AArch64 - calling sprintf from EL2 and EL1

Little Tree 0
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I have written a simple arm64 bare-metal program to switch between EL2 and EL1. In EL2 and EL1, I am calling sprintf function as shown below.

void EL2Handler()
{
   char buffer[100];
   sprintf(buffer, "Current Exception Level is 2");
   ...
}

void EL1Handler()
{
   char buffer[100];
   sprintf(buffer, "Current Exception Level is 1");
   ...
}

When the sprintf called from EL1, it throws a synchronous exception. What could be the reason? Could it be related to memory access permissions? I am emulating this code on QEMU using virt machine.

The code is compile using

aarch64-none-elf-gcc -I.   -nostartfiles -ffreestanding --specs=rdimon.specs -L. -Wl,-T,qemu-virt-aarch64.ld -o test.elf startup.s test.c

The execute line is

qemu-system-aarch64 -semihosting -m 1024M -nographic  -machine virt,gic-version=2,virtualization=on -cpu max -kernel test.elf -S -gdb tcp::9000

This instruction causes the exception,

 0x400012cc <sprintf+60> ldp q16, q17, [x1]. 
 (gdb) p /x $x1 $2 = 0x47effdf8  
 (gdb) p /x $sp $3 = 0x47effdc0  
 (gdb) p /x $ESR_EL1 $5 = 0x1fe00000

The exception class in ESR_EL1 is 0b000111 "Access to SVE, Advanced SIMD or floating-point functionality trapped by CPACR_EL1.FPEN, CPTR_EL2.FPEN, CPTR_EL2.TFP, or CPTR_EL3.TFP control......". Is there a chance for floating point/sve/simd not implemented in EL1?

arm64 arm
0 Answers
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