[Qemu-discuss] Segmentation fault on target tricore

[Konopik, Andreas]

Hello,

I am wondering why the "Hello world"-program available in TASKING 
(v6.2r1) generates a segfault.

I compiled the program for the 'TC1796' Processor (Infineon TriCore 1 
Family -> AUDO NextGeneration Family).
QEMU was built with gcc 9.1.0 and I added a memory region, that was 
necessary [1].
Running QEMU with following options:
`./qemu/build/tricore-softmmu/qemu-system-tricore -nographic -M 
tricore_testboard -cpu tc1796 -kernel hello.elf`
led to a segfault in a short time


Using gdb and valgrind I found out that:
- 'gen_mtcr()' and 'gen_mfcr()' access uninitialized values, i.e. CSFRs, 
which leads to the Segfault
- The uninitialised values were created by stack allocation of 
DisasContext in 'gen_intermediate_code()'


The segfault does not occur when configuring QEMU with '--enable-debug' 
flag, so i suspect it might be a compiler error while building QEMU.
It did not come up before target/tricore implemented the 
DisasContextBase API (commit d013d220c710054a6d755941460f88c186fef7b5).

Does anybody else have this problem?


Regards,

Andreas



[1] Memory-layout addition (according to TASKING memory-layout):

> diff --git a/hw/tricore/tricore_testboard.c 
> b/hw/tricore/tricore_testboard.c
> index aef3289f8c..c287e0e7f5 100644
> --- a/hw/tricore/tricore_testboard.c
> +++ b/hw/tricore/tricore_testboard.c
> @@ -59,6 +59,7 @@ static void tricore_testboard_init(MachineState 
> *machine, int board_id)
>     CPUTriCoreState *env;
>
>     MemoryRegion *sysmem = get_system_memory();
> +    MemoryRegion *pflash = g_new(MemoryRegion, 1);
>     MemoryRegion *ext_cram = g_new(MemoryRegion, 1);
>     MemoryRegion *ext_dram = g_new(MemoryRegion, 1);
>     MemoryRegion *int_cram = g_new(MemoryRegion, 1);
> @@ -68,6 +69,8 @@ static void tricore_testboard_init(MachineState 
> *machine, int board_id)
>
>     cpu = TRICORE_CPU(cpu_create(machine->cpu_type));
>     env = &cpu->env;
> +    memory_region_init_ram(pflash, NULL, "pflash",
> +                           2 * MiB, &error_fatal);
>     memory_region_init_ram(ext_cram, NULL, "powerlink_ext_c.ram",
>                            2 * MiB, &error_fatal);
>     memory_region_init_ram(ext_dram, NULL, "powerlink_ext_d.ram",
> @@ -81,6 +84,7 @@ static void tricore_testboard_init(MachineState 
> *machine, int board_id)
>     memory_region_init_ram(pcp_text, NULL, "powerlink_pcp_text.ram",
>                            32 * KiB, &error_fatal);
>
> +    memory_region_add_subregion(sysmem, 0xa0000000, pflash);
>     memory_region_add_subregion(sysmem, 0x80000000, ext_cram);
>     memory_region_add_subregion(sysmem, 0xa1000000, ext_dram);
>     memory_region_add_subregion(sysmem, 0xd4000000, int_cram);