From mboxrd@z Thu Jan 1 00:00:00 1970 From: ard.biesheuvel@linaro.org (Ard Biesheuvel) Date: Tue, 9 Feb 2016 10:30:59 +0100 Subject: [PATCH v3 0/3] kallsyms: remove special handling for CONFIG_ARM Message-ID: <1455010262-28894-1-git-send-email-ard.biesheuvel@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org The kallsyms symbol address table generation contains a workaround for CONFIG_ARM to address an issue with perf when it sees symbols whose addresses are close to 0x0. The workaround is only enabled if XIP_KERNEL=n, not because the issue itself only exists in that case, but because the chosen workaround cannot deal with [_stext,_etext] living below PAGE_OFFSET. So let's fix this properly, by emitting the stubs symbols at a more reasonable offset, which is more likely to be the actual location of the vectors and stubs sections at runtime, and will prevent the symbols from being mistaken for userland symbols by perf. Changes since v2: - Move back to the original arrangement, where .stubs follows .vectors, and both are emitted outside of the ordinary kernel VMA space - Move .vectors and .stubs sections to VMA 0xffff0000/0xffff1000, respectively. As Russell pointed out, this is the most reasonable value, since modern CPUs actually execute the vectors and stubs from there, and it fixes the kallsyms perf issue all the same. - Rebased onto latest -next, which contains related ARM patch 8514/1, and updated kallsyms base relative patches (queued via akpm's tree) Changes since v1: - added Nico's ack - use PROVIDE() for vector_fiq_offset since vector_fiq itself is not always defined - put __stubs_start/_end inside the section definition so that the value of the start symbol equals the start of the section after alignment (fixes an issue on XIP spotted by Chris) Patch #1 moves the .stubs and .vectors section back into the kernel VMA, while preserving the guaranteed virtual offset of 4 KB. This results in all symbols that kallsyms sees to be in a reasonable interval. Patch #2 removes the special case for CONFIG_ARM && !CONFIG_XIP_KERNEL in the invocation of scripts/kallsyms Patch #3 removes the now unused --page-offset command line argument handling from scripts/kallsyms.c Patch #4 is included as an RFC, it removes the magic constant 0x1000 which is the offset between the start of the .vectors section and the start of the .stubs section. Ard Biesheuvel (3): ARM: move .vectors and .stubs sections back into the kernel VMA kallsyms: remove special lower address limit for CONFIG_ARM kallsyms: remove --page-offset command line option arch/arm/kernel/entry-armv.S | 3 +-- arch/arm/kernel/vmlinux.lds.S | 6 ++++-- scripts/kallsyms.c | 8 -------- scripts/link-vmlinux.sh | 4 ---- 4 files changed, 5 insertions(+), 16 deletions(-) -- 2.5.0