boot_params_facts.c

// This file is part of KASLD - https://github.com/bcoles/kasld
//
// Emit x86 boot_params scalar facts: the exact in-memory kernel size
// (init_size, emitted as both SF_IMAGE_SIZE_MIN and SF_IMAGE_SIZE_MAX since it
// is sound in both directions) and SF_PHYS_KERNEL_ALIGN (CONFIG_PHYSICAL_ALIGN
// slot granularity). x86 only; the readers return 0 elsewhere.
// ---
// <bcoles@gmail.com>
#define _POSIX_C_SOURCE 200809L /* pread() in boot_params.h */
#include "include/kasld/api.h"
#include "include/kasld/boot_params.h"

KASLD_EXPLAIN("Reads /sys/kernel/boot_params/data for the exact kernel "
              "init_size and CONFIG_PHYSICAL_ALIGN, emitted as scalar facts "
              "tightening the KASLR ceiling and slot granularity. x86 only.");
KASLD_META("method:parsed\n"
           "phase:inference\n"
           "discloses:facts\n");

int main(void) {
  unsigned long v;
  if ((v = kasld_read_boot_init_size())) {
    /* Exact footprint: feeds both the ceiling (MIN) and the floor (MAX). */
    kasld_emit_scalar(SF_IMAGE_SIZE_MIN, v, CONF_PARSED);
    kasld_emit_scalar(SF_IMAGE_SIZE_MAX, v, CONF_PARSED);
  }
  if ((v = kasld_read_boot_kernel_align()))
    kasld_emit_scalar(SF_PHYS_KERNEL_ALIGN, v, CONF_PARSED);
  return 0;
}