d0e3378ad7
Per the GCC bug listed below, the way we do linker lists is relying on undefined behavior that seems to work in gcc, but doesn't always work in clang. Andrew suggests rewriting our start/end macros in a different way (as implemented here, from what he said in comment 1) to avoid these problems. Reported-by: AdityaK <appujee@google.com> Suggested-by: Andrew Pinski <apinski@marvell.com> Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108915 Signed-off-by: Tom Rini <trini@konsulko.com> Reviewed-by: Simon Glass <sjg@chromium.org> Reviewed-by: Andrew Pinski <apinski@marvell.com>
287 lines
8.6 KiB
C
287 lines
8.6 KiB
C
/* SPDX-License-Identifier: GPL-2.0+ */
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/*
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* include/linker_lists.h
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*
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* Implementation of linker-generated arrays
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*
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* Copyright (C) 2012 Marek Vasut <marex@denx.de>
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*/
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#ifndef __LINKER_LISTS_H__
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#define __LINKER_LISTS_H__
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#include <linux/compiler.h>
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/*
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* There is no use in including this from ASM files.
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* So just don't define anything when included from ASM.
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*/
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#if !defined(__ASSEMBLY__)
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/**
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* llsym() - Access a linker-generated array entry
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* @_type: Data type of the entry
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* @_name: Name of the entry
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* @_list: name of the list. Should contain only characters allowed
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* in a C variable name!
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*/
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#define llsym(_type, _name, _list) \
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((_type *)&_u_boot_list_2_##_list##_2_##_name)
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/**
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* ll_entry_declare() - Declare linker-generated array entry
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* @_type: Data type of the entry
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* @_name: Name of the entry
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* @_list: name of the list. Should contain only characters allowed
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* in a C variable name!
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*
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* This macro declares a variable that is placed into a linker-generated
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* array. This is a basic building block for more advanced use of linker-
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* generated arrays. The user is expected to build their own macro wrapper
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* around this one.
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*
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* A variable declared using this macro must be compile-time initialized.
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*
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* Special precaution must be made when using this macro:
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*
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* 1) The _type must not contain the "static" keyword, otherwise the
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* entry is generated and can be iterated but is listed in the map
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* file and cannot be retrieved by name.
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*
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* 2) In case a section is declared that contains some array elements AND
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* a subsection of this section is declared and contains some elements,
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* it is imperative that the elements are of the same type.
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*
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* 3) In case an outer section is declared that contains some array elements
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* AND an inner subsection of this section is declared and contains some
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* elements, then when traversing the outer section, even the elements of
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* the inner sections are present in the array.
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*
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* Example:
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*
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* ::
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*
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* ll_entry_declare(struct my_sub_cmd, my_sub_cmd, cmd_sub) = {
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* .x = 3,
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* .y = 4,
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* };
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*/
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#define ll_entry_declare(_type, _name, _list) \
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_type _u_boot_list_2_##_list##_2_##_name __aligned(4) \
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__attribute__((unused)) \
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__section("__u_boot_list_2_"#_list"_2_"#_name)
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/**
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* ll_entry_declare_list() - Declare a list of link-generated array entries
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* @_type: Data type of each entry
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* @_name: Name of the entry
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* @_list: name of the list. Should contain only characters allowed
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* in a C variable name!
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*
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* This is like ll_entry_declare() but creates multiple entries. It should
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* be assigned to an array.
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*
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* ::
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*
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* ll_entry_declare_list(struct my_sub_cmd, my_sub_cmd, cmd_sub) = {
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* { .x = 3, .y = 4 },
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* { .x = 8, .y = 2 },
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* { .x = 1, .y = 7 }
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* };
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*/
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#define ll_entry_declare_list(_type, _name, _list) \
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_type _u_boot_list_2_##_list##_2_##_name[] __aligned(4) \
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__attribute__((unused)) \
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__section("__u_boot_list_2_"#_list"_2_"#_name)
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/*
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* We need a 0-byte-size type for iterator symbols, and the compiler
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* does not allow defining objects of C type 'void'. Using an empty
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* struct is allowed by the compiler, but causes gcc versions 4.4 and
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* below to complain about aliasing. Therefore we use the next best
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* thing: zero-sized arrays, which are both 0-byte-size and exempt from
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* aliasing warnings.
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*/
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/**
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* ll_entry_start() - Point to first entry of linker-generated array
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* @_type: Data type of the entry
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* @_list: Name of the list in which this entry is placed
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*
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* This function returns ``(_type *)`` pointer to the very first entry of a
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* linker-generated array placed into subsection of __u_boot_list section
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* specified by _list argument.
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*
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* Since this macro defines an array start symbol, its leftmost index
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* must be 2 and its rightmost index must be 1.
