perf symbols: Fix kallsyms perf test on ppc64le

ppc64le functions have a Global Entry Point (GEP) and a Local Entry
Point (LEP). While placing a probe, we always prefer the LEP since it
catches function calls through both the GEP and the LEP. In order to do
this, we fixup the function entry points during elf symbol table lookup
to point to the LEPs. This works, but breaks 'perf test kallsyms' since
the symbols loaded from the symbol table (pointing to the LEP) do not
match the symbols in kallsyms.

To fix this, we do not adjust all the symbols during symbol table load.
Instead, we note down st_other in a newly introduced arch-specific
member of perf symbol structure, and later use this to adjust the probe
trace point.

Reported-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Acked-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Acked-by: Balbir Singh <bsingharora@gmail.com>
Cc: Mark Wielaard <mjw@redhat.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
Cc: linuxppc-dev@lists.ozlabs.org
Link: http://lkml.kernel.org/r/6be7c2b17e370100c2f79dd444509df7929bdd3e.1460451721.git.naveen.n.rao@linux.vnet.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 20 insertions, 8 deletions

diff --git a/tools/perf/arch/powerpc/util/sym-handling.c b/tools/perf/arch/powerpc/util/sym-handling.c
index 6974ba0fa065..c6d0f91731a1 100644
--- a/tools/perf/arch/powerpc/util/sym-handling.c
+++ b/tools/perf/arch/powerpc/util/sym-handling.c
@@ -19,12 +19,6 @@ bool elf__needs_adjust_symbols(GElf_Ehdr ehdr)
                ehdr.e_type == ET_DYN;
 }
 
-#if defined(_CALL_ELF) && _CALL_ELF == 2
-void arch__elf_sym_adjust(GElf_Sym *sym)
-{
-        sym->st_value += PPC64_LOCAL_ENTRY_OFFSET(sym->st_other);
-}
-#endif
 #endif
 
 #if !defined(_CALL_ELF) || _CALL_ELF != 2
@@ -65,11 +59,21 @@ bool arch__prefers_symtab(void)
         return true;
 }
 
+#ifdef HAVE_LIBELF_SUPPORT
+void arch__sym_update(struct symbol *s, GElf_Sym *sym)
+{
+        s->arch_sym = sym->st_other;
+}
+#endif
+
 #define PPC64LE_LEP_OFFSET      8
 
 void arch__fix_tev_from_maps(struct perf_probe_event *pev,
-                             struct probe_trace_event *tev, struct map *map)
+                             struct probe_trace_event *tev, struct map *map,
+                             struct symbol *sym)
 {
+        int lep_offset;
+
         /*
          * When probing at a function entry point, we normally always want the
          * LEP since that catches calls to the function through both the GEP and
@@ -82,10 +86,18 @@ void arch__fix_tev_from_maps(struct perf_probe_event *pev,
          *
          * In addition, we shouldn't specify an offset for kretprobes.
          */
-        if (pev->point.offset || pev->point.retprobe || !map)
+        if (pev->point.offset || pev->point.retprobe || !map || !sym)
                 return;
 
+        lep_offset = PPC64_LOCAL_ENTRY_OFFSET(sym->arch_sym);
+
         if (map->dso->symtab_type == DSO_BINARY_TYPE__KALLSYMS)
                 tev->point.offset += PPC64LE_LEP_OFFSET;
+        else if (lep_offset) {
+                if (pev->uprobes)
+                        tev->point.address += lep_offset;
+                else
+                        tev->point.offset += lep_offset;
+        }
 }
 #endif