From 914d52e46490b6599b7f03fad233f4f19bf23cf7 Mon Sep 17 00:00:00 2001
From: Ilya Leoshkevich <iii@linux.ibm.com>
Date: Thu, 4 Jul 2019 16:18:15 +0200
Subject: [PATCH] s390: implement perf_arch_fetch_caller_regs
On s390 bpf_get_stack_raw_tp() returns 0 entries for both kernel and
user stacks. While there is no practical unwinding solution for userspace
on s390 at this moment, there certainly is a kernel unwinder. However,
it is not properly integrated with BPF.
In order to start unwinding, bpf_get_stack_raw_tp() obtains the current
kernel register values using perf_fetch_caller_regs(), which is not
implemented for s390. The actual unwinding then happens by passing those
registers to perf_callchain_kernel().
Implement perf_arch_fetch_caller_regs() for s390, where
__builtin_frame_address(0) points to back_chain.
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
---
arch/s390/include/asm/perf_event.h | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/arch/s390/include/asm/perf_event.h b/arch/s390/include/asm/perf_event.h
index 4652ffffe0b2f..b9da71632827f 100644
--- a/arch/s390/include/asm/perf_event.h
+++ b/arch/s390/include/asm/perf_event.h
@@ -12,6 +12,7 @@
#include <linux/perf_event.h>
#include <linux/device.h>
+#include <asm/stacktrace.h>
/* Per-CPU flags for PMU states */
#define PMU_F_RESERVED 0x1000
@@ -73,4 +74,10 @@ struct perf_sf_sde_regs {
#define SDB_FULL_BLOCKS(hwc) (SAMPL_FLAGS(hwc) & PERF_CPUM_SF_FULL_BLOCKS)
#define SAMPLE_FREQ_MODE(hwc) (SAMPL_FLAGS(hwc) & PERF_CPUM_SF_FREQ_MODE)
+#define perf_arch_fetch_caller_regs(regs, __ip) do { \
+ (regs)->psw.addr = (__ip); \
+ (regs)->gprs[15] = (unsigned long)__builtin_frame_address(0) - \
+ offsetof(struct stack_frame, back_chain); \
+} while (0)
+
#endif /* _ASM_S390_PERF_EVENT_H */
--
2.30.2