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authorNicholas Piggin <npiggin@gmail.com>2018-04-08 16:49:38 +1000
committerStewart Smith <stewart@linux.ibm.com>2018-04-18 20:23:07 -0500
commit3fdd2629516dd8be2b52a3a13e7ef5713411c7bf (patch)
tree5001a42b2b3d17fa03500ca97849c658715a1c6e /asm
parent8514e4dc9a82f3ff85d40138f2c8e8a1dc64efa4 (diff)
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core/opal: Emergency stack for re-entry
This detects OPAL being re-entered by the OS, and switches to an emergency stack if it was. This protects the firmware's main stack from re-entrancy and allows the OS to use NMI facilities for crash / debug functionality. Further nested re-entry will destroy the previous emergency stack and prevent returning, but those should be rare cases. This stack is sized at 16kB, which doubles the size of CPU stacks, so as not to introduce a regression in primary stack size. The 16kB stack originally had a 4kB machine check stack at the top, which was removed by 80eee1946 ("opal: Remove machine check interrupt patching in OPAL."). So it is possible the size could be tightened again, but that would require further analysis. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Stewart Smith <stewart@linux.ibm.com>
Diffstat (limited to 'asm')
-rw-r--r--asm/head.S22
1 files changed, 18 insertions, 4 deletions
diff --git a/asm/head.S b/asm/head.S
index eeefcaa..48d3acb 100644
--- a/asm/head.S
+++ b/asm/head.S
@@ -30,12 +30,17 @@
#define PPC_INST_STOP .long 0x4c0002e4
-#define GET_STACK(stack_reg,pir_reg) \
- sldi stack_reg,pir_reg,STACK_SHIFT; \
- addis stack_reg,stack_reg,CPU_STACKS_OFFSET@ha; \
+#define GET_STACK(stack_reg,pir_reg) \
+ sldi stack_reg,pir_reg,STACK_SHIFT; \
+ addis stack_reg,stack_reg,CPU_STACKS_OFFSET@ha; \
addi stack_reg,stack_reg,CPU_STACKS_OFFSET@l;
-#define GET_CPU() \
+#define GET_EMERGENCY_STACK(stack_reg,pir_reg) \
+ sldi stack_reg,pir_reg,STACK_SHIFT; \
+ addis stack_reg,stack_reg,EMERGENCY_CPU_STACKS_OFFSET@ha; \
+ addi stack_reg,stack_reg,EMERGENCY_CPU_STACKS_OFFSET@l;
+
+#define GET_CPU() \
clrrdi %r13,%r1,STACK_SHIFT
#define SAVE_GPR(reg,sp) std %r##reg,STACK_GPR##reg(sp)
@@ -1013,8 +1018,17 @@ opal_entry:
b 1b
4: /* Quiesce protocol done, get our per CPU stack */
+ /* Emergency stack if we have re-entered OPAL */
+ lwz %r11,CPUTHREAD_IN_OPAL_CALL(%r12)
+ cmpwi %r11,1
+
mfspr %r12,SPR_PIR
+ beq 5f
GET_STACK(%r12,%r12)
+ b 6f
+5:
+ GET_EMERGENCY_STACK(%r12,%r12)
+6:
stdu %r12,-STACK_FRAMESIZE(%r12)
/* Save caller r1, establish new r1 */