powerpc/opalcore: export /sys/firmware/opal/core for analysing opal crashes

Export /sys/firmware/opal/core file to analyze opal crashes. Since OPAL
core can be generated independent of CONFIG_FA_DUMP support in kernel,
add this support under a new kernel config option CONFIG_OPAL_CORE.
Also, avoid code duplication by moving common code used while exporting
/proc/vmcore and/or /sys/firmware/opal/core file(s).
Signed-off-by: Hari Bathini <hbathini@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/156821378503.5656.3693769384945087756.stgit@hbathini.in.ibm.com

arch/powerpc/Kconfig

@@ -592,6 +592,15 @@ config PRESERVE_FA_DUMP
 	  memory preserving kernel boot would process this crash data.
 	  Petitboot kernel is the typical usecase for this option.
 
+config OPAL_CORE
+	bool "Export OPAL memory as /sys/firmware/opal/core"
+	depends on PPC64 && PPC_POWERNV
+	help
+	  This option uses the MPIPL support in firmware to provide an
+	  ELF core of OPAL memory after a crash. The ELF core is exported
+	  as /sys/firmware/opal/core file which is helpful in debugging
+	  OPAL crashes using GDB.
+
 config IRQ_ALL_CPUS
 	bool "Distribute interrupts on all CPUs by default"
 	depends on SMP

arch/powerpc/platforms/powernv/Makefile

@@ -9,6 +9,7 @@ obj-y			+= ultravisor.o
 obj-$(CONFIG_SMP)	+= smp.o subcore.o subcore-asm.o
 obj-$(CONFIG_FA_DUMP)	+= opal-fadump.o
 obj-$(CONFIG_PRESERVE_FA_DUMP)	+= opal-fadump.o
+obj-$(CONFIG_OPAL_CORE)	+= opal-core.o
 obj-$(CONFIG_PCI)	+= pci.o pci-ioda.o npu-dma.o pci-ioda-tce.o
 obj-$(CONFIG_CXL_BASE)	+= pci-cxl.o
 obj-$(CONFIG_EEH)	+= eeh-powernv.o

arch/powerpc/platforms/powernv/opal-fadump.c

@@ -85,6 +85,10 @@ static const struct opal_fadump_mem_struct *opal_fdm_active;
 static const struct opal_mpipl_fadump *opal_cpu_metadata;
 static struct opal_fadump_mem_struct *opal_fdm;
 
+#ifdef CONFIG_OPAL_CORE
+extern bool kernel_initiated;
+#endif
+
 static int opal_fadump_unregister(struct fw_dump *fadump_conf);
 
 static void opal_fadump_update_config(struct fw_dump *fadump_conf,
@@ -349,62 +353,6 @@ static void opal_fadump_cleanup(struct fw_dump *fadump_conf)
 		pr_warn("Could not reset (%llu) kernel metadata tag!\n", ret);
 }
 
-static inline void opal_fadump_set_regval_regnum(struct pt_regs *regs,
-						 u32 reg_type, u32 reg_num,
-						 u64 reg_val)
-{
-	if (reg_type == HDAT_FADUMP_REG_TYPE_GPR) {
-		if (reg_num < 32)
-			regs->gpr[reg_num] = reg_val;
-		return;
-	}
-
-	switch (reg_num) {
-	case SPRN_CTR:
-		regs->ctr = reg_val;
-		break;
-	case SPRN_LR:
-		regs->link = reg_val;
-		break;
-	case SPRN_XER:
-		regs->xer = reg_val;
-		break;
-	case SPRN_DAR:
-		regs->dar = reg_val;
-		break;
-	case SPRN_DSISR:
-		regs->dsisr = reg_val;
-		break;
-	case HDAT_FADUMP_REG_ID_NIP:
-		regs->nip = reg_val;
-		break;
-	case HDAT_FADUMP_REG_ID_MSR:
-		regs->msr = reg_val;
-		break;
-	case HDAT_FADUMP_REG_ID_CCR:
-		regs->ccr = reg_val;
-		break;
-	}
-}
-
-static inline void opal_fadump_read_regs(char *bufp, unsigned int regs_cnt,
-					 unsigned int reg_entry_size,
-					 struct pt_regs *regs)
-{
-	struct hdat_fadump_reg_entry *reg_entry;
-	int i;
-
-	memset(regs, 0, sizeof(struct pt_regs));
-
-	for (i = 0; i < regs_cnt; i++, bufp += reg_entry_size) {
-		reg_entry = (struct hdat_fadump_reg_entry *)bufp;
-		opal_fadump_set_regval_regnum(regs,
-					      be32_to_cpu(reg_entry->reg_type),
-					      be32_to_cpu(reg_entry->reg_num),
-					      be64_to_cpu(reg_entry->reg_val));
-	}
-}
-
 /*
  * Verify if CPU state data is available. If available, do a bit of sanity
  * checking before processing this data.
@@ -529,7 +477,7 @@ opal_fadump_build_cpu_notes(struct fw_dump *fadump_conf,
 			continue;
 
 		opal_fadump_read_regs((bufp + regs_offset), regs_cnt,
-				      reg_esize, &regs);
+				      reg_esize, true, &regs);
 		note_buf = fadump_regs_to_elf_notes(note_buf, &regs);
 		pr_debug("CPU PIR: 0x%x - R1 : 0x%lx, NIP : 0x%lx\n",
 			 thread_pir, regs.gpr[1], regs.nip);
@@ -573,6 +521,18 @@ static int __init opal_fadump_process(struct fw_dump *fadump_conf)
 		return rc;
 	}
 
+#ifdef CONFIG_OPAL_CORE
+	/*
+	 * If this is a kernel initiated crash, crashing_cpu would be set
+	 * appropriately and register data of the crashing CPU saved by
+	 * crashing kernel. Add this saved register data of crashing CPU
+	 * to elf notes and populate the pt_regs for the remaining CPUs
+	 * from register state data provided by firmware.
+	 */
+	if (fdh->crashing_cpu != FADUMP_CPU_UNKNOWN)
+		kernel_initiated = true;
+#endif
+
 	rc = opal_fadump_build_cpu_notes(fadump_conf, fdh);
 	if (rc)
 		return rc;

arch/powerpc/platforms/powernv/opal-fadump.h

@@ -8,6 +8,8 @@
 #ifndef _POWERNV_OPAL_FADUMP_H
 #define _POWERNV_OPAL_FADUMP_H
 
+#include <asm/reg.h>
+
 /*
  * OPAL FADump metadata structure format version
  *
@@ -77,4 +79,64 @@ struct hdat_fadump_reg_entry {
 	__be64		reg_val;
 } __packed;
 
+static inline void opal_fadump_set_regval_regnum(struct pt_regs *regs,
+						 u32 reg_type, u32 reg_num,
+						 u64 reg_val)
+{
+	if (reg_type == HDAT_FADUMP_REG_TYPE_GPR) {
+		if (reg_num < 32)
+			regs->gpr[reg_num] = reg_val;
+		return;
+	}
+
+	switch (reg_num) {
+	case SPRN_CTR:
+		regs->ctr = reg_val;
+		break;
+	case SPRN_LR:
+		regs->link = reg_val;
+		break;
+	case SPRN_XER:
+		regs->xer = reg_val;
+		break;
+	case SPRN_DAR:
+		regs->dar = reg_val;
+		break;
+	case SPRN_DSISR:
+		regs->dsisr = reg_val;
+		break;
+	case HDAT_FADUMP_REG_ID_NIP:
+		regs->nip = reg_val;
+		break;
+	case HDAT_FADUMP_REG_ID_MSR:
+		regs->msr = reg_val;
+		break;
+	case HDAT_FADUMP_REG_ID_CCR:
+		regs->ccr = reg_val;
+		break;
+	}
+}
+
+static inline void opal_fadump_read_regs(char *bufp, unsigned int regs_cnt,
+					 unsigned int reg_entry_size,
+					 bool cpu_endian,
+					 struct pt_regs *regs)
+{
+	struct hdat_fadump_reg_entry *reg_entry;
+	u64 val;
+	int i;
+
+	memset(regs, 0, sizeof(struct pt_regs));
+
+	for (i = 0; i < regs_cnt; i++, bufp += reg_entry_size) {
+		reg_entry = (struct hdat_fadump_reg_entry *)bufp;
+		val = (cpu_endian ? be64_to_cpu(reg_entry->reg_val) :
+		       reg_entry->reg_val);
+		opal_fadump_set_regval_regnum(regs,
+					      be32_to_cpu(reg_entry->reg_type),
+					      be32_to_cpu(reg_entry->reg_num),
+					      val);
+	}
+}
+
 #endif /* _POWERNV_OPAL_FADUMP_H */