objtool: Replace custom macros in elf.c with shared ones

The source file tools/objtool/elf.c defines the macros ALIGN_UP(),
ALIGN_UP_POW2() and MAX(). These macros unnecessarily duplicate
functionality already available under tools/include/, specifically ALIGN(),
roundup_pow_of_two() and max().

More importantly, the definition of ALIGN_UP_POW2() is incorrect when the
input is 1, as it results in a call to __builtin_clz(0), which produces an
undefined result. This issue impacts the function elf_alloc_reloc(). When
adding the first relocation to a section, the function allocates an
undefined number of relocations.

Replace the custom macros with the shared functionality to resolve these
issues.

Fixes: 2c05ca0 ("objtool: Add elf_create_reloc() and elf_init_reloc()")
Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>
Link: https://patch.msgid.link/20260126151356.3924887-1-petr.pavlu@suse.com
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>

Author: petrpavlu

tools/objtool/elf.c

@@ -18,15 +18,14 @@
 #include <errno.h>
 #include <libgen.h>
 #include <ctype.h>
+#include <linux/align.h>
+#include <linux/kernel.h>
 #include <linux/interval_tree_generic.h>
+#include <linux/log2.h>
 #include <objtool/builtin.h>
 #include <objtool/elf.h>
 #include <objtool/warn.h>
 
-#define ALIGN_UP(x, align_to) (((x) + ((align_to)-1)) & ~((align_to)-1))
-#define ALIGN_UP_POW2(x) (1U << ((8 * sizeof(x)) - __builtin_clz((x) - 1U)))
-#define MAX(a, b) ((a) > (b) ? (a) : (b))
-
 static inline u32 str_hash(const char *str)
 {
 	return jhash(str, strlen(str), 0);
@@ -1336,7 +1335,7 @@ unsigned int elf_add_string(struct elf *elf, struct section *strtab, const char
 		return -1;
 	}
 
-	offset = ALIGN_UP(strtab->sh.sh_size, strtab->sh.sh_addralign);
+	offset = ALIGN(strtab->sh.sh_size, strtab->sh.sh_addralign);
 
 	if (!elf_add_data(elf, strtab, str, strlen(str) + 1))
 		return -1;
@@ -1378,7 +1377,7 @@ void *elf_add_data(struct elf *elf, struct section *sec, const void *data, size_
 	sec->data->d_size = size;
 	sec->data->d_align = 1;
 
-	offset = ALIGN_UP(sec->sh.sh_size, sec->sh.sh_addralign);
+	offset = ALIGN(sec->sh.sh_size, sec->sh.sh_addralign);
 	sec->sh.sh_size = offset + size;
 
 	mark_sec_changed(elf, sec, true);
@@ -1502,7 +1501,7 @@ static int elf_alloc_reloc(struct elf *elf, struct section *rsec)
 	rsec->data->d_size = nr_relocs_new * elf_rela_size(elf);
 	rsec->sh.sh_size   = rsec->data->d_size;
 
-	nr_alloc = MAX(64, ALIGN_UP_POW2(nr_relocs_new));
+	nr_alloc = max(64UL, roundup_pow_of_two(nr_relocs_new));
 	if (nr_alloc <= rsec->nr_alloc_relocs)
 		return 0;