[Qemu-devel] [Bug 657006] Re: arm v7M - svc insn doesn't trigger PendSV handler
OK, I'll re-read the documentation maybe I am wrong!
It does say synchronous in the description and I don't understand how it can
work if it is asynchronous because for Cortex the SVC argument is not
transfered to a register and the only way the exception code can access it is
by reading it from the opcode. If the exception is asynchonous the PC may have
moved on and the code won't be able to find the SVC opcode?!
--
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/657006
Title:
arm v7M - svc insn doesn't trigger PendSV handler
Status in QEMU:
New
Bug description:
The svc instruction doesn't work as expected.
- qemu 0.13.0 rc1 (git)
Test : demo with freeRTOS (for example
FreeRTOS-6.0.5/Demo/CORTEX_LM3S811_GCC) with the card lm3s811evb.
If we start the scheduler, it will call that function (__attribute__
(( naked ))) :
void vPortStartFirstTask( void )
{
__asm volatile(
ldr r0, =0xE000ED08 \n /*
Use the NVIC offset register to locate the stack. */
ldr r0, [r0]
\n
ldr r0, [r0]
\n
msr msp, r0
\n /* Set the msp back to the start of the stack. */
svc 0
\n /* System call to start first task. */
);
}
The 4 first lines in asm work fine. The scv 0 call will rise the right
interrupt in qemu (line 151, in arm_gic.c, best_irq = 15). However, it will
never call the PendSV Handler (xPortPendSVHandler here). This function is
recorded in the nvic vector.
Next, (after the svc), the processor will execute the line after in code
(this is a naked function) so the next function written after
vPortStartFirstTask in the code.
command line :
console 1 : qemu-system-arm -M lm3s6965evb -kernel gcc/RTOSDemo.axf -s -S
console 2 : arm-none-eabi-gdb -ex target remote localhost:1234
gcc/RTOSDemo.axf
arm-none-eabi from
http://www.codesourcery.com/sgpp/lite/arm/portal/release1294
Same error with another project with arm-elf
processor : arm cortex m3
host : gentoo (2.6.35-r9) (without kqemu)
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/657006/+subscriptions
[Qemu-devel] [Bug 657006] Re: arm v7M - svc insn doesn't trigger PendSV handler
In particular table 2-16 of DUI0552A_Cortex_m3_dgug.pdf states that the
Activation of the SVC exception is Synchronous.
And after the table it states For an asynchronous exception, other than reset,
the processor can execute another instruction
between when the exception is triggered and when the processor enters the
exception handler. which sort of implies that for a Synchronous exception
another opcode can not be executed before the exception?!
--
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/657006
Title:
arm v7M - svc insn doesn't trigger PendSV handler
Status in QEMU:
New
Bug description:
The svc instruction doesn't work as expected.
- qemu 0.13.0 rc1 (git)
Test : demo with freeRTOS (for example
FreeRTOS-6.0.5/Demo/CORTEX_LM3S811_GCC) with the card lm3s811evb.
If we start the scheduler, it will call that function (__attribute__
(( naked ))) :
void vPortStartFirstTask( void )
{
__asm volatile(
ldr r0, =0xE000ED08 \n /*
Use the NVIC offset register to locate the stack. */
ldr r0, [r0]
\n
ldr r0, [r0]
\n
msr msp, r0
\n /* Set the msp back to the start of the stack. */
svc 0
\n /* System call to start first task. */
);
}
The 4 first lines in asm work fine. The scv 0 call will rise the right
interrupt in qemu (line 151, in arm_gic.c, best_irq = 15). However, it will
never call the PendSV Handler (xPortPendSVHandler here). This function is
recorded in the nvic vector.
Next, (after the svc), the processor will execute the line after in code
(this is a naked function) so the next function written after
vPortStartFirstTask in the code.
command line :
console 1 : qemu-system-arm -M lm3s6965evb -kernel gcc/RTOSDemo.axf -s -S
console 2 : arm-none-eabi-gdb -ex target remote localhost:1234
gcc/RTOSDemo.axf
arm-none-eabi from
http://www.codesourcery.com/sgpp/lite/arm/portal/release1294
Same error with another project with arm-elf
processor : arm cortex m3
host : gentoo (2.6.35-r9) (without kqemu)
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/657006/+subscriptions
[Qemu-devel] [Bug 657006] Re: arm v7M - svc insn doesn't trigger PendSV handler
ok, I'll double check that backing out the local patches doesn't make a
difference. If it still happens I will try and come up with a reduced
test case.
What do you expect to happen?
Should the SVC exception 11 run immediately?
