4:09 a.m.
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.
Signed-off-by: Sean Fu <fxinrong(a)gmail.com>
---
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
8:35 a.m.
Sean Fu wrote on Sat, Sep 29, 2018:
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.
Instead of making that an option it could be possible to autodetect this
by looking at __start_init_task / __end_init_task symbols, the
difference should be the proper size (the symbols have been around since
91ed140d6c1e168b11bbbddac4f6066f40a0c6b5 in 4.7 so that might not be old
enough for you though, as your commit dates 3.15 ; but there might be
other methods of getting stack size I haven't thought of, I only grepped
in a recent kernel)
--
Dominique Martinet
8:37 a.m.
----- 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(a)gmail.com>
---
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
1:59 a.m.
On Mon, Oct 01, 2018 at 09:37:10AM -0400, Dave Anderson wrote:
----- 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;
}
}
I compiled latest kernel and latest crash and run a qemu guest machine with the
latest compliled kernel
image.
In this case, STRUCT_SIZE_INIT initialized size_table.task_union and
size_table.thread_union with -1. So machdep->stacksize did NOT get
overridden.
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?
kernel version is upstream Linux
4.18 (commit#94710cac0ef4ee177a63b5227664b38c95bbf703)
(git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git).
"bt" command in crash shows "bt: invalid RSP: ffffc9000069bc08
bt->stackbase/stacktop: ffffc90000698000/ffffc9000069a000 cpu: 0".
BestRegards
Sean
Thanks,
Dave
>
> Signed-off-by: Sean Fu <fxinrong(a)gmail.com>
> ---
> 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
>
>
8:39 a.m.
----- Original Message -----
On Mon, Oct 01, 2018 at 09:37:10AM -0400, Dave Anderson wrote:
>
>
> ----- 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;
> }
> }
>
I compiled latest kernel and latest crash and run a qemu guest machine with
the latest compliled kernel
image.
In this case, STRUCT_SIZE_INIT initialized size_table.task_union and
size_table.thread_union with -1. So machdep->stacksize did NOT get
overridden.
> 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?
kernel version is upstream Linux 4.18
(commit#94710cac0ef4ee177a63b5227664b38c95bbf703)
(git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git).
"bt" command in crash shows "bt: invalid RSP: ffffc9000069bc08
bt->stackbase/stacktop: ffffc90000698000/ffffc9000069a000 cpu: 0".
BestRegards
Sean
Ok, the most recent 4.18 kernel I have on hand is this one:
crash> sys | grep RELEASE
RELEASE: 4.18.0-20.el8.x86_64
crash>
and its debuginfo data contains the "thread_union" information:
crash> thread_union
union thread_union {
struct task_struct task;
unsigned long stack[2048];
}
SIZE: 16384
crash>
but if it did not, then code should then calculate the stack
size from the difference between the "__start_init_task" and
"__end_init_task" symbols:
crash> sym __start_init_task
ffffffffa7800000 (D) __start_init_task
crash> sym __end_init_task
ffffffffa7804000 (D) __end_init_task
crash>
Does your kernel not show/contain those 2 symbols?
Dave
>
> Thanks,
> Dave
>
>
>
>
> >
> > Signed-off-by: Sean Fu <fxinrong(a)gmail.com>
> > ---
> > 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
> >
> >
11:03 p.m.
On Tue, Oct 09, 2018 at 09:39:10AM -0400, Dave Anderson wrote:
----- Original Message -----
> On Mon, Oct 01, 2018 at 09:37:10AM -0400, Dave Anderson wrote:
> >
> >
> > ----- 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;
> > }
> > }
> >
> I compiled latest kernel and latest crash and run a qemu guest machine with
> the latest compliled kernel
> image.
> In this case, STRUCT_SIZE_INIT initialized size_table.task_union and
> size_table.thread_union with -1. So machdep->stacksize did NOT get
> overridden.
> > 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?
> kernel version is upstream Linux 4.18
> (commit#94710cac0ef4ee177a63b5227664b38c95bbf703)
> (git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git).
>
> "bt" command in crash shows "bt: invalid RSP: ffffc9000069bc08
> bt->stackbase/stacktop: ffffc90000698000/ffffc9000069a000 cpu: 0".
