Currently uprobes and the Arm Guarded Control Stack (GCS) feature are exclusive of each other. This restriction needs to be lifted in order to utilize GCS for generic Linux distro images where the expectation is that core debugging features like uprobes work.
This series adds some user accessors to read/push/pop the userspace shadow stack. It then utilizes those functions in the uprobe paths as needed to synchronize GCS with the changes in control flow at probe locations. Along the way we fix a bug in the core gcs task handling and export some uprobe quality of life functionality for use in arch specific code. The KCONFIG restriction is then dropped. Jeremy Linton (7): arm64/gcs: task_gcs_el0_enable() should use passed task arm64: probes: Break ret out from bl/blr arm64: uaccess: Add additional userspace GCS accessors arm64: probes: Add GCS support to bl/blr/ret arm64: uprobes: Add GCS support to uretprobes uprobes: Allow the use of uprobe_warn() in arch code arm64: Kconfig: Remove GCS restrictions on UPROBES arch/arm64/Kconfig | 1 - arch/arm64/include/asm/gcs.h | 2 +- arch/arm64/include/asm/uaccess.h | 42 ++++++++++++++++++++++++ arch/arm64/kernel/probes/decode-insn.c | 7 ++-- arch/arm64/kernel/probes/simulate-insn.c | 42 +++++++++++++++++++++--- arch/arm64/kernel/probes/simulate-insn.h | 3 +- arch/arm64/kernel/probes/uprobes.c | 34 +++++++++++++++++++ include/linux/uprobes.h | 1 + kernel/events/uprobes.c | 2 +- 9 files changed, 122 insertions(+), 12 deletions(-) -- 2.48.1
