[Crash-utility] [PATCH] Using crash with newer xen versions fails

[Dave Anderson]

Hi Dietmar,

Your patches are queued for crash-7.2.6:

  https://github.com/crash-utility/crash/commit/c6f0db666191df2342f536945f89cfcad88d265a

Thanks,
  Dave

----- Original Message -----
> Hi Dave,
> 
> when trying to debug the xen hypervisor on a vmcore file it doesn't work for me.
> xen_version: 4.11.0_08-1
> 
> ...
> This GDB was configured as "x86_64-unknown-linux-gnu"...
> 
> crash: invalid kernel virtual address: bf45ffa0001ef8  type: "fill_pcpu_struct"
> WARNING: cannot fill pcpu_struct.
> 
> crash: cannot read cpu_info.
> 
> I had a look at this and found a change in the struct tss_struct when trying
> to read the rsp0. The change in the xen-git-tree was done with commit 98dffb05ce4.
> Old:
> struct tss_struct {
>     unsigned short      back_link,__blh;
>     union { u64 rsp0, esp0; };
>     ...
> New:
> struct __packed __cacheline_aligned tss_struct {
>     uint32_t :32;
>     uint64_t rsp0, rsp1, rsp2;
> 
> After fixing this in the crash command I got:
> ...
> This GDB was configured as "x86_64-unknown-linux-gnu"...
> 
>    KERNEL: xen-syms
>  DUMPFILE: vmcore
>      CPUS: 4
>   DOMAINS: 3
>    UPTIME: --:--:--
>   MACHINE: Intel(R) Xeon(R) CPU           E5520  @ 2.27GHz  (2266 Mhz)
>    MEMORY: 12 GB
> Segmentation fault (core dumped)
> 
> It seems that the commit 4e1dca21 in xen_hyper.c isn't sufficient
> anymore.
> Because reading the symbol "dom0" is successful but the address is zero.
> My suggestion now is simply to switch the if statement.
> First ask for the symbol "hardware_domain" (introduced in xen version 4.5.0)
> and if it isn't found use the symbol "dom0".
> 
> This works for me with vmcore's with xen-4.4.4.
> 
> Dietmar.
> 
> ---
> 
>  x86_64.c    | 6 +++++-
>  xen_hyper.c | 8 ++++----
>  2 files changed, 9 insertions(+), 5 deletions(-)
> 
> diff --git a/x86_64.c b/x86_64.c
> index 0f6c584..26eb286 100644
> --- a/x86_64.c
> +++ b/x86_64.c
> @@ -7903,7 +7903,11 @@ x86_64_init_hyper(int when)
>  	case POST_GDB:
>  		XEN_HYPER_STRUCT_SIZE_INIT(cpuinfo_x86, "cpuinfo_x86");
>  		XEN_HYPER_STRUCT_SIZE_INIT(tss_struct, "tss_struct");
> -		XEN_HYPER_ASSIGN_OFFSET(tss_struct_rsp0) = MEMBER_OFFSET("tss_struct",
> "__blh") + sizeof(short unsigned int);
> +		if (MEMBER_EXISTS("tss_struct", "__blh")) {
> +			XEN_HYPER_ASSIGN_OFFSET(tss_struct_rsp0) = MEMBER_OFFSET("tss_struct",
> "__blh") + sizeof(short unsigned int);
> +		} else {
> +			XEN_HYPER_ASSIGN_OFFSET(tss_struct_rsp0) = MEMBER_OFFSET("tss_struct",
> "rsp0");
> +		}
>  		XEN_HYPER_MEMBER_OFFSET_INIT(tss_struct_ist, "tss_struct", "ist");
>  		if (symbol_exists("cpu_data")) {
>  			xht->cpu_data_address = symbol_value("cpu_data");
> diff --git a/xen_hyper.c b/xen_hyper.c
> index 20072e9..f2f00e6 100644
> --- a/xen_hyper.c
> +++ b/xen_hyper.c
> @@ -1060,8 +1060,8 @@ xen_hyper_get_domains(void)
>  	long domain_next_in_list;
>  	int i, j;
>  
> -	if (!try_get_symbol_data("dom0", sizeof(void *), &domain))
> -		get_symbol_data("hardware_domain", sizeof(void *), &domain);
> +	if (!try_get_symbol_data("hardware_domain", sizeof(void *), &domain))
> +		get_symbol_data("dom0", sizeof(void *), &domain);
>  
>  	domain_next_in_list = MEMBER_OFFSET("domain", "next_in_list");
>  	i = 0;
> @@ -1103,8 +1103,8 @@ xen_hyper_get_domain_next(int mod, ulong *next)
>  		if (xhdt->dom0) {
>  			*next = xhdt->dom0->domain;
>  		} else {
> -			if (!try_get_symbol_data("dom0", sizeof(void *), next))
> -				get_symbol_data("hardware_domain", sizeof(void *), next);
> +			if (!try_get_symbol_data("hardware_domain", sizeof(void *), next))
> +				get_symbol_data("dom0", sizeof(void *), next);
>  		}
>  		return xhdt->domain_struct;
>  		break;
> --
> 2.12.3
> 
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