>
> BestRegards
> Sean
Ok, the most recent 4.18 kernel I have on hand is this one:
crash> sys | grep RELEASE
RELEASE: 4.18.0-20.el8.x86_64
crash>
and its debuginfo data contains the "thread_union" information:
crash> thread_union
union thread_union {
struct task_struct task;
unsigned long stack[2048];
}
SIZE: 16384
crash>
but if it did not, then code should then calculate the stack
size from the difference between the "__start_init_task" and
"__end_init_task" symbols:
crash> sym __start_init_task
ffffffffa7800000 (D) __start_init_task
crash> sym __end_init_task
ffffffffa7804000 (D) __end_init_task
crash>
Does your kernel not show/contain those 2 symbols?
Sure, my test kernel contains these 2 symbols.
crash> sys | grep RELEASE
RELEASE: 4.18.0-1-default+
crash> thread_union
crash: command not found: thread_union
crash> struct thread_union
struct: invalid data structure reference: thread_union
crash> sym __start_init_task
ffffffff82000000 (D) __start_init_task
crash> sym __end_init_task
ffffffff82004000 (D) __end_init_task
Agree with you, Automatic calculation stack size from the difference
between__start_init_task and __end_init_task should be better.
Calculating and assignning stack size should be add into "x86_64_init", Do you
think so?
Thanks
Sean
Dave
> >
> > Thanks,
> > Dave
> >
> >
> >
> >
> > >
> > > Signed-off-by: Sean Fu <fxinrong(a)gmail.com>
> > > ---
> > > 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
> > >
> > >
>
8:45 a.m.
----- Original Message -----
On Tue, Oct 09, 2018 at 09:39:10AM -0400, Dave Anderson wrote:
>
>
> ----- Original Message -----
> > On Mon, Oct 01, 2018 at 09:37:10AM -0400, Dave Anderson wrote:
> > >
> > >
> > > ----- 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;
> > > }
> > > }
> > >
> > I compiled latest kernel and latest crash and run a qemu guest machine
> > with
> > the latest compliled kernel
> > image.
> > In this case, STRUCT_SIZE_INIT initialized size_table.task_union and
> > size_table.thread_union with -1. So machdep->stacksize did NOT get
> > overridden.
> > > 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?
> > kernel version is upstream Linux 4.18
> > (commit#94710cac0ef4ee177a63b5227664b38c95bbf703)
> > (git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git).
> >
> > "bt" command in crash shows "bt: invalid RSP: ffffc9000069bc08
> > bt->stackbase/stacktop: ffffc90000698000/ffffc9000069a000 cpu: 0".
> >
> > BestRegards
> > Sean
>
>
>
> Ok, the most recent 4.18 kernel I have on hand is this one:
>
> crash> sys | grep RELEASE
> RELEASE: 4.18.0-20.el8.x86_64
> crash>
>
> and its debuginfo data contains the "thread_union" information:
>
> crash> thread_union
> union thread_union {
> struct task_struct task;
> unsigned long stack[2048];
> }
> SIZE: 16384
> crash>
>
> but if it did not, then code should then calculate the stack
> size from the difference between the "__start_init_task" and
> "__end_init_task" symbols:
>
> crash> sym __start_init_task
> ffffffffa7800000 (D) __start_init_task
> crash> sym __end_init_task
> ffffffffa7804000 (D) __end_init_task
> crash>
>
> Does your kernel not show/contain those 2 symbols?
>
Sure, my test kernel contains these 2 symbols.
crash> sys | grep RELEASE
RELEASE: 4.18.0-1-default+
crash> thread_union
crash: command not found: thread_union
crash> struct thread_union
struct: invalid data structure reference: thread_union
crash> sym __start_init_task
ffffffff82000000 (D) __start_init_task
crash> sym __end_init_task
ffffffff82004000 (D) __end_init_task
Agree with you, Automatic calculation stack size from the difference
between__start_init_task and __end_init_task should be better.
Calculating and assignning stack size should be add into "x86_64_init", Do
you think so?
No, because the calculation is being done in an architecture-neutral manner
by task_init(), here in task.c:
437 if (VALID_SIZE(task_union) && (SIZE(task_union) != STACKSIZE()))
{
438 error(WARNING, "\nnon-standard stack size: %ld\n",
439 len = SIZE(task_union));
440 machdep->stacksize = len;
441 } else if (VALID_SIZE(thread_union) &&
442 ((len = SIZE(thread_union)) != STACKSIZE())) {
443 machdep->stacksize = len;
444 } else if (!VALID_SIZE(thread_union) && !VALID_SIZE(task_union))
{
445 if (kernel_symbol_exists("__start_init_task")
&&
446 kernel_symbol_exists("__end_init_task")) {
447 len = symbol_value("__end_init_task");
448 len -= symbol_value("__start_init_task");
449 ASSIGN_SIZE(thread_union) = len;
450 machdep->stacksize = len;
451 }
452 }
I see that "thread_union" is not found in your debuginfo data, but I don't
understand
how your kernel gets past the second "else" segment above where the
__start_init_task
and __end_init_task symbol values are checked.
