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[PATCH] ARM: Identify the hard-float ABI in older ARM binaries
- From: Steve McIntyre <steve dot mcintyre at linaro dot org>
- To: libc-ports at sourceware dot org
- Cc: Carlos O'Donell <carlos at systemhalted dot org>, "Joseph S. Myers" <joseph at codesourcery dot com>, Marcus Shawcroft <marcus dot shawcroft at linaro dot org>
- Date: Mon, 3 Dec 2012 15:41:54 +0000
- Subject: [PATCH] ARM: Identify the hard-float ABI in older ARM binaries
- References: <20121203153446.GD22509@einval.com> <20121203153747.GE22509@einval.com>
Hi,
I expect this one to be more controversial and I'll understand if
people don't want to accept it! It's a variation on the code that's in
use today in Debian/Ubuntu to be able to distinguish between soft- and
hard-float ABI libraries. In time, the new ELF flags will make this
obsolete. Until that time, this adds a fallback for older binaries
created before those flags went into binutils.
==============================
Identify the hard-float ABI in older ARM binaries
* ports/sysdeps/unix/sysv/linux/arm/readelflib.c (read_uleb128):
New function.
(is_library_hf): Ditto.
(process_elf_file): Call is_library_hf() to detect HF ABI if
we don't have clear evidence from the ELF flags.
Signed-off-by: Steve McIntyre <steve.mcintyre@linaro.org>
---
ports/sysdeps/unix/sysv/linux/arm/readelflib.c | 129 ++++++++++++++++++++++++
1 file changed, 129 insertions(+)
diff --git a/ports/sysdeps/unix/sysv/linux/arm/readelflib.c b/ports/sysdeps/unix/sysv/linux/arm/readelflib.c
index e4ba2b0..0287644 100644
--- a/ports/sysdeps/unix/sysv/linux/arm/readelflib.c
+++ b/ports/sysdeps/unix/sysv/linux/arm/readelflib.c
@@ -25,6 +25,133 @@ int process_elf64_file (const char *file_name, const char *lib, int *flag,
unsigned int *osversion, char **soname,
void *file_contents, size_t file_length);
+#undef __ELF_NATIVE_CLASS
+#define __ELF_NATIVE_CLASS 32
+
+/* Read an unsigned leb128 value from P, store the value in VAL, return
+ P incremented past the value. We assume that a word is large enough to
+ hold any value so encoded; if it is smaller than a pointer on some target,
+ pointers should not be leb128 encoded on that target. */
+static const unsigned char *
+read_uleb128 (const unsigned char *p, unsigned long *val)
+{
+ unsigned int shift = 0;
+ unsigned char byte;
+ unsigned long result;
+
+ result = 0;
+ do
+ {
+ byte = *p++;
+ result |= (byte & 0x7f) << shift;
+ shift += 7;
+ }
+ while (byte & 0x80);
+
+ *val = result;
+ return p;
+}
+
+#define ATTR_TAG_FILE 1
+#define ABI_VFP_args 28
+#define VFP_ARGS_IN_VFP_REGS 1
+
+/* Check the ABI in the ARM attributes. Search through the section
+ headers looking for the ARM attributes section, then check the
+ VFP_ARGS attribute. */
+static int is_library_hf(const char *file_name, void *file_contents, size_t file_length)
+{
+ unsigned int i;
+ ElfW(Ehdr) *ehdr = (ElfW(Ehdr) *) file_contents;
+ ElfW(Shdr) *shdrs;
+
+ shdrs = file_contents + ehdr->e_shoff;
+ for (i = 0; i < ehdr->e_shnum; i++)
+ {
+ if (SHT_ARM_ATTRIBUTES == shdrs[i].sh_type)
+ {
+ /* We've found a likely section. Load the contents and
+ * check the tags */
+ unsigned char *p = (unsigned char *)file_contents + shdrs[i].sh_offset;
+ unsigned char * end;
+
+ /* Sanity-check the attribute section details. Make sure
+ * that it's the "aeabi" section, that's all we care
+ * about. */
+ if (*p == 'A')
+ {
+ unsigned long len = shdrs[i].sh_size - 1;
+ unsigned long namelen;
+ p++;
+
+ while (len > 0)
+ {
+ unsigned long section_len = p[0] | p[1] << 8 | p[2] << 16 | p[3] << 24;
+ if (section_len > len)
+ section_len = len;
+
+ p += 4;
+ len -= section_len;
+ section_len -= 4;
+
+ if (0 != strcmp((char *)p, "aeabi"))
+ {
+ p += section_len;
+ continue;
+ }
+ namelen = strlen((char *)p) + 1;
+ p += namelen;
+ section_len -= namelen;
+
+ /* We're in a valid section. Walk through this
+ * section looking for the tag we care about
+ * (ABI_VFP_args) */
+ while (section_len > 0)
+ {
+ unsigned long tag, val = 0;
+ unsigned long size;
+
+ end = p;
+ tag = (*p++);
+ size = p[0] | p[1] << 8 | p[2] << 16 | p[3] << 24;
+ if (size > section_len)
+ size = section_len;
+ p += 4;
+
+ section_len -= size;
+ end += size;
+ if (ATTR_TAG_FILE != tag)
+ {
+ /* ignore, we don't care */
+ p = end;
+ continue;
+ }
+ while (p < end)
+ {
+ p = read_uleb128 (p, &tag);
+ /* Handle the different types of tag. */
+ if ( (tag == 4) || (tag == 5) || (tag == 67) )
+ {
+ /* Special cases for string values */
+ namelen = strlen((char *)p) + 1;
+ p += namelen;
+ }
+ else
+ {
+ p = read_uleb128 (p, &val);
+ }
+ if ( (tag == ABI_VFP_args) && (val == VFP_ARGS_IN_VFP_REGS) )
+ return 1;
+ }
+ }
+ }
+ }
+ }
+ }
+ return 0;
+}
+
+
/* Returns 0 if everything is ok, != 0 in case of error. */
int
process_elf_file (const char *file_name, const char *lib, int *flag,
@@ -47,6 +174,8 @@ process_elf_file (const char *file_name, const char *lib, int *flag,
*flag = FLAG_ARM_LIBHF|FLAG_ELF_LIBC6;
else if (elf32_header->e_flags & EF_ARM_ABI_FLOAT_SOFT)
*flag = FLAG_ELF_LIBC6;
+ else if (is_library_hf(file_name, file_contents, file_length))
+ *flag = FLAG_ARM_LIBHF|FLAG_ELF_LIBC6;
}
}
else
--
1.7.10.4
Cheers,
--
Steve McIntyre steve.mcintyre@linaro.org
<http://www.linaro.org/> Linaro.org | Open source software for ARM SoCs