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authorDamien Le Moal <damien.lemoal@wdc.com>2021-04-17 10:10:08 +0900
committerGreg Ungerer <gerg@linux-m68k.org>2021-04-19 09:56:37 +1000
commit04d82a6d0881ef1ab1e9f66f10805177ee2fb1e8 (patch)
tree24c5ead3c1bb507a8682a01b98a278eb95108adb /fs/binfmt_flat.c
parentbf05bf16c76bb44ab5156223e1e58e26dfe30a88 (diff)
downloadlwn-04d82a6d0881ef1ab1e9f66f10805177ee2fb1e8.tar.gz
lwn-04d82a6d0881ef1ab1e9f66f10805177ee2fb1e8.zip
binfmt_flat: allow not offsetting data start
Commit 2217b9826246 ("binfmt_flat: revert "binfmt_flat: don't offset the data start"") restored offsetting the start of the data section by a number of words defined by MAX_SHARED_LIBS. As a result, since MAX_SHARED_LIBS is never 0, a gap between the text and data sections always exists. For architectures which cannot support a such gap between the text and data sections (e.g. riscv nommu), flat binary programs cannot be executed. To allow an architecture to request no data start offset to allow for contiguous text and data sections for binaries flagged with FLAT_FLAG_RAM, introduce the new config option CONFIG_BINFMT_FLAT_NO_DATA_START_OFFSET. Using this new option, the macro DATA_START_OFFSET_WORDS is conditionally defined in binfmt_flat.c to MAX_SHARED_LIBS for architectures tolerating or needing the data start offset (CONFIG_BINFMT_FLAT_NO_DATA_START_OFFSET disabled case) and to 0 when CONFIG_BINFMT_FLAT_NO_DATA_START_OFFSET is enabled. DATA_START_OFFSET_WORDS is used in load_flat_file() to calculate the data section length and start position. Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com> Signed-off-by: Greg Ungerer <gerg@linux-m68k.org>
Diffstat (limited to 'fs/binfmt_flat.c')
-rw-r--r--fs/binfmt_flat.c18
1 files changed, 13 insertions, 5 deletions
diff --git a/fs/binfmt_flat.c b/fs/binfmt_flat.c
index b9c658e0548e..a1072c6a2341 100644
--- a/fs/binfmt_flat.c
+++ b/fs/binfmt_flat.c
@@ -74,6 +74,12 @@
#define MAX_SHARED_LIBS (1)
#endif
+#ifdef CONFIG_BINFMT_FLAT_NO_DATA_START_OFFSET
+#define DATA_START_OFFSET_WORDS (0)
+#else
+#define DATA_START_OFFSET_WORDS (MAX_SHARED_LIBS)
+#endif
+
struct lib_info {
struct {
unsigned long start_code; /* Start of text segment */
@@ -576,7 +582,8 @@ 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 +
+ DATA_START_OFFSET_WORDS * sizeof(unsigned long);
len = PAGE_ALIGN(len);
realdatastart = vm_mmap(NULL, 0, len,
PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE, 0);
@@ -591,7 +598,7 @@ static int load_flat_file(struct linux_binprm *bprm,
goto err;
}
datapos = ALIGN(realdatastart +
- MAX_SHARED_LIBS * sizeof(unsigned long),
+ DATA_START_OFFSET_WORDS * sizeof(unsigned long),
FLAT_DATA_ALIGN);
pr_debug("Allocated data+bss+stack (%u bytes): %lx\n",
@@ -622,7 +629,8 @@ 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 +
+ DATA_START_OFFSET_WORDS * sizeof(u32);
len = PAGE_ALIGN(len);
textpos = vm_mmap(NULL, 0, len,
PROT_READ | PROT_EXEC | PROT_WRITE, MAP_PRIVATE, 0);
@@ -638,7 +646,7 @@ static int load_flat_file(struct linux_binprm *bprm,
realdatastart = textpos + ntohl(hdr->data_start);
datapos = ALIGN(realdatastart +
- MAX_SHARED_LIBS * sizeof(u32),
+ DATA_START_OFFSET_WORDS * sizeof(u32),
FLAT_DATA_ALIGN);
reloc = (__be32 __user *)
@@ -714,7 +722,7 @@ static int load_flat_file(struct linux_binprm *bprm,
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));
+ DATA_START_OFFSET_WORDS * sizeof(u32));
goto err;
}
}