Dave
11:39 p.m.
On Wed, Oct 10, 2018 at 09:45:48AM -0400, Dave Anderson wrote:
----- Original Message -----
> On Tue, Oct 09, 2018 at 09:39:10AM -0400, Dave Anderson wrote:
> >
> >
> > ----- Original Message -----
> > > On Mon, Oct 01, 2018 at 09:37:10AM -0400, Dave Anderson wrote:
> > > >
> > > >
> > > > ----- 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;
> > > > }
> > > > }
> > > >
> > > I compiled latest kernel and latest crash and run a qemu guest machine
> > > with
> > > the latest compliled kernel
> > > image.
> > > In this case, STRUCT_SIZE_INIT initialized size_table.task_union and
> > > size_table.thread_union with -1. So machdep->stacksize did NOT get
> > > overridden.
> > > > 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?
> > > kernel version is upstream Linux 4.18
> > > (commit#94710cac0ef4ee177a63b5227664b38c95bbf703)
> > > (git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git).
> > >
> > > "bt" command in crash shows "bt: invalid RSP:
ffffc9000069bc08
> > > bt->stackbase/stacktop: ffffc90000698000/ffffc9000069a000 cpu:
0".
> > >
> > > BestRegards
> > > Sean
> >
> >
> >
> > Ok, the most recent 4.18 kernel I have on hand is this one:
> >
> > crash> sys | grep RELEASE
> > RELEASE: 4.18.0-20.el8.x86_64
> > crash>
> >
> > and its debuginfo data contains the "thread_union" information:
> >
> > crash> thread_union
> > union thread_union {
> > struct task_struct task;
> > unsigned long stack[2048];
> > }
> > SIZE: 16384
> > crash>
> >
> > but if it did not, then code should then calculate the stack
> > size from the difference between the "__start_init_task" and
> > "__end_init_task" symbols:
> >
> > crash> sym __start_init_task
> > ffffffffa7800000 (D) __start_init_task
> > crash> sym __end_init_task
> > ffffffffa7804000 (D) __end_init_task
> > crash>
> >
> > Does your kernel not show/contain those 2 symbols?
> >
> Sure, my test kernel contains these 2 symbols.
>
> crash> sys | grep RELEASE
> RELEASE: 4.18.0-1-default+
> crash> thread_union
> crash: command not found: thread_union
> crash> struct thread_union
> struct: invalid data structure reference: thread_union
> crash> sym __start_init_task
> ffffffff82000000 (D) __start_init_task
> crash> sym __end_init_task
> ffffffff82004000 (D) __end_init_task
>
> Agree with you, Automatic calculation stack size from the difference
> between__start_init_task and __end_init_task should be better.
> Calculating and assignning stack size should be add into "x86_64_init",
Do
> you think so?
No, because the calculation is being done in an architecture-neutral manner
by task_init(), here in task.c:
437 if (VALID_SIZE(task_union) && (SIZE(task_union) != STACKSIZE()))
{
438 error(WARNING, "\nnon-standard stack size: %ld\n",
439 len = SIZE(task_union));
440 machdep->stacksize = len;
441 } else if (VALID_SIZE(thread_union) &&
442 ((len = SIZE(thread_union)) != STACKSIZE())) {
443 machdep->stacksize = len;
444 } else if (!VALID_SIZE(thread_union) && !VALID_SIZE(task_union))
{
445 if (kernel_symbol_exists("__start_init_task")
&&
446 kernel_symbol_exists("__end_init_task")) {
447 len = symbol_value("__end_init_task");
448 len -= symbol_value("__start_init_task");
449 ASSIGN_SIZE(thread_union) = len;
450 machdep->stacksize = len;
451 }
452 }
I see that "thread_union" is not found in your debuginfo data, but I don't
understand
how your kernel gets past the second "else" segment above where the
__start_init_task
and __end_init_task symbol values are checked.
Your code is different from mine.
