linux-toradex.git/kernel/kallsyms.c, branch v5.5

kallsyms: Don't let kallsyms_lookup_size_offset() fail on retrieving the first symbol

2019-08-27T15:19:56+00:00

An arm64 kernel configured with

  CONFIG_KPROBES=y
  CONFIG_KALLSYMS=y
  # CONFIG_KALLSYMS_ALL is not set
  CONFIG_KALLSYMS_BASE_RELATIVE=y

reports the following kprobe failure:

  [    0.032677] kprobes: failed to populate blacklist: -22
  [    0.033376] Please take care of using kprobes.

It appears that kprobe fails to retrieve the symbol at address
0xffff000010081000, despite this symbol being in System.map:

  ffff000010081000 T __exception_text_start

This symbol is part of the first group of aliases in the
kallsyms_offsets array (symbol names generated using ugly hacks in
scripts/kallsyms.c):

  kallsyms_offsets:
          .long   0x1000 // do_undefinstr
          .long   0x1000 // efi_header_end
          .long   0x1000 // _stext
          .long   0x1000 // __exception_text_start
          .long   0x12b0 // do_cp15instr

Looking at the implementation of get_symbol_pos(), it returns the
lowest index for aliasing symbols. In this case, it return 0.

But kallsyms_lookup_size_offset() considers 0 as a failure, which
is obviously wrong (there is definitely a valid symbol living there).
In turn, the kprobe blacklisting stops abruptly, hence the original
error.

A CONFIG_KALLSYMS_ALL kernel wouldn't fail as there is always
some random symbols at the beginning of this array, which are never
looked up via kallsyms_lookup_size_offset.

Fix it by considering that get_symbol_pos() is always successful
(which is consistent with the other uses of this function).

Fixes: ffc5089196446 ("[PATCH] Create kallsyms_lookup_size_offset()")
Reviewed-by: Masami Hiramatsu 
Cc: Arnaldo Carvalho de Melo 
Cc: Peter Zijlstra 
Cc: Will Deacon 
Cc: Catalin Marinas 
Signed-off-by: Marc Zyngier 
Signed-off-by: Will Deacon

treewide: Add SPDX license identifier for missed files

2019-05-21T08:50:45+00:00

Add SPDX license identifiers to all files which:

 - Have no license information of any form

 - Have EXPORT_.*_SYMBOL_GPL inside which was used in the
   initial scan/conversion to ignore the file

These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:

  GPL-2.0-only

Signed-off-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

bpf: Add module name [bpf] to ksymbols for bpf programs

2019-01-21T20:38:56+00:00

With this patch, /proc/kallsyms will show BPF programs as

   t bpf_prog__ [bpf]

Signed-off-by: Song Liu 
Reviewed-by: Arnaldo Carvalho de Melo 
Tested-by: Arnaldo Carvalho de Melo 
Acked-by: Peter Zijlstra 
Cc: Alexei Starovoitov 
Cc: Daniel Borkmann 
Cc: Peter Zijlstra 
Cc: kernel-team@fb.com
Cc: netdev@vger.kernel.org
Link: http://lkml.kernel.org/r/20190117161521.1341602-10-songliubraving@fb.com
Signed-off-by: Arnaldo Carvalho de Melo

kallsyms: reduce size a little on 64-bit

2018-09-10T13:54:33+00:00

Both kallsyms_num_syms and kallsyms_markers[] don't really need to use
unsigned long as their (base) types; unsigned int fully suffices.

Signed-off-by: Jan Beulich 
Signed-off-by: Masahiro Yamada

kallsyms, x86: Export addresses of PTI entry trampolines

2018-08-14T22:12:29+00:00

Currently, the addresses of PTI entry trampolines are not exported to
user space. Kernel profiling tools need these addresses to identify the
kernel code, so add a symbol and address for each CPU's PTI entry
trampoline.

Signed-off-by: Alexander Shishkin 
Acked-by: Andi Kleen 
Acked-by: Peter Zijlstra (Intel) 
Cc: Andy Lutomirski 
Cc: Dave Hansen 
Cc: H. Peter Anvin 
Cc: Jiri Olsa 
Cc: Joerg Roedel 
Cc: Thomas Gleixner 
Cc: x86@kernel.org
Link: http://lkml.kernel.org/r/1528289651-4113-3-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo

kallsyms: Simplify update_iter_mod()

2018-08-14T22:10:23+00:00

The logic in update_iter_mod() is overcomplicated and gets worse every
time another get_ksymbol_* function is added.

In preparation for adding another get_ksymbol_* function, simplify logic
in update_iter_mod().

Signed-off-by: Adrian Hunter 
Tested-by: (ftrace changes only) Steven Rostedt (VMware) 
Acked-by: Andi Kleen 
Acked-by: Peter Zijlstra (Intel) 
Cc: Alexander Shishkin 
Cc: Andy Lutomirski 
Cc: Dave Hansen 
Cc: H. Peter Anvin 
Cc: Jiri Olsa 
Cc: Joerg Roedel 
Cc: Thomas Gleixner 
Cc: x86@kernel.org
Link: http://lkml.kernel.org/r/1528289651-4113-2-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk

2018-02-01T21:36:15+00:00

Pull printk updates from Petr Mladek:

 - Add a console_msg_format command line option:

     The value "default" keeps the old "[time stamp] text\n" format. The
     value "syslog" allows to see the syslog-like "[timestamp] text" format.

     This feature was requested by people doing regression tests, for
     example, 0day robot. They want to have both filtered and full logs
     at hands.

 - Reduce the risk of softlockup:

     Pass the console owner in a busy loop.

