Javier Martín wrote:
> But you negate any performance gain when you _do_ traverse the list to
> add an entry to it instead of just make it the new head as I do.
> Besides, even for that, double indirection should be avoided in the
> structure previous pointer because it makes things oh-so-incredibly
> confusing.
I was thinking about code size then about performance or easy of
understanding. On my system this code results in 91 addition bytes in
core image (63 if I remove grub_error). Do you have any idea how it
would be possible to do an error message without description or put some
generic description?
>
> Besides, I think the "user" (i.e. module) visible type returned by _add
> and taken by _remove should be a "blank hidden type", i.e. you don't
> need to declare "struct grub_preboot_t" in loader.h because the public
> interface only uses _pointers_ to it, whose size is known. This is all
> the C compiler requires and you avoid polluting the namespace with
> internal implementation details. I recommend the following typedefs:
>
> typedef struct grub_preboot_t* grub_preboot_hnd;
> typedef grub_err_t *(grub_preboot_func)(int noreturn);
>
> So that the prototypes would look
>
> grub_preboot_hnd add(grub_preboot_func f);
> void remove(grub_preboot_hnd handle);
I noticed that actually no code needs the size of grub_preoot_hnd. So I
changed it to void *
Vladimir Serbinenko
Index: kern/loader.c
===================================================================
--- kern/loader.c (revision 1845)
+++ kern/loader.c (working copy)
@@ -22,12 +22,54 @@
#include <grub/err.h>
#include <grub/kernel.h>
+#define PREBOOT_HND(x) (((struct grub_preboot_t *)x))
+
+struct grub_preboot_t
+{
+ grub_err_t (*preboot_func) (int);
+ struct grub_preboot_t *next;
+ struct grub_preboot_t **prev_pointer;
+};
+
static grub_err_t (*grub_loader_boot_func) (void);
static grub_err_t (*grub_loader_unload_func) (void);
static int grub_loader_noreturn;
static int grub_loader_loaded;
+static struct grub_preboot_t *grub_loader_preboots=0;
+
+void *
+grub_loader_add_preboot (grub_err_t (*preboot_func) (int))
+{
+ struct grub_preboot_t *cur;
+ if (!preboot_func)
+ return 0;
+ cur=(struct grub_preboot_t *)grub_malloc (sizeof (struct grub_preboot_t));
+ if (!cur)
+ {
+ grub_error (GRUB_ERR_OUT_OF_MEMORY, "hook not added");
+ return 0;
+ }
+ cur->next=grub_loader_preboots;
+ cur->prev_pointer=0;
+ cur->next->prev_pointer=&(cur->next);
+ cur->preboot_func=preboot_func;
+ grub_loader_preboots=cur;
+ return cur;
+}
+
+void
+grub_loader_remove_preboot (void *p)
+{
+ if (!p)
+ return;
+ *(PREBOOT_HND(p)->prev_pointer)=PREBOOT_HND(p)->next;
+ if (PREBOOT_HND(p)->next)
+ PREBOOT_HND(p)->next->prev_pointer=PREBOOT_HND(p)->prev_pointer;
+ grub_free (p);
+}
+
int
grub_loader_is_loaded (void)
{
@@ -64,12 +106,18 @@
grub_err_t
grub_loader_boot (void)
{
+ struct grub_preboot_t *iter=grub_loader_preboots;
if (! grub_loader_loaded)
return grub_error (GRUB_ERR_NO_KERNEL, "no loaded kernel");
if (grub_loader_noreturn)
grub_machine_fini ();
-
+ while (iter)
+ {
+ if (iter->preboot_func)
+ iter->preboot_func (grub_loader_noreturn);
+ iter=iter->next;
+ }
return (grub_loader_boot_func) ();
}
Index: include/grub/loader.h
===================================================================
--- include/grub/loader.h (revision 1845)
+++ include/grub/loader.h (working copy)
@@ -25,6 +25,7 @@
#include <grub/err.h>
#include <grub/types.h>
+
/* Check if a loader is loaded. */
int EXPORT_FUNC(grub_loader_is_loaded) (void);
@@ -37,6 +38,12 @@
/* Unset current loader, if any. */
void EXPORT_FUNC(grub_loader_unset) (void);
+/*Add a preboot function*/
+void *EXPORT_FUNC(grub_loader_add_preboot) (grub_err_t (*preboot_func) (int noreturn));
+
+/*Remove given preboot function*/
+void EXPORT_FUNC(grub_loader_remove_preboot) (void *hnd);
+
/* Call the boot hook in current loader. This may or may not return,
depending on the setting by grub_loader_set. */
grub_err_t EXPORT_FUNC(grub_loader_boot) (void);
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