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arm exception level emulator entry examples

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Ciro Santilli 六四事件 法轮功
2018-11-20 00:00:01 +00:00
parent 07000300ab
commit 35684b1b7e
3 changed files with 79 additions and 8 deletions
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68
README.adoc
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@@ -10396,19 +10396,77 @@ help architecture
shows ARM version up to `armv6`, so maybe `armv6` is not implemented?
=== ARM EL
=== ARM exception level
Find the ARM EL: https://stackoverflow.com/questions/31787617/what-is-the-current-execution-mode-exception-level-etc
ARM exception levels are analogous to x86 <<ring0,rings>>.
Prints the EL at the beginning of a baremetal simulation:
Print the EL at the beginning of a baremetal simulation:
....
./run --arch arm --baremetal arch/arm/el
./run --arch aarch64 --baremetal arch/aarch64/el
....
Source: link:baremetal/arch/aarch64/el.c[]
Sources:
The lower ELs are not mandatory, and in gem5 at least you can configure the lowest EL with configuration options TODO which, example.
* link:baremetal/arch/arm/el.c[]
* link:baremetal/arch/aarch64/el.c[]
The instructions that find the ARM EL are explained at: https://stackoverflow.com/questions/31787617/what-is-the-current-execution-mode-exception-level-etc
The lower ELs are not mandated by the architecture, and can be controlled through command line options in QEMU and gem5.
In QEMU, you can configure the lowest EL as explained at https://stackoverflow.com/questions/42824706/qemu-system-aarch64-entering-el1-when-emulating-a53-power-up
....
./run --arch arm --baremetal arch/arm/el
./run --arch arm --baremetal arch/arm/el -- -machine virtualization=on
./run --arch arm --baremetal arch/arm/el -- -machine secure=on
./run --arch aarch64 --baremetal arch/aarch64/el
./run --arch aarch64 --baremetal arch/aarch64/el -- -machine virtualization=on
./run --arch aarch64 --baremetal arch/aarch64/el -- -machine secure=on
....
outputs respectively:
....
19
19
19
1
2
3
....
TODO: why is `arm` stuck at `19` which equals Supervisor mode?
In gem5, you can configure the lowest EL with:
....
./run --arch arm --baremetal arch/arm/el --gem5
cat "$(./getvar --arch arm --gem5 gem5_guest_terminal_file)"
./run --arch arm --baremetal arch/arm/el --gem5 -- --param 'system.have_virtualization = True'
cat "$(./getvar --arch arm --gem5 gem5_guest_terminal_file)"
./run --arch arm --baremetal arch/arm/el --gem5 -- --param 'system.have_security = True'
cat "$(./getvar --arch arm --gem5 gem5_guest_terminal_file)"
./run --arch aarch64 --baremetal arch/aarch64/el --gem5
cat "$(./getvar --arch aarch64 --gem5 gem5_guest_terminal_file)"
./run --arch aarch64 --baremetal arch/aarch64/el --gem5 -- --param 'system.have_virtualization = True'
cat "$(./getvar --arch aarch64 --gem5 gem5_guest_terminal_file)"
./run --arch aarch64 --baremetal arch/aarch64/el --gem5 -- --param 'system.have_security = True'
cat "$(./getvar --arch aarch64 --gem5 gem5_guest_terminal_file)"
....
output:
....
19
26
19
1
2
3
....
=== How we got some baremetal stuff to work

8
baremetal/arch/aarch64/el.c
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@@ -1,9 +1,11 @@
/* https://github.com/cirosantilli/linux-kernel-module-cheat#arm-exception-level */
#include <stdio.h>
#include <inttypes.h>
int main(void) {
register uint64_t x0 __asm__ ("x0");
__asm__ ("mrs x0, CurrentEL;" : : : "%x0");
printf("%" PRIu64 "\n", x0);
register uint64_t x0 __asm__ ("x0");
__asm__ ("mrs x0, CurrentEL;" : : : "%x0");
printf("%" PRIu64 "\n", x0 >> 2);
return 0;
}

11
baremetal/arch/arm/el.c Normal file
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@@ -0,0 +1,11 @@
/* https://github.com/cirosantilli/linux-kernel-module-cheat#arm-exception-level */
#include <stdio.h>
#include <inttypes.h>
int main(void) {
register uint32_t r0 __asm__ ("r0");
__asm__ ("mrs r0, CPSR" : : : "%r0");
printf("%" PRIu32 "\n", r0 & 0x1F);
return 0;
}