Re: [Xen-devel] [PATCH RFC 6/6] xen: Add backtrace for serious issues.

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Mon, 29 Jun 2015, Konrad Rzeszutek Wilk wrote:
> When debugging issues that caused the emulator to kill itself
> or skipping certain operations (unable to write to host
> registers) an stack trace will most definitly aid in debugging
> the problem.
> 
> As such this patch uses the most basic backtrace to print out
> details.
> 
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>

I think it could be useful, but it cannot be done as a xen-hvm.c thing.
It should be somewhere generic, maybe under util? Stefan, any
suggestions?


>  hw/xen/xen_pt.c             |  3 +++
>  include/hw/xen/xen_common.h |  1 +
>  xen-hvm.c                   | 16 ++++++++++++++++
>  3 files changed, 20 insertions(+)
> 
> diff --git a/hw/xen/xen_pt.c b/hw/xen/xen_pt.c
> index ea1ceda..1d256b9 100644
> --- a/hw/xen/xen_pt.c
> +++ b/hw/xen/xen_pt.c
> @@ -407,6 +407,7 @@ out:
>  
>          if (rc < 0) {
>              XEN_PT_ERR(d, "xen_host_pci_set_block failed. return value: 
> %d.\n", rc);
> +            xen_dump_stack();
>          }
>      }
>  }
> @@ -421,6 +422,7 @@ static uint64_t xen_pt_bar_read(void *o, hwaddr addr,
>       * misconfiguration of the IOMMU. */
>      XEN_PT_ERR(d, "Should not read BAR through QEMU. @0x"TARGET_FMT_plx"\n",
>                 addr);
> +    xen_dump_stack();
>      return 0;
>  }
>  static void xen_pt_bar_write(void *o, hwaddr addr, uint64_t val,
> @@ -430,6 +432,7 @@ static void xen_pt_bar_write(void *o, hwaddr addr, 
> uint64_t val,
>      /* Same comment as xen_pt_bar_read function */
>      XEN_PT_ERR(d, "Should not write BAR through QEMU. @0x"TARGET_FMT_plx"\n",
>                 addr);
> +    xen_dump_stack();
>  }
>  
>  static const MemoryRegionOps ops = {
> diff --git a/include/hw/xen/xen_common.h b/include/hw/xen/xen_common.h
> index 38f29fb..3983cfb 100644
> --- a/include/hw/xen/xen_common.h
> +++ b/include/hw/xen/xen_common.h
> @@ -165,6 +165,7 @@ void destroy_hvm_domain(bool reboot);
>  
>  /* shutdown/destroy current domain because of an error */
>  void xen_shutdown_fatal_error(const char *fmt, ...) GCC_FMT_ATTR(1, 2);
> +void xen_dump_stack(void);
>  
>  #ifdef HVM_PARAM_VMPORT_REGS_PFN
>  static inline int xen_get_vmport_regs_pfn(XenXC xc, domid_t dom,
> diff --git a/xen-hvm.c b/xen-hvm.c
> index a92bc14..8bf4a57 100644
> --- a/xen-hvm.c
> +++ b/xen-hvm.c
> @@ -10,6 +10,7 @@
>  
>  #include <sys/mman.h>
>  
> +#include <execinfo.h>
>  #include "hw/pci/pci.h"
>  #include "hw/i386/pc.h"
>  #include "hw/xen/xen_common.h"
> @@ -1328,6 +1329,20 @@ void xen_register_framebuffer(MemoryRegion *mr)
>      framebuffer = mr;
>  }
>  
> +void xen_dump_stack(void)
> +{
> +    int nptrs;
> +#define SIZE 1024
> +    void *buffer[SIZE];
> +
> +    nptrs = backtrace(buffer, SIZE);
> +    if (!nptrs)
> +        return;
> +
> +    backtrace_symbols_fd(buffer, nptrs, STDERR_FILENO);
> +#undef SIZE
> +}
> +
>  void xen_shutdown_fatal_error(const char *fmt, ...)
>  {
>      va_list ap;
> @@ -1335,6 +1350,7 @@ void xen_shutdown_fatal_error(const char *fmt, ...)
>      va_start(ap, fmt);
>      vfprintf(stderr, fmt, ap);
>      va_end(ap);
> +    xen_dump_stack();
>      fprintf(stderr, "Will destroy the domain.\n");
>      /* destroy the domain */
>      qemu_system_shutdown_request();
> -- 
> 2.1.0
> 

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