mm: unexport vm_brk_flags() and eliminate vm_flags parameter

This function is only used by elf_load(), and that is a static function
that doesn't need an exported symbol to invoke an internal function, so
un-EXPORT_SYMBOLS() it.

Also, the vm_flags parameter is unnecessary, as we only ever set VM_EXEC,
so simply make this parameter a boolean.

While we're here, clean up the mm.h definitions for the various vm_xxx()
helpers so we actually specify parameter names and elide the redundant
extern's.

Link: https://lkml.kernel.org/r/7bada48ddf3f9dbd3e6c4fc50ec2f4de97706f52.1774034900.git.ljs@kernel.org
Signed-off-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Acked-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Alexandre Ghiti <alex@ghiti.fr>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Cc: "Borislav Petkov (AMD)" <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Hildenbrand <david@kernel.org>
Cc: Dinh Nguyen <dinguyen@kernel.org>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: Kees Cook <kees@kernel.org>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Ondrej Mosnacek <omosnace@redhat.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Paul Moore <paul@paul-moore.com>
Cc: Pedro Falcato <pfalcato@suse.de>
Cc: Richard Weinberger <richard@nod.at>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Stephen Smalley <stephen.smalley.work@gmail.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vineet Gupta <vgupta@kernel.org>
Cc: WANG Xuerui <kernel@xen0n.name>
Cc: Will Deacon <will@kernel.org>
Cc: xu xin <xu.xin16@zte.com.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

fs/binfmt_elf.c

@@ -453,14 +453,13 @@ static unsigned long elf_load(struct file *filep, unsigned long addr,
 		zero_end = ELF_PAGEALIGN(zero_end);
 
 		error = vm_brk_flags(zero_start, zero_end - zero_start,
-				     prot & PROT_EXEC ? VM_EXEC : 0);
+				     prot & PROT_EXEC);
 		if (error)
 			map_addr = error;
 	}
 	return map_addr;
 }
 
-
 static unsigned long total_mapping_size(const struct elf_phdr *phdr, int nr)
 {
 	elf_addr_t min_addr = -1;

include/linux/mm.h

@@ -3991,12 +3991,12 @@ static inline void mm_populate(unsigned long addr, unsigned long len) {}
 #endif
 
 /* This takes the mm semaphore itself */
-extern int __must_check vm_brk_flags(unsigned long, unsigned long, unsigned long);
-extern int vm_munmap(unsigned long, size_t);
-extern unsigned long __must_check vm_mmap(struct file *, unsigned long,
-        unsigned long, unsigned long,
-        unsigned long, unsigned long);
-extern unsigned long __must_check vm_mmap_shadow_stack(unsigned long addr,
+int __must_check vm_brk_flags(unsigned long addr, unsigned long request, bool is_exec);
+int vm_munmap(unsigned long start, size_t len);
+unsigned long __must_check vm_mmap(struct file *file, unsigned long addr,
+		unsigned long len, unsigned long prot,
+		unsigned long flag, unsigned long offset);
+unsigned long __must_check vm_mmap_shadow_stack(unsigned long addr,
 		unsigned long len, unsigned long flags);
 
 struct vm_unmapped_area_info {

mm/mmap.c

@@ -1201,8 +1201,9 @@ out:
 	return ret;
 }
 
-int vm_brk_flags(unsigned long addr, unsigned long request, vm_flags_t vm_flags)
+int vm_brk_flags(unsigned long addr, unsigned long request, bool is_exec)
 {
+	const vm_flags_t vm_flags = is_exec ? VM_EXEC : 0;
 	struct mm_struct *mm = current->mm;
 	struct vm_area_struct *vma = NULL;
 	unsigned long len;
@@ -1217,10 +1218,6 @@ int vm_brk_flags(unsigned long addr, unsigned long request, vm_flags_t vm_flags)
 	if (!len)
 		return 0;
 
-	/* Until we need other flags, refuse anything except VM_EXEC. */
-	if ((vm_flags & (~VM_EXEC)) != 0)
-		return -EINVAL;
-
 	if (mmap_write_lock_killable(mm))
 		return -EINTR;
 
@@ -1246,7 +1243,6 @@ limits_failed:
 	mmap_write_unlock(mm);
 	return ret;
 }
-EXPORT_SYMBOL(vm_brk_flags);
 
 static
 unsigned long tear_down_vmas(struct mm_struct *mm, struct vma_iterator *vmi,