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Subject[PATCH 14/15] binfmt_flat: don't offset the data start
Date
Ever since the initial commit of the binfmt_flat shared library
support back in the bitkeeper days we've offset the actual in-memory
.data start by one field per possible shared library, or 1 in case
shared library support isn't enabled. I can't find anything in the
loader that actually makes use of it, nor was it present before
shared library support it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
fs/binfmt_flat.c | 20 ++++++++------------
1 file changed, 8 insertions(+), 12 deletions(-)

diff --git a/fs/binfmt_flat.c b/fs/binfmt_flat.c
index 2c7f32d5435f..e1ccc9f14150 100644
--- a/fs/binfmt_flat.c
+++ b/fs/binfmt_flat.c
@@ -572,7 +572,7 @@ static int load_flat_file(struct linux_binprm *bprm,
goto err;
}

- len = data_len + extra + MAX_SHARED_LIBS * sizeof(unsigned long);
+ len = data_len + extra;
len = PAGE_ALIGN(len);
realdatastart = vm_mmap(NULL, 0, len,
PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE, 0);
@@ -586,9 +586,7 @@ static int load_flat_file(struct linux_binprm *bprm,
vm_munmap(textpos, text_len);
goto err;
}
- datapos = ALIGN(realdatastart +
- MAX_SHARED_LIBS * sizeof(unsigned long),
- FLAT_DATA_ALIGN);
+ datapos = ALIGN(realdatastart, FLAT_DATA_ALIGN);

pr_debug("Allocated data+bss+stack (%u bytes): %lx\n",
data_len + bss_len + stack_len, datapos);
@@ -618,7 +616,7 @@ static int load_flat_file(struct linux_binprm *bprm,
memp_size = len;
} else {

- len = text_len + data_len + extra + MAX_SHARED_LIBS * sizeof(u32);
+ len = text_len + data_len + extra;
len = PAGE_ALIGN(len);
textpos = vm_mmap(NULL, 0, len,
PROT_READ | PROT_EXEC | PROT_WRITE, MAP_PRIVATE, 0);
@@ -633,9 +631,7 @@ static int load_flat_file(struct linux_binprm *bprm,
}

realdatastart = textpos + ntohl(hdr->data_start);
- datapos = ALIGN(realdatastart +
- MAX_SHARED_LIBS * sizeof(u32),
- FLAT_DATA_ALIGN);
+ datapos = ALIGN(realdatastart, FLAT_DATA_ALIGN);

reloc = (__be32 __user *)
(datapos + (ntohl(hdr->reloc_start) - text_len));
@@ -652,8 +648,9 @@ static int load_flat_file(struct linux_binprm *bprm,
(text_len + full_data
- sizeof(struct flat_hdr)),
0);
- memmove((void *) datapos, (void *) realdatastart,
- full_data);
+ if (datapos != realdatastart)
+ memmove((void *)datapos, (void *)realdatastart,
+ full_data);
#else
/*
* This is used on MMU systems mainly for testing.
@@ -709,8 +706,7 @@ static int load_flat_file(struct linux_binprm *bprm,
if (IS_ERR_VALUE(result)) {
ret = result;
pr_err("Unable to read code+data+bss, errno %d\n", ret);
- vm_munmap(textpos, text_len + data_len + extra +
- MAX_SHARED_LIBS * sizeof(u32));
+ vm_munmap(textpos, text_len + data_len + extra);
goto err;
}
}
--
2.20.1
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