I wrote ACPI driver for Ace and try to load it into kernel. It was failing with the error message symbol not found.
The log file content says AcpiGetName was not found.
$ cat log.txt
Driver for id acpi : acpi.sys
../src/kernel/pm/elf.c:343:FindElfSymbolByName(): Symbol not found AcpiGetName(c01a2148:1869) string table c01aa619
After exploring the Acpi-CA source code and Ace kernel code, I couldn’t figure out why the symbol is missing. Then I tried to dump the symbol table for Acpi library and kernel.sys.
$ nm build/default/src/kernel/libacpi.a | grep GetName
U AcpiExGetNameString
000001e3 T AcpiExGetNameString
000001b7 T AcpiPsGetName
000000f4 T AcpiGetName
$ nm build/default/src/kernel/kernel.sys | grep GetName
c0135163 T AcpiExGetNameString
c0137bfb T AcpiPsGetName
Then I started thinking how linux kernel is avoiding this problem and I it flashed seeing EXPORT_SYMBOL kind of macro in some source. So I googled for it and got the answer – use the symbol in storage, so that it will be referenced, so that linker will include it in the output.
struct kernel_symbol
{
unsigned long symbol;
char * name;
};
#ifndef MODULE_SYMBOL_PREFIX
#define MODULE_SYMBOL_PREFIX ""
#endif
#define __EXPORT_SYMBOL(sym, sec) \
static const char __kstrtab_##sym[] \
__attribute__((section("__ksymtab_strings"))) \
= MODULE_SYMBOL_PREFIX#sym; \
static const struct kernel_symbol __ksymtab_##sym \
__attribute__((section("__ksymtab" sec), unused)) \
= { (unsigned long)&sym, __kstrtab_##sym }
#define EXPORT_SYMBOL(sym) \
__EXPORT_SYMBOL(sym, "")
then to clean I have to write how to delete the object files. With waf the problem is simplified, you have to tell what all source files and it will take care of how to compile and link. It will also take care of how to clean the project and the dependency between files are also taken care, so no need for gcc –M and dependency files etc. The feature I liked in waf is it has colored output with progress bar :)
Posts
