[PATCH] perf probe arm64: Fix symbol fixup issues due to ELF type

[PATCH] perf probe arm64: Fix symbol fixup issues due to ELF type

[Kim Phillips]

On an arm64 machine running a CONFIG_RANDOMIZE_BASE=y kernel, perf
kernel symbol resolution fails.  Debugging saw symsrc_init calling the
default elf__needs_adjust_symbols() where checks for an ET_DYN (3)
ehdr.e_type failed when they should have succeeded.

Fix by adopting powerpc version of the weak elf__needs_adjust_symbols()
function, as done in commit d2332098331f ("perf probe ppc: Fix symbol
fixup issues due to ELF type").

Prior to this patch, perf test 1 would fail:

$ sudo oldperf test -v 1 |& head
 1: vmlinux symtab matches kallsyms                       :
test child forked, pid 33374
Looking at the vmlinux_path (8 entries long)
Using /usr/lib/debug/boot/vmlinux for symbols
ERR : 0xfffe0000100f1000: do_undefinstr not on kallsyms
ERR : 0xfffe0000100f1320: do_sysinstr not on kallsyms
ERR : 0xfffe0000100f13b0: do_debug_exception not on kallsyms
ERR : 0xfffe0000100f1498: do_mem_abort not on kallsyms
ERR : 0xfffe0000100f1580: do_sp_pc_abort not on kallsyms
...

After applying this patch, perf test 1 now succeeds:

$ sudo ./newperf test -v 1 |& head
 1: vmlinux symtab matches kallsyms                       :
test child forked, pid 33378
Looking at the vmlinux_path (8 entries long)
Using /usr/lib/debug/boot/vmlinux for symbols
WARN: 0xffff000008081000: diff name v: do_undefinstr k:
__exception_text_start
WARN: 0xffff0000080819e8: diff name v: __irqentry_text_end k:
__softirqentry_text_start
WARN: 0xffff000008081d08: diff name v: __entry_text_start k:
__softirqentry_text_end
WARN: 0xffff00000809db5c: diff name v: flush_icache_range k:
__flush_cache_user_range
WARN: 0xffff000008101908: diff name v: sys_ni_syscall k: sys_vm86old
...

Signed-off-by: Kim Phillips <kim.phillips@arm.com>
---
 tools/perf/arch/arm64/util/Build          |  1 +
 tools/perf/arch/arm64/util/sym-handling.c | 22 ++++++++++++++++++++++
 2 files changed, 23 insertions(+)
 create mode 100644 tools/perf/arch/arm64/util/sym-handling.c

diff --git a/tools/perf/arch/arm64/util/Build b/tools/perf/arch/arm64/util/Build
index b1ab72d2a42e..e04f6cdd6f32 100644
--- a/tools/perf/arch/arm64/util/Build
+++ b/tools/perf/arch/arm64/util/Build
@@ -1,4 +1,5 @@
 libperf-y += header.o
+libperf-y += sym-handling.o
 libperf-$(CONFIG_DWARF)     += dwarf-regs.o
 libperf-$(CONFIG_LOCAL_LIBUNWIND) += unwind-libunwind.o
 
diff --git a/tools/perf/arch/arm64/util/sym-handling.c b/tools/perf/arch/arm64/util/sym-handling.c
new file mode 100644
index 000000000000..0051b1ee8450
--- /dev/null
+++ b/tools/perf/arch/arm64/util/sym-handling.c
@@ -0,0 +1,22 @@
+/*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License, version 2, as
+ * published by the Free Software Foundation.
+ *
+ * Copyright (C) 2015 Naveen N. Rao, IBM Corporation
+ */
+
+#include "debug.h"
+#include "symbol.h"
+#include "map.h"
+#include "probe-event.h"
+#include "probe-file.h"
+
+#ifdef HAVE_LIBELF_SUPPORT
+bool elf__needs_adjust_symbols(GElf_Ehdr ehdr)
+{
+	return ehdr.e_type == ET_EXEC ||
+	       ehdr.e_type == ET_REL ||
+	       ehdr.e_type == ET_DYN;
+}
+#endif
-- 
2.15.1

[PATCH] perf probe arm64: Fix symbol fixup issues due to ELF type

[Arnaldo Carvalho de Melo]

Em Thu, Dec 14, 2017 at 05:52:42PM -0600, Kim Phillips escreveu:
> On an arm64 machine running a CONFIG_RANDOMIZE_BASE=y kernel, perf
> kernel symbol resolution fails.  Debugging saw symsrc_init calling the
> default elf__needs_adjust_symbols() where checks for an ET_DYN (3)
> ehdr.e_type failed when they should have succeeded.
> 
> Fix by adopting powerpc version of the weak elf__needs_adjust_symbols()
> function, as done in commit d2332098331f ("perf probe ppc: Fix symbol
> fixup issues due to ELF type").
> 
> Prior to this patch, perf test 1 would fail:

Thanks, applied.

- Arnaldo