s bank %" PRIu32 " doesn't exist (the maximum is %" PRIu32 ")",
typeInfo.name.c_str(), bank, typeInfo.lastBank);
}
@@ -357,22 +373,64 @@ static void setSectionType(SectionType type, uint32_t bank) {
static void setAddr(uint32_t addr) {
auto const &context = lexerStack.back();
if (activeType == SECTTYPE_INVALID) {
scriptError(context, "Cannot set the current address: no memory region is active");
return;
}
auto &pc = curAddr[activeType][activeBankIdx];
auto const &typeInfo = sectionTypeInfo[activeType];
if (addr < pc) {
scriptError(context, "ORG cannot be used to go backwards (from $%04x to $%04x)", pc, addr);
scriptError(context, "Cannot decrease the current address (from $%04x to $%04x)", pc, addr);
} else if (addr > endaddr(activeType)) { // Allow "one past the end" sections.
scriptError(context, "Cannot go to $%04" PRIx32 ": %s ends at $%04" PRIx16 "",
scriptError(context, "Cannot set the current address to $%04" PRIx32 ": %s ends at $%04" PRIx16 "",
addr, typeInfo.name.c_str(), endaddr(activeType));
pc = endaddr(activeType);
} else {
pc = addr;
}
isPcFloating = false;
}
static void makeAddrFloating(void) {
auto const &context = lexerStack.back();
if (activeType == SECTTYPE_INVALID) {
scriptError(context, "Cannot make the current address floating: no memory region is active");
return;
}
isPcFloating = true;
floatingAlignMask = 0;
floatingAlignOffset = 0;
}
static void alignTo(uint32_t alignment, uint32_t alignOfs) {
auto const &context = lexerStack.back();
if (activeType == SECTTYPE_INVALID) {
scriptError(context, "Cannot align: no memory region is active");
return;
}
if (isPcFloating) {
if (alignment >= 16) {
setAddr(floatingAlignOffset);
} else {
uint32_t alignSize = 1u << alignment;
if (alignOfs >= alignSize) {
scriptError(context, "Cannot align: The alignment offset (%" PRIu32
") must be less than alignment size (%" PRIu32 ")\n",
alignOfs, alignSize);
return;
}
floatingAlignMask = alignSize - 1;
floatingAlignOffset = alignOfs % alignSize;
}
return;
}
auto const &typeInfo = sectionTypeInfo[activeType];
auto &pc = curAddr[activeType][activeBankIdx];
@@ -391,7 +449,7 @@ static void alignTo(uint32_t alignment, uint32_t alignOfs) {
if (alignOfs >= alignSize) {
scriptError(context, "Cannot align: The alignment offset (%" PRIu32
") must be less than alignment size (%" PRIu32 ")\n",
alignOfs, 1 << alignment);
alignOfs, alignSize);
return;
}
@@ -411,23 +469,30 @@ static void alignTo(uint32_t alignment, uint32_t alignOfs) {
static void pad(uint32_t length) {
auto const &context = lexerStack.back();
if (activeType == SECTTYPE_INVALID) {
scriptError(context, "Cannot increase the current address: no memory region is active");
return;
}
if (isPcFloating) {
floatingAlignOffset = (floatingAlignOffset + length) & floatingAlignMask;
return;
}
auto const &typeInfo = sectionTypeInfo[activeType];
auto &pc = curAddr[activeType][activeBankIdx];
assert(pc >= typeInfo.startAddr);
if (uint16_t offset = pc - typeInfo.startAddr; length + offset > typeInfo.size) {
scriptError(context, "Cannot pad by %u bytes: only %u bytes to $%04" PRIx16,
scriptError(context, "Cannot increase the current address by %u bytes: only %u bytes to $%04" PRIx16,
length, typeInfo.size - offset, (uint16_t)(endaddr(activeType) + 1));
} else {
pc += length;
}
}
static void placeSection(std::string const &name) {
static void placeSection(std::string const &name, bool isOptional) {
auto const &context = lexerStack.back();
auto const &typeInfo = sectionTypeInfo[activeType];
// A type *must* be active.
