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Date:   Mon, 17 Feb 2020 22:54:43 +0100
From:   Heinrich Schuchardt <xypron.glpk@....de>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org,
        Heinrich Schuchardt <xypron.glpk@....de>
Subject: [PATCH v2 1/1] efi/libstub: describe memory functions

Provide descriptions of:

* efi_get_memory_map()
* efi_low_alloc_above()
* efi_free()

Signed-off-by: Heinrich Schuchardt <xypron.glpk@....de>
---
v2:
	point out how efi_free() is rounding up the memory size
---
 drivers/firmware/efi/libstub/mem.c | 36 ++++++++++++++++++++++++++++--
 1 file changed, 34 insertions(+), 2 deletions(-)

diff --git a/drivers/firmware/efi/libstub/mem.c b/drivers/firmware/efi/libstub/mem.c
index c25fd9174b74..49116b9b0801 100644
--- a/drivers/firmware/efi/libstub/mem.c
+++ b/drivers/firmware/efi/libstub/mem.c
@@ -16,6 +16,15 @@ static inline bool mmap_has_headroom(unsigned long buff_size,
 	return slack / desc_size >= EFI_MMAP_NR_SLACK_SLOTS;
 }

+/**
+ * efi_get_memory_map() - get memory map
+ * @map		on return pointer to memory map
+ *
+ * Retrieve the UEFI memory map. The allocated memory leaves room for
+ * up to EFI_MMAP_NR_SLACK_SLOTS additional memory map entries.
+ *
+ * Return:	status code
+ */
 efi_status_t efi_get_memory_map(struct efi_boot_memmap *map)
 {
 	efi_memory_desc_t *m = NULL;
@@ -109,8 +118,20 @@ efi_status_t efi_allocate_pages(unsigned long size, unsigned long *addr,
 	}
 	return EFI_SUCCESS;
 }
-/*
- * Allocate at the lowest possible address that is not below 'min'.
+/**
+ * efi_low_alloc_above() - allocate pages at or above given address
+ * @size:	size of the memory area to allocate
+ * @align:	minimum alignment of the allocated memory area. It should
+ *		a power of two.
+ * @addr:	on exit the address of the allocated memory
+ * @min:	minimum address to used for the memory allocation
+ *
+ * Allocate at the lowest possible address that is not below 'min' as
+ * EFI_LOADER_DATA. The allocated pages are aligned according to 'align' but at
+ * least EFI_ALLOC_ALIGN. The first allocated page will not below the address
+ * given by 'min'.
+ *
+ * Return:	status code
  */
 efi_status_t efi_low_alloc_above(unsigned long size, unsigned long align,
 				 unsigned long *addr, unsigned long min)
@@ -187,6 +208,17 @@ efi_status_t efi_low_alloc_above(unsigned long size, unsigned long align,
 	return status;
 }

+/**
+ * efi_free() - free memory pages
+ * @size	size of the memory area to free in bytes
+ * @addr	start of the memory area to free (must be EFI_PAGE_SIZE
+ *		aligned)
+ *
+ * 'size' is rounded up to a multiple of EFI_ALLOC_ALIGN which is an
+ * architecture specific multiple of EFI_PAGE_SIZE. So this function should
+ * only be used to return pages allocated with efi_allocate_pages() or
+ * efi_low_alloc_above().
+ */
 void efi_free(unsigned long size, unsigned long addr)
 {
 	unsigned long nr_pages;
--
2.25.0

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