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Remove a.out interpreter support in ELF loader
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Following the deprecation schedule the a.out ELF interpreter support
is removed now with this patch. a.out ELF interpreters were an transition
feature for moving a.out systems to ELF, but they're unlikely to be still
needed. Pure a.out systems will still work of course. This allows to
simplify the hairy ELF loader.

Signed-off-by: Andi Kleen <ak@suse.de>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Andi Kleen authored and Linus Torvalds committed Feb 8, 2008
1 parent 48d13e4 commit d20894a
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Showing 2 changed files with 21 additions and 163 deletions.
11 changes: 0 additions & 11 deletions Documentation/feature-removal-schedule.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -99,17 +99,6 @@ Who: Eric Biederman <ebiederm@xmission.com>

---------------------------

What: a.out interpreter support for ELF executables
When: 2.6.25
Files: fs/binfmt_elf.c
Why: Using a.out interpreters for ELF executables was a feature for
transition from a.out to ELF. But now it is unlikely to be still
needed anymore and removing it would simplify the hairy ELF
loader code.
Who: Andi Kleen <ak@suse.de>

---------------------------

What: remove EXPORT_SYMBOL(kernel_thread)
When: August 2006
Files: arch/*/kernel/*_ksyms.c
Expand Down
173 changes: 21 additions & 152 deletions fs/binfmt_elf.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -134,8 +134,7 @@ static int padzero(unsigned long elf_bss)

static int
create_elf_tables(struct linux_binprm *bprm, struct elfhdr *exec,
int interp_aout, unsigned long load_addr,
unsigned long interp_load_addr)
unsigned long load_addr, unsigned long interp_load_addr)
{
unsigned long p = bprm->p;
int argc = bprm->argc;
Expand Down Expand Up @@ -223,12 +222,7 @@ create_elf_tables(struct linux_binprm *bprm, struct elfhdr *exec,

sp = STACK_ADD(p, ei_index);

items = (argc + 1) + (envc + 1);
if (interp_aout) {
items += 3; /* a.out interpreters require argv & envp too */
} else {
items += 1; /* ELF interpreters only put argc on the stack */
}
items = (argc + 1) + (envc + 1) + 1;
bprm->p = STACK_ROUND(sp, items);

/* Point sp at the lowest address on the stack */
Expand All @@ -251,16 +245,8 @@ create_elf_tables(struct linux_binprm *bprm, struct elfhdr *exec,
/* Now, let's put argc (and argv, envp if appropriate) on the stack */
if (__put_user(argc, sp++))
return -EFAULT;
if (interp_aout) {
argv = sp + 2;
envp = argv + argc + 1;
if (__put_user((elf_addr_t)(unsigned long)argv, sp++) ||
__put_user((elf_addr_t)(unsigned long)envp, sp++))
return -EFAULT;
} else {
argv = sp;
envp = argv + argc + 1;
}
argv = sp;
envp = argv + argc + 1;

/* Populate argv and envp */
p = current->mm->arg_end = current->mm->arg_start;
Expand Down Expand Up @@ -513,61 +499,6 @@ static unsigned long load_elf_interp(struct elfhdr *interp_elf_ex,
return error;
}

#ifdef CONFIG_ARCH_SUPPORTS_AOUT
static unsigned long load_aout_interp(struct exec *interp_ex,
struct file *interpreter)
{
unsigned long text_data, elf_entry = ~0UL;
char __user * addr;
loff_t offset;

current->mm->end_code = interp_ex->a_text;
text_data = interp_ex->a_text + interp_ex->a_data;
current->mm->end_data = text_data;
current->mm->brk = interp_ex->a_bss + text_data;

switch (N_MAGIC(*interp_ex)) {
case OMAGIC:
offset = 32;
addr = (char __user *)0;
break;
case ZMAGIC:
case QMAGIC:
offset = N_TXTOFF(*interp_ex);
addr = (char __user *)N_TXTADDR(*interp_ex);
break;
default:
goto out;
}

down_write(&current->mm->mmap_sem);
do_brk(0, text_data);
up_write(&current->mm->mmap_sem);
if (!interpreter->f_op || !interpreter->f_op->read)
goto out;
if (interpreter->f_op->read(interpreter, addr, text_data, &offset) < 0)
goto out;
flush_icache_range((unsigned long)addr,
(unsigned long)addr + text_data);

down_write(&current->mm->mmap_sem);
do_brk(ELF_PAGESTART(text_data + ELF_MIN_ALIGN - 1),
interp_ex->a_bss);
up_write(&current->mm->mmap_sem);
elf_entry = interp_ex->a_entry;

out:
return elf_entry;
}
#else
/* dummy extern - the function should never be called if !CONFIG_AOUT_BINFMT */
static inline unsigned long load_aout_interp(struct exec *interp_ex,
struct file *interpreter)
{
return -ELIBACC;
}
#endif

/*
* These are the functions used to load ELF style executables and shared
* libraries. There is no binary dependent code anywhere else.
Expand All @@ -576,13 +507,6 @@ static inline unsigned long load_aout_interp(struct exec *interp_ex,
#define INTERPRETER_NONE 0
#define INTERPRETER_ELF 2

#ifdef CONFIG_ARCH_SUPPORTS_AOUT
#define INTERPRETER_AOUT 1
#define IS_AOUT_INTERP(x) ((x) == INTERPRETER_AOUT)
#else
#define IS_AOUT_INTERP(x) (0)
#endif

