OE tree imported from monotone branch org.openembedded.oz354fam083 at revision 8b12e3...

[familiar-h63xx-build.git] / org.handhelds.familiar / packages / uclibc / uclibc-0.9.28 / thumb-resolve.patch

# This change reimplements the ARM _dl_linux_resolve entry point - this is
# called to resolve DLL PLT entries.  The assembler is changed to be thumb
# compatible and slightly faster, the C function, _dl_linux_resolver (note
# the extra r) is changed to take a byte address in place of an 8 byte
# count (faster in caller and callee, and slightly easier to understand).
#
--- uClibc-0.9.28/.pc/thumb-resolve.patch/ldso/ldso/arm/elfinterp.c     2005-08-17 15:49:41.000000000 -0700
+++ uClibc-0.9.28/ldso/ldso/arm/elfinterp.c     2005-09-17 12:55:26.379172744 -0700
@@ -55,7 +55,7 @@
 
        rel_addr = (ELF_RELOC *) tpnt->dynamic_info[DT_JMPREL];
 
-       this_reloc = rel_addr + (reloc_entry >> 3);
+       this_reloc = rel_addr + reloc_entry;
        reloc_type = ELF32_R_TYPE(this_reloc->r_info);
        symtab_index = ELF32_R_SYM(this_reloc->r_info);
 
@@ -84,7 +84,9 @@
                _dl_exit(1);
        };
 #if defined (__SUPPORT_LD_DEBUG__)
+#if !defined __SUPPORT_LD_DEBUG_EARLY__
        if ((unsigned long) got_addr < 0x40000000)
+#endif
        {
                if (_dl_debug_bindings)
                {
--- uClibc-0.9.28/.pc/thumb-resolve.patch/ldso/ldso/arm/resolve.S       2005-08-17 15:49:41.000000000 -0700
+++ uClibc-0.9.28/ldso/ldso/arm/resolve.S       2005-09-17 11:02:27.860627464 -0700
@@ -1,43 +1,163 @@
 /*
- * This function is _not_ called directly.  It is jumped to (so no return
- * address is on the stack) when attempting to use a symbol that has not yet
- * been resolved.  The first time a jump symbol (such as a function call inside
- * a shared library) is used (before it gets resolved) it will jump here to
- * _dl_linux_resolve.  When we get called the stack looks like this:
- *     reloc_entry
- *     tpnt
- *
- * This function saves all the registers, puts a copy of reloc_entry and tpnt
- * on the stack (as function arguments) then make the function call
- * _dl_linux_resolver(tpnt, reloc_entry).  _dl_linux_resolver() figures out
- * where the jump symbol is _really_ supposed to have jumped to and returns
- * that to us.  Once we have that, we overwrite tpnt with this fixed up
- * address. We then clean up after ourselves, put all the registers back how we
- * found them, then we jump to the fixed up address, which is where the jump
- * symbol that got us here really wanted to jump to in the first place.
- *  -Erik Andersen
+ * On ARM the PLT contains the following three instructions (for ARM calls):
+ *
+ *     add   ip, pc, #0xNN00000
+ *     add   ip, ip, #0xNN000
+ *     ldr   pc, [ip, #0xNNN]!
+ *
+ * So that, effectively, causes the following to happen:
+ *
+ *     ip := pc+0x0NNNNNNN
+ *     pc := *ip
+ *
+ * For thumb the above fragment is preceded by "bx pc, nop" to switch to ARM
+ * mode and the thumb 'bl' must go to PLT-4 - the PLT entry is expanded by
+ * four bytes to accomodate the trampoline code.
+ *
+ * 0x0NNNNNNN is the offset of the GOT entry for this function relative to
+ * the PLT entry for this function (where the code is).  So the code in the
+ * PLT causes a branch to whatever is in the GOT, leaving the actual address
+ * of the GOT entry in ip.  (Note that the GOT must follow the PLT - the
+ * added value is 28 bit unsigned).
+ *
+ * ip is a pointer to the GOT entry for this function, the first time round
+ * *ip points to this code:
+ *
+ *     str   lr, [sp, #-4]!    @ save lr
+ *     ldr   lr, [pc, #4]      @ lr := *dat (&GOT_TABLE[0]-.)
+ *     add   lr, pc, lr        @ lr += &dat (so lr == &GOT_TABLE[0])
+ *     ldr   pc, [lr, #8]!     @ pc := GOT_TABLE[2]
+ *dat: .long &GOT_TABLE[0] - .
+ *
+ * (this code is actually held in the first entry of the PLT).  The code
+ * preserves lr then uses it as a scratch register (this preserves the ip
+ * value calculated above).  GOT_TABLE[2] is initialized by INIT_GOT in
+ * dl-sysdep.h to point to _dl_linux_resolve - this function.  The first
+ * three entries in the GOT are reserved, then they are followed by the
+ * entries for the PLT entries, in order.
+ *
+ * The linker initialises the following (non-reserved) GOT entries to
+ * the offset of the PLT with an associated relocation so that on load
+ * the entry is relocated to point to the PLT - the above code.
+ *
+ * The net effect of all this is that on the first call to an external (as
+ * yet unresolved) function all seven of the above instructions are
+ * executed in sequence and the program ends up executing _dl_linux_resolve
+ * with the following important values in registers:
+ *
+ *     ip - a pointer to the GOT entry for the as yet unresolved function
+ *     lr - &GOT_TABLE[2]
+ *
+ * GOT_TABLE[2] has already been initialised to _dl_linux_resolve, and
+ * GOT_TABLE[1] is a pointer to the (elf_resolve*) from INIT_GOT.
+ * _dl_linux_resolve unfrobnicates the ip and lr values to obtain arguments
+ * for a call to _dl_linux_resolver (not the additional 'r' on the end) -
+ * this is in elfinterp.c in this directory.  The call takes arguments:
+ *
+ *     _dl_linux_resolver(struct elf_resolve *tpnt, int reloc_entry)
+ *
+ * And returns the address of the function, it also overwrites the GOT
+ * table entry so that the next time round only the first code fragment will
+ * be executed - it will call the function directly.
+ *
+ * [[Of course, this simply doesn't work on ARM 4T with a thumb target - because
+ * 4T did not do the thumb/arm change on ldr pc!  It can be made to work by
+ * changing _dl_linux_resolver to return __%s_from_arm for an STT_TFUNC, but
+ * this hasn't been done, and there is no guarantee that the linker generated
+ * that glue anyway.]]
+ *
+ * _dl_linux_resolve gets the arguments to call the resolver as follows:
+ *
+ *     tpnt            GOT_TABLE[1], [lr-4]
+ *     reloc-entry     &GOT-&GOT_TABLE[3], (ip - lr - 4)/4
+ *
+ * (I.e. 'GOT' means the table entry for this function, the thing for which
+ * ip holds the address.)  The reloc-entry is passed as an index, since
+ * since the GOT table has 4 byte entries the code needs to divide this by 4
+ * to get the actual index.
+ *
+ * John Bowler, August 13, 2005 - determined by experiment and examination
+ * of generated ARM code (there was no documentation...)
+ *
+ * This code is all ARM code - not thumb - _dl_linux_resolver may, itself,
+ * be thumb, in which case the linker will insert the appropriate glue.  A
+ * call from thumb to the PLT hits the trampoline code described above.
+ * This code (now) builds a proper stack frame.
+ *
+ * The code does *not* set sb (r9,v6) - to do that the basic PLT instructions
+ * would need to save sb and load the new value and that would require
+ * support in the linker since it generates those instructions.  (Also note
+ * that linux/uclibc seems to be using r10 - sl - as a PIC base register - see
+ * dl-startup.c).
  */
-
-#define sl r10
-#define fp r11
-#define ip r12
+#include <sys/syscall.h>
 
 .text
+.align 4       @ 16 byte boundary and there are 32 bytes below (arm case)
+#if !defined(__thumb__)
+.arm
 .globl _dl_linux_resolve
 .type _dl_linux_resolve,%function
-.align 4;
 
 _dl_linux_resolve:
-       stmdb sp!, {r0, r1, r2, r3, sl, fp}
-       sub r1, ip, lr
-       sub r1, r1, #4
-       add r1, r1, r1
-       ldr r0, [lr, #-4]
-       mov r3,r0
+       @ _dl_linux_resolver is a standard subroutine call, therefore it
+       @ preserves everything except r0-r3 (a1-a4), ip and lr.  This
+       @ function must branch to the real function, and that expects
+       @ r0-r3 and lr to be as they were before the whole PLT stuff -
+       @ ip can be trashed.
+       stmdb sp!, {r0-r3}
+       ldr r0, [lr, #-4]       @ r0 := [lr-4] (GOT_TABLE[1])
+       sub r1, lr, ip          @ r1 := (lr-ip) (a multple of 4)
+       mvn r1, r1, ASR #2      @ r1 := ~((lr-ip)>>2), since -x = (1+~x)
+                               @ ~x = -x-1, therefore ~(r1>>2) = (-((lr-ip)>>2)-1)
+                               @ = - ((lr-ip)/4) - 1 = (ip - lr - 4)/4, as required
 
