----- Original Message -----
> Since Xen commit 666aca08175b ("sched: use the auto-generated list of
> schedulers") crash cannot open Xen vmcores, because symbol 'schedulers'
> does not exits. Xen 4.7 implemented schedulers as its own section.
>
> xen/arch/x86/xen.lds.S
> __start_schedulers_array = .;
> *(.data.schedulers)
> __end_schedulers_array = .;
>
> Crash must not look up for "schedulers" symbol and fails, if symbol is
> not found. It must check if __start_schedulers_array exits, and if it
> does, use it and get size of the section. Otherwise, crash fallback to
> looking up "schedulers" symbol. That way, crash can open vmcore before
> and after Xen 4.7.
>
> Signed-off-by: Nikola Pajkovsky <npajkovsky@xxxxxxx>
Hi Nikola,
I'm not at at familiar with this code, but xen_hyper_schedule_init() declares
scheduler_buf[] with a fixed size of XEN_HYPER_SCHEDULERS_ARRAY_CNT (10):
long schedulers_buf[XEN_HYPER_SCHEDULERS_ARRAY_CNT];
If the new __start_schedulers_array size (and therefore xen_hyper_nr_schedulers)
could ever exceed 10, then there would be a buffer overflow when the buffer
is filled. So probably it would be best to dynamically allocate the buffer
with GETBUF/FREEBUF, or at least limit it to 10? Maybe 10 was picked as an
absurdly large number that will never be reached?
Dave
> ---
> xen_hyper.c | 40 +++++++++++++++++++++++++++++++++-------
> 1 file changed, 33 insertions(+), 7 deletions(-)
>
> diff --git a/xen_hyper.c b/xen_hyper.c
> index 27e44c6e733d..e8268cf40c78 100644
> --- a/xen_hyper.c
> +++ b/xen_hyper.c
> @@ -438,6 +438,19 @@ xen_hyper_misc_init(void)
> #define XEN_HYPER_SCHEDULERS_ARRAY_CNT 10
> #define XEN_HYPER_SCHEDULER_NAME 1024
>
> +/*
> + * does similar function exits in crash??
> + */
> +static int section_size(char *start_section, char *end_section)
> +{
> + ulong sp_start, sp_end;
> +
> + sp_start = symbol_value(start_section);
> + sp_end = symbol_value(end_section);
> +
> + return (sp_end - sp_start) / sizeof(size_t);
> +}
> +
> static void
> xen_hyper_schedule_init(void)
> {
> @@ -448,6 +461,8 @@ xen_hyper_schedule_init(void)
> char *buf;
> char opt_name_buf[XEN_HYPER_OPT_SCHED_SIZE];
> int i, cpuid, flag;
> + char *sp_name;
> + int xen_hyper_nr_schedulers;
>
> /* get scheduler information */
> if((xhscht->scheduler_struct =
> @@ -469,21 +484,32 @@ xen_hyper_schedule_init(void)
> XEN_HYPER_OPT_SCHED_SIZE, "opt_sched,", RETURN_ON_ERROR)) {
> error(FATAL, "cannot read opt_sched,.\n");
> }
> - schedulers = symbol_value("schedulers");
> +
> + if (symbol_exists("__start_schedulers_array")) {
> + sp_name = "__start_schedulers_array";
> + xen_hyper_nr_schedulers = section_size("__start_schedulers_array",
> + "__end_schedulers_array");
> + } else {
> + sp_name = "schedulers";
> + xen_hyper_nr_schedulers = XEN_HYPER_SCHEDULERS_ARRAY_CNT;
> + }
> +
> + schedulers = symbol_value(sp_name);
> +
> addr = schedulers;
> while (xhscht->name == NULL) {
> if (!readmem(addr, KVADDR, schedulers_buf,
> - sizeof(long) * XEN_HYPER_SCHEDULERS_ARRAY_CNT,
> - "schedulers", RETURN_ON_ERROR)) {
> + sizeof(long) * xen_hyper_nr_schedulers,
> + sp_name, RETURN_ON_ERROR)) {
> error(FATAL, "cannot read schedulers.\n");
> }
> - for (i = 0; i < XEN_HYPER_SCHEDULERS_ARRAY_CNT; i++) {
> + for (i = 0; i < xen_hyper_nr_schedulers; i++) {
> if (schedulers_buf[i] == 0) {
> error(FATAL, "schedule data not found.\n");
> }
> if (!readmem(schedulers_buf[i], KVADDR,
> - xhscht->scheduler_struct, XEN_HYPER_SIZE(scheduler),
> - "scheduler", RETURN_ON_ERROR)) {
> + xhscht->scheduler_struct, XEN_HYPER_SIZE(scheduler),
> + "scheduler", RETURN_ON_ERROR)) {
> error(FATAL, "cannot read scheduler.\n");
> }
> opt_name = ULONG(xhscht->scheduler_struct +
> @@ -514,7 +540,7 @@ xen_hyper_schedule_init(void)
> strncpy(xhscht->name, buf, strlen(buf));
> break;
> }
> - addr += sizeof(long) * XEN_HYPER_SCHEDULERS_ARRAY_CNT;
> + addr += sizeof(long) * xen_hyper_nr_schedulers;
> }
> FREEBUF(buf);
>
> --
> 2.13.6
>
> --
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