Load program symbol tables.

sortix/elf.cpp

@@ -35,6 +35,7 @@
 #include <sortix/kernel/platform.h>
 #include <sortix/kernel/memorymanagement.h>
 #include <sortix/kernel/process.h>
+#include <sortix/kernel/symbol.h>
 
 #include "elf.h"
 
@@ -60,7 +61,11 @@ static int ToProgramSectionType(int flags)
 	}
 }
 
-addr_t Construct32(Process* process, const void* file, size_t filelen)
+// TODO: This code doesn't respect that the size of program headers and section
+//       headers may vary depending on the ELF header and that using a simple
+//       table indexation isn't enough.
+
+addr_t Construct32(Process* process, const uint8_t* file, size_t filelen)
 {
 	if ( filelen < sizeof(Header32) )
 		return 0;
@@ -145,10 +150,71 @@ addr_t Construct32(Process* process, const void* file, size_t filelen)
 		memset(memdest + pht->filesize, 0, pht->memorysize - pht->filesize);
 	}
 
+	// Find the location of the section headers.
+	addr_t shtblpos = (addr_t) file + header->sectionheaderoffset;
+	const SectionHeader32* shtbl = (const SectionHeader32*) shtblpos;
+
+	const SectionHeader32* section_names_section = shtbl + header->sectionheaderstringindex;
+	const char* section_names = (const char*) (file + section_names_section->offset);
+
+	// Find the string table.
+	const SectionHeader32* string_table_section = NULL;
+	for ( size_t i = 0; i < header->numsectionheaderentries; i++ )
+		if ( !strcmp(section_names + shtbl[i].name, ".strtab") )
+		{
+			string_table_section = shtbl + i;
+			break;
+		}
+
+	// Find the symbol table.
+	const SectionHeader32* symbol_table_section = NULL;
+	for ( size_t i = 0; i < header->numsectionheaderentries; i++ )
+		if ( !strcmp(section_names + shtbl[i].name, ".symtab") )
+		{
+			symbol_table_section = shtbl + i;
+			break;
+		}
+
+	if ( !string_table_section || !symbol_table_section )
+		return entry;
+
+	// Prepare copying debug information.
+	const char* elf_string_table = (const char*) (file + string_table_section->offset);
+	size_t elf_string_table_size = string_table_section->size;
+	const Symbol32* elf_symbols = (const Symbol32*) (file + symbol_table_section->offset);
+	size_t elf_symbol_count = symbol_table_section->size / sizeof(Symbol32);
+
+	// Duplicate the string table.
+	char* string_table = new char[elf_string_table_size];
+	if ( !string_table )
+		return entry;
+	memcpy(string_table, elf_string_table, elf_string_table_size);
+
+	// Duplicate the symbol table.
+	Symbol* symbol_table = new Symbol[elf_symbol_count-1];
+	if ( !symbol_table )
+	{
+		delete[] string_table;
+		return entry;
+	}
+
+	// Copy all entires except the leading null entry.
+	for ( size_t i = 1; i < elf_symbol_count; i++ )
+	{
+		symbol_table[i-1].address = elf_symbols[i].st_value;
+		symbol_table[i-1].size = elf_symbols[i].st_size;
+		symbol_table[i-1].name = string_table + elf_symbols[i].st_name;
+	}
+
+	process->string_table = string_table;
+	process->string_table_length = elf_string_table_size;
+	process->symbol_table = symbol_table;
+	process->symbol_table_length = elf_symbol_count-1;
+
 	return entry;
 }
 
-addr_t Construct64(Process* process, const void* file, size_t filelen)
+addr_t Construct64(Process* process, const uint8_t* file, size_t filelen)
 {
 #ifndef PLATFORM_X64
 	(void) process;
@@ -241,6 +307,67 @@ addr_t Construct64(Process* process, const void* file, size_t filelen)
 		memset(memdest + pht->filesize, 0, pht->memorysize - pht->filesize);
 	}
 
+	// Find the location of the section headers.
+	addr_t shtblpos = (addr_t) file + header->sectionheaderoffset;
+	const SectionHeader64* shtbl = (const SectionHeader64*) shtblpos;
+
+	const SectionHeader64* section_names_section = shtbl + header->sectionheaderstringindex;
+	const char* section_names = (const char*) (file + section_names_section->offset);
+
+	// Find the string table.
+	const SectionHeader64* string_table_section = NULL;
+	for ( size_t i = 0; i < header->numsectionheaderentries; i++ )
+		if ( !strcmp(section_names + shtbl[i].name, ".strtab") )
+		{
+			string_table_section = shtbl + i;
+			break;
+		}
+
+	// Find the symbol table.
+	const SectionHeader64* symbol_table_section = NULL;
+	for ( size_t i = 0; i < header->numsectionheaderentries; i++ )
+		if ( !strcmp(section_names + shtbl[i].name, ".symtab") )
+		{
+			symbol_table_section = shtbl + i;
+			break;
+		}
+
+	if ( !string_table_section || !symbol_table_section )
+		return entry;
+
+	// Prepare copying debug information.
+	const char* elf_string_table = (const char*) (file + string_table_section->offset);
+	size_t elf_string_table_size = string_table_section->size;
+	const Symbol64* elf_symbols = (const Symbol64*) (file + symbol_table_section->offset);
+	size_t elf_symbol_count = symbol_table_section->size / sizeof(Symbol64);
+
+	// Duplicate the string table.
+	char* string_table = new char[elf_string_table_size];
+	if ( !string_table )
+		return entry;
+	memcpy(string_table, elf_string_table, elf_string_table_size);
+
+	// Duplicate the symbol table.
+	Symbol* symbol_table = new Symbol[elf_symbol_count-1];
+	if ( !symbol_table )
+	{
+		delete[] string_table;
+		return entry;
+	}
+
+	// Copy all entires except the leading null entry.
+	for ( size_t i = 1; i < elf_symbol_count; i++ )
+	{
+		symbol_table[i-1].address = elf_symbols[i].st_value;
+		symbol_table[i-1].size = elf_symbols[i].st_size;
+		symbol_table[i-1].name = string_table + elf_symbols[i].st_name;
+	}
+
+	process->string_table = string_table;
+	process->string_table_length = elf_string_table_size;
+	process->symbol_table = symbol_table;
+	process->symbol_table_length = elf_symbol_count-1;
+
 	return entry;
 #endif
 }
@@ -258,8 +385,8 @@ addr_t Construct(Process* process, const void* file, size_t filelen)
 
