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Diffstat (limited to 'src/core/uheap.c')
| -rw-r--r-- | src/core/uheap.c | 197 |
1 files changed, 197 insertions, 0 deletions
diff --git a/src/core/uheap.c b/src/core/uheap.c new file mode 100644 index 000000000..3f93bc030 --- /dev/null +++ b/src/core/uheap.c @@ -0,0 +1,197 @@ +/* + * Copyright (C) 2025 Michael Brown <mbrown@fensystems.co.uk>. + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License as + * published by the Free Software Foundation; either version 2 of the + * License, or (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA + * 02110-1301, USA. + * + * You can also choose to distribute this program under the terms of + * the Unmodified Binary Distribution Licence (as given in the file + * COPYING.UBDL), provided that you have satisfied its requirements. + */ + +FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL ); + +#include <ipxe/io.h> +#include <ipxe/memmap.h> +#include <ipxe/malloc.h> +#include <ipxe/umalloc.h> + +/** @file + * + * External ("user") heap + * + * This file implements an external heap (for umalloc()) that grows + * downwards from the top of the largest contiguous accessible block + * in the system memory map. + */ + +/** + * Alignment for external heap allocations + * + * Historically, umalloc() has produced page-aligned allocations, and + * the hidden region in the system memory map has been aligned to a + * page boundary. Preserve this behaviour, to avoid needing to + * inspect and update large amounts of driver code, and also because + * it keeps the resulting memory maps easy to read. + */ +#define UHEAP_ALIGN PAGE_SIZE + +static struct heap uheap; + +/** Minimum possible start of external heap */ +physaddr_t uheap_limit; + +/** Start of external heap */ +physaddr_t uheap_start; + +/** End of external heap */ +physaddr_t uheap_end; + +/** In-use memory region */ +struct used_region uheap_used __used_region = { + .name = "uheap", +}; + +/** + * Adjust size of external heap in-use memory region + * + * @v delta Size change + */ +static void uheap_resize ( ssize_t delta ) { + + /* Update in-use memory region */ + assert ( ( delta & ( UHEAP_ALIGN - 1 ) ) == 0 ); + uheap_start -= delta; + assert ( uheap_limit <= uheap_start ); + assert ( uheap_start <= uheap_end ); + assert ( ( uheap_limit & ( UHEAP_ALIGN - 1 ) ) == 0 ); + assert ( ( uheap_start & ( UHEAP_ALIGN - 1 ) ) == 0 ); + assert ( ( uheap_end & ( UHEAP_ALIGN - 1 ) ) == 0 ); + memmap_use ( &uheap_used, uheap_start, ( uheap_end - uheap_start ) ); + DBGC ( &uheap, "UHEAP now at (%#08lx)...[%#08lx,%#08lx)\n", + uheap_limit, uheap_start, uheap_end ); + memmap_dump_all ( 1 ); +} + +/** + * Find an external heap region + * + */ +static void uheap_find ( void ) { + physaddr_t start; + physaddr_t end; + size_t before; + size_t after; + size_t strip; + size_t size; + + /* Sanity checks */ + assert ( uheap_start == uheap_end ); + assert ( uheap_limit == uheap_end ); + assert ( uheap_used.size == 0 ); + + /* Find the largest region within the system memory map */ + size = memmap_largest ( &start ); + end = ( start + size ); + DBGC ( &uheap, "UHEAP largest region is [%#08lx,%#08lx)\n", + start, end ); + + /* Align start and end addresses, and prevent overflow to zero */ + after = ( end ? ( end & ( UHEAP_ALIGN - 1 ) ) : UHEAP_ALIGN ); + before = ( ( -start ) & ( UHEAP_ALIGN - 1 ) ); + strip = ( before + after ); + if ( strip > size ) + return; + start += before; + end -= after; + size -= strip; + assert ( ( end - start ) == size ); + + /* Record region */ + uheap_limit = start; + uheap_start = end; + uheap_end = end; + uheap_resize ( 0 ); +} + +/** + * Attempt to grow external heap + * + * @v size Failed allocation size + * @ret grown Heap has grown: retry allocations + */ +static unsigned int uheap_grow ( size_t size ) { + void *new; + + /* Initialise heap, if it does not yet exist */ + if ( uheap_limit == uheap_end ) + uheap_find(); + + /* Fail if insufficient space remains */ + if ( size > ( uheap_start - uheap_limit ) ) + return 0; + + /* Grow heap */ + new = ( phys_to_virt ( uheap_start ) - size ); + heap_populate ( &uheap, new, size ); + uheap_resize ( size ); + + return 1; +} + +/** + * Allow external heap to shrink + * + * @v ptr Start of free block + * @v size Size of free block + * @ret shrunk Heap has shrunk: discard block + */ +static unsigned int uheap_shrink ( void *ptr, size_t size ) { + + /* Do nothing unless this is the lowest block in the heap */ + if ( virt_to_phys ( ptr ) != uheap_start ) + return 0; + + /* Shrink heap */ + uheap_resize ( -size ); + + return 1; +} + +/** The external heap */ +static struct heap uheap = { + .blocks = LIST_HEAD_INIT ( uheap.blocks ), + .align = UHEAP_ALIGN, + .ptr_align = UHEAP_ALIGN, + .grow = uheap_grow, + .shrink = uheap_shrink, +}; + +/** + * Reallocate external memory + * + * @v old_ptr Memory previously allocated by umalloc(), or NULL + * @v new_size Requested size + * @ret new_ptr Allocated memory, or NULL + * + * Calling urealloc() with a new size of zero is a valid way to free a + * memory block. + */ +static void * uheap_realloc ( void *old_ptr, size_t new_size ) { + + return heap_realloc ( &uheap, old_ptr, new_size ); +} + +PROVIDE_UMALLOC ( uheap, urealloc, uheap_realloc ); |