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powerpc/64s/exception: remove bad stack branch 

The bad stack test in interrupt handlers has a few problems. For
performance it is taken in the common case, which is a fetch bubble
and a waste of i-cache.

For code development and maintainence, it requires yet another stack
frame setup routine, and that constrains all exception handlers to
follow the same register save pattern which inhibits future
optimisation.

Remove the test/branch and replace it with a trap. Teach the program
check handler to use the emergency stack for this case.

This does not result in quite so nice a message, however the SRR0 and
SRR1 of the crashed interrupt can be seen in r11 and r12, as is the
original r1 (adjusted by INT_FRAME_SIZE). These are the most important
parts to debugging the issue.

The original r9-12 and cr0 is lost, which is the main downside.

  kernel BUG at linux/arch/powerpc/kernel/exceptions-64s.S:847!
  Oops: Exception in kernel mode, sig: 5 [#1]
  BE SMP NR_CPUS=2048 NUMA PowerNV
  Modules linked in:
  CPU: 0 PID: 1 Comm: swapper/0 Not tainted
  NIP:  c000000000009108 LR: c000000000cadbcc CTR: c0000000000090f0
  REGS: c0000000fffcbd70 TRAP: 0700   Not tainted
  MSR:  9000000000021032 <SF,HV,ME,IR,DR,RI>  CR: 28222448  XER: 20040000
  CFAR: c000000000009100 IRQMASK: 0
  GPR00: 000000000000003d fffffffffffffd00 c0000000018cfb00 c0000000f02b3166
  GPR04: fffffffffffffffd 0000000000000007 fffffffffffffffb 0000000000000030
  GPR08: 0000000000000037 0000000028222448 0000000000000000 c000000000ca8de0
  GPR12: 9000000002009032 c000000001ae0000 c000000000010a00 0000000000000000
  GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
  GPR20: c0000000f00322c0 c000000000f85200 0000000000000004 ffffffffffffffff
  GPR24: fffffffffffffffe 0000000000000000 0000000000000000 000000000000000a
  GPR28: 0000000000000000 0000000000000000 c0000000f02b391c c0000000f02b3167
  NIP [c000000000009108] decrementer_common+0x18/0x160
  LR [c000000000cadbcc] .vsnprintf+0x3ec/0x4f0
  Call Trace:
  Instruction dump:
  996d098a 994d098b 38610070 480246ed 48005518 60000000 38200000 718a4000
  7c2a0b78 3821fd00 41c20008 e82d0970 <0981fd00> f92101a0 f9610170 f9810178

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
alistair/sunxi64-5.4-dsi
Nicholas Piggin 2019-06-28 16:33:18 +10:00 committed by Michael Ellerman
parent f30a5e68f0
commit 0a882e2846
5 changed files with 21 additions and 86 deletions
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7
arch/powerpc/include/asm/exception-64s.h
View File

@ -48,13 +48,6 @@
*/
#define MAX_MCE_DEPTH 4
/*
* EX_R3 is only used by the bad_stack handler. bad_stack reloads and
* saves DAR from SPRN_DAR, and EX_DAR is not used. So EX_R3 can overlap
* with EX_DAR.
*/
#define EX_R3 EX_DAR
#ifdef __ASSEMBLY__
#define STF_ENTRY_BARRIER_SLOT \

2
arch/powerpc/include/asm/paca.h
View File

@ -170,7 +170,9 @@ struct paca_struct {
u64 kstack; /* Saved Kernel stack addr */
u64 saved_r1; /* r1 save for RTAS calls or PM or EE=0 */
u64 saved_msr; /* MSR saved here by enter_rtas */
#ifdef CONFIG_PPC_BOOK3E
u16 trap_save; /* Used when bad stack is encountered */
#endif
u8 irq_soft_mask; /* mask for irq soft masking */
u8 irq_happened; /* irq happened while soft-disabled */
u8 irq_work_pending; /* IRQ_WORK interrupt while soft-disable */

2
arch/powerpc/kernel/asm-offsets.c
View File

@ -270,7 +270,9 @@ int main(void)
OFFSET(ACCOUNT_STARTTIME_USER, paca_struct, accounting.starttime_user);
OFFSET(ACCOUNT_USER_TIME, paca_struct, accounting.utime);
OFFSET(ACCOUNT_SYSTEM_TIME, paca_struct, accounting.stime);
#ifdef CONFIG_PPC_BOOK3E
OFFSET(PACA_TRAP_SAVE, paca_struct, trap_save);
#endif
OFFSET(PACA_SPRG_VDSO, paca_struct, sprg_vdso);
#else /* CONFIG_PPC64 */
#ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE

94
arch/powerpc/kernel/exceptions-64s.S
View File

@ -411,14 +411,8 @@ END_FTR_SECTION_NESTED(CPU_FTR_CFAR, CPU_FTR_CFAR, 66); \
subi r1,r1,INT_FRAME_SIZE; /* alloc frame on kernel stack */ \
beq- 1f; \
ld r1,PACAKSAVE(r13); /* kernel stack to use */ \
1: cmpdi cr1,r1,-INT_FRAME_SIZE; /* check if r1 is in userspace */ \
blt+ cr1,3f; /* abort if it is */ \
li r1,(trap); /* will be reloaded later */ \
sth r1,PACA_TRAP_SAVE(r13); \
std r3,area+EX_R3(r13); \
addi r3,r13,area; /* r3 -> where regs are saved*/ \
RESTORE_CTR(r1, area); \
b bad_stack; \
1: tdgei r1,-INT_FRAME_SIZE; /* trap if r1 is in userspace */ \
EMIT_BUG_ENTRY 1b,__FILE__,__LINE__,0; \
3: EXCEPTION_PROLOG_COMMON_1(); \
kuap_save_amr_and_lock r9, r10, cr1, cr0; \
beq 4f; /* if from kernel mode */ \
@ -428,7 +422,6 @@ END_FTR_SECTION_NESTED(CPU_FTR_CFAR, CPU_FTR_CFAR, 66); \
EXCEPTION_PROLOG_COMMON_3(trap); \
ACCOUNT_STOLEN_TIME
/*
* Exception where stack is already set in r1, r1 is saved in r10.
* PPR save and CPU accounting is not done (for some reason).
@ -1453,21 +1446,25 @@ EXC_COMMON_BEGIN(program_check_common)
* we switch to the emergency stack if we're taking a TM Bad Thing from
* the kernel.
*/
li r10,MSR_PR /* Build a mask of MSR_PR .. */
oris r10,r10,0x200000@h /* .. and SRR1_PROGTM */
and r10,r10,r12 /* Mask SRR1 with that. */
srdi r10,r10,8 /* Shift it so we can compare */
cmpldi r10,(0x200000 >> 8) /* .. with an immediate. */
bne 1f /* If != go to normal path. */
/* SRR1 had PR=0 and SRR1_PROGTM=1, so use the emergency stack */
andi. r10,r12,MSR_PR; /* Set CR0 correctly for label */
andi. r10,r12,MSR_PR
bne 2f /* If userspace, go normal path */
andis. r10,r12,(SRR1_PROGTM)@h
bne 1f /* If TM, emergency */
cmpdi r1,-INT_FRAME_SIZE /* check if r1 is in userspace */
blt 2f /* normal path if not */
/* Use the emergency stack */
1: andi. r10,r12,MSR_PR /* Set CR0 correctly for label */
/* 3 in EXCEPTION_PROLOG_COMMON */
mr r10,r1 /* Save r1 */
ld r1,PACAEMERGSP(r13) /* Use emergency stack */
subi r1,r1,INT_FRAME_SIZE /* alloc stack frame */
b 3f /* Jump into the macro !! */
1: EXCEPTION_COMMON(PACA_EXGEN, 0x700)
2:
EXCEPTION_COMMON(PACA_EXGEN, 0x700)
bl save_nvgprs
RECONCILE_IRQ_STATE(r10, r11)
addi r3,r1,STACK_FRAME_OVERHEAD
@ -2408,67 +2405,6 @@ handle_dabr_fault:
bl bad_page_fault
b ret_from_except
/*
* Here we have detected that the kernel stack pointer is bad.
* R9 contains the saved CR, r13 points to the paca,
* r10 contains the (bad) kernel stack pointer,
* r11 and r12 contain the saved SRR0 and SRR1.
* We switch to using an emergency stack, save the registers there,
* and call kernel_bad_stack(), which panics.
*/
bad_stack:
ld r1,PACAEMERGSP(r13)
subi r1,r1,64+INT_FRAME_SIZE
std r9,_CCR(r1)
std r10,GPR1(r1)
std r11,_NIP(r1)
std r12,_MSR(r1)
mfspr r11,SPRN_DAR
mfspr r12,SPRN_DSISR
std r11,_DAR(r1)
std r12,_DSISR(r1)
mflr r10
mfctr r11
mfxer r12
std r10,_LINK(r1)
std r11,_CTR(r1)
std r12,_XER(r1)
SAVE_GPR(0,r1)
SAVE_GPR(2,r1)
ld r10,EX_R3(r3)
std r10,GPR3(r1)
SAVE_GPR(4,r1)
SAVE_4GPRS(5,r1)
ld r9,EX_R9(r3)
ld r10,EX_R10(r3)
SAVE_2GPRS(9,r1)
ld r9,EX_R11(r3)
ld r10,EX_R12(r3)
ld r11,EX_R13(r3)
std r9,GPR11(r1)
std r10,GPR12(r1)
std r11,GPR13(r1)
BEGIN_FTR_SECTION
ld r10,EX_CFAR(r3)
std r10,ORIG_GPR3(r1)
END_FTR_SECTION_IFSET(CPU_FTR_CFAR)
SAVE_8GPRS(14,r1)
SAVE_10GPRS(22,r1)
lhz r12,PACA_TRAP_SAVE(r13)
std r12,_TRAP(r1)
addi r11,r1,INT_FRAME_SIZE
std r11,0(r1)
li r12,0
std r12,0(r11)
ld r2,PACATOC(r13)
ld r11,exception_marker@toc(r2)
std r12,RESULT(r1)
std r11,STACK_FRAME_OVERHEAD-16(r1)
1: addi r3,r1,STACK_FRAME_OVERHEAD
bl kernel_bad_stack
b 1b
_ASM_NOKPROBE_SYMBOL(bad_stack);
/*
* When doorbell is triggered from system reset wakeup, the message is
* not cleared, so it would fire again when EE is enabled.

2
arch/powerpc/xmon/xmon.c
View File

@ -2454,7 +2454,9 @@ static void dump_one_paca(int cpu)
DUMP(p, canary, "%#-*lx");
#endif
DUMP(p, saved_r1, "%#-*llx");
#ifdef CONFIG_PPC_BOOK3E
DUMP(p, trap_save, "%#-*x");
#endif
DUMP(p, irq_soft_mask, "%#-*x");
DUMP(p, irq_happened, "%#-*x");
#ifdef CONFIG_MMIOWB