path: root/arch/powerpc/kernel/head_64.S
diff options
authorPaul Mackerras <paulus@samba.org>2008-08-30 11:43:47 +1000
committerPaul Mackerras <paulus@samba.org>2008-09-15 11:08:38 -0700
commit549e8152de8039506f69c677a4546e5427aa6ae7 (patch)
treee03a4f46143a23045e456f96fc08beba12e73073 /arch/powerpc/kernel/head_64.S
parente31aa453bbc4886a7bd33e5c2afa526d6f55bd7a (diff)
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>
Diffstat (limited to 'arch/powerpc/kernel/head_64.S')
1 files changed, 23 insertions, 3 deletions
diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
index 6cdfd44d8ef..84856bee33a 100644
--- a/arch/powerpc/kernel/head_64.S
+++ b/arch/powerpc/kernel/head_64.S
@@ -1360,6 +1360,12 @@ _INIT_STATIC(__boot_from_prom)
rldicr r1,r1,0,59
+ /* Relocate code for where we are now */
+ mr r3,r26
+ bl .relocate
/* Restore parameters */
mr r3,r31
mr r4,r30
@@ -1368,11 +1374,19 @@ _INIT_STATIC(__boot_from_prom)
mr r7,r27
/* Do all of the interaction with OF client interface */
+ mr r8,r26
bl .prom_init
/* We never return */
+ /* 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
* We need to run with _stext at physical address PHYSICAL_START.
@@ -1381,10 +1395,9 @@ _STATIC(__after_prom_start)
* 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 @@ _INIT_STATIC(start_here_multiplatform)
ori r6,r6,MSR_RI
mtmsrd r6 /* RI on */
+ /* 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)
/* 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 */