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https://github.com/RGBCube/serenity
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b6590b7f83
The LinkDemo program calls dlopen/dlsym/dlclose to try and load a dyanmic library from /usr/lib. It read a global variable and calls a global function (extern "C" of course :) ). There a few hacks left in the LinkLib dynamic library, however. In order to get the linker to stop complaining, we have to use -nostartfiles -ffreestanding otherwise it will link crt0.o to our shared object, which is definitely not right as the _init function for a main program (that calls main) is not suitable for our lib
72 lines
2.3 KiB
C++
72 lines
2.3 KiB
C++
#include <AK/kstdio.h>
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#include <AK/String.h>
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#include <assert.h>
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#include <stdio.h>
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// FIXME: See Makefile. We need -ffreestanding and -nostartfiles to
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// Get GCC to stop linking crt0.o w/our .so.
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// So, we need __dso_handle. ... Yikes
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extern void* __dso_handle __attribute__((__section__(".sdata")));
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extern void* __dso_handle __attribute__((__visibility__("hidden")));
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void* __dso_handle = (void*)1234; // FIXME: Is the dynamic linker supposed to set this value?
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// FIXME: Things defined in crt0 >:(
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__thread int errno;
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char* __static_environ[] = { nullptr }; // We don't get the environment without some libc workarounds..
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char** environ = __static_environ;
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bool __environ_is_malloced = false;
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extern unsigned __stack_chk_guard;
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unsigned __stack_chk_guard = (unsigned)0xc0000c13;
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[[noreturn]] void __stack_chk_fail()
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{
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ASSERT_NOT_REACHED();
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}
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// FIXME: Because we need to call printf, and we don't have access to the stout file descriptor
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// from the main executable, we need to create our own copy in __stdio_init :/
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// Same deal for malloc init. We're essentially manually calling __libc_init here.
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extern "C" void __stdio_init();
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extern "C" void __malloc_init();
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class Global {
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public:
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Global(int i)
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: m_i(i)
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{
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__malloc_init();
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__stdio_init();
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}
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int get_i() const { return m_i; }
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private:
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int m_i = 0;
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};
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// This object exists to call __stdio_init and __malloc_init. Also to show that global vars work
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Global g_glob { 5 };
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extern "C" {
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int global_lib_variable = 1234;
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void global_lib_function()
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{
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printf("Hello from Dynamic Lib! g_glob::m_i == %d\n", g_glob.get_i());
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}
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const char* other_lib_function(int my_argument)
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{
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dbgprintf("Hello from Dynamic Lib, now from the debug port! g_glob::m_i == %d\n", g_glob.get_i());
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int sum = my_argument + global_lib_variable;
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// FIXME: We can't just return AK::String::format across the lib boundary here.
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// It will use malloc from our DSO's copy of LibC, and then probably be free'd into
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// the malloc of the main program which would be what they call 'very crash'.
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// Feels very Windows :)
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static String s_string;
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s_string = String::format("Here's your string! Sum of argument and global_lib_variable: %d", sum);
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return s_string.characters();
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}
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}
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