if (activeType == SECTTYPE_INVALID) {
scriptError(context, "No memory region has been specified to place section \"%s\" in",
name.c_str());
@@ -436,10 +501,13 @@ static void placeSection(std::string const &name) {
auto *section = sect_GetSection(name.c_str());
if (!section) {
scriptError(context, "Unknown section \"%s\"", name.c_str());
if (!isOptional) {
scriptError(context, "Unknown section \"%s\"", name.c_str());
}
return;
}
auto const &typeInfo = sectionTypeInfo[activeType];
assert(section->offset == 0);
// Check that the linker script doesn't contradict what the code says.
if (section->type == SECTTYPE_INVALID) {
@@ -460,28 +528,37 @@ static void placeSection(std::string const &name) {
section->isBankFixed = true;
section->bank = bank;
uint16_t &org = curAddr[activeType][activeBankIdx];
if (section->isAddressFixed && org != section->org) {
scriptError(context, "The linker script assigns section \"%s\" to address $%04" PRIx16 ", but it was already at $%04" PRIx16,
name.c_str(), org, section->org);
} else if (section->isAlignFixed && (org & section->alignMask) != section->alignOfs) {
uint8_t alignment = std::countr_one(section->alignMask);
scriptError(context, "The linker script assigns section \"%s\" to address $%04" PRIx16 ", but that would be ALIGN[%" PRIu8 ", %" PRIu16 "] instead of the requested ALIGN[%" PRIu8 ", %" PRIu16 "]",
name.c_str(), org, alignment, (uint16_t)(org & section->alignMask), alignment, section->alignOfs);
}
section->isAddressFixed = true;
section->isAlignFixed = false; // This can't be set when the above is.
section->org = org;
if (!isPcFloating) {
uint16_t &org = curAddr[activeType][activeBankIdx];
if (section->isAddressFixed && org != section->org) {
scriptError(context, "The linker script assigns section \"%s\" to address $%04" PRIx16 ", but it was already at $%04" PRIx16,
name.c_str(), org, section->org);
} else if (section->isAlignFixed && (org & section->alignMask) != section->alignOfs) {
uint8_t alignment = std::countr_one(section->alignMask);
scriptError(context, "The linker script assigns section \"%s\" to address $%04" PRIx16 ", but that would be ALIGN[%" PRIu8 ", %" PRIu16 "] instead of the requested ALIGN[%" PRIu8 ", %" PRIu16 "]",
name.c_str(), org, alignment, (uint16_t)(org & section->alignMask), alignment, section->alignOfs);
}
section->isAddressFixed = true;
section->isAlignFixed = false; // This can't be set when the above is.
section->org = org;
uint16_t curOfs = org - typeInfo.startAddr;
if (section->size > typeInfo.size - curOfs) {
scriptError(context, "The linker script assigns section \"%s\" to address $%04" PRIx16 ", but then it would overflow %s by %" PRIx16 " bytes",
name.c_str(), org, typeInfo.name.c_str(),
(uint16_t)(section->size - (typeInfo.size - curOfs)));
// Fill as much as possible without going out of bounds.
org = typeInfo.startAddr + typeInfo.size;
uint16_t curOfs = org - typeInfo.startAddr;
if (section->size > typeInfo.size - curOfs) {
scriptError(context, "The linker script assigns section \"%s\" to address $%04" PRIx16 ", but then it would overflow %s by %" PRIx16 " bytes",
name.c_str(), org, typeInfo.name.c_str(),
(uint16_t)(section->size - (typeInfo.size - curOfs)));
// Fill as much as possible without going out of bounds.
org = typeInfo.startAddr + typeInfo.size;
} else {
org += section->size;
}
} else {
org += section->size;
section->isAddressFixed = false;
section->isAlignFixed = floatingAlignMask != 0;
section->alignMask = floatingAlignMask;
section->alignOfs = floatingAlignOffset;
floatingAlignOffset = (floatingAlignOffset + section->size) & floatingAlignMask;
}
}