perf bpf: Fix bpf prologue generation
Issue:
bpf_probe_read() is no longer available for architecture which has
overlapping address space. Hence bpf prologue generation fails
Fix:
Use bpf_probe_read_kernel for kernel member access. For user attribute
access in kprobes, use bpf_probe_read_user.
Other:
@user attribute was introduced in commit 1e032f7cfa ("perf-probe: Add
user memory access attribute support")
Test:
1. ulimit -l 128 ; ./perf record -e tests/bpf_sched_setscheduler.c
2. cat tests/bpf_sched_setscheduler.c
static void (*bpf_trace_printk)(const char *fmt, int fmt_size, ...) =
(void *) 6;
static int (*bpf_probe_read_user)(void *dst, __u32 size,
const void *unsafe_ptr) = (void *) 112;
static int (*bpf_probe_read_kernel)(void *dst, __u32 size,
const void *unsafe_ptr) = (void *) 113;
SEC("func=do_sched_setscheduler pid policy param->sched_priority@user")
int bpf_func__setscheduler(void *ctx, int err, pid_t pid, int policy,
int param)
{
char fmt[] = "prio: %ld";
bpf_trace_printk(fmt, sizeof(fmt), param);
return 1;
}
char _license[] SEC("license") = "GPL";
int _version SEC("version") = LINUX_VERSION_CODE;
3. ./perf script
sched 305669 [000] 1614458.838675: perf_bpf_probe:func: (2904e508)
pid=261614 policy=2 sched_priority=1
4. cat /sys/kernel/debug/tracing/trace
<...>-309956 [006] .... 1616098.093957: 0: prio: 1
Committer testing:
I had to add some missing headers in the bpf_sched_setscheduler.c test
proggie, then instead of using record+script I used 'perf trace' to
drive everything in one go:
# cat bpf_sched_setscheduler.c
#include <linux/types.h>
#include <bpf.h>
static void (*bpf_trace_printk)(const char *fmt, int fmt_size, ...) = (void *) 6;
static int (*bpf_probe_read_user)(void *dst, __u32 size, const void *unsafe_ptr) = (void *) 112;
static int (*bpf_probe_read_kernel)(void *dst, __u32 size, const void *unsafe_ptr) = (void *) 113;
SEC("func=do_sched_setscheduler pid policy param->sched_priority@user")
int bpf_func__setscheduler(void *ctx, int err, pid_t pid, int policy, int param)
{
char fmt[] = "prio: %ld";
bpf_trace_printk(fmt, sizeof(fmt), param);
return 1;
}
char _license[] SEC("license") = "GPL";
int _version SEC("version") = LINUX_VERSION_CODE;
#
#
# perf trace -e bpf_sched_setscheduler.c chrt -f 42 sleep 1
0.000 chrt/80125 perf_bpf_probe:func(__probe_ip: -1676607808, policy: 1, sched_priority: 42)
#
And even with backtraces :-)
# perf trace -e bpf_sched_setscheduler.c/max-stack=8/ chrt -f 42 sleep 1
0.000 chrt/79805 perf_bpf_probe:func(__probe_ip: -1676607808, policy: 1, sched_priority: 42)
do_sched_setscheduler ([kernel.kallsyms])
__x64_sys_sched_setscheduler ([kernel.kallsyms])
do_syscall_64 ([kernel.kallsyms])
entry_SYSCALL_64 ([kernel.kallsyms])
__GI___sched_setscheduler (/usr/lib64/libc-2.30.so)
#
Signed-off-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
Reviewed-by: Thomas Richter <tmricht@linux.ibm.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Ilya Leoshkevich <iii@linux.ibm.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: bpf@vger.kernel.org
LPU-Reference: 20200609081019.60234-3-sumanthk@linux.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
d38c692f16