cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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memory.c (3133B)

      1// SPDX-License-Identifier: GPL-2.0-only
      2/* -*- linux-c -*- ------------------------------------------------------- *
      3 *
      4 *   Copyright (C) 1991, 1992 Linus Torvalds
      5 *   Copyright 2007 rPath, Inc. - All Rights Reserved
      6 *   Copyright 2009 Intel Corporation; author H. Peter Anvin
      7 *
      8 * ----------------------------------------------------------------------- */
      9
     10/*
     11 * Memory detection code
     12 */
     13
     14#include "boot.h"
     15
     16#define SMAP	0x534d4150	/* ASCII "SMAP" */
     17
     18static void detect_memory_e820(void)
     19{
     20	int count = 0;
     21	struct biosregs ireg, oreg;
     22	struct boot_e820_entry *desc = boot_params.e820_table;
     23	static struct boot_e820_entry buf; /* static so it is zeroed */
     24
     25	initregs(&ireg);
     26	ireg.ax  = 0xe820;
     27	ireg.cx  = sizeof(buf);
     28	ireg.edx = SMAP;
     29	ireg.di  = (size_t)&buf;
     30
     31	/*
     32	 * Note: at least one BIOS is known which assumes that the
     33	 * buffer pointed to by one e820 call is the same one as
     34	 * the previous call, and only changes modified fields.  Therefore,
     35	 * we use a temporary buffer and copy the results entry by entry.
     36	 *
     37	 * This routine deliberately does not try to account for
     38	 * ACPI 3+ extended attributes.  This is because there are
     39	 * BIOSes in the field which report zero for the valid bit for
     40	 * all ranges, and we don't currently make any use of the
     41	 * other attribute bits.  Revisit this if we see the extended
     42	 * attribute bits deployed in a meaningful way in the future.
     43	 */
     44
     45	do {
     46		intcall(0x15, &ireg, &oreg);
     47		ireg.ebx = oreg.ebx; /* for next iteration... */
     48
     49		/* BIOSes which terminate the chain with CF = 1 as opposed
     50		   to %ebx = 0 don't always report the SMAP signature on
     51		   the final, failing, probe. */
     52		if (oreg.eflags & X86_EFLAGS_CF)
     53			break;
     54
     55		/* Some BIOSes stop returning SMAP in the middle of
     56		   the search loop.  We don't know exactly how the BIOS
     57		   screwed up the map at that point, we might have a
     58		   partial map, the full map, or complete garbage, so
     59		   just return failure. */
     60		if (oreg.eax != SMAP) {
     61			count = 0;
     62			break;
     63		}
     64
     65		*desc++ = buf;
     66		count++;
     67	} while (ireg.ebx && count < ARRAY_SIZE(boot_params.e820_table));
     68
     69	boot_params.e820_entries = count;
     70}
     71
     72static void detect_memory_e801(void)
     73{
     74	struct biosregs ireg, oreg;
     75
     76	initregs(&ireg);
     77	ireg.ax = 0xe801;
     78	intcall(0x15, &ireg, &oreg);
     79
     80	if (oreg.eflags & X86_EFLAGS_CF)
     81		return;
     82
     83	/* Do we really need to do this? */
     84	if (oreg.cx || oreg.dx) {
     85		oreg.ax = oreg.cx;
     86		oreg.bx = oreg.dx;
     87	}
     88
     89	if (oreg.ax > 15*1024) {
     90		return;	/* Bogus! */
     91	} else if (oreg.ax == 15*1024) {
     92		boot_params.alt_mem_k = (oreg.bx << 6) + oreg.ax;
     93	} else {
     94		/*
     95		 * This ignores memory above 16MB if we have a memory
     96		 * hole there.  If someone actually finds a machine
     97		 * with a memory hole at 16MB and no support for
     98		 * 0E820h they should probably generate a fake e820
     99		 * map.
    100		 */
    101		boot_params.alt_mem_k = oreg.ax;
    102	}
    103}
    104
    105static void detect_memory_88(void)
    106{
    107	struct biosregs ireg, oreg;
    108
    109	initregs(&ireg);
    110	ireg.ah = 0x88;
    111	intcall(0x15, &ireg, &oreg);
    112
    113	boot_params.screen_info.ext_mem_k = oreg.ax;
    114}
    115
    116void detect_memory(void)
    117{
    118	detect_memory_e820();
    119
    120	detect_memory_e801();
    121
    122	detect_memory_88();
    123}