UEFI - malloc call does not return

i will try to keep this as short as possible.

I created an UEFI application which uses just a simple malloc but it never returns from the call:

main.c:

#include <efi.h>
#include <efilib.h>
#include <stdlib.h>

EFI_STATUS
EFIAPI
efi_main (EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE *SystemTable) 
{
    InitializeLib(ImageHandle, SystemTable);

    Print(L"trying to allocate memory\n");
    malloc(16);
    Print(L"allocated successfully\n");

    return EFI_SUCCESS;
}

output:

trying to allocate memory

The system is a QEMU virtual machine under linux-ubuntu:

"qemu-system-x86_64 -cpu qemu64 -bios Bios/bios.bin -drive file=Bios/app.disk,format=raw -global isa-debugcon.iobase=0x402 -debugcon file:app.ovmf.log"

bios.bin is the UEFI firmware https://wiki.ubuntu.com/UEFI/OVMF.

main.efi is written to app.disk with

dd if=/dev/zero of=Bios/app.disk bs=1 count=1 seek=$(( (128 * 1024) - 1))
sudo mkfs.vfat Bios/app.disk
mkdir Bios/mnt_app
cp Bios/app.disk Bios/mnt_app
sudo mount Bios/app.disk Bios/mnt_app
sudo cp kernel/main.efi Bios/mnt_app

build process of main.c is almost complete copy paste from https://www.rodsbooks.com/efi-programming/hello.html:

ARCH            = $(shell uname -m | sed s,i[3456789]86,ia32,)

OBJS            = main.o
TARGET          = main.efi

EFIINC          = /usr/include/efi
EFIINCS         = -I$(EFIINC) -I$(EFIINC)/$(ARCH) -I$(EFIINC)/protocol
EFILIB          = /usr/lib
EFI_CRT_OBJS    = $(EFILIB)/crt0-efi-$(ARCH).o
EFI_LDS         = $(EFILIB)/elf_$(ARCH)_efi.lds

CFLAGS          = $(EFIINCS) -fno-stack-protector -fpic \
          -fshort-wchar -mno-red-zone -Wall 

ifeq ($(ARCH),x86_64)
  CFLAGS += -DEFI_FUNCTION_WRAPPER
endif

LDFLAGS         = -nostdlib -znocombreloc -T $(EFI_LDS) -shared \
          -Bsymbolic -L $(EFILIB) $(EFI_CRT_OBJS) 

all: $(TARGET)

main.so: $(OBJS)
    ld $(LDFLAGS) $(OBJS) -o $@ -lefi -lgnuefi

%.efi: %.so
    objcopy -j .text -j .sdata -j .data -j .dynamic \
        -j .dynsym  -j .rel -j .rela -j .reloc \
        --target=efi-app-$(ARCH) $^ $@

    @echo   done building target

Solution

for reasons i don't know, malloc is just not working and is probably not intended to be used - at least it seems like that. if you need dynamic memory allocation, create your own malloc with memory pools:

void * malloc(UINTN poolSize)
{
    EFI_STATUS status;
    void * handle;
    Print(L"allocating memory pool\n");
    status = uefi_call_wrapper(BS->AllocatePool, 3, EfiLoaderData, poolSize, &handle);

    if(status == EFI_OUT_OF_RESOURCES)
    {
        Print(L"out of resources for pool\n");
        return 0;
    }
    else if(status == EFI_INVALID_PARAMETER)
    {
        Print(L"invalid pool type\n");
        return 0;
    }
    else
    {
        Print(L"memory pool successfully allocated\n");
        return handle;
    }
}

free equivalent:

void free(void * pool)
{
    EFI_STATUS status;
    Print(L"freeing memory pool\n");
    status = uefi_call_wrapper(BS->FreePool, 1, pool);

    if(status == EFI_INVALID_PARAMETER)
    {
        Print(L"invalid pool pointer\n");
    }
    else
    {
        Print(L"memory pool successfully freed\n");
    }
}

use it like you would usually use malloc and free:

EFI_STATUS
EFIAPI
efi_main (EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE *SystemTable) 
{
    InitializeLib(ImageHandle, SystemTable);

    void * memoryPointer = malloc(1024);
    free(memoryPointer);

    return EFI_SUCCESS;
}

output:

allocating memory pool
memory pool successfully allocated
freeing memory pool
memory pool successfully freed