Public bug reported:
Hi,
I don't know if this is a bug or a feature in new QEMU software. I was
following an online tutorial using QEMU to develop a simple bare-metal
program for qemu-system-arm. I decided to try a more recent software and
I got surprised when I found the small code can not run on newer QEMU
software (all newer than 2.0.0) but can run on the old QEMU from Ubuntu
(Debian 2.0.0+dfsg-2ubuntu1.22) and the stock version from website.
After putting the qemu-system-arm in single step and saving the log, the
following is the output which you can see the 1st instruction stores R3
at [fp, #-8] and the second instruction can not restores the value from
the same address to R0:
0x00010074: e50b3008 str r3, [fp, #-8]
R00=00000000 R01=00000000 R02=00000000 R03=0001008c
R04=00000000 R05=00000000 R06=00000000 R07=00000000
R08=00000000 R09=00000000 R10=00000000 R11=00011094
R12=00000000 R13=00011088 R14=00010008 R15=00010074
PSR=400001d3 -Z-- A S svc32
----------------
IN: kmain
0x00010078: e51b0008 ldr r0, [fp, #-8]
R00=00000000 R01=00000000 R02=00000000 R03=0001008c
R04=00000000 R05=00000000 R06=00000000 R07=00000000
R08=00000000 R09=00000000 R10=00000000 R11=00011094
R12=00000000 R13=00011088 R14=00010008 R15=00010078
PSR=400001d3 -Z-- A S svc32
----------------
IN: kmain
0x0001007c: ebffffe3 bl 0x10010
R00=00000000 R01=00000000 R02=00000000 R03=0001008c
R04=00000000 R05=00000000 R06=00000000 R07=00000000
R08=00000000 R09=00000000 R10=00000000 R11=00011094
R12=00000000 R13=00011088 R14=00010008 R15=0001007c
PSR=400001d3 -Z-- A S svc32
--------------------------------------
Meanwhile the older version of QEMU 2.0.0 does this very well and can execute
the program normally:
0x00010074: e50b3008 str r3, [fp, #-8]
R00=00000000 R01=00000000 R02=00000000 R03=0001008c
R04=00000000 R05=00000000 R06=00000000 R07=00000000
R08=00000000 R09=00000000 R10=00000000 R11=00011094
R12=00000000 R13=00011088 R14=00010008 R15=00010074
PSR=400001d3 -Z-- A svc32
----------------
IN: kmain
0x00010078: e51b0008 ldr r0, [fp, #-8]
R00=00000000 R01=00000000 R02=00000000 R03=0001008c
R04=00000000 R05=00000000 R06=00000000 R07=00000000
R08=00000000 R09=00000000 R10=00000000 R11=00011094
R12=00000000 R13=00011088 R14=00010008 R15=00010078
PSR=400001d3 -Z-- A svc32
----------------
IN: kmain
0x0001007c: ebffffe3 bl 0x10010
R00=0001008c R01=00000000 R02=00000000 R03=0001008c
R04=00000000 R05=00000000 R06=00000000 R07=00000000
R08=00000000 R09=00000000 R10=00000000 R11=00011094
R12=00000000 R13=00011088 R14=00010008 R15=0001007c
PSR=400001d3 -Z-- A svc32
----------------
The command line to use was:
qemu-system-arm -M vexpress-a9 -cpu cortex-a9 -smp 1 -m 64M -nographic
-kernel kernel.elf -singlestep -D file.log -d in_asm,cpu
The kernel.elf is a simple program (elf) file, created from two sources:
boot.S:
.global _RESET
_RESET:
LDR sp, =_STACK
BL kmain
B .
And kernel.c:
# define UART0_MEM 0x10009000
volatile unsigned int * const UART0 = (unsigned int *) UART0_MEM;
void dprint(const char* message){
while(*message != 0) {
*UART0=*message;
++message;
}
}
void kmain() {
const char *hi="Hello!";
dprint(hi);
};
The linker scripts is:
ENTRY(_RESET)
SECTIONS
{
. = 0x10000;
.boot . : { boot.o(.text) }
.text : { *(.text) }
.data : { *(.data) }
.bss : { *(.bss COMMON) }
. = ALIGN(8);
. = . + 0x1000; /* 4kB of stack memory */
_STACK = .;
}
This error cases the dprint function to find *message as 0 and do not
print the output in newer QEMU software.
Thank you for consideration.
