On Sun, Aug 08, 2021 at 03:31:41PM +0200, Patrick Steinhardt wrote:
> Currently, all platforms will set up their heap on initialization of the
> platform code. While this works mostly fine, it poses some limitations
> on memory management on us. Most notably, allocating big chunks of
> memory in the gigabyte range would require us to pre-request this many
> bytes from the firmware and add it to the heap from the beginning on
> some platforms like EFI. As this isn't needed for most configurations,
> it is inefficient and may even negatively impact some usecases when
s/when/when, e.g.,/
> chainloading. Nonetheless, allocating big chunks of memory is required
> sometimes, where one example is the upcoming support for the Argon2 key
> derival function in LUKS2.
>
> In order to avoid pre-allocating big chunks of memory, this commit
> implements a runtime mechanism to add more pages to the system. When
> a given allocation cannot be currently be satisfied, we'll call a given
s/currently be/currently/
> callback set up by the platform's own memory management subsystem,
> asking it to add a memory area with at least `n` bytes. If this
> succeeds, we retry searching for a valid memory region, which should now
> succeed.
>
> Signed-off-by: Patrick Steinhardt <p...@pks.im>
> ---
> grub-core/kern/mm.c | 11 ++++++++++-
> include/grub/mm.h | 13 +++++++++++++
> 2 files changed, 23 insertions(+), 1 deletion(-)
>
> diff --git a/grub-core/kern/mm.c b/grub-core/kern/mm.c
> index c070afc62..3c003a2f9 100644
> --- a/grub-core/kern/mm.c
> +++ b/grub-core/kern/mm.c
> @@ -81,6 +81,7 @@
>
>
> grub_mm_region_t grub_mm_base;
> +grub_mm_region_func_t grub_mm_region_fn;
>
> /* Get a header from the pointer PTR, and set *P and *R to a pointer
> to the header and a pointer to its region, respectively. PTR must
> @@ -360,8 +361,16 @@ grub_memalign (grub_size_t align, grub_size_t size)
> count++;
> goto again;
>
> -#if 0
> case 1:
> + /* Request additional pages. */
> + count++;
> +
> + if (grub_mm_region_fn && grub_mm_region_fn (size,
> GRUB_MM_REGION_CONSECUTIVE) == GRUB_ERR_NONE)
> + goto again;
> +
> + /* fallthrough */
> +#if 0
> + case 2:
> /* Unload unneeded modules. */
> grub_dl_unload_unneeded ();
Please drop this dead code together with grub_dl_unload_unneeded()
function in a preparatory patch.
> count++;
> diff --git a/include/grub/mm.h b/include/grub/mm.h
> index 9c38dd3ca..deff15f17 100644
> --- a/include/grub/mm.h
> +++ b/include/grub/mm.h
> @@ -20,6 +20,7 @@
> #ifndef GRUB_MM_H
> #define GRUB_MM_H 1
>
> +#include <grub/err.h>
> #include <grub/types.h>
> #include <grub/symbol.h>
> #include <config.h>
> @@ -28,6 +29,18 @@
> # define NULL ((void *) 0)
> #endif
>
> +enum {
> + GRUB_MM_REGION_CONSECUTIVE = 1 << 0,
> +};
I prefer define instead of enum here.
> +/* Function used to request memory regions of `grub_size_t` bytes. The second
> + * parameter is a bitfield of `GRUB_MM_REGION` flags. */
Please format comments according to [1].
> +typedef grub_err_t (*grub_mm_region_func_t) (grub_size_t, unsigned);
s/unsigned/unsigned int/
> +/* Set this function pointer to enable adding memory-regions at runtime in
> case
> + * a memory allocation cannot be satisfied with existing regions. */
> +extern grub_mm_region_func_t EXPORT_VAR(grub_mm_region_fn);
> +
> void grub_mm_init_region (void *addr, grub_size_t size);
> void *EXPORT_FUNC(grub_calloc) (grub_size_t nmemb, grub_size_t size);
> void *EXPORT_FUNC(grub_malloc) (grub_size_t size);
Daniel
[1] https://www.gnu.org/software/grub/manual/grub-dev/grub-dev.html#Comments
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