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arch-arm: inform bootloader of kernel position with a register

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Before the commit, the bootloader had a hardcoded entry point that it
would jump to.

However, the Linux kernel arm64 v5.8 forced us to change the kernel
entry point because the required memory alignment has changed at:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/
commit/?h=v5.8&id=cfa7ede20f133cc81cef01dc3a516dda3a9721ee

Therefore the only way to have a single bootloader that boots both
pre-v5.8 and post-v5.8 kernels is to pass that information from gem5
to the bootloader, which we do in this patch via registers.

This approach was already used by the 32-bit bootloader, which passed
that value via r3, and we try to use the same register x3 in 64-bit.

Since we are now passing this information, the this patch also removes
the hardcoding of DTB and cpu-release-addr, and also passes those
values via registers.

We store the cpu-release-addr in x5 as that value appears to have a
function similar to flags_addr, which is used only in 32-bit arm and
gets stored in r5.

This commit renames atags_addr to dtb_addr, since both are mutually
exclusive, and serve a similar purpose, DTB being the newer recommended
approach.

Similarly, flags_addr is renamed to cpu_release_addr, and it is moved
from ArmSystem into ArmFsWorkload, since it is not an intrinsic system
property, and should be together with dtb_addr instead.

Before this commit, flags_addr was being set from FSConfig.py and
configs/example/arm/devices.py to self.realview.realview_io.pio_addr
+ 0x30. This commit moves that logic into RealView.py instead, and
sets the flags address 8 bytes before the start of the DTB address.

JIRA: https://gem5.atlassian.net/browse/GEM5-787
Change-Id: If70bea9690be04b84e6040e256a9b03e46710e10
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/35076
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>
This commit is contained in:
Ciro Santilli
2020-09-21 17:11:59 +01:00
parent eb4382af0e
commit 6ecf110b06
11 changed files with 73 additions and 45 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
configs/common/FSConfig.py
View File

@@ -250,7 +250,7 @@ def makeArmSystem(mem_mode, machine_type, num_cpus=1, mdesc=None,
if bare_metal:
# EOT character on UART will end the simulation
self.realview.uart[0].end_on_eot = True
self.workload = ArmFsWorkload(atags_addr=0)
self.workload = ArmFsWorkload(dtb_addr=0)
else:
workload = ArmFsLinux()
@@ -269,8 +269,6 @@ def makeArmSystem(mem_mode, machine_type, num_cpus=1, mdesc=None,
if hasattr(self.realview.gic, 'cpu_addr'):
self.gic_cpu_addr = self.realview.gic.cpu_addr
self.flags_addr = self.realview.realview_io.pio_addr + 0x30
# This check is for users who have previously put 'android' in
# the disk image filename to tell the config scripts to
# prepare the kernel with android-specific boot options. That

1
configs/example/arm/devices.py
View File

@@ -308,7 +308,6 @@ def simpleSystem(BaseSystem, caches, mem_size, platform=None, **kwargs):
if hasattr(self.realview.gic, 'cpu_addr'):
self.gic_cpu_addr = self.realview.gic.cpu_addr
self.flags_addr = self.realview.realview_io.pio_addr + 0x30
self.membus = MemBus()

4
configs/example/arm/workloads.py
View File

@@ -47,7 +47,7 @@ from common.SysPaths import binary, disk
class ArmBaremetal(ArmFsWorkload):
""" Baremetal workload """
atags_addr = 0
dtb_addr = 0
def __init__(self, obj, system, **kwargs):
super(ArmBaremetal, self).__init__(**kwargs)
@@ -72,7 +72,7 @@ class ArmTrustedFirmware(ArmFsWorkload):
https://github.com/ARM-software/arm-trusted-firmware
"""
atags_addr = 0
dtb_addr = 0
def __init__(self, obj, system, **kwargs):
super(ArmTrustedFirmware, self).__init__(**kwargs)

6
src/arch/arm/ArmFsWorkload.py
View File

@@ -1,4 +1,4 @@
# Copyright (c) 2009, 2012-2013, 2015-2019 ARM Limited
# Copyright (c) 2009, 2012-2013, 2015-2020 ARM Limited
# All rights reserved.
#
# The license below extends only to copyright in the software and shall
@@ -57,11 +57,11 @@ class ArmFsWorkload(KernelWorkload):
dtb_filename = Param.String("",
"File that contains the Device Tree Blob. Don't use DTB if empty.")
dtb_addr = Param.Addr(0, "DTB or ATAGS address")
cpu_release_addr = Param.Addr(0, "cpu-release-addr property")
machine_type = Param.ArmMachineType('DTOnly',
"Machine id from http://www.arm.linux.org.uk/developer/machines/")
atags_addr = Param.Addr("Address where default atags structure should " \
"be written")
early_kernel_symbols = Param.Bool(False,
"enable early kernel symbol tables before MMU")
enable_context_switch_stats_dump = Param.Bool(False,

