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[patch] linux: RFC: elf_check_arch() rework

To: linux-mips@fnet.fr, linux-mips@oss.sgi.com
Subject: [patch] linux: RFC: elf_check_arch() rework
From: "Maciej W. Rozycki" <macro@ds2.pg.gda.pl>
Date: Wed, 24 Jul 2002 19:05:36 +0200 (MET DST)
Organization: Technical University of Gdansk
Reply-to: "Maciej W. Rozycki" <macro@ds2.pg.gda.pl>
Sender: owner-linux-mips@oss.sgi.com
Hello,

 After noticing I cannot run a trivial ELF64 program because of the
EF_MIPS_ARCH_3 flag (quite a reasonable setting for a 64-bit executable,
isn't it?), I concluded a considerable rework of elf_check_arch() is
needed as what we currently have is inadequate. 

 Here is my proposal.  I think binfmt_elf.c for mips and binfmt_elf32.c
for mips64 should accept all ELF32 binaries either with no ABI mark (as
produced by most versions of binutils) or with a 32 (aka o32) ABI one and
binfmt_elf.c for mips64 should accept all ELF32 binaries with an n32 ABI
mark and all ELF64 ones (which essentially means the 64 aka n64 ABI). 
Everything else (i.e. o64 and EABIs) is rejected.  The patch adds
necessary ELF file header flag definitions and synchronizes a few wrong
ones to the binutils' definitions as well. 

 It removes the bogus check of architecture flags as they are really
irrelevant -- the code is intended to handle executable formats and not
execution of code.  If a user incorporates unsupported opcodes, he'll just
get SIGILL at one moment.  We may actually check if an architecture is
supported even no other Linux port seems to care, but then the comparison
should be against mips_cpu.isa_level and not against hardcoded constants. 

 Note, this is an RFC at this stage -- I haven't tested the code
adequately for an immediate inclusion, even if it looks obvious.  There
should be no problems with code made with old binutils as unset flags are
treated as (o)32. 

  Maciej

-- 
+  Maciej W. Rozycki, Technical University of Gdansk, Poland   +
+--------------------------------------------------------------+
+        e-mail: macro@ds2.pg.gda.pl, PGP key available        +

patch-mips-2.4.19-rc1-20020719-mips64-elf-2
diff -up --recursive --new-file 
linux-mips-2.4.19-rc1-20020719.macro/arch/mips64/kernel/binfmt_elf32.c 
linux-mips-2.4.19-rc1-20020719/arch/mips64/kernel/binfmt_elf32.c
--- linux-mips-2.4.19-rc1-20020719.macro/arch/mips64/kernel/binfmt_elf32.c      
2002-06-29 03:01:44.000000000 +0000
+++ linux-mips-2.4.19-rc1-20020719/arch/mips64/kernel/binfmt_elf32.c    
2002-07-23 23:15:27.000000000 +0000
@@ -27,8 +27,26 @@ typedef elf_greg_t elf_gregset_t[ELF_NGR
 typedef double elf_fpreg_t;
 typedef elf_fpreg_t elf_fpregset_t[ELF_NFPREG];
 
-#define elf_check_arch(x)      \
-       ((x)->e_machine == EM_MIPS)
+/*
+ * This is used to ensure we don't load something for the wrong architecture.
+ */
+#define elf_check_arch(hdr)                                            \
+({                                                                     \
+       int __res = 1;                                                  \
+       struct elfhdr *__h = (hdr);                                     \
+                                                                       \
+       if (__h->e_machine != EM_MIPS)                                  \
+               __res = 0;                                              \
+       if (__h->e_ident[EI_CLASS] != ELFCLASS32)                       \
+               __res = 0;                                              \
+       if ((__h->e_flags & EF_MIPS_ABI2) != 0)                         \
+               __res = 0;                                              \
+       if (((__h->e_flags & EF_MIPS_ABI) != 0) &&                      \
+           ((__h->e_flags & EF_MIPS_ABI) != EF_MIPS_ABI_O32))          \
+               __res = 0;                                              \
+                                                                       \
+       __res;                                                          \
+})
 
