path: root/arch/powerpc/kernel/head_64.S
diff options
authorPaul Mackerras <paulus@samba.org>2008-08-30 11:40:24 +1000
committerPaul Mackerras <paulus@samba.org>2008-09-15 11:08:08 -0700
commit1f6a93e4c35e75d547b51f56ba8139ab1a91628c (patch)
treec755528c7f299fa407b3eda77a3e08af78b0b25c /arch/powerpc/kernel/head_64.S
parent9a95516740c924675d52c472d7d170c62eab176c (diff)
powerpc: Make it possible to move the interrupt handlers away from the kernel
This changes the way that the exception prologs transfer control to the handlers in 64-bit kernels with the aim of making it possible to have the prologs separate from the main body of the kernel. Now, instead of computing the address of the handler by taking the top 32 bits of the paca address (to get the 0xc0000000........ part) and ORing in something in the bottom 16 bits, we get the base address of the kernel by doing a load from the paca and add an offset. This also replaces an mfmsr and an ori to compute the MSR value for the handler with a load from the paca. That makes it unnecessary to have a separate version of EXCEPTION_PROLOG_PSERIES that forces 64-bit mode. We can no longer use a direct branches in the exception prolog code, which means that the SLB miss handlers can't branch directly to .slb_miss_realmode any more. Instead we have to compute the address and do an indirect branch. This is conditional on CONFIG_RELOCATABLE; for non-relocatable kernels we use a direct branch as before. (A later change will allow CONFIG_RELOCATABLE to be set on 64-bit powerpc.) Since the secondary CPUs on pSeries start execution in the first 0x100 bytes of real memory and then have to get to wherever the kernel is, we can't use a direct branch to get there. Instead this changes __secondary_hold_spinloop from a flag to a function pointer. When it is set to a non-NULL value, the secondary CPUs jump to the function pointed to by that value. Finally this eliminates one code difference between 32-bit and 64-bit by making __secondary_hold be the text address of the secondary CPU spinloop rather than a function descriptor for it. Signed-off-by: Paul Mackerras <paulus@samba.org>
Diffstat (limited to 'arch/powerpc/kernel/head_64.S')
1 files changed, 55 insertions, 16 deletions
diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
index 27935d1ab6a..97bb6e6f67b 100644
--- a/arch/powerpc/kernel/head_64.S
+++ b/arch/powerpc/kernel/head_64.S
@@ -82,7 +82,11 @@ END_FTR_SECTION(0, 1)
/* Catch branch to 0 in real mode */
- /* Secondary processors spin on this value until it goes to 1. */
+ /* Secondary processors spin on this value until it becomes nonzero.
+ * When it does it contains the real address of the descriptor
+ * of the function that the cpu should jump to to continue
+ * initialization.
+ */
.globl __secondary_hold_spinloop
.llong 0x0
@@ -109,8 +113,11 @@ __secondary_hold_acknowledge:
* before the bulk of the kernel has been relocated. This code
* is relocated to physical address 0x60 before prom_init is run.
* All of it must fit below the first exception vector at 0x100.
+ * Use .globl here not _GLOBAL because we want __secondary_hold
+ * to be the actual text address, not a descriptor.
+ .globl __secondary_hold
mfmsr r24
ori r24,r24,MSR_RI
mtmsrd r24 /* RI on */
@@ -126,11 +133,11 @@ _GLOBAL(__secondary_hold)
/* All secondary cpus wait here until told to start. */
100: ld r4,__secondary_hold_spinloop@l(0)
- cmpdi 0,r4,1
- bne 100b
+ cmpdi 0,r4,0
+ beq 100b
#if defined(CONFIG_SMP) || defined(CONFIG_KEXEC)
- LOAD_REG_IMMEDIATE(r4, .generic_secondary_smp_init)
+ ld r4,0(r4) /* deref function descriptor */
mtctr r4
mr r3,r24
@@ -147,6 +154,10 @@ exception_marker:
* This is the start of the interrupt handlers for pSeries
* This code runs with relocation off.