1
src/arch/arm/ArmSystem.py
View File

@@ -48,7 +48,6 @@ class ArmSystem(System):
cxx_header = "arch/arm/system.hh"
multi_proc = Param.Bool(True, "Multiprocessor system?")
gic_cpu_addr = Param.Addr(0, "Addres of the GIC CPU interface")
flags_addr = Param.Addr(0, "Address of the flags register for MP booting")
have_security = Param.Bool(False,
"True if Security Extensions are implemented")
have_virtualization = Param.Bool(False,

6
src/arch/arm/freebsd/fs_workload.cc
View File

@@ -95,7 +95,7 @@ FsFreebsd::initState()
// Kernel supports flattened device tree and dtb file specified.
// Using Device Tree Blob to describe system configuration.
inform("Loading DTB file: %s at address %#x\n", params().dtb_filename,
params().atags_addr + _loadAddrOffset);
params().dtb_addr + _loadAddrOffset);
auto *dtb_file = new ::Loader::DtbFile(params().dtb_filename);
@@ -108,7 +108,7 @@ FsFreebsd::initState()
bootReleaseAddr = ra & ~ULL(0x7F);
dtb_file->buildImage().
offset(params().atags_addr + _loadAddrOffset).
offset(params().dtb_addr + _loadAddrOffset).
write(system->physProxy);
delete dtb_file;
@@ -116,7 +116,7 @@ FsFreebsd::initState()
for (auto *tc: system->threads) {
tc->setIntReg(0, 0);
tc->setIntReg(1, params().machine_type);
tc->setIntReg(2, params().atags_addr + _loadAddrOffset);
tc->setIntReg(2, params().dtb_addr + _loadAddrOffset);
}
}

14
src/arch/arm/fs_workload.cc
View File

@@ -1,5 +1,5 @@
/*
* Copyright (c) 2010, 2012-2013, 2015,2017-2019 ARM Limited
* Copyright (c) 2010, 2012-2013, 2015,2017-2020 ARM Limited
* All rights reserved
*
* The license below extends only to copyright in the software and shall
@@ -117,21 +117,21 @@ FsWorkload::initState()
inform("Using bootloader at address %#x", bootldr->entryPoint());
// Put the address of the boot loader into r7 so we know
// The address of the boot loader so we know
// where to branch to after the reset fault
// All other values needed by the boot loader to know what to do
fatal_if(!arm_sys->params().flags_addr,
"flags_addr must be set with bootloader");
fatal_if(!params().cpu_release_addr,
"cpu_release_addr must be set with bootloader");
fatal_if(!arm_sys->params().gic_cpu_addr && is_gic_v2,
"gic_cpu_addr must be set with bootloader");
for (auto *tc: arm_sys->threads) {
if (!arm_sys->highestELIs64())
tc->setIntReg(3, kernelEntry);
tc->setIntReg(3, kernelEntry);
if (is_gic_v2)
tc->setIntReg(4, arm_sys->params().gic_cpu_addr);
tc->setIntReg(5, arm_sys->params().flags_addr);
if (getArch() == Loader::Arm)
tc->setIntReg(5, params().cpu_release_addr);
}
inform("Using kernel entry physical address at %#x\n", kernelEntry);
} else {

31
src/arch/arm/linux/fs_workload.cc
View File

@@ -1,5 +1,5 @@
/*
* Copyright (c) 2010-2013, 2016 ARM Limited
* Copyright (c) 2010-2013, 2016, 2020 ARM Limited
* All rights reserved
*
* The license below extends only to copyright in the software and shall
@@ -92,7 +92,7 @@ FsLinux::initState()
// Kernel supports flattened device tree and dtb file specified.
// Using Device Tree Blob to describe system configuration.
inform("Loading DTB file: %s at address %#x\n", params().dtb_filename,
params().atags_addr + _loadAddrOffset);
params().dtb_addr);
auto *dtb_file = new ::Loader::DtbFile(params().dtb_filename);
@@ -102,9 +102,8 @@ FsLinux::initState()
params().dtb_filename);
}
dtb_file->buildImage().
offset(params().atags_addr + _loadAddrOffset).
write(system->physProxy);
dtb_file->buildImage().offset(params().dtb_addr)
.write(system->physProxy);
delete dtb_file;
} else {
// Using ATAGS
@@ -152,17 +151,27 @@ FsLinux::initState()
DPRINTF(Loader, "Boot atags was %d bytes in total\n", size << 2);
DDUMP(Loader, boot_data, size << 2);
system->physProxy.writeBlob(params().atags_addr + _loadAddrOffset,
system->physProxy.writeBlob(params().dtb_addr + _loadAddrOffset,
boot_data, size << 2);
delete[] boot_data;
}
// Kernel boot requirements to set up r0, r1 and r2 in ARMv7
for (auto *tc: system->threads) {
tc->setIntReg(0, 0);
tc->setIntReg(1, params().machine_type);
tc->setIntReg(2, params().atags_addr + _loadAddrOffset);
if (getArch() == Loader::Arm64) {
// We inform the bootloader of the kernel entry point. This was added
// originally done because the entry offset changed in kernel v5.8.
// Previously the bootloader just used a hardcoded address.
for (auto *tc: system->threads) {
tc->setIntReg(0, params().dtb_addr);
tc->setIntReg(5, params().cpu_release_addr);
}
} else {
// Kernel boot requirements to set up r0, r1 and r2 in ARMv7
for (auto *tc: system->threads) {
tc->setIntReg(0, 0);
tc->setIntReg(1, params().machine_type);
tc->setIntReg(2, params().dtb_addr + _loadAddrOffset);
}
}
}