 	switch ( header->fileclass )
 	{
-		case CLASS32: return Construct32(process, file, filelen);
-		case CLASS64: return Construct64(process, file, filelen);
+		case CLASS32: return Construct32(process, (const uint8_t*) file, filelen);
+		case CLASS64: return Construct64(process, (const uint8_t*) file, filelen);
 		default:
 			return 0;
 	}

sortix/elf.h

@@ -178,12 +178,12 @@ struct Symbol32
 
 struct Symbol64
 {
-	   uint32_t st_name;
-	   uint8_t st_info;
-	   uint8_t st_other;
-	   uint16_t st_shndx;
-	   uint64_t st_value;
-	   uint64_t st_size;
+	uint32_t st_name;
+	uint8_t st_info;
+	uint8_t st_other;
+	uint16_t st_shndx;
+	uint64_t st_value;
+	uint64_t st_size;
 };
 
 // Reads the elf file into the current address space and returns the entry

sortix/include/sortix/kernel/process.h

@@ -48,6 +48,7 @@ struct ProcessSegment;
 struct ProcessTimer;
 struct ioctx_struct;
 typedef struct ioctx_struct ioctx_t;
+struct Symbol;
 
 const int SEG_NONE = 0;
 const int SEG_TEXT = 1;
@@ -88,6 +89,10 @@ private:
 	static pid_t AllocatePID();
 
 public:
+	char* string_table;
+	size_t string_table_length;
+	Symbol* symbol_table;
+	size_t symbol_table_length;
 	char* program_image_path;
 	addr_t addrspace;
 	pid_t pid;

sortix/process.cpp

@@ -36,6 +36,7 @@
 #include <sortix/kernel/syscall.h>
 #include <sortix/kernel/sortedlist.h>
 #include <sortix/kernel/scheduler.h>
+#include <sortix/kernel/symbol.h>
 #include <sortix/kernel/process.h>
 #include <sortix/kernel/thread.h>
 #include <sortix/kernel/time.h>
@@ -107,6 +108,10 @@ namespace Sortix
 
 	Process::Process()
 	{
+		string_table = NULL;
+		string_table_length = 0;
+		symbol_table = NULL;
+		symbol_table_length = 0;
 		addrspace = 0;
 		segments = NULL;
 		parent = NULL;
@@ -139,6 +144,8 @@ namespace Sortix
 
 	Process::~Process()
 	{
+		delete[] string_table;
+		delete[] symbol_table;
 		if ( alarm_timer.IsAttached() )
 			alarm_timer.Detach();
 		if ( program_image_path )
@@ -280,6 +287,10 @@ namespace Sortix
                                     curthread);
 		addrspace = 0;
 
+		// Unload the process symbol and string tables.
+		delete[] symbol_table; symbol_table = NULL;
+		delete[] string_table; string_table = NULL;
+
 		// Init is nice and will gladly raise our orphaned children and zombies.
 		Process* init = Scheduler::GetInitProcess();
 		assert(init);
@@ -618,6 +629,28 @@ namespace Sortix
 		if ( !(clone->program_image_path = String::Clone(program_image_path)) )
 			failure = false;
 
+		if ( string_table && (clone->string_table = new char[string_table_length]) )
+		{
+			memcpy(clone->string_table, string_table, string_table_length);
+			clone->string_table_length = string_table_length;
+		}
+
+		if ( clone->string_table && symbol_table &&
+			 (clone->symbol_table = new Symbol[symbol_table_length]) )
+		{
+			for ( size_t i = 0; i < symbol_table_length; i++ )
+			{
+				clone->symbol_table[i].address = symbol_table[i].address;
+				clone->symbol_table[i].size = symbol_table[i].size;
+				clone->symbol_table[i].name =
+					(const char*)((uintptr_t) symbol_table[i].name -
+						          (uintptr_t) string_table +
+						          (uintptr_t) clone->string_table);
+			}
+			clone->symbol_table_length = symbol_table_length;
+		}
+
+
 		if ( pid == 1)
 			assert(dtable->Get(1));
 
@@ -640,6 +673,11 @@ namespace Sortix
 	{
 		// TODO: Delete all threads and their stacks.
 
+		string_table_length = 0;
+		symbol_table_length = 0;
+		delete[] string_table; string_table = NULL;
+		delete[] symbol_table; symbol_table = NULL;
+
 		DeleteTimers();
 
 		ResetAddressSpace();