On Fri, Jul 17, 2020 at 01:30:03PM -0400, Steven Rostedt wrote:
On Fri, 17 Jul 2020 16:33:38 +0200 gregory.herrero@oracle.com wrote:
From: Gregory Herrero gregory.herrero@oracle.com Currently, if a section has a relocation to '_mcount' symbol, a new __mcount_loc entry will be added whatever the relocation type is. This is problematic when a relocation to '_mcount' is in the middle of a section and is not a call for ftrace use.
Such relocation could be generated with below code for example: bool is_mcount(unsigned long addr) { return (target == (unsigned long) &_mcount); }
With this snippet of code, ftrace will try to patch the mcount location generated by this code on module load and fail with:
Call trace: ftrace_bug+0xa0/0x28c ftrace_process_locs+0x2f4/0x430 ftrace_module_init+0x30/0x38 load_module+0x14f0/0x1e78 __do_sys_finit_module+0x100/0x11c __arm64_sys_finit_module+0x28/0x34 el0_svc_common+0x88/0x194 el0_svc_handler+0x38/0x8c el0_svc+0x8/0xc ---[ end trace d828d06b36ad9d59 ]--- ftrace failed to modify [<ffffa2dbf3a3a41c>] 0xffffa2dbf3a3a41c actual: 66:a9:3c:90 Initializing ftrace call sites ftrace record flags: 2000000 (0) expected tramp: ffffa2dc6cf66724So Limit the relocation type to R_AARCH64_CALL26 as in perl version of recordmcount.
I'd rather have this go through the arm64 tree, as they can test it better than I can.
Acked-by: Steven Rostedt (VMware) rostedt@goodmis.org
Thanks Steve.
Fixes: ed60453fa8f8 ("ARM: 6511/1: ftrace: add ARM support for C version of recordmcount")
This Fixes tag looks wrong. The above commit was for arm32.