[PATCH v7 0/2] ARM: Implement MODULE_PLT support in FTRACE

Florian Fainelli f.fainelli at gmail.com
Wed Feb 3 13:23:36 EST 2021

On 1/27/21 3:09 AM, Alexander A Sverdlin wrote:
> From: Alexander Sverdlin <alexander.sverdlin at nokia.com>
> FTRACE's function tracer currently doesn't always work on ARM with
> MODULE_PLT option enabled. If the module is loaded too far, FTRACE's
> code modifier cannot cope with introduced veneers and turns the
> function tracer off globally.
> ARM64 already has a solution for the problem, refer to the following
> patches:
> arm64: ftrace: emit ftrace-mod.o contents through code
> arm64: module-plts: factor out PLT generation code for ftrace
> arm64: ftrace: fix !CONFIG_ARM64_MODULE_PLTS kernels
> arm64: ftrace: fix building without CONFIG_MODULES
> arm64: ftrace: add support for far branches to dynamic ftrace
> arm64: ftrace: don't validate branch via PLT in ftrace_make_nop()
> But the presented ARM variant has just a half of the footprint in terms of
> the changed LoCs. It also retains the code validation-before-modification
> instead of switching it off.

Ard, Russell should this be sent to the patch tracker?

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