+ * Code from here to __end_interrupts gets copied down to real
+ * address 0x100 when we are running a relocatable kernel.
+ * Therefore any relative branches in this section must only
+ * branch to labels in this section.
. = 0x100
.globl __start_interrupts
@@ -200,7 +211,20 @@ data_access_slb_pSeries:
mfspr r10,SPRN_SPRG1
std r10,PACA_EXSLB+EX_R13(r13)
mfspr r12,SPRN_SRR1 /* and SRR1 */
- b .slb_miss_realmode /* Rel. branch works in real mode */
+ b .slb_miss_realmode
+ /*
+ * We can't just use a direct branch to .slb_miss_realmode
+ * because the distance from here to there depends on where
+ * the kernel ends up being put.
+ */
+ mfctr r11
+ ld r10,PACAKBASE(r13)
+ LOAD_HANDLER(r10, .slb_miss_realmode)
+ mtctr r10
+ bctr
STD_EXCEPTION_PSERIES(0x400, instruction_access)
@@ -225,7 +249,15 @@ instruction_access_slb_pSeries:
mfspr r10,SPRN_SPRG1
std r10,PACA_EXSLB+EX_R13(r13)
mfspr r12,SPRN_SRR1 /* and SRR1 */
- b .slb_miss_realmode /* Rel. branch works in real mode */
+ b .slb_miss_realmode
+ mfctr r11
+ ld r10,PACAKBASE(r13)
+ LOAD_HANDLER(r10, .slb_miss_realmode)
+ mtctr r10
+ bctr
MASKABLE_EXCEPTION_PSERIES(0x500, hardware_interrupt)
STD_EXCEPTION_PSERIES(0x600, alignment)
@@ -244,14 +276,12 @@ BEGIN_FTR_SECTION
beq- 1f
mr r9,r13
- mfmsr r10
mfspr r13,SPRN_SPRG3
mfspr r11,SPRN_SRR0
- clrrdi r12,r13,32
- oris r12,r12,system_call_common@h
- ori r12,r12,system_call_common@l
+ ld r12,PACAKBASE(r13)
+ ld r10,PACAKMSR(r13)
+ LOAD_HANDLER(r12, system_call_entry)
mtspr SPRN_SRR0,r12
- ori r10,r10,MSR_IR|MSR_DR|MSR_RI
mfspr r12,SPRN_SRR1
mtspr SPRN_SRR1,r10
@@ -379,7 +409,10 @@ __end_interrupts:
* Code from here down to __end_handlers is invoked from the
- * exception prologs above.
+ * exception prologs above. Because the prologs assemble the
+ * addresses of these handlers using the LOAD_HANDLER macro,
+ * which uses an addi instruction, these handlers must be in
+ * the first 32k of the kernel image.
/*** Common interrupt handlers ***/
@@ -419,6 +452,10 @@ machine_check_common:
STD_EXCEPTION_COMMON(0x1800, cbe_thermal, .cbe_thermal_exception)
#endif /* CONFIG_CBE_RAS */
+ .align 7
+ b system_call_common
* Here we have detected that the kernel stack pointer is bad.
* R9 contains the saved CR, r13 points to the paca,
@@ -562,6 +599,9 @@ unrecov_user_slb:
mflr r10
+ mtctr r11
stw r9,PACA_EXSLB+EX_CCR(r13) /* save CR in exc. frame */
std r10,PACA_EXSLB+EX_LR(r13) /* save LR */
@@ -612,11 +652,10 @@ BEGIN_FW_FTR_SECTION
mfspr r11,SPRN_SRR0
- clrrdi r10,r13,32
+ ld r10,PACAKBASE(r13)
mtspr SPRN_SRR0,r10
- mfmsr r10
- ori r10,r10,MSR_IR|MSR_DR|MSR_RI
+ ld r10,PACAKMSR(r13)
mtspr SPRN_SRR1,r10
b .