[RFC PATCH v2 3/4] riscv: Add perf_arch_misc_flags callback

[Mayuresh Chitale]

Similar to X86, add perf_arch_misc_flags callback so that
PERF_RECORD_MISC flags may be set based on the regs provided by the
SBI PMU perf driver.

Signed-off-by: Mayuresh Chitale <mayuresh.chitale@xxxxxxxxxxxxxxxx>

diff --git a/arch/riscv/include/asm/perf_event.h b/arch/riscv/include/asm/perf_event.h
index bcc928fd3785..cf13702b185f 100644
--- a/arch/riscv/include/asm/perf_event.h
+++ b/arch/riscv/include/asm/perf_event.h
@@ -9,6 +9,14 @@
 #define _ASM_RISCV_PERF_EVENT_H
 
 #ifdef CONFIG_PERF_EVENTS
+/* Use sstatus bit 2 to convey whether an epc in the sample is precise or not */
+#define PERF_SR_PRECISE	_AC(0x00000004, UL)
+
+struct pt_regs;
+extern unsigned long perf_arch_misc_flags(struct pt_regs *regs);
+#define perf_arch_misc_flags(regs)	perf_arch_misc_flags(regs)
+#define perf_arch_instruction_pointer(regs)	instruction_pointer(regs)
+
 #include <linux/perf_event.h>
 #define perf_arch_bpf_user_pt_regs(regs) (struct user_regs_struct *)regs
 
diff --git a/arch/riscv/kernel/perf_callchain.c b/arch/riscv/kernel/perf_callchain.c
index b465bc9eb870..9b68d21b3a51 100644
--- a/arch/riscv/kernel/perf_callchain.c
+++ b/arch/riscv/kernel/perf_callchain.c
@@ -6,6 +6,21 @@
 
 #include <asm/stacktrace.h>
 
+unsigned long perf_arch_misc_flags(struct pt_regs *regs)
+{
+	unsigned long misc;
+
+	if (user_mode(regs))
+		misc = PERF_RECORD_MISC_USER;
+	else
+		misc = PERF_RECORD_MISC_KERNEL;
+
+	if (regs->status & PERF_SR_PRECISE)
+		misc |= PERF_RECORD_MISC_EXACT_IP;
+
+	return misc;
+}
+
 static bool fill_callchain(void *entry, unsigned long pc)
 {
 	return perf_callchain_store(entry, pc) == 0;