Commit 914d52e4 authored by Ilya Leoshkevich's avatar Ilya Leoshkevich Committed by Vasily Gorbik
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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: default avatarIlya Leoshkevich <iii@linux.ibm.com>
Acked-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
parent ea1f56fa

arch/s390/include/asm/perf_event.h

+7 −0
Original line number Diff line number Diff line
@@ -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 */