From 8ed37072c07ee0c8be2ed8d9e2ede19333856e86 Mon Sep 17 00:00:00 2001 From: Vaibhav Jain Date: Fri, 27 Apr 2018 14:30:07 +0530 Subject: asm/head: Fix comparison in opal_entry for switching to emergency Commit 3fdd2629516d ("core/opal: Emergency stack for re-entry") introduced an emergency stack for re-entrant OPAL calls. A branch was added in opal_entry() that switches to emergency stack checks if current thread is already in an active opal call. However the conditional branch that checks the value cpu_thread->in_opal_call is reverse forcing the use of emergency stack in even in non re-entrant cases. This causes a opal stack guard routine __mcount_stack_check() to falsely assume that stack is overflown as stack pointer of EMERGENCY_STACK is compared against the bounds of NORMAL_STACK, forcing the function to call abort() with an error message of this form: INIT: Starting kernel at 0x20010000, fdt at 0x3073f708 53664 bytes) CPU 0004 Stack overflow detected ! pc=3001d8ec sp=31c27c90 (gap=30488) token=70 Aborting! CPU 0004 Backtrace: S: 0000000031c27b20 R: 000000003001ca2c E ._abort+0x60 S: 0000000031c27bb0 R: 0000000030013e10 E .__mcount_stack_check+0x168 S: 0000000031c27c90 R: 000000003001d8ec E .opal_entry_check+0x1c S: 0000000031c27d20 R: 00000000300051a4 E opal_entry+0xf4 --- OPAL call token: 0x46 caller R1: 0xc0000000011e3e50 --- So this patch update the 'bne' branch in opal_entry() to 'bgt' branch so that switch to emergency stack only happens when current cpu_thread->is_opal_call is greater than 1 indicating an re-entrant opal call. Fixes: 3fdd2629516d ("core/opal: Emergency stack for re-entry") Signed-off-by: Vaibhav Jain Signed-off-by: Mahesh J Salgaonkar Reviewed-by: Nicholas Piggin Signed-off-by: Stewart Smith --- asm/head.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'asm') diff --git a/asm/head.S b/asm/head.S index 48d3acb..2cf4a6b 100644 --- a/asm/head.S +++ b/asm/head.S @@ -1023,7 +1023,7 @@ opal_entry: cmpwi %r11,1 mfspr %r12,SPR_PIR - beq 5f + bgt 5f GET_STACK(%r12,%r12) b 6f 5: -- cgit v1.1