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Date: Mon, 17 Feb 2020 15:09:53 +0100 From: Alexander X Sverdlin <alexander.sverdlin@...ia.com> To: linux-arm-kernel@...ts.infradead.org Cc: Alexander Sverdlin <alexander.sverdlin@...ia.com>, linux-kernel@...r.kernel.org, Russell King <linux@...linux.org.uk>, Steven Rostedt <rostedt@...dmis.org>, Ingo Molnar <mingo@...hat.com>, Ard Biesheuvel <ard.biesheuvel@...aro.org> Subject: [PATCH v6 0/2] ARM: Implement MODULE_PLT support in FTRACE From: Alexander Sverdlin <alexander.sverdlin@...ia.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(-) -- 2.4.6
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