----- Original Message -----
> Implemented support for 16k stack size that was introduced by commit
> 6538b8ea886e472f4431db8ca1d60478f838d14b titled "x86_64: expand kernel
> stack to 16K".
> Without the patch, kernels has 16k stack, leading to errors in commands
> such as "bt" and any command regarding 8K stack.
> Add a new "--machdep stacksize=<value>" option that can be used to
> override the default machdep->stacksize value which is 8k.
The x86_64 default value of 8K is basically a leftover value that each of
the architectures originally used for setting machdep->stacksize. But for
quite some time now, those values should get overridden later on here
in task_init():
STRUCT_SIZE_INIT(task_union, "task_union");
STRUCT_SIZE_INIT(thread_union, "thread_union");
if (VALID_SIZE(task_union) && (SIZE(task_union) != STACKSIZE())) {
error(WARNING, "\nnon-standard stack size: %ld\n",
len = SIZE(task_union));
machdep->stacksize = len;
} else if (VALID_SIZE(thread_union) &&
((len = SIZE(thread_union)) != STACKSIZE())) {
machdep->stacksize = len;
} else if (!VALID_SIZE(thread_union) && !VALID_SIZE(task_union)) {
if (kernel_symbol_exists("__start_init_task") &&
kernel_symbol_exists("__end_init_task")) {
len = symbol_value("__end_init_task");
len -= symbol_value("__start_init_task");
ASSIGN_SIZE(thread_union) = len;
machdep->stacksize = len;
}
}
As of Linux 4.18 at least, x86_64 still uses the thread_union declaration.
For example:
crash> thread_union
union thread_union {
struct task_struct task;
unsigned long stack[2048];
}
SIZE: 16384
crash>
On what kernel version are you seeing the obsolete 8k stacksize being used?
What does the command above show on your system?
Thanks,
Dave
>
> Signed-off-by: Sean Fu <fxinrong@xxxxxxxxx>
> ---
> x86_64.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/x86_64.c b/x86_64.c
> index 7d01140..1798f05 100644
> --- a/x86_64.c
> +++ b/x86_64.c
> @@ -5716,6 +5716,15 @@ parse_cmdline_args(void)
> continue;
> }
> }
> + } else if (STRNEQ(arglist[i], "stacksize=")) {
> + p = arglist[i] + strlen("stacksize=");
> + if (strlen(p)) {
> + value = stol(p, RETURN_ON_ERROR|QUIET, &errflag);
> + if (!errflag) {
> + machdep->stacksize = value;
> + continue;
> + }
> + }
> }
>
> error(WARNING, "ignoring --machdep option: %s\n", arglist[i]);
> --
> 2.6.2
>
>
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