 #define TASK32_SIZE            0x80000000UL
 #undef ELF_ET_DYN_BASE
diff -up --recursive --new-file 
linux-mips-2.4.19-rc1-20020719.macro/include/asm-mips/elf.h 
linux-mips-2.4.19-rc1-20020719/include/asm-mips/elf.h
--- linux-mips-2.4.19-rc1-20020719.macro/include/asm-mips/elf.h 2002-04-25 
02:57:43.000000000 +0000
+++ linux-mips-2.4.19-rc1-20020719/include/asm-mips/elf.h       2002-07-23 
22:50:48.000000000 +0000
@@ -16,10 +16,11 @@
 #define EF_MIPS_ARCH_3      0x20000000  /* -mips3 code.  */
 #define EF_MIPS_ARCH_4      0x30000000  /* -mips4 code.  */
 #define EF_MIPS_ARCH_5      0x40000000  /* -mips5 code.  */
-#define EF_MIPS_ARCH_32     0x60000000  /* MIPS32 code.  */
-#define EF_MIPS_ARCH_64     0x70000000  /* MIPS64 code.  */
-#define EF_MIPS_ARCH_32R2   0x80000000  /* MIPS32 code.  */
-#define EF_MIPS_ARCH_64R2   0x90000000  /* MIPS64 code.  */
+#define EF_MIPS_ARCH_32     0x50000000  /* MIPS32 code.  */
+#define EF_MIPS_ARCH_64     0x60000000  /* MIPS64 code.  */
+/* The ABI of the file. */
+#define EF_MIPS_ABI_O32     0x00001000  /* O32 ABI.  */
+#define EF_MIPS_ABI_O64     0x00002000  /* O32 extended for 64 bit.  */
 
 typedef unsigned long elf_greg_t;
 typedef elf_greg_t elf_gregset_t[ELF_NGREG];
@@ -37,10 +38,12 @@ typedef elf_fpreg_t elf_fpregset_t[ELF_N
                                                                        \
        if (__h->e_machine != EM_MIPS)                                  \
                __res = 0;                                              \
-       if (((__h->e_flags & EF_MIPS_ARCH) != EF_MIPS_ARCH_1) &&        \
-           ((__h->e_flags & EF_MIPS_ARCH) != EF_MIPS_ARCH_2) &&        \
-           ((__h->e_flags & EF_MIPS_ARCH) != EF_MIPS_ARCH_32) &&       \
-           ((__h->e_flags & EF_MIPS_ARCH) != EF_MIPS_ARCH_32R2))       \
+       if (__h->e_ident[EI_CLASS] != ELFCLASS32)                       \
+               __res = 0;                                              \
+       if ((__h->e_flags & EF_MIPS_ABI2) != 0)                         \
+               __res = 0;                                              \
+       if (((__h->e_flags & EF_MIPS_ABI) != 0) &&                      \
+           ((__h->e_flags & EF_MIPS_ABI) != EF_MIPS_ABI_O32))          \
                __res = 0;                                              \
                                                                        \
        __res;                                                          \
diff -up --recursive --new-file 
linux-mips-2.4.19-rc1-20020719.macro/include/asm-mips64/elf.h 
linux-mips-2.4.19-rc1-20020719/include/asm-mips64/elf.h
--- linux-mips-2.4.19-rc1-20020719.macro/include/asm-mips64/elf.h       
2002-07-22 08:49:30.000000000 +0000
+++ linux-mips-2.4.19-rc1-20020719/include/asm-mips64/elf.h     2002-07-23 
23:12:28.000000000 +0000
@@ -9,21 +9,23 @@
 #include <asm/ptrace.h>
 #include <asm/user.h>
 
