Question

我在QEMU中运行了一些裸机AARCH64软件。我试图从EL2访问GICv3系统寄存器ICH_ *，但在读/写时我一直遇到异常。

ESR 0x2000000: ec 0x0, il 0x2000000, iss 0x0


x0  0xffffffff000bd2c0 x1                 0x3 x2  0xffff00004808cd50 x3  0xffff00004808cd20
x4          0x77616974 x5          0x65766e74 x6          0x74696d72 x7                   0
x8                   0 x9          0xffffffff x10 0xffff0000401fc870 x11 0x4a49524200000000
x12                  0 x13 0xffffffff00131000 x14 0xffff000042290000 x15 0xffff0000401fc730
x16 0xffffffff00117100 x17 0xffff0000401feb80 x18 0xffffffff00117100 x19 0xffff00004808ccb0
x20                  0 x21 0xffff0083dd174db8 x22 0xffff00004808cd38 x23 0xffff00004806eba8
x24 0xffff00004806f028 x25 0xffff00004808ccc8 x26 0xffff0083dd174e18 x27            0x80000
x28                0x1 x29 0xffff0083dd174d50 lr  0xffffffff000bc5a0 usp                  0
elr  0xffffffff000bd2c0
spsr         0x20000305

我通过设置ICC_SRE_EL2寄存器

启用了SRE

我错过了什么吗？

-kim

Answer 1

以下是您的用例的最小，完整和可验证的示例：

a）在/tmp中创建#define ICH_HCR_EL2 S3_4_C12_C11_0 .arch armv8-a .globl _start .text _start: #ifdef __RETURN_CURRENT_EL__ // test only - returning CurrentEL mrs x0, CurrentEL ubfx x0, x0,2,2 #else mrs x0, ICH_HCR_EL2 #endif // exiting/returning w0 using Angel/Semihosting interface adr x1, status str w0, [x1] mov w0, #0x18 adr x1, code hlt #0xf000 .data .balign 8 code: .dword 0x00020026 status: .dword 0x00000000 .end文件：

ich_hcr_l2.sh

b）在/tmp中创建一个名为#!/bin/bash # Absolute path to this script. /home/user/bin/foo.sh SCRIPT=$(readlink -f $BASH_SOURCE) # Absolute path this script is in. /home/user/bin SCRIPTPATH=$(dirname $SCRIPT) set -e QEMU_VERSION=2.11.0 QEMU_SYSTEM_ARM=${SCRIPTPATH}/qemu/bin/qemu-system-aarch64 build_qemu() { if [ ! -f ${SCRIPTPATH}/qemu/bin/qemu-system-aarch64 ] then if [ ! -f ${SCRIPTPATH}/qemu-${QEMU_VERSION}.tar.xz ] then wget https://download.qemu.org/qemu-${QEMU_VERSION}.tar.xz fi rm -rf ${SCRIPTPATH}/qemu-${QEMU_VERSION} tar Jxf ${SCRIPTPATH}/qemu-${QEMU_VERSION}.tar.xz -C ${SCRIPTPATH} pushd qemu-${QEMU_VERSION} ./configure --target-list="aarch64-softmmu" --prefix=${SCRIPTPATH}/qemu make all install popd fi } build_example() { aarch64-linux-gnu-gcc ${CFLAGS} -nostartfiles -nodefaultlibs -Wl,-Ttext=0x0000000042000000 -o ${SCRIPTPATH}/ich_hcr_l2.elf ${SCRIPTPATH}/ich_hcr_l2.S aarch64-linux-gnu-objdump -D ${SCRIPTPATH}/ich_hcr_l2.elf > ${SCRIPTPATH}/ich_hcr_l2.lst } run_example() { # exit code will be the context at w0 register. ${QEMU_SYSTEM_ARM} -m 256M -semihosting -machine virt,gic-version=3,virtualization=on,secure=${SECURE} -monitor telnet:127.0.0.1:1235,server,nowait -cpu cortex-a53 -nographic -kernel ${SCRIPTPATH}/ich_hcr_l2.elf printf "Program returned with w0=%d\n" $? } # main build_example build_qemu set +e # testing program - should return CurrentEL=2 CFLAGS="-D__RETURN_CURRENT_EL__" SECURE=off build_example run_example # testing program - should return CurrentEL=3 CFLAGS="-D__RETURN_CURRENT_EL__" SECURE=on build_example run_example # actual test case: retrieving ICH_HCR_L2 at EL2: CFLAGS="" SECURE=off build_example run_example的可执行shell脚本：

Program returned with w0=2
Program returned with w0=3
Program returned with w0=0

c）make / tmp你当前的工作目录，并执行ich_hcr_l2.sh，然后耐心等待：脚本将下载，然后从源代码构建qemu-system-aarch64 2.11.0。

过了一会儿，你会看到显示以下两个：

/home/eperie/aarch64/ich_hcr_l2.elf:     file format elf64-littleaarch64


Disassembly of section .text:

0000000042000000 <_start>:
    42000000:   d53ccb00        mrs     x0, s3_4_c12_c11_0
    42000004:   100800e1        adr     x1, 42010020 <status>
    42000008:   b9000020        str     w0, [x1]
    4200000c:   52800300        mov     w0, #0x18                       // #24
    42000010:   10080041        adr     x1, 42010018 <code>
    42000014:   d45e0000        hlt     #0xf000

Disassembly of section .note.gnu.build-id:

0000000000400120 <.note.gnu.build-id>:
  400120:       00000004        .inst   0x00000004 ; undefined
  400124:       00000014        .inst   0x00000014 ; undefined
  400128:       00000003        .inst   0x00000003 ; undefined
  40012c:       00554e47        .inst   0x00554e47 ; undefined
  400130:       e7c953ee        .inst   0xe7c953ee ; undefined
  400134:       d3437b0f        ubfx    x15, x24, #3, #28
  400138:       2edb19d4        .inst   0x2edb19d4 ; undefined
  40013c:       9350921e        sbfx    x30, x16, #16, #21
  400140:       ea5adf9d        ands    x29, x28, x26, lsr #55

Disassembly of section .data:

0000000042010018 <code>:
    42010018:   00020026        .word   0x00020026
    4201001c:   00000000        .word   0x00000000

0000000042010020 <status>:
        ...

和/tmp/ich_hcr_l2.lst应包含：

{{1}}

从QEMU GICv3上的EL2访问系统寄存器时出现异常

1 个答案: