[PATCH 2/2] powerpc: Save Come-From Address Register (CFAR) in exception frame
Paul Mackerras
paulus at samba.org
Mon May 2 15:48:20 EST 2011
Recent 64-bit server processors (POWER6 and POWER7) have a "Come-From
Address Register" (CFAR), that records the address of the most recent
branch or rfid (return from interrupt) instruction for debugging purposes.
This saves the value of the CFAR in the exception entry code and stores
it in the exception frame. We also make xmon print the CFAR value in
its register dump code.
Rather than extend the pt_regs struct at this time, we steal the orig_gpr3
field, which is only used for system calls, and use it for the CFAR value
for all exceptions/interrupts other than system calls. This means we
don't save the CFAR on system calls, which is not a great problem since
system calls tend not to happen unexpectedly, and also avoids adding the
overhead of reading the CFAR to the system call entry path.
Signed-off-by: Paul Mackerras <paulus at samba.org>
---
arch/powerpc/include/asm/cputable.h | 6 ++++--
arch/powerpc/include/asm/exception-64s.h | 9 +++++++++
arch/powerpc/include/asm/paca.h | 6 +++---
arch/powerpc/include/asm/reg.h | 1 +
arch/powerpc/kernel/exceptions-64s.S | 4 ++++
arch/powerpc/xmon/xmon.c | 4 ++++
6 files changed, 25 insertions(+), 5 deletions(-)
diff --git a/arch/powerpc/include/asm/cputable.h b/arch/powerpc/include/asm/cputable.h
index 3db2476..b0069ed 100644
--- a/arch/powerpc/include/asm/cputable.h
+++ b/arch/powerpc/include/asm/cputable.h
@@ -197,6 +197,7 @@ extern const char *powerpc_base_platform;
#define CPU_FTR_STCX_CHECKS_ADDRESS LONG_ASM_CONST(0x0200000000000000)
#define CPU_FTR_POPCNTB LONG_ASM_CONST(0x0400000000000000)
#define CPU_FTR_POPCNTD LONG_ASM_CONST(0x0800000000000000)
+#define CPU_FTR_CFAR LONG_ASM_CONST(0x1000000000000000)
#ifndef __ASSEMBLY__
@@ -411,14 +412,15 @@ extern const char *powerpc_base_platform;
CPU_FTR_COHERENT_ICACHE | \
CPU_FTR_PURR | CPU_FTR_SPURR | CPU_FTR_REAL_LE | \
CPU_FTR_DSCR | CPU_FTR_UNALIGNED_LD_STD | \
- CPU_FTR_STCX_CHECKS_ADDRESS | CPU_FTR_POPCNTB)
+ CPU_FTR_STCX_CHECKS_ADDRESS | CPU_FTR_POPCNTB | CPU_FTR_CFAR)
#define CPU_FTRS_POWER7 (CPU_FTR_USE_TB | CPU_FTR_LWSYNC | \
CPU_FTR_PPCAS_ARCH_V2 | CPU_FTR_CTRL | CPU_FTR_HVMODE_206 |\
CPU_FTR_MMCRA | CPU_FTR_SMT | \
CPU_FTR_COHERENT_ICACHE | \
CPU_FTR_PURR | CPU_FTR_SPURR | CPU_FTR_REAL_LE | \
CPU_FTR_DSCR | CPU_FTR_SAO | CPU_FTR_ASYM_SMT | \
- CPU_FTR_STCX_CHECKS_ADDRESS | CPU_FTR_POPCNTB | CPU_FTR_POPCNTD)
+ CPU_FTR_STCX_CHECKS_ADDRESS | CPU_FTR_POPCNTB | CPU_FTR_POPCNTD |\
+ CPU_FTR_CFAR)
#define CPU_FTRS_CELL (CPU_FTR_USE_TB | CPU_FTR_LWSYNC | \
CPU_FTR_PPCAS_ARCH_V2 | CPU_FTR_CTRL | \
CPU_FTR_ALTIVEC_COMP | CPU_FTR_MMCRA | CPU_FTR_SMT | \
diff --git a/arch/powerpc/include/asm/exception-64s.h b/arch/powerpc/include/asm/exception-64s.h
index 96ccef1..f5dfe34 100644
--- a/arch/powerpc/include/asm/exception-64s.h
+++ b/arch/powerpc/include/asm/exception-64s.h
@@ -46,6 +46,7 @@
#define EX_CCR 60
#define EX_R3 64
#define EX_LR 72
+#define EX_CFAR 80
/*
* We're short on space and time in the exception prolog, so we can't
@@ -66,6 +67,10 @@
std r10,area+EX_R10(r13); \
std r11,area+EX_R11(r13); \
std r12,area+EX_R12(r13); \
+ BEGIN_FTR_SECTION_NESTED(66); \
+ mfspr r10,SPRN_CFAR; \
+ std r10,area+EX_CFAR(r13); \
+ END_FTR_SECTION_NESTED(CPU_FTR_CFAR, CPU_FTR_CFAR, 66); \
GET_SCRATCH0(r9); \
std r9,area+EX_R13(r13); \
mfcr r9
@@ -130,6 +135,10 @@
std r9,GPR11(r1); \
std r10,GPR12(r1); \
std r11,GPR13(r1); \
+ BEGIN_FTR_SECTION_NESTED(66); \
+ ld r10,area+EX_CFAR(r13); \
+ std r10,ORIG_GPR3(r1); \
+ END_FTR_SECTION_NESTED(CPU_FTR_CFAR, CPU_FTR_CFAR, 66); \
ld r2,PACATOC(r13); /* get kernel TOC into r2 */ \
mflr r9; /* save LR in stackframe */ \
std r9,_LINK(r1); \
diff --git a/arch/powerpc/include/asm/paca.h b/arch/powerpc/include/asm/paca.h
index 65c13c4..7412676 100644
--- a/arch/powerpc/include/asm/paca.h
+++ b/arch/powerpc/include/asm/paca.h
@@ -92,9 +92,9 @@ struct paca_struct {
* Now, starting in cacheline 2, the exception save areas
*/
/* used for most interrupts/exceptions */
- u64 exgen[10] __attribute__((aligned(0x80)));
- u64 exmc[10]; /* used for machine checks */
- u64 exslb[10]; /* used for SLB/segment table misses
+ u64 exgen[11] __attribute__((aligned(0x80)));
+ u64 exmc[11]; /* used for machine checks */
+ u64 exslb[11]; /* used for SLB/segment table misses
* on the linear mapping */
/* SLB related definitions */
u16 vmalloc_sllp;
diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
index 1f9ac12..47e3416 100644
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -188,6 +188,7 @@
#define SPRN_CTR 0x009 /* Count Register */
#define SPRN_DSCR 0x11
+#define SPRN_CFAR 0x1c /* Come From Address Register */
#define SPRN_CTRLF 0x088
#define SPRN_CTRLT 0x098
#define CTRL_CT 0xc0000000 /* current thread */
diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index 27ca8b7..0ec3b42 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -474,6 +474,10 @@ bad_stack:
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)
diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
index 60593ad..909804a 100644
--- a/arch/powerpc/xmon/xmon.c
+++ b/arch/powerpc/xmon/xmon.c
@@ -1497,6 +1497,10 @@ static void prregs(struct pt_regs *fp)
#endif
printf("pc = ");
xmon_print_symbol(fp->nip, " ", "\n");
+ if (TRAP(fp) != 0xc00 && cpu_has_feature(CPU_FTR_CFAR)) {
+ printf("cfar= ");
+ xmon_print_symbol(fp->orig_gpr3, " ", "\n");
+ }
printf("lr = ");
xmon_print_symbol(fp->link, " ", "\n");
printf("msr = "REG" cr = %.8lx\n", fp->msr, fp->ccr);
--
1.7.4.1
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