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Sumanth Korikkar d38c692f16 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>
2020-06-09 12:40:04 -03:00
arch s390 updates for the 5.8 merge window 2020-06-08 12:05:31 -07:00
block for-5.8/drivers-2020-06-01 2020-06-02 15:37:03 -07:00
certs .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
crypto crypto: engine - do not requeue in case of fatal error 2020-05-28 17:27:52 +10:00
Documentation remoteproc updates for v5.8 2020-06-08 13:01:08 -07:00
drivers remoteproc updates for v5.8 2020-06-08 13:01:08 -07:00
fs The highlights are: 2020-06-08 12:49:18 -07:00
include remoteproc updates for v5.8 2020-06-08 13:01:08 -07:00
init kernel/sysctl: support setting sysctl parameters from kernel command line 2020-06-08 11:05:56 -07:00
ipc ipc/namespace.c: use a work queue to free_ipc 2020-06-08 11:05:56 -07:00
kernel module: move the set_fs hack for flush_icache_range to m68k 2020-06-08 11:05:58 -07:00
lib Merge branch 'akpm' (patches from Andrew) 2020-06-08 11:11:38 -07:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
mm Merge branch 'akpm' (patches from Andrew) 2020-06-08 11:11:38 -07:00
net The highlights are: 2020-06-08 12:49:18 -07:00
samples Kbuild updates for v5.8 2020-06-06 12:00:25 -07:00
scripts Fix for arch/sh build regression with newer binutils, removal of SH5, 2020-06-06 15:22:01 -07:00
security Tag summary 2020-06-07 16:04:49 -07:00
sound powerpc updates for 5.8 2020-06-05 12:39:30 -07:00
tools perf bpf: Fix bpf prologue generation 2020-06-09 12:40:04 -03:00
usr bpfilter: match bit size of bpfilter_umh to that of the kernel 2020-05-17 18:52:01 +09:00
virt mm/gup.c: convert to use get_user_{page|pages}_fast_only() 2020-06-08 11:05:56 -07:00
.clang-format block: add bio_for_each_bvec_all() 2020-05-25 11:25:24 +02:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore modpost: generate vmlinux.symvers and reuse it for the second modpost 2020-06-06 23:38:12 +09:00
.mailmap A fair amount of stuff this time around, dominated by yet another massive 2020-06-01 15:45:27 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS mailmap: change email for Ricardo Ribalda 2020-05-25 18:59:59 -06:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS remoteproc updates for v5.8 2020-06-08 13:01:08 -07:00
Makefile Kbuild updates for v5.8 2020-06-06 12:00:25 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.