[PATCH] core dump: user_regset writeback

[PATCH] core dump: user_regset writeback

[Roland McGrath]

This makes the user_regset-based core dump code call user_regset
writeback hooks when available.  This is necessary groundwork to
allow IA64 to set CORE_DUMP_USE_REGSET.

CC: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Roland McGrath <roland@redhat.com>
---
 fs/binfmt_elf.c |   15 +++++++++++++++
 1 files changed, 15 insertions(+), 0 deletions(-)

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 41a958a..eb7cca3 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1424,6 +1424,18 @@ struct elf_note_info {
 	int thread_notes;
 };
 
+/*
+ * When a regset has a writeback hook, we call it on each thread before
+ * dumping user memory.  On register window machines, this makes sure the
+ * user memory backing the register data is up to date before we read it.
+ */
+static void do_thread_regset_writeback(struct task_struct *task,
+				       const struct user_regset *regset)
+{
+	if (regset->writeback)
+		regset->writeback(task, regset, 1);
+}
+
 static int fill_thread_core_info(struct elf_thread_core_info *t,
 				 const struct user_regset_view *view,
 				 long signr, size_t *total)
@@ -1445,6 +1457,8 @@ static int fill_thread_core_info(struct elf_thread_core_info *t,
 		  sizeof(t->prstatus), &t->prstatus);
 	*total += notesize(&t->notes[0]);
 
+	do_thread_regset_writeback(t->task, &view->regsets[0]);
+
 	/*
 	 * Each other regset might generate a note too.  For each regset
 	 * that has no core_note_type or is inactive, we leave t->notes[i]
@@ -1452,6 +1466,7 @@ static int fill_thread_core_info(struct elf_thread_core_info *t,
 	 */
 	for (i = 1; i < view->n; ++i) {
 		const struct user_regset *regset = &view->regsets[i];
+		do_thread_regset_writeback(t->task, regset);
 		if (regset->core_note_type &&
 		    (!regset->active || regset->active(t->task, regset))) {
 			int ret;

Re: [PATCH] core dump: user_regset writeback

[Andrew Morton]

On Wed, 27 Feb 2008 12:06:38 -0800 (PST)
Roland McGrath <roland@redhat.com> wrote:

> 
> This makes the user_regset-based core dump code call user_regset
> writeback hooks when available.  This is necessary groundwork to
> allow IA64 to set CORE_DUMP_USE_REGSET.
> 
> CC: Shaohua Li <shaohua.li@intel.com>
> Signed-off-by: Roland McGrath <roland@redhat.com>
> ---
>  fs/binfmt_elf.c |   15 +++++++++++++++
>  1 files changed, 15 insertions(+), 0 deletions(-)
> 
> diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
> index 41a958a..eb7cca3 100644
> --- a/fs/binfmt_elf.c
> +++ b/fs/binfmt_elf.c
> @@ -1424,6 +1424,18 @@ struct elf_note_info {
>  	int thread_notes;
>  };
>  
> +/*
> + * When a regset has a writeback hook, we call it on each thread before
> + * dumping user memory.  On register window machines, this makes sure the
> + * user memory backing the register data is up to date before we read it.
> + */
> +static void do_thread_regset_writeback(struct task_struct *task,
> +				       const struct user_regset *regset)
> +{
> +	if (regset->writeback)
> +		regset->writeback(task, regset, 1);
> +}
> +
>  static int fill_thread_core_info(struct elf_thread_core_info *t,
>  				 const struct user_regset_view *view,
>  				 long signr, size_t *total)
> @@ -1445,6 +1457,8 @@ static int fill_thread_core_info(struct elf_thread_core_info *t,
>  		  sizeof(t->prstatus), &t->prstatus);
>  	*total += notesize(&t->notes[0]);
>  
> +	do_thread_regset_writeback(t->task, &view->regsets[0]);
> +
>  	/*
>  	 * Each other regset might generate a note too.  For each regset
>  	 * that has no core_note_type or is inactive, we leave t->notes[i]
> @@ -1452,6 +1466,7 @@ static int fill_thread_core_info(struct elf_thread_core_info *t,
>  	 */
>  	for (i = 1; i < view->n; ++i) {
>  		const struct user_regset *regset = &view->regsets[i];
> +		do_thread_regset_writeback(t->task, regset);
>  		if (regset->core_note_type &&
>  		    (!regset->active || regset->active(t->task, regset))) {
>  			int ret;

Is there a need for this in 2.6.25?

Re: [PATCH] core dump: user_regset writeback

[Roland McGrath]

> Is there a need for this in 2.6.25?

It is a prerequisite for ia64 to switch on CORE_DUMP_USE_REGSET.  (It's
also a very low-impact patch easy to convince oneself does nothing on other
machines, and it's in new 2.6.25 code so far used only on x86, powerpc, and
sparc.)  I think those patches are on their way to being merged by ia64
maintainers.  But I don't know what their targets are.  I'm guessing not
til after .25.  Shaohua Li is driving that effort.


Thanks,
Roland