Add kernel symbol support.

sortix/Makefile

@@ -122,6 +122,7 @@ serialterminal.o \
 signal.o \
 sound.o \
 string.o \
+symbol.o \
 syscall.o \
 textbuffer.o \
 textterminal.o \

sortix/elf.h

@@ -166,6 +166,26 @@ namespace Sortix
 		const uint32_t PF_W = (1<<1);
 		const uint32_t PF_R = (1<<2);
 
+		struct Symbol32
+		{
+			uint32_t st_name;
+			uint32_t st_value;
+			uint32_t st_size;
+			uint8_t st_info;
+			uint8_t st_other;
+			uint16_t st_shndx;
+		};
+
+		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;
+		};
+
 		// Reads the elf file into the current address space and returns the
 		// entry address of the program, or 0 upon failure.
 		addr_t Construct(Process* process, const void* file, size_t filelen);

sortix/include/sortix/kernel/symbol.h

@@ -0,0 +1,49 @@
+/*******************************************************************************
+
+    Copyright(C) Jonas 'Sortie' Termansen 2013.
+
+    This file is part of Sortix.
+
+    Sortix is free software: you can redistribute it and/or modify it under the
+    terms of the GNU General Public License as published by the Free Software
+    Foundation, either version 3 of the License, or (at your option) any later
+    version.
+
+    Sortix is distributed in the hope that it will be useful, but WITHOUT ANY
+    WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+    FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
+    details.
+
+    You should have received a copy of the GNU General Public License along with
+    Sortix. If not, see <http://www.gnu.org/licenses/>.
+
+    sortix/kernel/symbol.h
+    Symbol table declarations.
+
+*******************************************************************************/
+
+#ifndef INCLUDE_SORTIX_KERNEL_SYMBOL_H
+#define INCLUDE_SORTIX_KERNEL_SYMBOL_H
+
+namespace Sortix {
+
+struct Symbol
+{
+	uintptr_t address;
+	size_t size;
+	const char* name;
+};
+
+void SetKernelSymbolTable(Symbol* table, size_t length);
+const Symbol* GetKernelSymbolTable(size_t* length = NULL);
+const Symbol* GetKernelSymbol(uintptr_t address);
+
+static inline const char* GetKernelSymbolName(uintptr_t address)
+{
+	const Symbol* symbol = GetKernelSymbol(address);
+	return symbol ? symbol->name : NULL;
+}
+
+} // namespace Sortix
+
+#endif

sortix/kernel.cpp

@@ -49,6 +49,7 @@
 #include <sortix/kernel/string.h>
 #include <sortix/kernel/user-timer.h>
 #include <sortix/kernel/signal.h>
+#include <sortix/kernel/symbol.h>
 #include <sortix/kernel/process.h>
 #include <sortix/kernel/thread.h>
 
@@ -243,6 +244,114 @@ extern "C" void KernelInit(unsigned long magic, multiboot_info_t* bootinfo)
 	// Initialize the kernel heap.
 	_init_heap();
 
