Re: [Qemu-devel] [PATCH 2/2] ppc: Add dump-stack implementation

[Markus Armbruster <armbru@redhat.com>]

Suraj Jitindar Singh <sjitindarsingh@gmail.com> writes:

> The monitor function dump-stack is used to dump the stack for a cpu.
> This can be useful for debugging purposes when the stack cannot be
> dumped by another means.
>
> Add a ppc implementation ppc_cpu_dump_stack().
> The stack pointer is stored in R1 with the back pointer at offset 0 and
> the link register at offset 2.
> Also dump the registers from the stack frame if the marker "regshere" is
> found.
> This only dumps the kernel stack, stopping if a non-kernel address is
> found in the stack.
>
> Sample output:
> (qemu) dump-stack
> sp: 0xc00000007bfc5690 lr: 0xc0000000000974b8
> sp: 0xc00000007bfc56f0 lr: 0xc00000000065aab4
> sp: 0xc00000007bfc5720 lr: 0xc00000000065ab04
> sp: 0xc00000007bfc5740 lr: 0xc0000000000c29b8
> sp: 0xc00000007bfc57b0 lr: 0xc0000000000bc9e8
> sp: 0xc00000007bfc57e0 lr: 0xc0000000000bd584
> sp: 0xc00000007bfc5800 lr: 0xc0000000000bee14
> sp: 0xc00000007bfc5ac0 lr: 0xc0000000000c2100
> sp: 0xc00000007bfc5c60 lr: 0xc000000000029460
> sp: 0xc00000007bfc5ca0 lr: 0xc00000000010b5e8
> sp: 0xc00000007bfc5d00 lr: 0xc000000000105f34
> 	trap : 0x0000000000000700
> 	pc   : 0xc000000000104490
> 	msr  : 0x9000000002843003
> 	lr   : 0xc000000000103ffc
> 	gpr 0: 0x0000000000000001
> 	gpr 1: 0xc00000005051f530
> 	gpr 2: 0xc000000001088200
> 	gpr 3: 0x0000000000000001
> 	gpr 4: 0xc000000032d60000
> 	gpr 5: 0xc0000000014b8f00
> 	gpr 6: 0x0000000000c835e0
> 	gpr 7: 0x0000000000000000
> 	gpr 8: 0x0000000000000000
> 	gpr 9: 0xc000000032f00000
> 	gpr10: 0x9000000002803033
> 	gpr11: 0xc000000000b60f00
> 	gpr12: 0x0000000000002000
> 	gpr13: 0xc000000001250000
> 	gpr14: 0x0000000000000000
> 	gpr15: 0x0000000000000008
> 	gpr16: 0x0000000000000000
> 	gpr17: 0xc00000000114f790
> 	gpr18: 0x00000000ffffffff
> 	gpr19: 0xc00000005051f8e8
> 	gpr20: 0x0000000000000001
> 	gpr21: 0x0000000000000000
> 	gpr22: 0x0000000000000001
> 	gpr23: 0x0000000000000001
> 	gpr24: 0x0000000000000001
> 	gpr25: 0xc0000000014b8f70
> 	gpr26: 0x0000000000000000
> 	gpr27: 0x0000000000000001
> 	gpr28: 0x0000000000000001
> 	gpr29: 0x0000000000000000
> 	gpr30: 0xc0000000014b8f00
> 	gpr31: 0xc0000000014b8f00
> sp: 0xc00000005051f530 lr: 0x0000000000000000
> sp: 0xc00000005051f600 lr: 0xc000000000103ffc
> sp: 0xc00000005051f670 lr: 0xc0000000000f60a8
> sp: 0xc00000005051f850 lr: 0xc0000000000f18c0
> sp: 0xc00000005051fa10 lr: 0xc0000000000f5184
> sp: 0xc00000005051fae0 lr: 0xc0000000000ddf54
> sp: 0xc00000005051fb00 lr: 0xc0000000000dab9c
> sp: 0xc00000005051fb90 lr: 0xc0000000000cbf88
> sp: 0xc00000005051fd00 lr: 0xc0000000003e7480
> sp: 0xc00000005051fdb0 lr: 0xc0000000003e7ce4
> sp: 0xc00000005051fe00 lr: 0xc0000000003e7d88
> sp: 0xc00000005051fe20 lr: 0xc00000000000b3a4
> 	trap : 0x0000000000000c01
> 	pc   : 0x00007fffa6c9d8d0
> 	msr  : 0x900000000280f033
> 	lr   : 0x0000000010090f40
> 	gpr 0: 0x0000000000000036
> 	gpr 1: 0x00007fffa62fdd70
> 	gpr 2: 0x00007fffa6d57300
> 	gpr 3: 0x000000000000000d
> 	gpr 4: 0x000000002000ae80
> 	gpr 5: 0x0000000000000000
> 	gpr 6: 0x0000000000000537
> 	gpr 7: 0x0000000000000000
> 	gpr 8: 0x000000000000000d
> 	gpr 9: 0x0000000000000000
> 	gpr10: 0x0000000000000000
> 	gpr11: 0x0000000000000000
> 	gpr12: 0x0000000000000000
> 	gpr13: 0x00007fffa6306380
> 	gpr14: 0x0000000000000000
> 	gpr15: 0x0000000000000001
> 	gpr16: 0x0000000039ba6928
> 	gpr17: 0x0000000000000000
> 	gpr18: 0x0000000000000000
> 	gpr19: 0x00007fffa6d702f0
> 	gpr20: 0x00007fffa62fddf0
> 	gpr21: 0x0000000000000080
> 	gpr22: 0x0000000000000004
> 	gpr23: 0x0000000000000000
> 	gpr24: 0x0000000010ac85c0
> 	gpr25: 0x0000000000000008
> 	gpr26: 0x00007fffa62fde10
> 	gpr27: 0x0000000000000000
> 	gpr28: 0x0000000000000002
> 	gpr29: 0x0000000000000000
> 	gpr30: 0x0000000039ba6900
> 	gpr31: 0x0000000010ac85c0
> sp: 0x00007fffa62fdd70
>
> Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
> ---
>  target/ppc/cpu.h                |  1 +
>  target/ppc/translate.c          | 60 +++++++++++++++++++++++++++++++++++++++++
>  target/ppc/translate_init.inc.c |  1 +
>  3 files changed, 62 insertions(+)

The diffstat doesn't look prohibitive.  However, I fear implementations
for more ornery targets such as x86 might take much more code.

