Commit 13d543cd authored by Bharat Bhushan's avatar Bharat Bhushan Committed by Benjamin Herrenschmidt

powerpc: Restore dbcr0 on user space exit

On BookE (Branch taken + Single Step) is as same as Branch Taken
on BookS and in Linux we simulate BookS behavior for BookE as well.
When doing so, in Branch taken handling we want to set DBCR0_IC but
we update the current->thread->dbcr0 and not DBCR0.

Now on 64bit the current->thread.dbcr0 (and other debug registers)
is synchronized ONLY on context switch flow. But after handling
Branch taken in debug exception if we return back to user space
without context switch then single stepping change (DBCR0_ICMP)
does not get written in h/w DBCR0 and Instruction Complete exception
does not happen.

This fixes using ptrace reliably on BookE-PowerPC

lmbench latency test (lat_syscall) Results are (they varies a little
on each run)

1) ./lat_syscall <action> /dev/shm/uImage

action:	Open	read	write	stat	fstat	null
Before:	3.8618	0.2017	0.2851	1.6789	0.2256	0.0856
After:	3.8580	0.2017	0.2851	1.6955	0.2255	0.0856

1) ./lat_syscall -P 2 -N 10 <action> /dev/shm/uImage
action:	Open	read	write	stat	fstat	null
Before:	4.1388	0.2238	0.3066	1.7106	0.2256	0.0856
After:	4.1413	0.2236	0.3062	1.7107	0.2256	0.0856

[ Slightly modified to avoid extra branch in the fast path
  on Book3S and fix build on all non-BookE 64-bit -- BenH
]
Signed-off-by: default avatarBharat Bhushan <bharat.bhushan@freescale.com>
Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
parent d8899bb2
...@@ -105,9 +105,6 @@ int main(void) ...@@ -105,9 +105,6 @@ int main(void)
DEFINE(KSP_VSID, offsetof(struct thread_struct, ksp_vsid)); DEFINE(KSP_VSID, offsetof(struct thread_struct, ksp_vsid));
#else /* CONFIG_PPC64 */ #else /* CONFIG_PPC64 */
DEFINE(PGDIR, offsetof(struct thread_struct, pgdir)); DEFINE(PGDIR, offsetof(struct thread_struct, pgdir));
#if defined(CONFIG_4xx) || defined(CONFIG_BOOKE)
DEFINE(THREAD_DBCR0, offsetof(struct thread_struct, dbcr0));
#endif
#ifdef CONFIG_SPE #ifdef CONFIG_SPE
DEFINE(THREAD_EVR0, offsetof(struct thread_struct, evr[0])); DEFINE(THREAD_EVR0, offsetof(struct thread_struct, evr[0]));
DEFINE(THREAD_ACC, offsetof(struct thread_struct, acc)); DEFINE(THREAD_ACC, offsetof(struct thread_struct, acc));
...@@ -115,6 +112,9 @@ int main(void) ...@@ -115,6 +112,9 @@ int main(void)
DEFINE(THREAD_USED_SPE, offsetof(struct thread_struct, used_spe)); DEFINE(THREAD_USED_SPE, offsetof(struct thread_struct, used_spe));
#endif /* CONFIG_SPE */ #endif /* CONFIG_SPE */
#endif /* CONFIG_PPC64 */ #endif /* CONFIG_PPC64 */
#if defined(CONFIG_4xx) || defined(CONFIG_BOOKE)
DEFINE(THREAD_DBCR0, offsetof(struct thread_struct, dbcr0));
#endif
#ifdef CONFIG_KVM_BOOK3S_32_HANDLER #ifdef CONFIG_KVM_BOOK3S_32_HANDLER
DEFINE(THREAD_KVM_SVCPU, offsetof(struct thread_struct, kvm_shadow_vcpu)); DEFINE(THREAD_KVM_SVCPU, offsetof(struct thread_struct, kvm_shadow_vcpu));
#endif #endif
......
...@@ -629,21 +629,43 @@ _GLOBAL(ret_from_except_lite) ...@@ -629,21 +629,43 @@ _GLOBAL(ret_from_except_lite)
CURRENT_THREAD_INFO(r9, r1) CURRENT_THREAD_INFO(r9, r1)
ld r3,_MSR(r1) ld r3,_MSR(r1)
#ifdef CONFIG_PPC_BOOK3E
ld r10,PACACURRENT(r13)
#endif /* CONFIG_PPC_BOOK3E */
ld r4,TI_FLAGS(r9) ld r4,TI_FLAGS(r9)
andi. r3,r3,MSR_PR andi. r3,r3,MSR_PR
beq resume_kernel beq resume_kernel
#ifdef CONFIG_PPC_BOOK3E
lwz r3,(THREAD+THREAD_DBCR0)(r10)
#endif /* CONFIG_PPC_BOOK3E */
/* Check current_thread_info()->flags */ /* Check current_thread_info()->flags */
andi. r0,r4,_TIF_USER_WORK_MASK andi. r0,r4,_TIF_USER_WORK_MASK
#ifdef CONFIG_PPC_BOOK3E
bne 1f
/*
* Check to see if the dbcr0 register is set up to debug.
* Use the internal debug mode bit to do this.
*/
andis. r0,r3,DBCR0_IDM@h
beq restore beq restore
mfmsr r0
andi. r0,r4,_TIF_NEED_RESCHED rlwinm r0,r0,0,~MSR_DE /* Clear MSR.DE */
beq 1f mtmsr r0
mtspr SPRN_DBCR0,r3
li r10, -1
mtspr SPRN_DBSR,r10
b restore
#else
beq restore
#endif
1: andi. r0,r4,_TIF_NEED_RESCHED
beq 2f
bl .restore_interrupts bl .restore_interrupts
SCHEDULE_USER SCHEDULE_USER
b .ret_from_except_lite b .ret_from_except_lite
1: bl .save_nvgprs 2: bl .save_nvgprs
bl .restore_interrupts bl .restore_interrupts
addi r3,r1,STACK_FRAME_OVERHEAD addi r3,r1,STACK_FRAME_OVERHEAD
bl .do_notify_resume bl .do_notify_resume
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment