powerpc: Make the 64-bit kernel as a position-independent executable

[firefly-linux-kernel-4.4.55.git] / arch / powerpc / kernel / reloc_64.S

diff --git a/arch/powerpc/kernel/reloc_64.S b/arch/powerpc/kernel/reloc_64.S
new file mode 100644 (file)
index 0000000..b47a0e1
--- /dev/null
+++ b/arch/powerpc/kernel/reloc_64.S
@@ -0,0 +1,87 @@
+/*
+ * Code to process dynamic relocations in the kernel.
+ *
+ * Copyright 2008 Paul Mackerras, IBM Corp.
+ *
+ *  This program is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU General Public License
+ *  as published by the Free Software Foundation; either version
+ *  2 of the License, or (at your option) any later version.
+ */
+
+#include <asm/ppc_asm.h>
+
+RELA = 7
+RELACOUNT = 0x6ffffff9
+R_PPC64_RELATIVE = 22
+
+/*
+ * r3 = desired final address of kernel
+ */
+_GLOBAL(relocate)
+       mflr    r0
+       bcl     20,31,$+4
+0:     mflr    r12             /* r12 has runtime addr of label 0 */
+       mtlr    r0
+       ld      r11,(p_dyn - 0b)(r12)
+       add     r11,r11,r12     /* r11 has runtime addr of .dynamic section */
+       ld      r9,(p_rela - 0b)(r12)
+       add     r9,r9,r12       /* r9 has runtime addr of .rela.dyn section */
+       ld      r10,(p_st - 0b)(r12)
+       add     r10,r10,r12     /* r10 has runtime addr of _stext */
+
+       /*
+        * Scan the dynamic section for the RELA and RELACOUNT entries.
+        */
+       li      r7,0
+       li      r8,0
+1:     ld      r6,0(r11)       /* get tag */
+       cmpdi   r6,0
+       beq     4f              /* end of list */
+       cmpdi   r6,RELA
+       bne     2f
+       ld      r7,8(r11)       /* get RELA pointer in r7 */
+       b       3f
+2:     addis   r6,r6,(-RELACOUNT)@ha
+       cmpdi   r6,RELACOUNT@l
+       bne     3f
+       ld      r8,8(r11)       /* get RELACOUNT value in r8 */
+3:     addi    r11,r11,16
+       b       1b
+4:     cmpdi   r7,0            /* check we have both RELA and RELACOUNT */
+       cmpdi   cr1,r8,0
+       beq     6f
+       beq     cr1,6f
+
+       /*
+        * Work out linktime address of _stext and hence the
+        * relocation offset to be applied.
+        * cur_offset [r7] = rela.run [r9] - rela.link [r7]
+        * _stext.link [r10] = _stext.run [r10] - cur_offset [r7]
+        * final_offset [r3] = _stext.final [r3] - _stext.link [r10]
+        */
+       subf    r7,r7,r9        /* cur_offset */
+       subf    r10,r7,r10
+       subf    r3,r10,r3       /* final_offset */
+
+       /*
+        * Run through the list of relocations and process the
+        * R_PPC64_RELATIVE ones.
+        */
+       mtctr   r8
+5:     lwz     r0,12(9)        /* ELF64_R_TYPE(reloc->r_info) */
+       cmpwi   r0,R_PPC64_RELATIVE
+       bne     6f
+       ld      r6,0(r9)        /* reloc->r_offset */
+       ld      r0,16(r9)       /* reloc->r_addend */
+       add     r0,r0,r3
+       stdx    r0,r7,r6
+       addi    r9,r9,24
+       bdnz    5b
+
+6:     blr
+
+p_dyn: .llong  __dynamic_start - 0b
+p_rela:        .llong  __rela_dyn_start - 0b
+p_st:  .llong  _stext - 0b
+