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s390: implement perf_arch_fetch_caller_regs

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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>
This commit is contained in:
Ilya Leoshkevich 2019-07-04 16:18:15 +02:00 • committed by Vasily Gorbik
parent ea1f56fa16
commit 914d52e464
1 changed files with 7 additions and 0 deletions
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7
arch/s390/include/asm/perf_event.h
View file

@ -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 */