Thomas Richter cf6383f73c perf report: Fix kernel symbol adjustment for s390x ... On s390x the kernel text segment starts at address 0x0. When perf report reads kernel symbols from vmlinux file it adds an offset of 0x1000. For example see symbol set_reset_devices: [root@s8360047 linux-devel]# nm -A vmlinux| fgrep set_reset_devices vmlinux:0000000001379000 t set_reset_devices [root@s8360047 linux-devel]# [root@s8360047 linux-devel]# fgrep set_reset_devices /proc/kallsyms 0000000001379000 t set_reset_devices [root@s8360047 linux-devel]# The kernel symbol table and the vmlinux file have the same address for symbol set_reset_devices namely 1379000. When perf report reads this symbols it displays it with address symbol__new: set_reset_devices 0x137a000-0x137a018 There is a difference between perf report and vmlinux of 0x1000. The reason for the difference is at kernel symbol load time in function dso__load_sym(). The vmlinux file is investigated with its ELF header. Command readelf shows this: Section Headers: [Nr] Name Type Address Offset Size EntSize Flags Link Info Align [ 0] NULL 0000000000000000 00000000 0000000000000000 0000000000000000 0 0 0 [ 1] .text PROGBITS 0000000000000000 00001000 0000000000b0e0c2 0000000000000000 AX 0 0 128 This leads to an invalid calculation of the symbol start address, see file utit/symbol-elf.c line 974: /* Adjust symbol to map to file offset */ if (adjust_kernel_syms) sym.st_value -= shdr.sh_addr - shdr.sh_offset; With shdr.sh_addr set to 0x0 and shdr.sh_offset set to 0x1000 as read from the ELF .text section 0x1000 is added to the symbol address. I would like to fix this by introducing an archticture specific function named elf__needs_adjust_symbols(). This is the same approach as done by PowerPC. The function currently does not exist for s390x and the default weak one is used. The s390x specific one returns false when symsrc_init() is invoked for kernel symbols and results in variable adjust_kernel_syms being false. This omits the adjustment and the correct address is displayed (when symbol resolvement does not work). The s390x specific function returns false for kernel symbol adjustment and returns true for kernel modules, processes and shared libraries. Signed-off-by: Thomas-Mich Richter <tmricht@linux.vnet.ibm.com> Cc: Hendrik Brueckner <brueckner@linux.vnet.ibm.com> Cc: Thomas-Mich Richter <tmricht@linux.vnet.ibm.com> LPU-Reference: 20170713130252.6167-1-tmricht@linux.vnet.ibm.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>		2017-07-25 11:23:50 -03:00
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alpha	perf tools: Add empty Build files for architectures lacking them	2015-08-06 16:24:15 -03:00
arm	perf coresight: Remove superfluous check before use	2017-06-19 15:27:08 -03:00
arm64	perf annotate: Fix AArch64 comment char	2017-05-04 10:03:00 -03:00
mips	perf tools: Add empty Build files for architectures lacking them	2015-08-06 16:24:15 -03:00
parisc	perf tools: Add empty Build files for architectures lacking them	2015-08-06 16:24:15 -03:00
powerpc	perf probe: Allow placing uprobes in alternate namespaces.	2017-07-18 23:14:10 -03:00
s390	perf report: Fix kernel symbol adjustment for s390x	2017-07-25 11:23:50 -03:00
sh	perf probe: Support probing on offline cross-arch binary	2016-09-01 12:41:09 -03:00
sparc	perf probe: Support probing on offline cross-arch binary	2016-09-01 12:41:09 -03:00
x86	perf intel-pt: Always set no branch for dummy event	2017-07-20 09:55:51 -03:00
xtensa	perf probe: Support probing on offline cross-arch binary	2016-09-01 12:41:09 -03:00
Build	perf tools: Fix build with ARCH=x86_64	2017-06-14 15:44:29 -03:00
common.c	perf annotate: Add missing powerpc triplet	2017-06-05 14:18:02 -03:00
common.h	perf tools: Export normalize_arch() function	2016-06-07 12:08:53 -03:00