What should happen if a clock tick interrupt is also pending at level 15 with a
higher (numerically lower) priority?
What I currently see happening is neither interrupts happen immediately, the
code continues to execute. Then one or more clock tick interrupts occur, before
finally I see the SVC interrupt code running.
Cheers
Mark
--
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/657006
Title:
arm v7M - svc insn doesn't trigger PendSV handler
Status in QEMU:
New
Bug description:
The svc instruction doesn't work as expected.
- qemu 0.13.0 rc1 (git)
Test : demo with freeRTOS (for example
FreeRTOS-6.0.5/Demo/CORTEX_LM3S811_GCC) with the card lm3s811evb.
If we start the scheduler, it will call that function (__attribute__
(( naked ))) :
void vPortStartFirstTask( void )
{
__asm volatile(
ldr r0, =0xE000ED08 \n /*
Use the NVIC offset register to locate the stack. */
ldr r0, [r0]
\n
ldr r0, [r0]
\n
msr msp, r0
\n /* Set the msp back to the start of the stack. */
svc 0
\n /* System call to start first task. */
);
}
The 4 first lines in asm work fine. The scv 0 call will rise the right
interrupt in qemu (line 151, in arm_gic.c, best_irq = 15). However, it will
never call the PendSV Handler (xPortPendSVHandler here). This function is
recorded in the nvic vector.
Next, (after the svc), the processor will execute the line after in code
(this is a naked function) so the next function written after
vPortStartFirstTask in the code.
command line :
console 1 : qemu-system-arm -M lm3s6965evb -kernel gcc/RTOSDemo.axf -s -S
console 2 : arm-none-eabi-gdb -ex target remote localhost:1234
gcc/RTOSDemo.axf
arm-none-eabi from
http://www.codesourcery.com/sgpp/lite/arm/portal/release1294
Same error with another project with arm-elf
processor : arm cortex m3
host : gentoo (2.6.35-r9) (without kqemu)
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/657006/+subscriptions
[Qemu-devel] [Bug 657006] Re: arm v7M - svc insn doesn't trigger PendSV handler
I have put together a test program and tried against a vanila copy of
qemu 1.1.1
The SVC wil be completely masked unless I apply patch 0002-target-arm-
Disable-priority_mask-feature.patch, which hacks arm_gic.c to initialise
the gic priority_mask to 0x100 instead of 0xf0. There doesn't appear to
be anyway to write to the gix priority_mask from arm code - maybe it
should be linked to the ARM Cortex BASEPRI?
Anyway the test code indicates execution does continue after the SVC
call before the exception is handled.
Where would you like me to upload/send the test code?
Cheers
Mark
--
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/657006
Title:
arm v7M - svc insn doesn't trigger PendSV handler
Status in QEMU:
New
Bug description:
The svc instruction doesn't work as expected.
- qemu 0.13.0 rc1 (git)
Test : demo with freeRTOS (for example
FreeRTOS-6.0.5/Demo/CORTEX_LM3S811_GCC) with the card lm3s811evb.
If we start the scheduler, it will call that function (__attribute__
(( naked ))) :
void vPortStartFirstTask( void )
{
__asm volatile(
ldr r0, =0xE000ED08 \n /*
Use the NVIC offset register to locate the stack. */
ldr r0, [r0]
\n
ldr r0, [r0]
\n
msr msp, r0
\n /* Set the msp back to the start of the stack. */
svc 0
\n /* System call to start first task. */
);
}
The 4 first lines in asm work fine. The scv 0 call will rise the right
interrupt in qemu (line 151, in arm_gic.c, best_irq = 15). However, it will
never call the PendSV Handler (xPortPendSVHandler here). This function is
recorded in the nvic vector.
Next, (after the svc), the processor will execute the line after in code
(this is a naked function) so the next function written after
vPortStartFirstTask in the code.
command line :
console 1 : qemu-system-arm -M lm3s6965evb -kernel gcc/RTOSDemo.axf -s -S
console 2 : arm-none-eabi-gdb -ex target remote localhost:1234
gcc/RTOSDemo.axf
arm-none-eabi from
http://www.codesourcery.com/sgpp/lite/arm/portal/release1294
Same error with another project with arm-elf
processor : arm cortex m3
host : gentoo (2.6.35-r9) (without kqemu)
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/657006/+subscriptions
[Qemu-devel] [Bug 657006] Re: arm v7M - svc insn doesn't trigger PendSV handler
I've made an interesting discovery:-
If I instrument the code to record the sequence of code/exceptions and
get a different, and apparently correct result!
