List loaded modules without any API calls (32-bit PEs only).

Win32ListLdrModules.cpp

#include <cstdio>
#include <windows.h>

#if !defined(_WIN32) || defined(_WIN64)
#error This snippet is only valid for x86 executables!
#endif

typedef struct _UNICODE_STRING {
    unsigned __int16 Length;
    unsigned __int16 MaximumLength;
    wchar_t* Buffer;
} UNICODE_STRING, *PUNICODE_STRING;

typedef struct _PEB_LDR_DATA {
	BYTE       Reserved1[8];
	PVOID      Reserved2[3];
	LIST_ENTRY InMemoryOrderModuleList;
} PEB_LDR_DATA, *PPEB_LDR_DATA;

typedef struct _LDR_DATA_TABLE_ENTRY {
    PVOID Reserved1[2];
    LIST_ENTRY InMemoryOrderLinks;
    PVOID Reserved2[2];
    PVOID DllBase;
    PVOID EntryPoint;
    PVOID Reserved3;
    UNICODE_STRING FullDllName;
    BYTE Reserved4[8];
    PVOID Reserved5[3];
    union {
        ULONG CheckSum;
        PVOID Reserved6;
    };
    ULONG TimeDateStamp;
} LDR_DATA_TABLE_ENTRY, *PLDR_DATA_TABLE_ENTRY;

typedef struct _RTL_USER_PROCESS_PARAMETERS {
    BYTE           Reserved1[16];
    PVOID          Reserved2[10];
    UNICODE_STRING ImagePathName;
    UNICODE_STRING CommandLine;
} RTL_USER_PROCESS_PARAMETERS, *PRTL_USER_PROCESS_PARAMETERS;

typedef struct _PEB {
    BYTE                         Reserved1[2];
    BYTE                         BeingDebugged;
    BYTE                         Reserved2[1];
    PVOID                        Reserved3[2];
    PPEB_LDR_DATA                Ldr;
    PRTL_USER_PROCESS_PARAMETERS ProcessParameters;
    PVOID                        Reserved4[3];
    PVOID                        AtlThunkSListPtr;
    PVOID                        Reserved5;
    ULONG                        Reserved6;
    PVOID                        Reserved7;
    ULONG                        Reserved8;
    ULONG                        AtlThunkSListPtr32;
    PVOID                        Reserved9[45];
    BYTE                         Reserved10[96];
    PVOID                        PostProcessInitRoutine;
    BYTE                         Reserved11[128];
    PVOID                        Reserved12[1];
    ULONG                        SessionId;
} PEB, *PPEB;

PPEB GetPebPointer()
{
    PPEB pPeb = 0;
    __asm {
        mov eax, fs:[0x30]
        mov pPeb, eax
    }
    return pPeb;
}

int main()
{
    auto pPeb = GetPebPointer();

    auto header = &pPeb->Ldr->InMemoryOrderModuleList;
    auto entry = pPeb->Ldr->InMemoryOrderModuleList.Flink;

    while (entry->Flink != header) {
        auto pLdrEntry = reinterpret_cast<PLDR_DATA_TABLE_ENTRY>(entry);

        wprintf(L"FullDllName: %s\n", pLdrEntry->FullDllName.Buffer);
        wprintf(L"DllBase: %p\n", pLdrEntry->DllBase);
        wprintf(L"\n");

        entry = entry->Flink;
    }
}