From 23bca58a68264657f176885c3564d07c9938b7f6 Mon Sep 17 00:00:00 2001 From: Patrick Steinhardt Date: Thu, 21 Apr 2022 15:24:18 +1000 Subject: [PATCH 1/5] mm: Allow dynamically requesting additional memory regions 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, 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 satisfied, we'll call a given 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. If this fails, we try asking for "n" bytes, possibly spread across multiple regions, in hopes that region merging means that we end up with enough memory for things to work out. Signed-off-by: Patrick Steinhardt Signed-off-by: Daniel Axtens Tested-by: Stefan Berger Reviewed-by: Daniel Kiper Tested-by: Patrick Steinhardt --- grub-core/kern/mm.c | 30 ++++++++++++++++++++++++++++++ include/grub/mm.h | 18 ++++++++++++++++++ 2 files changed, 48 insertions(+) diff --git a/grub-core/kern/mm.c b/grub-core/kern/mm.c index 5c0a624..0bd9f75 100644 --- a/grub-core/kern/mm.c +++ b/grub-core/kern/mm.c @@ -28,6 +28,9 @@ - multiple regions may be used as free space. They may not be contiguous. + - if existing regions are insufficient to satisfy an allocation, a new + region can be requested from firmware. + Regions are managed by a singly linked list, and the meta information is stored in the beginning of each region. Space after the meta information is used to allocate memory. @@ -77,6 +80,7 @@ grub_mm_region_t grub_mm_base; +grub_mm_add_region_func_t grub_mm_add_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 @@ -364,6 +368,32 @@ grub_memalign (grub_size_t align, grub_size_t size) goto again; #endif + case 1: + /* Request additional pages, contiguous */ + count++; + + if (grub_mm_add_region_fn != NULL && + grub_mm_add_region_fn (size, GRUB_MM_ADD_REGION_CONSECUTIVE) == GRUB_ERR_NONE) + goto again; + + /* fallthrough */ + + case 2: + /* Request additional pages, anything at all */ + count++; + + if (grub_mm_add_region_fn != NULL) + { + /* + * Try again even if this fails, in case it was able to partially + * satisfy the request + */ + grub_mm_add_region_fn (size, GRUB_MM_ADD_REGION_NONE); + goto again; + } + + /* fallthrough */ + default: break; } diff --git a/include/grub/mm.h b/include/grub/mm.h index 1754635..67faebf 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 #include #include #include @@ -28,6 +29,23 @@ # define NULL ((void *) 0) #endif +#define GRUB_MM_ADD_REGION_NONE 0 +#define GRUB_MM_ADD_REGION_CONSECUTIVE (1 << 0) + +/* + * Function used to request memory regions of `grub_size_t` bytes. The second + * parameter is a bitfield of `GRUB_MM_ADD_REGION` flags. + */ +typedef grub_err_t (*grub_mm_add_region_func_t) (grub_size_t, unsigned int); + +/* + * Set this function pointer to enable adding memory-regions at runtime in case + * a memory allocation cannot be satisfied with existing regions. + */ +#ifndef GRUB_MACHINE_EMU +extern grub_mm_add_region_func_t EXPORT_VAR(grub_mm_add_region_fn); +#endif + void grub_mm_init_region (void *addr, grub_size_t size); void *EXPORT_FUNC(grub_malloc) (grub_size_t size); void *EXPORT_FUNC(grub_zalloc) (grub_size_t size); -- 2.35.3