        bl _dl_linux_resolver
 
-       mov ip, r0
-       ldmia sp!, {r0, r1, r2, r3, sl, fp, lr}
-       mov pc,ip
+       mov   ip, r0
+       ldmia sp!, {r0-r3, lr}
+#if defined(__THUMB_INTERWORK__)
+       bx    ip
+#else
+       mov   pc, ip
+#endif
+.size _dl_linux_resolve, .-_dl_linux_resolve
+#else
+       @ In the thumb case _dl_linux_resolver is thumb.  If a bl is used
+       @ from arm code the linker will insert a stub call which, with
+       @ binutils 2.16, is not PIC.  Since this code is accessed by an
+       @ ldr pc the reasonable fix is to make _dl_linux_resolve thumb too.
+.thumb
+.globl _dl_linux_resolve
+.thumb_func
+.type _dl_linux_resolve,%function
+
+_dl_linux_resolve:
+       @ _dl_linux_resolver is a standard subroutine call, therefore it
+       @ preserves everything except r0-r3 (a1-a4), ip and lr.  This
+       @ function must branch to the real function, and that expects
+       @ r0-r3 and lr to be as they were before the whole PLT stuff -
+       @ ip can be trashed.
+       push    {r0-r3}
+       mov     r1, lr          @ &GOT_TABLE[2]
+       sub     r0, r1, #4
+       mov     r2, ip          @ &GOT[n]
+       ldr     r0, [r0]        @ r0 := GOT_TABLE[1]
+       @ for the function call r1 := n-3
+       sub     r1, r2
+       asr     r1, r1, #2
+       mvn     r1, r1          @ exactly as in the arm code above
+
+       bl      _dl_linux_resolver
+
+       @ r0 contains the branch address, the return address is above
+       @ the saved r0..r3
+       mov     ip, r0
+       ldr     r1, [sp, #16]
+       mov     lr, r1
+       pop     {r0-r3}
+       add     sp, #4
+       bx      ip
+
 .size _dl_linux_resolve, .-_dl_linux_resolve
+#endif
--- uClibc-0.9.28/.pc/thumb-resolve.patch/ldso/ldso/dl-hash.c   2005-08-17 15:49:41.000000000 -0700
+++ uClibc-0.9.28/ldso/ldso/dl-hash.c   2005-09-21 18:56:31.181689732 -0700
@@ -182,28 +182,52 @@
                strtab = (char *) (tpnt->dynamic_info[DT_STRTAB]);
 
                for (si = tpnt->elf_buckets[hn]; si != STN_UNDEF; si = tpnt->chains[si]) {
+                       char *result;
                        sym = &symtab[si];
 
-                       if (type_class & (sym->st_shndx == SHN_UNDEF))
+                       if (sym->st_shndx == SHN_UNDEF)
                                continue;
-                       if (_dl_strcmp(strtab + sym->st_name, name) != 0)
+                       if (ELF_ST_TYPE(sym->st_info) > STT_FUNC
+#if defined(__arm__) || defined(__thumb__)
+                               /* On ARM (only) STT_ARM_TFUNC is a function
+                                * and has a value >STT_FUNC, so this must
+                                * be checked specially.
+                                */
+                               && ELF_ST_TYPE(sym->st_info) != STT_ARM_TFUNC
+#endif
+                          )
                                continue;
-                       if (sym->st_value == 0)
+                       if (_dl_strcmp(strtab + sym->st_name, name) != 0)
                                continue;
-                       if (ELF_ST_TYPE(sym->st_info) > STT_FUNC)
+#if 0
+                       /* I don't know how to write this test - need to test shndx
+                        * to see if it is the PLT for this module.
+                        */
+                       if ((type_class & ELF_RTYPE_CLASS_PLT) && some test)
                                continue;
+#endif
 
+#if defined(__arm__) || defined(__thumb__)
+                       /* On ARM the caller needs to know that STT_ARM_TFUNC
+                        * is a thumb function call, this is now indicated by
+                        * setting the low bit of the value (and newer binutils
+                        * will do this and record STT_FUNC).
+                        */
+                       result = (char*)tpnt->loadaddr + (sym->st_value |
+                               (ELF_ST_TYPE(sym->st_info) == STT_ARM_TFUNC));
+#else
+                       result = (char*)tpnt->loadaddr + sym->st_value;
+#endif
                        switch (ELF_ST_BIND(sym->st_info)) {
                        case STB_WEAK:
-#if 0
-/* Perhaps we should support old style weak symbol handling
- * per what glibc does when you export LD_DYNAMIC_WEAK */
+                               /* Record for use later if we can't find a global. */
                                if (!weak_result)
-                                       weak_result = (char *)tpnt->loadaddr + sym->st_value;
+                                       weak_result = result;
                                break;
-#endif
+
                        case STB_GLOBAL:
-                               return (char*)tpnt->loadaddr + sym->st_value;
+                               return result;
+
                        default:        /* Local symbols not handled here */
                                break;
                        }