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Subject[patch -v2] flat: fix data sections alignment
From: Oskar Schirmer <os@emlix.com>

The flat loader uses an architecture's flat_stack_align() to align the
stack but assumes word-alignment is enough for the data sections.

However, on the Xtensa S6000 we have registers up to 128bit width
which can be used from userspace and therefor need userspace stack and
data-section alignment of at least this size.

This patch drops flat_stack_align() and uses the same alignment that
is required for slab caches, ARCH_SLAB_MINALIGN, or wordsize if it's
not defined by the architecture.

It also fixes m32r which was obviously kaput, aligning an
uninitialized stack entry instead of the stack pointer.

Signed-off-by: Oskar Schirmer <os@emlix.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Bryan Wu <cooloney@kernel.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Greg Ungerer <gerg@uclinux.org>
Signed-off-by: Johannes Weiner <jw@emlix.com>
---
arch/arm/include/asm/flat.h | 3 ---
arch/blackfin/include/asm/flat.h | 1 -
arch/h8300/include/asm/flat.h | 1 -
arch/m68k/include/asm/flat.h | 1 -
arch/sh/include/asm/flat.h | 1 -
fs/binfmt_flat.c | 37 ++++++++++++++++++++++---------------
include/asm-m32r/flat.h | 1 -
7 files changed, 22 insertions(+), 23 deletions(-)

Paul, please note that on sh ARCH_SLAB_MINALIGN is defined to be 8
while the userspace stack was aligned to 4 before. I suppose aligning
the stack (and data sections) to 8 as well is the right thing...?

version 2:
Align ARCH_SLAB_MINALIGN if defined, fall back to wordsize, drop all
the flat_stack_align()s as they mean the same

--- a/fs/binfmt_flat.c
+++ b/fs/binfmt_flat.c
@@ -41,6 +41,7 @@
#include <asm/uaccess.h>
#include <asm/unaligned.h>
#include <asm/cacheflush.h>
+#include <asm/page.h>

/****************************************************************************/

@@ -54,6 +55,12 @@
#define DBG_FLT(a...)
#endif

+#ifdef ARCH_SLAB_MINALIGN
+#define FLAT_DATA_ALIGN (ARCH_SLAB_MINALIGN)
+#else
+#define FLAT_DATA_ALIGN (sizeof(void *))
+#endif
+
#define RELOC_FAILED 0xff00ff01 /* Relocation incorrect somewhere */
#define UNLOADED_LIB 0x7ff000ff /* Placeholder for unused library */

@@ -114,20 +121,18 @@ static unsigned long create_flat_tables(
int envc = bprm->envc;
char uninitialized_var(dummy);

- sp = (unsigned long *) ((-(unsigned long)sizeof(char *))&(unsigned long) p);
-
- sp -= envc+1;
- envp = sp;
- sp -= argc+1;
- argv = sp;
+ sp = (unsigned long *)p;
+ sp -= (envc + argc + 2) + 1 + (flat_argvp_envp_on_stack() ? 2 : 0);
+ sp = (unsigned long *) ((unsigned long)sp & -FLAT_DATA_ALIGN);
+ argv = sp + 1 + (flat_argvp_envp_on_stack() ? 2 : 0);
+ envp = argv + (argc + 1);

- flat_stack_align(sp);
if (flat_argvp_envp_on_stack()) {
- --sp; put_user((unsigned long) envp, sp);
- --sp; put_user((unsigned long) argv, sp);
+ put_user((unsigned long) envp, sp + 2);
+ put_user((unsigned long) argv, sp + 1);
}

- put_user(argc,--sp);
+ put_user(argc,sp);
current->mm->arg_start = (unsigned long) p;
while (argc-->0) {
put_user((unsigned long) p, argv++);
@@ -558,7 +563,8 @@ static int load_flat_file(struct linux_b
ret = realdatastart;
goto err;
}
- datapos = realdatastart + MAX_SHARED_LIBS * sizeof(unsigned long);
+ datapos = ALIGN(realdatastart + MAX_SHARED_LIBS * sizeof(unsigned long),
+ FLAT_DATA_ALIGN);