10
src/dev/arm/RealView.py
View File

@@ -713,10 +713,11 @@ class RealView(Platform):
self._attach_mem(self._off_chip_memory(), bus, mem_ports)
self._attach_io(self._off_chip_devices(), bus, dma_ports)
def setupBootLoader(self, cur_sys, boot_loader, atags_addr, load_offset):
def setupBootLoader(self, cur_sys, boot_loader, dtb_addr, load_offset):
cur_sys.workload.boot_loader = boot_loader
cur_sys.workload.atags_addr = atags_addr
cur_sys.workload.load_addr_offset = load_offset
cur_sys.workload.dtb_addr = load_offset + dtb_addr
cur_sys.workload.cpu_release_addr = cur_sys.workload.dtb_addr - 8
def generateDeviceTree(self, state):
node = FdtNode("/") # Things in this module need to end up in the root
@@ -734,8 +735,11 @@ class RealView(Platform):
cpu.append(FdtPropertyStrings('enable-method', 'psci'))
else:
cpu.append(FdtPropertyStrings("enable-method", "spin-table"))
# The kernel writes the entry addres of secondary CPUs to this
# address before waking up secondary CPUs.
# The gem5 bootloader then makes secondary CPUs jump to it.
cpu.append(FdtPropertyWords("cpu-release-addr", \
state.addrCells(0x8000fff8)))
state.addrCells(system.workload.cpu_release_addr)))
class VExpress_EMM(RealView):
_mem_regions = [ AddrRange('2GB', size='2GB') ]

35
system/arm/bootloader/arm64/boot.S
View File

@@ -1,5 +1,5 @@
/*
* Copyright (c) 2012 ARM Limited
* Copyright (c) 2012, 2020 ARM Limited
* All rights reserved
*
* The license below extends only to copyright in the software and shall
@@ -40,6 +40,14 @@
.globl _start
_start:
/* Save some values initialized by gem5. */
/* DTB address. */
mov x21, x0
/* Kernel entry point. */
mov x20, x3
/* cpu-release-addr. */
mov x22, x5
/*
* EL3 initialisation
*/
@@ -153,8 +161,19 @@ start_ns:
* Secondary CPUs
*/
1: wfe
ldr x4, =PHYS_OFFSET + 0xfff8
ldr x4, [x4]
/* The Linux kernel v5.8 and older writes the entry point address
* of the secondary CPUs to this address, and does a SEV, waking up
* the secondary CPUs.
*
* gem5 informs the kernel the desired address via cpu-release-addr
* of the DTB.
*
* When this is first reached immediately after the bootloader starts,
* the value at that address must be 0, which is the default memory
* value set by gem5 for otherwise uninitialized memory, leading to
* WFE.
*/
ldr x4, [x22]
cbz x4, 1b
br x4 // branch to the given address
@@ -180,9 +199,13 @@ start_ns:
/*
* Primary CPU
*/
ldr x0, =PHYS_OFFSET + 0x8000000 // device tree blob
ldr x6, =PHYS_OFFSET + 0x80000 // kernel start address
br x6
// The kernel boot protocol specifies that the DTB address is placed
// in x0.
// https://github.com/torvalds/linux/blob/v5.7/Documentation/arm64/
// booting.rst#4-call-the-kernel-image
mov x0, x21
// Jump into the kernel entry point.
br x20
.ltorg

6
system/arm/bootloader/arm64/makefile
View File

@@ -34,11 +34,7 @@ BUILDDIR = .
DESTDIR = $(error Please set DESTDIR to wanted installation directory)
CFLAGS = -march=armv8-a
CPPFLAGS = -DPHYS_OFFSET=0x80000000 \
-DUART_BASE=0x1c090000 -DSYSREGS_BASE=0x1c010000 \
-Dkernel=0x80080000 \
-Dmbox=0x8000fff8 -Ddtb=0x80000100
CPPFLAGS = -DUART_BASE=0x1c090000 -DSYSREGS_BASE=0x1c010000
LDFLAGS = -N -Ttext 0x00000010 -static
.PHONY: all clean install mkdir