#ifndef STACK_RND_MASK
#define STACK_RND_MASK (0x7ff >> (PAGE_SHIFT - 12)) /* 8MB of VA */
#endif
Expand All @@ -609,7 +533,6 @@ static int load_elf_binary(struct linux_binprm *bprm, struct pt_regs *regs)
unsigned long load_addr = 0, load_bias = 0;
int load_addr_set = 0;
char * elf_interpreter = NULL;
unsigned int interpreter_type = INTERPRETER_NONE;
unsigned long error;
struct elf_phdr *elf_ppnt, *elf_phdata;
unsigned long elf_bss, elf_brk;
Expand All @@ -620,7 +543,6 @@ static int load_elf_binary(struct linux_binprm *bprm, struct pt_regs *regs)
unsigned long interp_load_addr = 0;
unsigned long start_code, end_code, start_data, end_data;
unsigned long reloc_func_desc = 0;
char passed_fileno[6];
struct files_struct *files;
int executable_stack = EXSTACK_DEFAULT;
unsigned long def_flags = 0;
Expand Down Expand Up @@ -789,62 +711,18 @@ static int load_elf_binary(struct linux_binprm *bprm, struct pt_regs *regs)

/* Some simple consistency checks for the interpreter */
if (elf_interpreter) {
static int warn;
#ifdef CONFIG_ARCH_SUPPORTS_AOUT
interpreter_type = INTERPRETER_ELF | INTERPRETER_AOUT;

/* Now figure out which format our binary is */
if ((N_MAGIC(loc->interp_ex) != OMAGIC) &&
(N_MAGIC(loc->interp_ex) != ZMAGIC) &&
(N_MAGIC(loc->interp_ex) != QMAGIC))
interpreter_type = INTERPRETER_ELF;
#else
interpreter_type = INTERPRETER_ELF;
#endif
if (memcmp(loc->interp_elf_ex.e_ident, ELFMAG, SELFMAG) != 0)
interpreter_type &= ~INTERPRETER_ELF;

if (IS_AOUT_INTERP(interpreter_type) && warn < 10) {
printk(KERN_WARNING "a.out ELF interpreter %s is "
"deprecated and will not be supported "
"after Linux 2.6.25\n", elf_interpreter);
warn++;
}

retval = -ELIBBAD;
if (!interpreter_type)
/* Not an ELF interpreter */
if (memcmp(loc->interp_elf_ex.e_ident, ELFMAG, SELFMAG) != 0)
goto out_free_dentry;

/* Make sure only one type was selected */
if ((interpreter_type & INTERPRETER_ELF) &&
interpreter_type != INTERPRETER_ELF) {
// FIXME - ratelimit this before re-enabling
// printk(KERN_WARNING "ELF: Ambiguous type, using ELF\n");
interpreter_type = INTERPRETER_ELF;
}
/* Verify the interpreter has a valid arch */
if ((interpreter_type == INTERPRETER_ELF) &&
!elf_check_arch(&loc->interp_elf_ex))
if (!elf_check_arch(&loc->interp_elf_ex))
goto out_free_dentry;
} else {
/* Executables without an interpreter also need a personality */
SET_PERSONALITY(loc->elf_ex, 0);
}

/* OK, we are done with that, now set up the arg stuff,
and then start this sucker up */
if (IS_AOUT_INTERP(interpreter_type) && !bprm->sh_bang) {
char *passed_p = passed_fileno;
sprintf(passed_fileno, "%d", elf_exec_fileno);

if (elf_interpreter) {
retval = copy_strings_kernel(1, &passed_p, bprm);
if (retval)
goto out_free_dentry;
bprm->argc++;
}
}

/* Flush all traces of the currently running executable */
retval = flush_old_exec(bprm);
if (retval)
Expand Down Expand Up @@ -1022,24 +900,19 @@ static int load_elf_binary(struct linux_binprm *bprm, struct pt_regs *regs)
}

if (elf_interpreter) {
if (IS_AOUT_INTERP(interpreter_type)) {
elf_entry = load_aout_interp(&loc->interp_ex,
interpreter);
} else {
unsigned long uninitialized_var(interp_map_addr);

elf_entry = load_elf_interp(&loc->interp_elf_ex,
interpreter,
&interp_map_addr,
load_bias);
if (!IS_ERR((void *)elf_entry)) {
/*
* load_elf_interp() returns relocation
* adjustment
*/
interp_load_addr = elf_entry;
elf_entry += loc->interp_elf_ex.e_entry;
}
unsigned long uninitialized_var(interp_map_addr);

elf_entry = load_elf_interp(&loc->interp_elf_ex,
interpreter,
&interp_map_addr,
load_bias);
if (!IS_ERR((void *)elf_entry)) {
/*
* load_elf_interp() returns relocation
* adjustment
*/
interp_load_addr = elf_entry;
elf_entry += loc->interp_elf_ex.e_entry;
}
if (BAD_ADDR(elf_entry)) {
force_sig(SIGSEGV, current);
Expand All @@ -1063,8 +936,7 @@ static int load_elf_binary(struct linux_binprm *bprm, struct pt_regs *regs)

kfree(elf_phdata);

if (!IS_AOUT_INTERP(interpreter_type))
sys_close(elf_exec_fileno);
sys_close(elf_exec_fileno);

set_binfmt(&elf_format);

Expand All @@ -1079,15 +951,12 @@ static int load_elf_binary(struct linux_binprm *bprm, struct pt_regs *regs)
compute_creds(bprm);
current->flags &= ~PF_FORKNOEXEC;
retval = create_elf_tables(bprm, &loc->elf_ex,
IS_AOUT_INTERP(interpreter_type),
load_addr, interp_load_addr);
if (retval < 0) {
send_sig(SIGKILL, current, 0);
goto out;
}
/* N.B. passed_fileno might not be initialized? */
if (IS_AOUT_INTERP(interpreter_type))
current->mm->arg_start += strlen(passed_fileno) + 1;
current->mm->end_code = end_code;
current->mm->start_code = start_code;
current->mm->start_data = start_data;
Expand Down

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