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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pci.c (3339B)

      1// SPDX-License-Identifier: GPL-2.0
      2/*
      3 * PCI-related functions used by the EFI stub on multiple
      4 * architectures.
      5 *
      6 * Copyright 2019 Google, LLC
      7 */
      8
      9#include <linux/efi.h>
     10#include <linux/pci.h>
     11
     12#include <asm/efi.h>
     13
     14#include "efistub.h"
     15
     16void efi_pci_disable_bridge_busmaster(void)
     17{
     18	efi_guid_t pci_proto = EFI_PCI_IO_PROTOCOL_GUID;
     19	unsigned long pci_handle_size = 0;
     20	efi_handle_t *pci_handle = NULL;
     21	efi_handle_t handle;
     22	efi_status_t status;
     23	u16 class, command;
     24	int i;
     25
     26	status = efi_bs_call(locate_handle, EFI_LOCATE_BY_PROTOCOL, &pci_proto,
     27			     NULL, &pci_handle_size, NULL);
     28
     29	if (status != EFI_BUFFER_TOO_SMALL) {
     30		if (status != EFI_SUCCESS && status != EFI_NOT_FOUND)
     31			efi_err("Failed to locate PCI I/O handles'\n");
     32		return;
     33	}
     34
     35	status = efi_bs_call(allocate_pool, EFI_LOADER_DATA, pci_handle_size,
     36			     (void **)&pci_handle);
     37	if (status != EFI_SUCCESS) {
     38		efi_err("Failed to allocate memory for 'pci_handle'\n");
     39		return;
     40	}
     41
     42	status = efi_bs_call(locate_handle, EFI_LOCATE_BY_PROTOCOL, &pci_proto,
     43			     NULL, &pci_handle_size, pci_handle);
     44	if (status != EFI_SUCCESS) {
     45		efi_err("Failed to locate PCI I/O handles'\n");
     46		goto free_handle;
     47	}
     48
     49	for_each_efi_handle(handle, pci_handle, pci_handle_size, i) {
     50		efi_pci_io_protocol_t *pci;
     51		unsigned long segment_nr, bus_nr, device_nr, func_nr;
     52
     53		status = efi_bs_call(handle_protocol, handle, &pci_proto,
     54				     (void **)&pci);
     55		if (status != EFI_SUCCESS)
     56			continue;
     57
     58		/*
     59		 * Disregard devices living on bus 0 - these are not behind a
     60		 * bridge so no point in disconnecting them from their drivers.
     61		 */
     62		status = efi_call_proto(pci, get_location, &segment_nr, &bus_nr,
     63					&device_nr, &func_nr);
     64		if (status != EFI_SUCCESS || bus_nr == 0)
     65			continue;
     66
     67		/*
     68		 * Don't disconnect VGA controllers so we don't risk losing
     69		 * access to the framebuffer. Drivers for true PCIe graphics
     70		 * controllers that are behind a PCIe root port do not use
     71		 * DMA to implement the GOP framebuffer anyway [although they
     72		 * may use it in their implementation of Gop->Blt()], and so
     73		 * disabling DMA in the PCI bridge should not interfere with
     74		 * normal operation of the device.
     75		 */
     76		status = efi_call_proto(pci, pci.read, EfiPciIoWidthUint16,
     77					PCI_CLASS_DEVICE, 1, &class);
     78		if (status != EFI_SUCCESS || class == PCI_CLASS_DISPLAY_VGA)
     79			continue;
     80
     81		/* Disconnect this handle from all its drivers */
     82		efi_bs_call(disconnect_controller, handle, NULL, NULL);
     83	}
     84
     85	for_each_efi_handle(handle, pci_handle, pci_handle_size, i) {
     86		efi_pci_io_protocol_t *pci;
     87
     88		status = efi_bs_call(handle_protocol, handle, &pci_proto,
     89				     (void **)&pci);
     90		if (status != EFI_SUCCESS || !pci)
     91			continue;
     92
     93		status = efi_call_proto(pci, pci.read, EfiPciIoWidthUint16,
     94					PCI_CLASS_DEVICE, 1, &class);
     95
     96		if (status != EFI_SUCCESS || class != PCI_CLASS_BRIDGE_PCI)
     97			continue;
     98
     99		/* Disable busmastering */
    100		status = efi_call_proto(pci, pci.read, EfiPciIoWidthUint16,
    101					PCI_COMMAND, 1, &command);
    102		if (status != EFI_SUCCESS || !(command & PCI_COMMAND_MASTER))
    103			continue;
    104
    105		command &= ~PCI_COMMAND_MASTER;
    106		status = efi_call_proto(pci, pci.write, EfiPciIoWidthUint16,
    107					PCI_COMMAND, 1, &command);
    108		if (status != EFI_SUCCESS)
    109			efi_err("Failed to disable PCI busmastering\n");
    110	}
    111
    112free_handle:
    113	efi_bs_call(free_pool, pci_handle);
    114}