>
> diff --git a/target/ppc/cpu.h b/target/ppc/cpu.h
> index 5e7cf54b2f..28c4dffca1 100644
> --- a/target/ppc/cpu.h
> +++ b/target/ppc/cpu.h
> @@ -1284,6 +1284,7 @@ struct PPCVirtualHypervisorClass {
>  void ppc_cpu_do_interrupt(CPUState *cpu);
>  bool ppc_cpu_exec_interrupt(CPUState *cpu, int int_req);
>  void ppc_cpu_dump_state(CPUState *cpu, FILE *f, int flags);
> +void ppc_cpu_dump_stack(CPUState *cpu, FILE *f);
>  void ppc_cpu_dump_statistics(CPUState *cpu, int flags);
>  hwaddr ppc_cpu_get_phys_page_debug(CPUState *cpu, vaddr addr);
>  int ppc_cpu_gdb_read_register(CPUState *cpu, uint8_t *buf, int reg);
> diff --git a/target/ppc/translate.c b/target/ppc/translate.c
> index 8d08625c33..b162998ce7 100644
> --- a/target/ppc/translate.c
> +++ b/target/ppc/translate.c
> @@ -7705,6 +7705,66 @@ void ppc_cpu_dump_state(CPUState *cs, FILE *f, int flags)
>  #undef RFPL
>  }
>  
> +struct ppc_pt_regs {
> +        unsigned long gpr[32];
> +        unsigned long nip;
> +        unsigned long msr;
> +        unsigned long orig_gpr3;
> +        unsigned long ctr;
> +        unsigned long link;
> +        unsigned long xer;
> +        unsigned long ccr;
> +        unsigned long softe;
> +        unsigned long trap;
> +        unsigned long dar;
> +        unsigned long dsisr;
> +        unsigned long result;
> +};
> +
> +void ppc_cpu_dump_stack(CPUState *cs, FILE *f)
> +{
> +#if defined(TARGET_PPC64)

Ignorant question: why do you need the #if here?

> +    PowerPCCPU *cpu = POWERPC_CPU(cs);
> +    CPUPPCState *env = &cpu->env;
> +    uint64_t sp, next_sp, lr, buf[4];
> +
> +    /* stack pointer stored in r1 */
> +    sp = env->gpr[1];
> +
> +    while (sp && (sp & (0xCUL << 60))) {
> +        uint64_t marker = 0UL;
> +
> +        /* read and print LR */
> +        cpu_physical_memory_read(sp & ~(0xCUL << 60), buf, sizeof(*buf) * 4);
> +        next_sp = buf[0];
> +        lr = buf[2];
> +        qemu_fprintf(f, "sp: 0x%.16lx lr: 0x%.16lx\n", sp, lr);
> +        sp &= ~(0xCUL << 60);
> +
> +        /* Does the stackframe contain regs? */
> +        cpu_physical_memory_read(sp + 96, &marker, sizeof(marker));
> +        if (marker == 0x7265677368657265) { /* regshere */
> +            struct ppc_pt_regs regs;
> +            int i;
> +
> +            cpu_physical_memory_read(sp + 112, &regs, sizeof(regs));
> +
> +            qemu_fprintf(f, "\ttrap : 0x%.16lx\n", regs.trap);
> +            qemu_fprintf(f, "\tpc   : 0x%.16lx\n", regs.nip);
> +            qemu_fprintf(f, "\tmsr  : 0x%.16lx\n", regs.msr);
> +            qemu_fprintf(f, "\tlr   : 0x%.16lx\n", regs.link);
> +            for (i = 0; i < 32; i++)
> +                qemu_fprintf(f, "\tgpr%2d: 0x%.16lx\n", i,
> +                            regs.gpr[i]);
> +        }
> +
> +        sp = next_sp;
> +    }
> +
> +    qemu_fprintf(f, "sp: 0x%.16lx\n", sp);
> +#endif
> +}
> +
>  void ppc_cpu_dump_statistics(CPUState *cs, int flags)
>  {
>  #if defined(DO_PPC_STATISTICS)
> diff --git a/target/ppc/translate_init.inc.c b/target/ppc/translate_init.inc.c
> index 0394a9ddad..3fd24f85cc 100644
> --- a/target/ppc/translate_init.inc.c
> +++ b/target/ppc/translate_init.inc.c
> @@ -10587,6 +10587,7 @@ static void ppc_cpu_class_init(ObjectClass *oc, void *data)
>      cc->do_interrupt = ppc_cpu_do_interrupt;
>      cc->cpu_exec_interrupt = ppc_cpu_exec_interrupt;
>      cc->dump_state = ppc_cpu_dump_state;
> +    cc->dump_stack = ppc_cpu_dump_stack;
>      cc->dump_statistics = ppc_cpu_dump_statistics;
>      cc->set_pc = ppc_cpu_set_pc;
>      cc->gdb_read_register = ppc_cpu_gdb_read_register;