powerpc: Make the 64-bit kernel as a position-independent executable
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>
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index 49b49c0..16326fd 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -35,6 +35,7 @@
paca.o cpu_setup_ppc970.o \
cpu_setup_pa6t.o \
firmware.o nvram_64.o
+obj64-$(CONFIG_RELOCATABLE) += reloc_64.o
obj-$(CONFIG_PPC64) += vdso64/
obj-$(CONFIG_ALTIVEC) += vecemu.o vector.o
obj-$(CONFIG_PPC_970_NAP) += idle_power4.o
diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
index 6cdfd44..84856be 100644
--- a/arch/powerpc/kernel/head_64.S
+++ b/arch/powerpc/kernel/head_64.S
@@ -1360,6 +1360,12 @@
*/
rldicr r1,r1,0,59
+#ifdef CONFIG_RELOCATABLE
+ /* Relocate code for where we are now */
+ mr r3,r26
+ bl .relocate
+#endif
+
/* Restore parameters */
mr r3,r31
mr r4,r30
@@ -1368,11 +1374,19 @@
mr r7,r27
/* Do all of the interaction with OF client interface */
+ mr r8,r26
bl .prom_init
/* We never return */
trap
_STATIC(__after_prom_start)
+#ifdef CONFIG_RELOCATABLE
+ /* process relocations for the final address of the kernel */
+ lis r25,PAGE_OFFSET@highest /* compute virtual base of kernel */
+ sldi r25,r25,32
+ mr r3,r25
+ bl .relocate
+#endif
/*
* We need to run with _stext at physical address PHYSICAL_START.
@@ -1381,10 +1395,9 @@
*
* Note: This process overwrites the OF exception vectors.
*/
- LOAD_REG_IMMEDIATE(r3, PHYSICAL_START) /* target addr */
- cmpd r3,r26 /* In some cases the loader may */
+ li r3,0 /* target addr */
+ mr. r4,r26 /* In some cases the loader may */
beq 9f /* have already put us at zero */
- mr r4,r26 /* source address */
lis r5,(copy_to_here - _stext)@ha
addi r5,r5,(copy_to_here - _stext)@l /* # bytes of memory to copy */
li r6,0x100 /* Start offset, the first 0x100 */
@@ -1617,6 +1630,13 @@
ori r6,r6,MSR_RI
mtmsrd r6 /* RI on */
+#ifdef CONFIG_RELOCATABLE
+ /* Save the physical address we're running at in kernstart_addr */
+ LOAD_REG_ADDR(r4, kernstart_addr)
+ clrldi r0,r25,2
+ std r0,0(r4)
+#endif
+
/* The following gets the stack set up with the regs */
/* pointing to the real addr of the kernel stack. This is */
/* all done to support the C function call below which sets */
diff --git a/arch/powerpc/kernel/paca.c b/arch/powerpc/kernel/paca.c
index 623e8c3..48a3471 100644
--- a/arch/powerpc/kernel/paca.c
+++ b/arch/powerpc/kernel/paca.c
@@ -12,6 +12,7 @@
#include <asm/lppaca.h>
#include <asm/paca.h>
+#include <asm/sections.h>
/* This symbol is provided by the linker - let it fill in the paca
* field correctly */
@@ -79,7 +80,7 @@
new_paca->lock_token = 0x8000;
new_paca->paca_index = cpu;
new_paca->kernel_toc = kernel_toc;
- new_paca->kernelbase = KERNELBASE;
+ new_paca->kernelbase = (unsigned long) _stext;
new_paca->kernel_msr = MSR_KERNEL;
new_paca->hw_cpu_id = 0xffff;
new_paca->slb_shadow_ptr = &slb_shadow[cpu];
diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
index 09455e1..3a2dc7e 100644
--- a/arch/powerpc/kernel/prom.c
+++ b/arch/powerpc/kernel/prom.c
@@ -1192,6 +1192,9 @@
/* Reserve LMB regions used by kernel, initrd, dt, etc... */
lmb_reserve(PHYSICAL_START, __pa(klimit) - PHYSICAL_START);
+ /* If relocatable, reserve first 32k for interrupt vectors etc. */
+ if (PHYSICAL_START > MEMORY_START)
+ lmb_reserve(MEMORY_START, 0x8000);
reserve_kdump_trampoline();
reserve_crashkernel();
early_reserve_mem();
diff --git a/arch/powerpc/kernel/prom_init.c b/arch/powerpc/kernel/prom_init.c
index 1f89885..7cf274a 100644
--- a/arch/powerpc/kernel/prom_init.c
+++ b/arch/powerpc/kernel/prom_init.c
@@ -2309,13 +2309,14 @@
unsigned long __init prom_init(unsigned long r3, unsigned long r4,
unsigned long pp,
- unsigned long r6, unsigned long r7)
+ unsigned long r6, unsigned long r7,
+ unsigned long kbase)
{
struct prom_t *_prom;
unsigned long hdr;
- unsigned long offset = reloc_offset();
#ifdef CONFIG_PPC32
+ unsigned long offset = reloc_offset();
reloc_got2(offset);
#endif
@@ -2349,9 +2350,11 @@
*/
RELOC(of_platform) = prom_find_machine_type();
+#ifndef CONFIG_RELOCATABLE
/* Bail if this is a kdump kernel. */
if (PHYSICAL_START > 0)
prom_panic("Error: You can't boot a kdump kernel from OF!\n");
+#endif
/*
* Check for an initrd
@@ -2371,7 +2374,7 @@
* Copy the CPU hold code
*/
if (RELOC(of_platform) != PLATFORM_POWERMAC)
- copy_and_flush(0, KERNELBASE + offset, 0x100, 0);
+ copy_and_flush(0, kbase, 0x100, 0);
/*
* Do early parsing of command line
@@ -2474,7 +2477,7 @@
reloc_got2(-offset);
#endif
- __start(hdr, KERNELBASE + offset, 0);
+ __start(hdr, kbase, 0);
return 0;
}
diff --git a/arch/powerpc/kernel/reloc_64.S b/arch/powerpc/kernel/reloc_64.S
new file mode 100644
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
+
diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
index 9f6c1ca..e6927fb 100644
--- a/arch/powerpc/kernel/vmlinux.lds.S
+++ b/arch/powerpc/kernel/vmlinux.lds.S
@@ -187,6 +187,21 @@
*(.machine.desc)
__machine_desc_end = . ;
}
+ . = ALIGN(8);
+ .dynsym : AT(ADDR(.dynsym) - LOAD_OFFSET) { *(.dynsym) }
+ .dynstr : AT(ADDR(.dynstr) - LOAD_OFFSET) { *(.dynstr) }
+ .dynamic : AT(ADDR(.dynamic) - LOAD_OFFSET)
+ {
+ __dynamic_start = .;
+ *(.dynamic)
+ }
+ .hash : AT(ADDR(.hash) - LOAD_OFFSET) { *(.hash) }
+ .interp : AT(ADDR(.interp) - LOAD_OFFSET) { *(.interp) }
+ .rela.dyn : AT(ADDR(.rela.dyn) - LOAD_OFFSET)
+ {
+ __rela_dyn_start = .;
+ *(.rela*)
+ }
/* freed after init ends here */
. = ALIGN(PAGE_SIZE);