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authorDavid Howells <dhowells@redhat.com>2009-01-08 12:04:47 +0000
committerDavid Howells <dhowells@redhat.com>2009-01-08 12:04:47 +0000
commit0f3e442a403a344a5d0a49af9ecd7632b7e7343a (patch)
tree6d9557c9b058e04d9afc3ea7032bc155ff79b97e
parentf4bbf51050a1e1dd485e9cd89eef4619a7453d71 (diff)
FLAT: Don't attempt to expand the userspace stack to fill the space allocated
Stop the FLAT binfmt from attempting to expand the userspace stack and brk segments to fill the space actually allocated for it. The space allocated may be rounded up by mmap(), and may be wasted. However, finding out how much space we actually obtained uses the contentious kobjsize() function which we'd like to get rid of as it doesn't necessarily work for all slab allocators. Signed-off-by: David Howells <dhowells@redhat.com> Tested-by: Mike Frysinger <vapier.adi@gmail.com> Acked-by: Paul Mundt <lethal@linux-sh.org>
-rw-r--r--fs/binfmt_flat.c34
1 files changed, 11 insertions, 23 deletions
diff --git a/fs/binfmt_flat.c b/fs/binfmt_flat.c
index 7bbd5c6b3725..5cebf0b37798 100644
--- a/fs/binfmt_flat.c
+++ b/fs/binfmt_flat.c
@@ -417,8 +417,8 @@ static int load_flat_file(struct linux_binprm * bprm,
unsigned long textpos = 0, datapos = 0, result;
unsigned long realdatastart = 0;
unsigned long text_len, data_len, bss_len, stack_len, flags;
- unsigned long len, reallen, memp = 0;
- unsigned long extra, rlim;
+ unsigned long len, memp = 0;
+ unsigned long memp_size, extra, rlim;
unsigned long *reloc = 0, *rp;
struct inode *inode;
int i, rev, relocs = 0;
@@ -543,17 +543,10 @@ static int load_flat_file(struct linux_binprm * bprm,
}
len = data_len + extra + MAX_SHARED_LIBS * sizeof(unsigned long);
+ len = PAGE_ALIGN(len);
down_write(&current->mm->mmap_sem);
realdatastart = do_mmap(0, 0, len,
PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE, 0);
- /* Remap to use all availabe slack region space */
- if (realdatastart && (realdatastart < (unsigned long)-4096)) {
- reallen = kobjsize((void *)realdatastart);
- if (reallen > len) {
- realdatastart = do_mremap(realdatastart, len,
- reallen, MREMAP_FIXED, realdatastart);
- }
- }
up_write(&current->mm->mmap_sem);
if (realdatastart == 0 || realdatastart >= (unsigned long)-4096) {
@@ -591,21 +584,14 @@ static int load_flat_file(struct linux_binprm * bprm,
reloc = (unsigned long *) (datapos+(ntohl(hdr->reloc_start)-text_len));
memp = realdatastart;
-
+ memp_size = len;
} else {
len = text_len + data_len + extra + MAX_SHARED_LIBS * sizeof(unsigned long);
+ len = PAGE_ALIGN(len);
down_write(&current->mm->mmap_sem);
textpos = do_mmap(0, 0, len,
PROT_READ | PROT_EXEC | PROT_WRITE, MAP_PRIVATE, 0);
- /* Remap to use all availabe slack region space */
- if (textpos && (textpos < (unsigned long) -4096)) {
- reallen = kobjsize((void *)textpos);
- if (reallen > len) {
- textpos = do_mremap(textpos, len, reallen,
- MREMAP_FIXED, textpos);
- }
- }
up_write(&current->mm->mmap_sem);
if (!textpos || textpos >= (unsigned long) -4096) {
@@ -622,7 +608,7 @@ static int load_flat_file(struct linux_binprm * bprm,
reloc = (unsigned long *) (textpos + ntohl(hdr->reloc_start) +
MAX_SHARED_LIBS * sizeof(unsigned long));
memp = textpos;
-
+ memp_size = len;
#ifdef CONFIG_BINFMT_ZFLAT
/*
* load it all in and treat it like a RAM load from now on
@@ -680,10 +666,12 @@ static int load_flat_file(struct linux_binprm * bprm,
* set up the brk stuff, uses any slack left in data/bss/stack
* allocation. We put the brk after the bss (between the bss
* and stack) like other platforms.
+ * Userspace code relies on the stack pointer starting out at
+ * an address right at the end of a page.
*/
current->mm->start_brk = datapos + data_len + bss_len;
current->mm->brk = (current->mm->start_brk + 3) & ~3;
- current->mm->context.end_brk = memp + kobjsize((void *) memp) - stack_len;
+ current->mm->context.end_brk = memp + memp_size - stack_len;
}
if (flags & FLAT_FLAG_KTRACE)
@@ -790,8 +778,8 @@ static int load_flat_file(struct linux_binprm * bprm,
/* zero the BSS, BRK and stack areas */
memset((void*)(datapos + data_len), 0, bss_len +
- (memp + kobjsize((void *) memp) - stack_len - /* end brk */
- libinfo->lib_list[id].start_brk) + /* start brk */
+ (memp + memp_size - stack_len - /* end brk */
+ libinfo->lib_list[id].start_brk) + /* start brk */
stack_len);
return 0;

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