Messages in this thread | | | Date | Tue, 8 Mar 2022 17:02:53 +0100 | Subject | Re: ftrace bug | From | Alexander Sverdlin <> |
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Hi Arend!
On 08/03/2022 16:20, Steven Rostedt wrote: >>> I wanted to use FTRACE on an ARM platform and I hit the following >>> warning which results in ftrace bug. This happens upon loading a module. >>> Looking up the warning I suspect the branch target is too far off. The >>> module is quite large and therefor not loaded in the modules section. Is >>> there a way to exclude a module. In ftrace_module_init I see a check for >>> !mod->num_ftrace_callsites. Is there a way to avoid creating ftrace >>> callsites in a module? >> Are you sure it's the size. Just want to make sure that's the reason before >> going with different solutions. > Interpreting the warning statement in insn.c and given the fact that the > module is loaded at 0xe3xxxxxx instead of kernel module space at > 0xbfxxxxxx I made this assumption, but .... > >>> Regards, >>> Arend >>> >>> ------------[ cut here ]------------ >>> >>> WARNING: CPU: 2 PID: 1525 at arch/arm/kernel/insn.c:47 >>> __arm_gen_branch+0x70/0x78 >>> >>> CPU: 2 PID: 1525 Comm: insmod Tainted: P 4.19.183 #2
This problem is addressed by:
commit 8113e622926ef6590771ede0f7f64821e1751b67 Author: Alex Sverdlin <alexander.sverdlin@nokia.com> Date: Mon Sep 27 14:02:45 2021 -0700
ARM: 9079/1: ftrace: Add MODULE_PLTS support
commit 79f32b221b18c15a98507b101ef4beb52444cc6f upstream
Teach ftrace_make_call() and ftrace_make_nop() about PLTs. Teach PLT code about FTRACE and all its callbacks. Otherwise the following might happen:
------------[ cut here ]------------ WARNING: CPU: 14 PID: 2265 at .../arch/arm/kernel/insn.c:14 __arm_gen_branch+0x83/0x8c() ... Hardware name: LSI Axxia AXM55XX [<c0314a49>] (unwind_backtrace) from [<c03115e9>] (show_stack+0x11/0x14) [<c03115e9>] (show_stack) from [<c0519f51>] (dump_stack+0x81/0xa8) [<c0519f51>] (dump_stack) from [<c032185d>] (warn_slowpath_common+0x69/0x90) [<c032185d>] (warn_slowpath_common) from [<c03218f3>] (warn_slowpath_null+0x17/0x1c) [<c03218f3>] (warn_slowpath_null) from [<c03143cf>] (__arm_gen_branch+0x83/0x8c) [<c03143cf>] (__arm_gen_branch) from [<c0314337>] (ftrace_make_nop+0xf/0x24) [<c0314337>] (ftrace_make_nop) from [<c038ebcb>] (ftrace_process_locs+0x27b/0x3e8) [<c038ebcb>] (ftrace_process_locs) from [<c0378d79>] (load_module+0x11e9/0x1a44) [<c0378d79>] (load_module) from [<c037974d>] (SyS_finit_module+0x59/0x84) [<c037974d>] (SyS_finit_module) from [<c030e981>] (ret_fast_syscall+0x1/0x18) ---[ end trace e1b64ced7a89adcc ]--- ------------[ cut here ]------------
And if you wanna stick with 4.19.y, it's included starting from v4.19.209.
-- Best regards, Alexander Sverdlin.
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