forked from Minki/linux
549e8152de
This implements CONFIG_RELOCATABLE for 64-bit by making the kernel as a position-independent executable (PIE) when it is set. This involves processing the dynamic relocations in the image in the early stages of booting, even if the kernel is being run at the address it is linked at, since the linker does not necessarily fill in words in the image for which there are dynamic relocations. (In fact the linker does fill in such words for 64-bit executables, though not for 32-bit executables, so in principle we could avoid calling relocate() entirely when we're running a 64-bit kernel at the linked address.) The dynamic relocations are processed by a new function relocate(addr), where the addr parameter is the virtual address where the image will be run. In fact we call it twice; once before calling prom_init, and again when starting the main kernel. This means that reloc_offset() returns 0 in prom_init (since it has been relocated to the address it is running at), which necessitated a few adjustments. This also changes __va and __pa to use an equivalent definition that is simpler. With the relocatable kernel, PAGE_OFFSET and MEMORY_START are constants (for 64-bit) whereas PHYSICAL_START is a variable (and KERNELBASE ideally should be too, but isn't yet). With this, relocatable kernels still copy themselves down to physical address 0 and run there. Signed-off-by: Paul Mackerras <paulus@samba.org>
88 lines
2.0 KiB
ArmAsm
88 lines
2.0 KiB
ArmAsm
/*
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* Code to process dynamic relocations in the kernel.
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*
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* Copyright 2008 Paul Mackerras, IBM Corp.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <asm/ppc_asm.h>
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RELA = 7
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RELACOUNT = 0x6ffffff9
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R_PPC64_RELATIVE = 22
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/*
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* r3 = desired final address of kernel
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*/
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_GLOBAL(relocate)
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mflr r0
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bcl 20,31,$+4
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0: mflr r12 /* r12 has runtime addr of label 0 */
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mtlr r0
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ld r11,(p_dyn - 0b)(r12)
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add r11,r11,r12 /* r11 has runtime addr of .dynamic section */
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ld r9,(p_rela - 0b)(r12)
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add r9,r9,r12 /* r9 has runtime addr of .rela.dyn section */
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ld r10,(p_st - 0b)(r12)
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add r10,r10,r12 /* r10 has runtime addr of _stext */
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/*
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* Scan the dynamic section for the RELA and RELACOUNT entries.
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*/
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li r7,0
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li r8,0
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1: ld r6,0(r11) /* get tag */
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cmpdi r6,0
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beq 4f /* end of list */
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cmpdi r6,RELA
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bne 2f
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ld r7,8(r11) /* get RELA pointer in r7 */
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b 3f
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2: addis r6,r6,(-RELACOUNT)@ha
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cmpdi r6,RELACOUNT@l
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bne 3f
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ld r8,8(r11) /* get RELACOUNT value in r8 */
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3: addi r11,r11,16
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b 1b
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4: cmpdi r7,0 /* check we have both RELA and RELACOUNT */
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cmpdi cr1,r8,0
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beq 6f
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beq cr1,6f
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/*
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* Work out linktime address of _stext and hence the
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* relocation offset to be applied.
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* cur_offset [r7] = rela.run [r9] - rela.link [r7]
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* _stext.link [r10] = _stext.run [r10] - cur_offset [r7]
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* final_offset [r3] = _stext.final [r3] - _stext.link [r10]
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*/
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subf r7,r7,r9 /* cur_offset */
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subf r10,r7,r10
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subf r3,r10,r3 /* final_offset */
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/*
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* Run through the list of relocations and process the
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* R_PPC64_RELATIVE ones.
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*/
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mtctr r8
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5: lwz r0,12(9) /* ELF64_R_TYPE(reloc->r_info) */
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cmpwi r0,R_PPC64_RELATIVE
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bne 6f
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ld r6,0(r9) /* reloc->r_offset */
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ld r0,16(r9) /* reloc->r_addend */
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add r0,r0,r3
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stdx r0,r7,r6
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addi r9,r9,24
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bdnz 5b
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6: blr
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p_dyn: .llong __dynamic_start - 0b
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p_rela: .llong __rela_dyn_start - 0b
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p_st: .llong _stext - 0b
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