[PATCH 2/2] powerpc: Use unstripped VDSO image for more accurate profiling data

[Anton Blanchard]

We are seeing a lot of hits in the VDSO that are not resolved by perf.
A while(1) gettimeofday() loop shows the issue:

27.64%  [vdso]  [.] 0x000000000000060c                        
22.57%  [vdso]  [.] 0x0000000000000628                        
16.88%  [vdso]  [.] 0x0000000000000610                        
12.39%  [vdso]  [.] __kernel_gettimeofday                     
 6.09%  [vdso]  [.] 0x00000000000005f8                        
 3.58%  test    [.] 00000037.plt_call.gettimeofday@@GLIBC_2.18
 2.94%  [vdso]  [.] __kernel_datapage_offset                  
 2.90%  test    [.] main                                      

We are using a stripped VDSO image which means only symbols with
relocation info can be resolved. There isn't a lot of point to
stripping the VDSO, the debug info is only about 1kB:

4680 arch/powerpc/kernel/vdso64/vdso64.so
5815 arch/powerpc/kernel/vdso64/vdso64.so.dbg

By using the unstripped image, we can resolve all the symbols in the
VDSO and the perf profile data looks much better:

76.53%  [vdso]  [.] __do_get_tspec                            
12.20%  [vdso]  [.] __kernel_gettimeofday                     
 5.05%  [vdso]  [.] __get_datapage                            
 3.20%  test    [.] main                                      
 2.92%  test    [.] 00000037.plt_call.gettimeofday@@GLIBC_2.18

Signed-off-by: Anton Blanchard <anton at samba.org>
---

diff --git a/arch/powerpc/kernel/vdso32/vdso32_wrapper.S b/arch/powerpc/kernel/vdso32/vdso32_wrapper.S
index 6e8f507..37e2e13 100644
--- a/arch/powerpc/kernel/vdso32/vdso32_wrapper.S
+++ b/arch/powerpc/kernel/vdso32/vdso32_wrapper.S
@@ -7,7 +7,7 @@
 	.globl vdso32_start, vdso32_end
 	.balign PAGE_SIZE
 vdso32_start:
-	.incbin "arch/powerpc/kernel/vdso32/vdso32.so"
+	.incbin "arch/powerpc/kernel/vdso32/vdso32.so.dbg"
 	.balign PAGE_SIZE
 vdso32_end:
 
diff --git a/arch/powerpc/kernel/vdso64/vdso64_wrapper.S b/arch/powerpc/kernel/vdso64/vdso64_wrapper.S
index b8553d6..01e7799 100644
--- a/arch/powerpc/kernel/vdso64/vdso64_wrapper.S
+++ b/arch/powerpc/kernel/vdso64/vdso64_wrapper.S
@@ -7,7 +7,7 @@
 	.globl vdso64_start, vdso64_end
 	.balign PAGE_SIZE
 vdso64_start:
-	.incbin "arch/powerpc/kernel/vdso64/vdso64.so"
+	.incbin "arch/powerpc/kernel/vdso64/vdso64.so.dbg"
 	.balign PAGE_SIZE
 vdso64_end: