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b43f70933e
Impact: fix failure of dynamic function tracer selftest In a course of development, a developer does several makes on their kernel. Sometimes, the make might do something abnormal. In the case of running the recordmcount.pl script on an object twice, the script will duplicate all the calls to mcount in the __mcount_loc section. On boot up, the dynamic function tracer is careful when it modifies code, and performs several consistency checks. One is to not modify the call site if it is not what it expects it to be. If a function call site is listed twice, the first entry will convert the site to a nop, and the second will fail because it expected to see a call to mcount, but instead it sees a nop. Thus, the function tracer is disabled. Eric Sesterhenn reported seeing: [ 1.055440] ftrace: converting mcount calls to 0f 1f 44 00 00 [ 1.055568] ftrace: allocating 29418 entries in 116 pages [ 1.061000] ------------[ cut here ]------------ [ 1.061000] WARNING: at kernel/trace/ftrace.c:441 [...] [ 1.060000] ---[ end trace 4eaa2a86a8e2da23 ]--- [ 1.060000] ftrace failed to modify [<c0118072>] check_corruption+0x3/0x2d [ 1.060000] actual: 0f:1f:44:00:00 This warning shows that check_corruption+0x3 already had a nop in its place (0x0f1f440000). After compiling another kernel the problem went away. Later Eric Paris notice the same type of issue. Luckily, he saved the vmlinux file that caused it. In the file we found a bunch of duplicate mcount call site records, which lead us to the script. Perhaps this problem only happens to people named Eric. This patch changes the script to test if the __mcount_loc already exists in the object file, and if it does, it will print out an error message and kill the compile. Reported-by: Eric Sesterhenn <snakebyte@gmx.de> Reported-by: Eric Paris <eparis@redhat.com> Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> |
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| .. | ||
| basic | ||
| genksyms | ||
| kconfig | ||
| ksymoops | ||
| mod | ||
| package | ||
| rt-tester | ||
| selinux | ||
| trace | ||
| tracing | ||
| .gitignore | ||
| bin2c.c | ||
| binoffset.c | ||
| bloat-o-meter | ||
| bootgraph.pl | ||
| checkincludes.pl | ||
| checkkconfigsymbols.sh | ||
| checkpatch.pl | ||
| checkstack.pl | ||
| checksyscalls.sh | ||
| checkversion.pl | ||
| cleanfile | ||
| cleanpatch | ||
| config | ||
| conmakehash.c | ||
| decodecode | ||
| diffconfig | ||
| export_report.pl | ||
| extract-ikconfig | ||
| gcc-version.sh | ||
| gcc-x86_64-has-stack-protector.sh | ||
| gen_initramfs_list.sh | ||
| headerdep.pl | ||
| headers.sh | ||
| headers_check.pl | ||
| headers_install.pl | ||
| ihex2fw.c | ||
| kallsyms.c | ||
| Kbuild.include | ||
| kernel-doc | ||
| Lindent | ||
| Makefile | ||
| Makefile.build | ||
| Makefile.clean | ||
| Makefile.fwinst | ||
| Makefile.headersinst | ||
| Makefile.host | ||
| Makefile.lib | ||
| Makefile.modinst | ||
| Makefile.modpost | ||
| makelst | ||
| markup_oops.pl | ||
| mkcompile_h | ||
| mkmakefile | ||
| mksysmap | ||
| mkuboot.sh | ||
| mkversion | ||
| namespace.pl | ||
| patch-kernel | ||
| pnmtologo.c | ||
| profile2linkerlist.pl | ||
| recordmcount.pl | ||
| setlocalversion | ||
| show_delta | ||
| strip-symbols | ||
| tags.sh | ||
| unifdef.c | ||
| ver_linux | ||