-#ifndef ELF_ARCH
-/* ELF register definitions */
-#define ELF_NGREG      45
-#define ELF_NFPREG     33
-
-/* ELF header e_flags defines. MIPS architecture level. */
+/* ELF header e_flags defines. */
+/* MIPS architecture level. */
 #define EF_MIPS_ARCH_1      0x00000000  /* -mips1 code.  */
 #define EF_MIPS_ARCH_2      0x10000000  /* -mips2 code.  */
 #define EF_MIPS_ARCH_3      0x20000000  /* -mips3 code.  */
 #define EF_MIPS_ARCH_4      0x30000000  /* -mips4 code.  */
 #define EF_MIPS_ARCH_5      0x40000000  /* -mips5 code.  */
-#define EF_MIPS_ARCH_32     0x60000000  /* MIPS32 code.  */
-#define EF_MIPS_ARCH_64     0x70000000  /* MIPS64 code.  */
-#define EF_MIPS_ARCH_32R2   0x80000000  /* MIPS32 code.  */
-#define EF_MIPS_ARCH_64R2   0x90000000  /* MIPS64 code.  */
+#define EF_MIPS_ARCH_32     0x50000000  /* MIPS32 code.  */
+#define EF_MIPS_ARCH_64     0x60000000  /* MIPS64 code.  */
+/* The ABI of the file. */
+#define EF_MIPS_ABI_O32     0x00001000  /* O32 ABI.  */
+#define EF_MIPS_ABI_O64     0x00002000  /* O32 extended for 64 bit.  */
+
+#ifndef ELF_ARCH
+/* ELF register definitions */
+#define ELF_NGREG      45
+#define ELF_NFPREG     33
 
 typedef unsigned long elf_greg_t;
 typedef elf_greg_t elf_gregset_t[ELF_NGREG];
@@ -41,14 +43,9 @@ typedef elf_fpreg_t elf_fpregset_t[ELF_N
                                                                        \
        if (__h->e_machine != EM_MIPS)                                  \
                __res = 0;                                              \
-       if (sizeof(elf_caddr_t) == 8 &&                                 \
-           __h->e_ident[EI_CLASS] == ELFCLASS32)                       \
-               __res = 0;                                              \
-       if (((__h->e_flags & EF_MIPS_ARCH) != EF_MIPS_ARCH_1) &&        \
-           ((__h->e_flags & EF_MIPS_ARCH) != EF_MIPS_ARCH_2) &&        \
-           ((__h->e_flags & EF_MIPS_ARCH) != EF_MIPS_ARCH_32) &&       \
-           ((__h->e_flags & EF_MIPS_ARCH) != EF_MIPS_ARCH_32R2))       \
-                __res = 0;                                             \
+       if ((__h->e_ident[EI_CLASS] == ELFCLASS32) &&                   \
+           ((__h->e_flags & EF_MIPS_ABI2) == 0))                       \
+               __res = 0;                                              \
                                                                        \
        __res;                                                          \
 })
diff -up --recursive --new-file 
linux-mips-2.4.19-rc1-20020719.macro/include/linux/elf.h 
linux-mips-2.4.19-rc1-20020719/include/linux/elf.h
--- linux-mips-2.4.19-rc1-20020719.macro/include/linux/elf.h    2002-07-22 
08:49:30.000000000 +0000
+++ linux-mips-2.4.19-rc1-20020719/include/linux/elf.h  2002-07-23 
22:18:54.000000000 +0000
@@ -37,6 +37,9 @@ typedef __s64 Elf64_Sxword;
 #define EF_MIPS_NOREORDER 0x00000001
 #define EF_MIPS_PIC       0x00000002
 #define EF_MIPS_CPIC      0x00000004
+#define EF_MIPS_ABI2      0x00000020
+#define EF_MIPS_32BITMODE 0x00000100
+#define EF_MIPS_ABI       0x0000f000
 #define EF_MIPS_ARCH      0xf0000000
 
 /* These constants define the different elf file types */


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