** Affects: qemu
Importance: Undecided
Status: New
--
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devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1549654
Title:
qemu-system-arm emulator
Status in QEMU:
New
Bug description:
Hi,
I don't know if this is a bug or a feature in new QEMU software. I was
following an online tutorial using QEMU to develop a simple bare-
metal program for qemu-system-arm. I decided to try a more recent
software and I got surprised when I found the small code can not run
on newer QEMU software (all newer than 2.0.0) but can run on the old
QEMU from Ubuntu (Debian 2.0.0+dfsg-2ubuntu1.22) and the stock version
from website. After putting the qemu-system-arm in single step and
saving the log, the following is the output which you can see the 1st
instruction stores R3 at [fp, #-8] and the second instruction can not
restores the value from the same address to R0:
0x00010074: e50b3008 str r3, [fp, #-8]
R00=00000000 R01=00000000 R02=00000000 R03=0001008c
R04=00000000 R05=00000000 R06=00000000 R07=00000000
R08=00000000 R09=00000000 R10=00000000 R11=00011094
R12=00000000 R13=00011088 R14=00010008 R15=00010074
PSR=400001d3 -Z-- A S svc32
----------------
IN: kmain
0x00010078: e51b0008 ldr r0, [fp, #-8]
R00=00000000 R01=00000000 R02=00000000 R03=0001008c
R04=00000000 R05=00000000 R06=00000000 R07=00000000
R08=00000000 R09=00000000 R10=00000000 R11=00011094
R12=00000000 R13=00011088 R14=00010008 R15=00010078
PSR=400001d3 -Z-- A S svc32
----------------
IN: kmain
0x0001007c: ebffffe3 bl 0x10010
R00=00000000 R01=00000000 R02=00000000 R03=0001008c
R04=00000000 R05=00000000 R06=00000000 R07=00000000
R08=00000000 R09=00000000 R10=00000000 R11=00011094
R12=00000000 R13=00011088 R14=00010008 R15=0001007c
PSR=400001d3 -Z-- A S svc32
--------------------------------------
Meanwhile the older version of QEMU 2.0.0 does this very well and can execute
the program normally:
0x00010074: e50b3008 str r3, [fp, #-8]
R00=00000000 R01=00000000 R02=00000000 R03=0001008c
R04=00000000 R05=00000000 R06=00000000 R07=00000000
R08=00000000 R09=00000000 R10=00000000 R11=00011094
R12=00000000 R13=00011088 R14=00010008 R15=00010074
PSR=400001d3 -Z-- A svc32
----------------
IN: kmain
0x00010078: e51b0008 ldr r0, [fp, #-8]
R00=00000000 R01=00000000 R02=00000000 R03=0001008c
R04=00000000 R05=00000000 R06=00000000 R07=00000000
R08=00000000 R09=00000000 R10=00000000 R11=00011094
R12=00000000 R13=00011088 R14=00010008 R15=00010078
PSR=400001d3 -Z-- A svc32
----------------
IN: kmain
0x0001007c: ebffffe3 bl 0x10010
R00=0001008c R01=00000000 R02=00000000 R03=0001008c
R04=00000000 R05=00000000 R06=00000000 R07=00000000
R08=00000000 R09=00000000 R10=00000000 R11=00011094
R12=00000000 R13=00011088 R14=00010008 R15=0001007c
PSR=400001d3 -Z-- A svc32
----------------
The command line to use was:
qemu-system-arm -M vexpress-a9 -cpu cortex-a9 -smp 1 -m 64M -nographic
-kernel kernel.elf -singlestep -D file.log -d in_asm,cpu
The kernel.elf is a simple program (elf) file, created from two
sources:
boot.S:
.global _RESET
_RESET:
LDR sp, =_STACK
BL kmain
B .
And kernel.c:
# define UART0_MEM 0x10009000
volatile unsigned int * const UART0 = (unsigned int *) UART0_MEM;
void dprint(const char* message){
while(*message != 0) {
*UART0=*message;
++message;
}
}
void kmain() {
const char *hi="Hello!";
dprint(hi);
};
The linker scripts is:
ENTRY(_RESET)
SECTIONS
{
. = 0x10000;
.boot . : { boot.o(.text) }
.text : { *(.text) }
.data : { *(.data) }
.bss : { *(.bss COMMON) }
. = ALIGN(8);
. = . + 0x1000; /* 4kB of stack memory */
_STACK = .;
}
This error cases the dprint function to find *message as 0 and do not
print the output in newer QEMU software.
Thank you for consideration.
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