     This is a new approach to the old problem. It was first proposed by
     Steven Rostedt on Kernel Summit 2017. It marks a context in which
     the console_lock owner calls console drivers and could not sleep.
     On the other side, printk() callers could detect this state and use
     a busy wait instead of a simple console_trylock(). Finally, the
     console_lock owner checks if there is a busy waiter at the end of
     the special context and eventually passes the console_lock to the
     waiter.

     The hand-off works surprisingly well and helps in many situations.
     Well, there is still a possibility of the softlockup, for example,
     when the flood of messages stops and the last owner still has too
     much to flush.

     There is increasing number of people having problems with
     printk-related softlockups. We might eventually need to get better
     solution. Anyway, this looks like a good start and promising
     direction.

 - Do not allow to schedule in console_unlock() called from printk():

     This reverts an older controversial commit. The reschedule helped
     to avoid softlockups. But it also slowed down the console output.
     This patch is obsoleted by the new console waiter logic described
     above. In fact, the reschedule made the hand-off less effective.

 - Deprecate "%pf" and "%pF" format specifier:

     It was needed on ia64, ppc64 and parisc64 to dereference function
     descriptors and show the real function address. It is done
     transparently by "%ps" and "pS" format specifier now.

     Sergey Senozhatsky found that all the function descriptors were in
     a special elf section and could be easily detected.

 - Remove printk_symbol() API:

     It has been obsoleted by "%pS" format specifier, and this change
     helped to remove few continuous lines and a less intuitive old API.

 - Remove redundant memsets:

     Sergey removed unnecessary memset when processing printk.devkmsg
     command line option.

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk: (27 commits)
  printk: drop redundant devkmsg_log_str memsets
  printk: Never set console_may_schedule in console_trylock()
  printk: Hide console waiter logic into helpers
  printk: Add console owner and waiter logic to load balance console writes
  kallsyms: remove print_symbol() function
  checkpatch: add pF/pf deprecation warning
  symbol lookup: introduce dereference_symbol_descriptor()
  parisc64: Add .opd based function descriptor dereference
  powerpc64: Add .opd based function descriptor dereference
  ia64: Add .opd based function descriptor dereference
  sections: split dereference_function_descriptor()
  openrisc: Fix conflicting types for _exext and _stext
  lib: do not use print_symbol()
  irq debug: do not use print_symbol()
  sysfs: do not use print_symbol()
  drivers: do not use print_symbol()
  x86: do not use print_symbol()
  unicore32: do not use print_symbol()
  sh: do not use print_symbol()
  mn10300: do not use print_symbol()
  ...

Merge branch 'for-4.16-print-symbol' into for-4.16

2018-01-22T09:40:50+00:00

kallsyms: remove print_symbol() function

2018-01-16T15:59:55+00:00

No more print_symbol()/__print_symbol() users left, remove these
symbols.

It was a very old API that encouraged people use continuous lines.
It had been obsoleted by %pS format specifier in a normal printk()
call.

Link: http://lkml.kernel.org/r/20180105102538.GC471@jagdpanzerIV
Cc: Andrew Morton 
Cc: Russell King 
Cc: Catalin Marinas 
Cc: Mark Salter 
Cc: Tony Luck 
Cc: David Howells 
Cc: Yoshinori Sato 
Cc: Guan Xuetao 
Cc: Borislav Petkov 
Cc: Greg Kroah-Hartman 
Cc: Thomas Gleixner 
Cc: Peter Zijlstra 
Cc: Vineet Gupta 
Cc: Fengguang Wu 
Cc: Steven Rostedt 
Cc: LKML 
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-c6x-dev@linux-c6x.org
Cc: linux-ia64@vger.kernel.org
Cc: linux-am33-list@redhat.com
Cc: linux-sh@vger.kernel.org
Cc: linux-edac@vger.kernel.org
Cc: x86@kernel.org
Cc: linux-snps-arc@lists.infradead.org
Cc: Sergey Senozhatsky 
Signed-off-by: Sergey Senozhatsky 
Suggested-by: Joe Perches 
[pmladek@suse.com: updated commit message]
Signed-off-by: Petr Mladek

symbol lookup: introduce dereference_symbol_descriptor()

2018-01-09T09:45:38+00:00

dereference_symbol_descriptor() invokes appropriate ARCH specific
function descriptor dereference callbacks:
- dereference_kernel_function_descriptor() if the pointer is a
  kernel symbol;

- dereference_module_function_descriptor() if the pointer is a
  module symbol.

This is the last step needed to make '%pS/%ps' smart enough to
handle function descriptor dereference on affected ARCHs and
to retire '%pF/%pf'.

To refresh it:
  Some architectures (ia64, ppc64, parisc64) use an indirect pointer
  for C function pointers - the function pointer points to a function
  descriptor and we need to dereference it to get the actual function
  pointer.

  Function descriptors live in .opd elf section and all affected
  ARCHs (ia64, ppc64, parisc64) handle it properly for kernel and
  modules. So we, technically, can decide if the dereference is
  needed by simply looking at the pointer: if it belongs to .opd
  section then we need to dereference it.

  The kernel and modules have their own .opd sections, obviously,
  that's why we need to split dereference_function_descriptor()
  and use separate kernel and module dereference arch callbacks.

Link: http://lkml.kernel.org/r/20171206043649.GB15885@jagdpanzerIV
Cc: Fenghua Yu 
Cc: Benjamin Herrenschmidt 
Cc: Paul Mackerras 
Cc: Michael Ellerman 
Cc: James Bottomley 
Cc: Andrew Morton 
Cc: Jessica Yu 
Cc: Steven Rostedt 
Cc: linux-ia64@vger.kernel.org
Cc: linux-parisc@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Sergey Senozhatsky 
Tested-by: Tony Luck  #ia64
Tested-by: Santosh Sivaraj  #powerpc
Tested-by: Helge Deller  #parisc64
Signed-off-by: Petr Mladek