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[Qemu-devel] [Bug 657006] Re: arm v7M - svc insn doesn't trigger PendSV
From: |
Mark Phillips |
Subject: |
[Qemu-devel] [Bug 657006] Re: arm v7M - svc insn doesn't trigger PendSV handler |
Date: |
Wed, 22 Aug 2012 16:47:35 -0000 |
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
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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)
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- [Qemu-devel] [Bug 657006] Re: arm v7M - svc insn doesn't trigger PendSV handler, Mark Phillips, 2012/08/20
- [Qemu-devel] [Bug 657006] Re: arm v7M - svc insn doesn't trigger PendSV handler, Mark Phillips, 2012/08/22
- [Qemu-devel] [Bug 657006] Re: arm v7M - svc insn doesn't trigger PendSV handler, Mark Phillips, 2012/08/22
- [Qemu-devel] [Bug 657006] Re: arm v7M - svc insn doesn't trigger PendSV handler, Peter Maydell, 2012/08/22
- [Qemu-devel] [Bug 657006] Re: arm v7M - svc insn doesn't trigger PendSV handler, Mark Phillips, 2012/08/22
- [Qemu-devel] [Bug 657006] Re: arm v7M - svc insn doesn't trigger PendSV handler, Mark Phillips, 2012/08/22
- [Qemu-devel] [Bug 657006] Re: arm v7M - svc insn doesn't trigger PendSV handler,
Mark Phillips <=