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*
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* Example:
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*
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* ::
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*
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* struct my_sub_cmd *msc = ll_entry_start(struct my_sub_cmd, cmd_sub);
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*/
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#define ll_entry_start(_type, _list) \
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({ \
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static char start[0] __aligned(CONFIG_LINKER_LIST_ALIGN) \
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__attribute__((unused)) \
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__section("__u_boot_list_2_"#_list"_1"); \
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_type * tmp = (_type *)&start; \
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asm("":"+r"(tmp)); \
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tmp; \
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})
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/**
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* ll_entry_end() - Point after last entry of linker-generated array
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* @_type: Data type of the entry
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* @_list: Name of the list in which this entry is placed
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* (with underscores instead of dots)
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*
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* This function returns ``(_type *)`` pointer after the very last entry of
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* a linker-generated array placed into subsection of __u_boot_list
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* section specified by _list argument.
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*
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* Since this macro defines an array end symbol, its leftmost index
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* must be 2 and its rightmost index must be 3.
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*
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* Example:
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*
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* ::
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*
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* struct my_sub_cmd *msc = ll_entry_end(struct my_sub_cmd, cmd_sub);
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*/
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#define ll_entry_end(_type, _list) \
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({ \
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static char end[0] __aligned(4) __attribute__((unused)) \
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__section("__u_boot_list_2_"#_list"_3"); \
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_type * tmp = (_type *)&end; \
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asm("":"+r"(tmp)); \
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tmp; \
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})
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/**
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* ll_entry_count() - Return the number of elements in linker-generated array
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* @_type: Data type of the entry
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* @_list: Name of the list of which the number of elements is computed
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*
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* This function returns the number of elements of a linker-generated array
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* placed into subsection of __u_boot_list section specified by _list
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* argument. The result is of an unsigned int type.
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*
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* Example:
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*
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* ::
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*
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* int i;
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* const unsigned int count = ll_entry_count(struct my_sub_cmd, cmd_sub);
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* struct my_sub_cmd *msc = ll_entry_start(struct my_sub_cmd, cmd_sub);
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* for (i = 0; i < count; i++, msc++)
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* printf("Entry %i, x=%i y=%i\n", i, msc->x, msc->y);
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*/
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#define ll_entry_count(_type, _list) \
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({ \
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_type *start = ll_entry_start(_type, _list); \
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_type *end = ll_entry_end(_type, _list); \
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unsigned int _ll_result = end - start; \
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_ll_result; \
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})
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/**
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* ll_entry_get() - Retrieve entry from linker-generated array by name
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* @_type: Data type of the entry
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* @_name: Name of the entry
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* @_list: Name of the list in which this entry is placed
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*
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* This function returns a pointer to a particular entry in linker-generated
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* array identified by the subsection of u_boot_list where the entry resides
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* and it's name.
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*
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* Example:
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*
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* ::
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*
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* ll_entry_declare(struct my_sub_cmd, my_sub_cmd, cmd_sub) = {
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* .x = 3,
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* .y = 4,
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* };
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* ...
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* struct my_sub_cmd *c = ll_entry_get(struct my_sub_cmd, my_sub_cmd, cmd_sub);
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*/
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#define ll_entry_get(_type, _name, _list) \
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({ \
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extern _type _u_boot_list_2_##_list##_2_##_name; \
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_type *_ll_result = \
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&_u_boot_list_2_##_list##_2_##_name; \
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_ll_result; \
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})
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/**
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* ll_entry_ref() - Get a reference to a linker-generated array entry
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*
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* Once an extern ll_entry_declare() has been used to declare the reference,
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* this macro allows the entry to be accessed.
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*
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* This is like ll_entry_get(), but without the extra code, so it is suitable
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* for putting into data structures.
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*
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* @_type: C type of the list entry, e.g. 'struct foo'
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* @_name: name of the entry
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* @_list: name of the list
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*/
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#define ll_entry_ref(_type, _name, _list) \
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((_type *)&_u_boot_list_2_##_list##_2_##_name)
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/**
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* ll_start() - Point to first entry of first linker-generated array
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* @_type: Data type of the entry
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*
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* This function returns ``(_type *)`` pointer to the very first entry of
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* the very first linker-generated array.
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*
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* Since this macro defines the start of the linker-generated arrays,
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* its leftmost index must be 1.
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*
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* Example:
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*
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* ::
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*
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* struct my_sub_cmd *msc = ll_start(struct my_sub_cmd);
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*/
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#define ll_start(_type) \
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({ \
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static char start[0] __aligned(4) __attribute__((unused)) \
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__section("__u_boot_list_1"); \
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_type * tmp = (_type *)&start; \
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asm("":"+r"(tmp)); \
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tmp; \
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})
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/**
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* ll_end() - Point after last entry of last linker-generated array
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* @_type: Data type of the entry
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*
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* This function returns ``(_type *)`` pointer after the very last entry of
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* the very last linker-generated array.
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*
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* Since this macro defines the end of the linker-generated arrays,
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* its leftmost index must be 3.
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*
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* Example:
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*
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* ::
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*
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* struct my_sub_cmd *msc = ll_end(struct my_sub_cmd);
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*/
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#define ll_end(_type) \
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({ \
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static char end[0] __aligned(4) __attribute__((unused)) \
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__section("__u_boot_list_3"); \
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_type * tmp = (_type *)&end; \
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asm("":"+r"(tmp)); \
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tmp; \
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})
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#endif /* __ASSEMBLY__ */
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#endif /* __LINKER_LISTS_H__ */
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