What Does the Gcc Error Message, "Error: Unsupported for 'Mov'", Mean

What does the GCC error message, Error: unsupported for `mov', mean?

You are attempting to compile 32-bit assembly code on a 64-bit machine. The inline assembly you list compiles to:

movl -24(%rbp), %ebx
movl %rsi, %ecx       <--- error here
movl -28(%rbp), %edx
movl $103, %eax
int $128
movl %eax, %r12d

As you can see, you're attempting to store a 64-bit register in a 32-bit register, which is illegal. More importantly, this isn't the 64-bit ABI system call protocol either.

Try compiling with -m32 to force 32-bit ABI.

unsupported instruction 'mov' in inline asm moving control register to uint32_t

The syntax is correct, but the error is more than likely because you're compiling for a 64-bit target, in which case the mov needs to be 64 bits. Just change faulting_address to a uint64_t and it will compile.

Alternatively, if you want it to be 32 bits, you'll need to use -m32 or other similar option to compile for a 32-bit target.

Error in simple g++ inline assembler

Your assembly code is not valid. Please carefully read on Extended Asm. Here's another good overview.
Here is a CPUID example code from here:

static inline void cpuid(int code, uint32_t* a, uint32_t* d)
{
    asm volatile ( "cpuid" : "=a"(*a), "=d"(*d) : "0"(code) : "ebx", "ecx" );
}

Note the format:

• first : followed by output operands: : "=a"(*a), "=d"(*d); "=a" is eax and "=b is ebx
• second : followed by input operands: : "0"(code); "0" means that code should occupy the same location as output operand 0 (eax in this case)
• third : followed by clobbered registers list: : "ebx", "ecx"

Assembly error when compiling with GCC

I think the following code will compile ("gcc" can compile .s and .S files and link them with C library by default but "as" do the same and don't link code with C library)
as :

.section .text
    .global _start
_start:
    mov $4,%eax
    mov $1,%ebx
    mov $message,%ecx
    mov msglength,%edx
    int  $0x80

    mov $1, %eax
    mov $0, %ebx
    int $0x80
.section .data
    message: .ascii "Hello world!"
    msglength: .word 12

gcc:

.section .text
    .global main
main:
    mov $4,%eax
    mov $1,%ebx
    mov $message,%ecx
    mov msglength,%edx
    int  $0x80

    mov $1, %eax
    mov $0, %ebx
    int $0x80
.section .data
    message: .ascii "Hello world!"
    msglength: .word 12

warnings while trying to compile old linux kernel with gcc 12.1.0

To compile older version of kernel I needed older compiler ("Linux kernel sources are in general not forward-compatible with new compilers"). In my case the kernel version was 5.16.0 and I could compile it with gcc 11. If you have gcc 11 specific warnings then try gcc 10 and so on.

Except CC flags, I also needed set to HOSTCC flags to use gcc-11 compiler:

make HOSTCC=gcc-11 CC=gcc-11

What is this GCC error on Linux, and how do I solve it? gcc: internal compiler error: Illegal instruction (program as)

Got it! I uninstalled gcc, installed gcc-4.7, and ... nothing.

I cleared out the end of gcc-4.6 and re-ran sudo apt-get install gcc-4.7 and ... nothing.

I updated binutils and ... it worked!

So, as didn't appear to be affected by updating GCC, but updating it more directly did it for me.

(It was from 2.22-7.1 to 2.22-8, if that helps anyone.)

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