DBG_FLT("BINFMT_FLAT: Allocated data+bss+stack (%d bytes): %x\n",
(int)(data_len + bss_len + stack_len), (int)datapos);
@@ -604,9 +610,10 @@ static int load_flat_file(struct linux_b
}

realdatastart = textpos + ntohl(hdr->data_start);
- datapos = realdatastart + MAX_SHARED_LIBS * sizeof(unsigned long);
- reloc = (unsigned long *) (textpos + ntohl(hdr->reloc_start) +
- MAX_SHARED_LIBS * sizeof(unsigned long));
+ datapos = ALIGN(realdatastart + MAX_SHARED_LIBS * sizeof(unsigned long),
+ FLAT_DATA_ALIGN);
+
+ reloc = (unsigned long *) (datapos+(ntohl(hdr->reloc_start)-text_len));
memp = textpos;
memp_size = len;
#ifdef CONFIG_BINFMT_ZFLAT
@@ -854,7 +861,7 @@ static int load_flat_binary(struct linux
stack_len = TOP_OF_ARGS - bprm->p; /* the strings */
stack_len += (bprm->argc + 1) * sizeof(char *); /* the argv array */
stack_len += (bprm->envc + 1) * sizeof(char *); /* the envp array */
-
+ stack_len += FLAT_DATA_ALIGN;

res = load_flat_file(bprm, &libinfo, 0, &stack_len);
if (res > (unsigned long)-4096)
--- a/arch/arm/include/asm/flat.h
+++ b/arch/arm/include/asm/flat.h
@@ -5,9 +5,6 @@
#ifndef __ARM_FLAT_H__
#define __ARM_FLAT_H__

-/* An odd number of words will be pushed after this alignment, so
- deliberately misalign the value. */
-#define flat_stack_align(sp) sp = (void *)(((unsigned long)(sp) - 4) | 4)
#define flat_argvp_envp_on_stack() 1
#define flat_old_ram_flag(flags) (flags)
#define flat_reloc_valid(reloc, size) ((reloc) <= (size))
--- a/arch/blackfin/include/asm/flat.h
+++ b/arch/blackfin/include/asm/flat.h
@@ -10,7 +10,6 @@

#include <asm/unaligned.h>

-#define flat_stack_align(sp) /* nothing needed */
#define flat_argvp_envp_on_stack() 0
#define flat_old_ram_flag(flags) (flags)

--- a/arch/h8300/include/asm/flat.h
+++ b/arch/h8300/include/asm/flat.h
@@ -5,7 +5,6 @@
#ifndef __H8300_FLAT_H__
#define __H8300_FLAT_H__

-#define flat_stack_align(sp) /* nothing needed */
#define flat_argvp_envp_on_stack() 1
#define flat_old_ram_flag(flags) 1
#define flat_reloc_valid(reloc, size) ((reloc) <= (size))
--- a/arch/m68k/include/asm/flat.h
+++ b/arch/m68k/include/asm/flat.h
@@ -5,7 +5,6 @@
#ifndef __M68KNOMMU_FLAT_H__
#define __M68KNOMMU_FLAT_H__

-#define flat_stack_align(sp) /* nothing needed */
#define flat_argvp_envp_on_stack() 1
#define flat_old_ram_flag(flags) (flags)
#define flat_reloc_valid(reloc, size) ((reloc) <= (size))
--- a/arch/sh/include/asm/flat.h
+++ b/arch/sh/include/asm/flat.h
@@ -12,7 +12,6 @@
#ifndef __ASM_SH_FLAT_H
#define __ASM_SH_FLAT_H

-#define flat_stack_align(sp) /* nothing needed */
#define flat_argvp_envp_on_stack() 0
#define flat_old_ram_flag(flags) (flags)
#define flat_reloc_valid(reloc, size) ((reloc) <= (size))
--- a/include/asm-m32r/flat.h
+++ b/include/asm-m32r/flat.h
@@ -12,7 +12,6 @@
#ifndef __ASM_M32R_FLAT_H
#define __ASM_M32R_FLAT_H

-#define flat_stack_align(sp) (*sp += (*sp & 3 ? (4 - (*sp & 3)): 0))
#define flat_argvp_envp_on_stack() 0
#define flat_old_ram_flag(flags) (flags)
#define flat_set_persistent(relval, p) 0

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