If I single step by starting the simulator with the following command
line qemu-system-arm -M lm3s6965evb -cpu cortex-m3 -kernel hack.bin
-nographic -serial /dev/null -s -S then connecting gdb and using stepi
I get very different behaviour.
It is beginning look like the buig may actually be that whilst using stepi to
advance the code somehow all exceptions are blocked!
If you just let the code free-run exceptions appear to happen.
Cheers
Mark
--
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/657006
Title:
arm v7M - svc insn doesn't trigger PendSV handler
Status in QEMU:
New
Bug description:
The svc instruction doesn't work as expected.
- qemu 0.13.0 rc1 (git)
Test : demo with freeRTOS (for example
FreeRTOS-6.0.5/Demo/CORTEX_LM3S811_GCC) with the card lm3s811evb.
If we start the scheduler, it will call that function (__attribute__
(( naked ))) :
void vPortStartFirstTask( void )
{
__asm volatile(
ldr r0, =0xE000ED08 \n /*
Use the NVIC offset register to locate the stack. */
ldr r0, [r0]
\n
ldr r0, [r0]
\n
msr msp, r0
\n /* Set the msp back to the start of the stack. */
svc 0
\n /* System call to start first task. */
);
}
The 4 first lines in asm work fine. The scv 0 call will rise the right
interrupt in qemu (line 151, in arm_gic.c, best_irq = 15). However, it will
never call the PendSV Handler (xPortPendSVHandler here). This function is
recorded in the nvic vector.
Next, (after the svc), the processor will execute the line after in code
(this is a naked function) so the next function written after
vPortStartFirstTask in the code.
command line :
console 1 : qemu-system-arm -M lm3s6965evb -kernel gcc/RTOSDemo.axf -s -S
console 2 : arm-none-eabi-gdb -ex target remote localhost:1234
gcc/RTOSDemo.axf
arm-none-eabi from
http://www.codesourcery.com/sgpp/lite/arm/portal/release1294
Same error with another project with arm-elf
processor : arm cortex m3
host : gentoo (2.6.35-r9) (without kqemu)
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/657006/+subscriptions
[Qemu-devel] [Bug 657006] Re: arm v7M - svc insn doesn't trigger PendSV handler
I have been experimenting with Sebastian's patches mentioned earlier
(http://git.rtems.org/rtems/tree/c/src/lib/libbsp/arm/lm3s69xx?id=e1ebfebf1bffe3e7731ac529409bd2576285467b)
and think I have found another major issue:-(
My reading of the ARM documentation is that the SVC opcode should perform a
synchronous exception.
It doesn't, the calling code continues to execute asynchronously.
This means that
1) When the execption handler runs, it will not be able to find the SVC
argument (because the PC in the execption frame will not allow it to locate the
SVC call
2) Code will be incorrectly executed. For example code after an OS suspend call
will be executed before the thread is suspended and resumed
Cheers
Mark
--
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/657006
Title:
arm v7M - svc insn doesn't trigger PendSV handler
Status in QEMU:
New
Bug description:
The svc instruction doesn't work as expected.
- qemu 0.13.0 rc1 (git)
Test : demo with freeRTOS (for example
FreeRTOS-6.0.5/Demo/CORTEX_LM3S811_GCC) with the card lm3s811evb.
If we start the scheduler, it will call that function (__attribute__
(( naked ))) :
void vPortStartFirstTask( void )
{
__asm volatile(
ldr r0, =0xE000ED08 \n /*
Use the NVIC offset register to locate the stack. */
ldr r0, [r0]
\n
ldr r0, [r0]
\n
msr msp, r0
\n /* Set the msp back to the start of the stack. */
svc 0
\n /* System call to start first task. */
);
}
The 4 first lines in asm work fine. The scv 0 call will rise the right
interrupt in qemu (line 151, in arm_gic.c, best_irq = 15). However, it will
never call the PendSV Handler (xPortPendSVHandler here). This function is
recorded in the nvic vector.
Next, (after the svc), the processor will execute the line after in code
(this is a naked function) so the next function written after
vPortStartFirstTask in the code.
command line :
console 1 : qemu-system-arm -M lm3s6965evb -kernel gcc/RTOSDemo.axf -s -S
console 2 : arm-none-eabi-gdb -ex target remote localhost:1234
gcc/RTOSDemo.axf
arm-none-eabi from
http://www.codesourcery.com/sgpp/lite/arm/portal/release1294
Same error with another project with arm-elf
processor : arm cortex m3
host : gentoo (2.6.35-r9) (without kqemu)
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/657006/+subscriptions
