Advanced System Call Return Values

int sysinfo(struct sysinfo *info);

The sysinfo system call uses a single input value, which points to a memory location to hold the structure
that contains the returned data. The man page also shows what this structure should look like:

struct sysinfo {long uptime; /* Seconds since boot */unsigned long loads[3]; /* 1, 5, and 15 minute load averages */unsigned long totalram; /* Total usable main memory size */unsigned long freeram; /* Available memory size */unsigned long sharedram; /* Amount of shared memory */unsigned long bufferram; /* Memory used by buffers */unsigned long totalswap; /* Total swap space size */unsigned long freeswap; /* swap space still available */unsigned short procs; /* Number of current processes */unsigned long totalhigh; /* Total high memory size */unsigned int mem_unit; /* Memory unit size in bytes */char _f[20-2*sizeof(long)-sizeof(int)]; /* Padding for libc5 */}

Using the return structure

.section .dataresult:uptime:.int 0load1:.int 0load5:.int 0load15:.int 0totalram:.int 0freeram:.int 0sharedram:.int 0bufferram:.int 0totalswap:.int 0freeswap:.int 0procs:.byte 0x00, 0x00totalhigh:.int 0memunit:.int 0.section .text.globl _start_start:nopmovl $result, %ebxmovl $116, %eaxint $0x80movl $0, %ebxmovl $1, %eaxint $0x80

The system call value for the sysinfo system call is placed in the EAX register, and the memory location
of the result label is placed in the EBX register as the input value. After the INT instruction is executed,
the return structure values are loaded into the memory location, and the memory labels can be used to
reference each individual value.