| Message ID | 20200217140955.211661-1-alexander.sverdlin@nokia.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | ARM: Implement MODULE_PLT support in FTRACE | expand |
Hi Alexander, On 2/17/2020 6:09 AM, Alexander X Sverdlin wrote: > From: Alexander Sverdlin <alexander.sverdlin@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. We have been using those patches and I was wondering what happened after this version since they did not show up upstream nor in Russell's patch tracker? Would you be willing to resubmit them? Thanks!
Hello Florian, On 27/01/2021 05:48, Florian Fainelli wrote: >> 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. > We have been using those patches and I was wondering what happened after > this version since they did not show up upstream nor in Russell's patch > tracker? Would you be willing to resubmit them? it's a pity, but nobody ever showed any interest to take them to fix real problem in FTRACE. A grain of salt would be to remind, that no-one also replied that the series helped him or a Tested-by: tag. This would probably wake more interest from maintainers side. Of course I can re-send them because I personally re-base them regularly.
From: Alexander Sverdlin <alexander.sverdlin@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. Changelog: v6: * rebased v5: * BUILD_BUG_ON() ensures fixed_plts[] always fits one PLT block * use "for" loop instead of "while" * scripts/recordmcount is filtering reloc types v4: * Fixed build without CONFIG_FUNCTION_TRACER * Reorganized pre-allocated PLTs handling in get_module_plt(), now compiler eliminates the whole FTRACE-related handling code if ARRAY_SIZE(fixed_plts) == 0 v3: * Only extend struct dyn_arch_ftrace when ARM_MODULE_PLTS is enabled v2: * As suggested by Steven Rostedt, refrain from tree-wide API modification, save module pointer in struct dyn_arch_ftrace instead (PowerPC way) Alexander Sverdlin (2): ARM: PLT: Move struct plt_entries definition to header ARM: ftrace: Add MODULE_PLTS support arch/arm/include/asm/ftrace.h | 3 +++ arch/arm/include/asm/module.h | 10 +++++++++ arch/arm/kernel/ftrace.c | 46 ++++++++++++++++++++++++++++++++++++++-- arch/arm/kernel/module-plts.c | 49 +++++++++++++++++++++++++++++++++---------- 4 files changed, 95 insertions(+), 13 deletions(-)