+	// Load the kernel symbols if provided by the bootloader.
+	do if ( bootinfo->flags & MULTIBOOT_INFO_ELF_SHDR )
+	{
+		// On i386 and x86_64 we identity map the first 4 MiB memory, if the
+		// debugging sections are outside that region, we can't access them
+		// directly and we'll have to memory map some physical memory.
+		// TODO: Correctly handle the memory being outside 4 MiB. You need to
+		//       teach the memory management code to reserve these ranges for
+		//       a while until we have used them and add additional complexity
+		//       in this code.
+		#define BELOW_4MIB(addr, length) ((addr) + (length) <= 4*1024*1024)
+
+		// Find and the verify the section table.
+		multiboot_elf_section_header_table_t* elf_sec = &bootinfo->u.elf_sec;
+		if ( !BELOW_4MIB(elf_sec->addr, elf_sec->size) )
+		{
+			Log::PrintF("Warning: the section table was loaded inappropriately by the boot loader, kernel debugging symbols will not be available.\n");
+			break;
+		}
+
+		#define SECTION(num) ((ELF::SectionHeader32*) ((uintptr_t) elf_sec->addr + (uintptr_t) elf_sec->size * (uintptr_t) (num)))
+
+		// Verify the section name section.
+		ELF::SectionHeader32* section_string_section = SECTION(elf_sec->shndx);
+		if ( !BELOW_4MIB(section_string_section->addr, section_string_section->size) )
+		{
+			Log::PrintF("Warning: the section string table was loaded inappropriately by the boot loader, kernel debugging symbols will not be available.\n");
+			break;
+		}
+
+		if ( !section_string_section )
+			break;
+
+		const char* section_string_table = (const char*) (uintptr_t) section_string_section->addr;
+
+		// Find the symbol table.
+		ELF::SectionHeader32* symbol_table_section = NULL;
+		for ( unsigned i = 0; i < elf_sec->num && !symbol_table_section; i++ )
+		{
+			ELF::SectionHeader32* section = SECTION(i);
+			if ( !strcmp(section_string_table + section->name, ".symtab") )
+				symbol_table_section = section;
+		}
+
+		if ( !symbol_table_section )
+			break;
+
+		if ( !BELOW_4MIB(symbol_table_section->addr, symbol_table_section->size) )
+		{
+			Log::PrintF("Warning: the symbol table was loaded inappropriately by the boot loader, kernel debugging symbols will not be available.\n");
+			break;
+		}
+
+		// Find the symbol string table.
+		ELF::SectionHeader32* string_table_section = NULL;
+		for ( unsigned i = 0; i < elf_sec->num && !string_table_section; i++ )
+		{
+			ELF::SectionHeader32* section = SECTION(i);
+			if ( !strcmp(section_string_table + section->name, ".strtab") )
+				string_table_section = section;
+		}
+
+		if ( !string_table_section )
+			break;
+
+		if ( !BELOW_4MIB(string_table_section->addr, string_table_section->size) )
+		{
+			Log::PrintF("Warning: the symbol string table was loaded inappropriately by the boot loader, kernel debugging symbols will not be available.\n");
+			break;
+		}
+
+		// Duplicate the data structures and convert them to the kernel symbol
+		// table format and register it for later debugging.
+		const char* elf_string_table = (const char*) (uintptr_t) string_table_section->addr;
+		size_t elf_string_table_size = string_table_section->size;
+		ELF::Symbol32* elf_symbols = (ELF::Symbol32*) (uintptr_t) symbol_table_section->addr;
+		size_t elf_symbol_count = symbol_table_section->size / sizeof(ELF::Symbol32);
+
+		if ( !elf_symbol_count || elf_symbol_count == 1 /* null symbol */)
+			break;
+
+		char* string_table = new char[elf_string_table_size];
+		if ( !string_table )
+		{
+			Log::PrintF("Warning: unable to allocate the kernel symbol string table, kernel debugging symbols will not be available.\n");
+			break;
+		}
+		memcpy(string_table, elf_string_table, elf_string_table_size);
+
+		Symbol* symbols = new Symbol[elf_symbol_count-1];
+		if ( !symbols )
+		{
+			Log::PrintF("Warning: unable to allocate the kernel symbol table, kernel debugging symbols will not be available.\n");
+			delete[] string_table;
+			break;
+		}
+
+		// Copy all entires except the leading null entry.
+		for ( size_t i = 1; i < elf_symbol_count; i++ )
+		{
+			symbols[i-1].address = elf_symbols[i].st_value;
+			symbols[i-1].size = elf_symbols[i].st_size;
+			symbols[i-1].name = string_table + elf_symbols[i].st_name;
+		}
+
+		SetKernelSymbolTable(symbols, elf_symbol_count-1);
+	} while ( false );
+
 	// Initialize the interrupt worker (before scheduling is enabled).
 	Interrupt::InitWorker();
 

sortix/symbol.cpp

@@ -0,0 +1,65 @@
+/*******************************************************************************
+
+    Copyright(C) Jonas 'Sortie' Termansen 2013.
+
+    This file is part of Sortix.
+
+    Sortix is free software: you can redistribute it and/or modify it under the
+    terms of the GNU General Public License as published by the Free Software
+    Foundation, either version 3 of the License, or (at your option) any later
+    version.
+
+    Sortix is distributed in the hope that it will be useful, but WITHOUT ANY
+    WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+    FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
+    details.
+
+    You should have received a copy of the GNU General Public License along with
+    Sortix. If not, see <http://www.gnu.org/licenses/>.
+
+    symbol.cpp
+    Symbol table access.
+
+*******************************************************************************/
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include <sortix/kernel/symbol.h>
+
+namespace Sortix {
+
+Symbol* kernel_symbol_table;
+size_t kernel_symbol_table_length;
+
+void SetKernelSymbolTable(Symbol* table, size_t length)
+{
+	kernel_symbol_table = table;
+	kernel_symbol_table_length = length;
+}
+
+const Symbol* GetKernelSymbolTable(size_t* length)
+{
+	if ( length )
+		*length = kernel_symbol_table_length;
+	return kernel_symbol_table;
+}
+
+static bool MatchesSymbol(const Symbol* symbol, uintptr_t address)
+{
+	return symbol->address <= address &&
+	       address <= symbol->address + symbol->size;
+}
+
+const Symbol* GetKernelSymbol(uintptr_t address)
+{
+	for ( size_t i = 0; i < kernel_symbol_table_length; i++ )
+	{
+		const Symbol* symbol = kernel_symbol_table + i;
+		if ( MatchesSymbol(symbol, address) )
+			return symbol;
+	}
+	return NULL;
+}
+
+} // namespace Sortix