The following is from my task.c:
436 if (VALID_SIZE(task_union) && (SIZE(task_union) != STACKSIZE())) {
437 error(WARNING, "\nnon-standard stack size: %ld\n",
438 len = SIZE(task_union));
439 machdep->stacksize = len;
440 } else if (VALID_SIZE(thread_union) &&
441 ((len = SIZE(thread_union)) != STACKSIZE()))
442 machdep->stacksize = len;
443
444 MEMBER_OFFSET_INIT(pid_namespace_idr, "pid_namespace",
"idr");
445 MEMBER_OFFSET_INIT(idr_idr_rt, "idr", "idr_rt");
My code repo:
sean@linux-zmni:~/work/source/upstream/crash> git remote -v
origin https://github.com/crash-utility/crash.git (fetch)
origin https://github.com/crash-utility/crash.git (push)
What's your crash version?
Thanks
Sean
Dave
11:49 p.m.
Sean Fu wrote on Thu, Oct 11, 2018:
Your code is different from mine. The following is from my task.c:
436 if (VALID_SIZE(task_union) && (SIZE(task_union) != STACKSIZE())) {
437 error(WARNING, "\nnon-standard stack size: %ld\n",
438 len = SIZE(task_union));
439 machdep->stacksize = len;
440 } else if (VALID_SIZE(thread_union) &&
441 ((len = SIZE(thread_union)) != STACKSIZE()))
442 machdep->stacksize = len;
443
444 MEMBER_OFFSET_INIT(pid_namespace_idr, "pid_namespace",
"idr");
445 MEMBER_OFFSET_INIT(idr_idr_rt, "idr", "idr_rt");
My code repo:
sean@linux-zmni:~/work/source/upstream/crash> git remote -v
origin https://github.com/crash-utility/crash.git (fetch)
origin https://github.com/crash-utility/crash.git (push)
What's your crash version?
Your checkout is a bit old, the extra check was added back in april in
this commit:
commit 6088a29f7e4ad7160e757679827db63ea41553df
Author: Dave Anderson <anderson(a)redhat.com>
Date: Thu Apr 5 11:07:59 2018 -0400
Fix for the "bt" command on 4.16 and later kernels size in which the
"thread_union" data structure is not contained in the vmlinux file's
debuginfo data. Without the patch, the kernel stack size is not
calculated correctly, and defaults to 8K. As a result "bt" fails
with the message "bt: invalid RSP: <address> bt->stackbase/stacktop:
<address>/<address> cpu: <number>".
(efault(a)gmx.de)
which is present in releases since 7.2.2 according to `git tag
--contains`, but development should probably always be done with an
updated tree
--
Domnique
9:50 p.m.
On Thu, Oct 11, 2018 at 06:49:10AM +0200, Dominique Martinet wrote:
Sean Fu wrote on Thu, Oct 11, 2018:
> Your code is different from mine. The following is from my task.c:
>
> 436 if (VALID_SIZE(task_union) && (SIZE(task_union) !=
STACKSIZE())) {
> 437 error(WARNING, "\nnon-standard stack size: %ld\n",
> 438 len = SIZE(task_union));
> 439 machdep->stacksize = len;
> 440 } else if (VALID_SIZE(thread_union) &&
> 441 ((len = SIZE(thread_union)) != STACKSIZE()))
> 442 machdep->stacksize = len;
> 443
> 444 MEMBER_OFFSET_INIT(pid_namespace_idr, "pid_namespace",
"idr");
> 445 MEMBER_OFFSET_INIT(idr_idr_rt, "idr", "idr_rt");
>
> My code repo:
> sean@linux-zmni:~/work/source/upstream/crash> git remote -v
> origin https://github.com/crash-utility/crash.git (fetch)
> origin https://github.com/crash-utility/crash.git (push)
>
> What's your crash version?
Your checkout is a bit old, the extra check was added back in april in
this commit:
commit 6088a29f7e4ad7160e757679827db63ea41553df
Author: Dave Anderson <anderson(a)redhat.com>
Date: Thu Apr 5 11:07:59 2018 -0400
Fix for the "bt" command on 4.16 and later kernels size in which the
"thread_union" data structure is not contained in the vmlinux file's
debuginfo data. Without the patch, the kernel stack size is not
calculated correctly, and defaults to 8K. As a result "bt" fails
with the message "bt: invalid RSP: <address> bt->stackbase/stacktop:
<address>/<address> cpu: <number>".
(efault(a)gmx.de)
which is present in releases since 7.2.2 according to `git tag
--contains`, but development should probably always be done with an
updated tree
Correct, The new crash tools with this patch works fine on my
machine.
Thanks
--
Domnique
2224
days inactive
2250
days old
devel@lists.crash-utility.osci.io
9 comments
3 participants
participants (3)
-
Dave Anderson -
Dominique Martinet -
Sean Fu