arm64/sve: ptrace and ELF coredump support
This patch defines and implements a new regset NT_ARM_SVE, which
describes a thread's SVE register state. This allows a debugger to
manipulate the SVE state, as well as being included in ELF
coredumps for post-mortem debugging.
Because the regset size and layout are dependent on the thread's
current vector length, it is not possible to define a C struct to
describe the regset contents as is done for existing regsets.
Instead, and for the same reasons, NT_ARM_SVE is based on the
freeform variable-layout approach used for the SVE signal frame.
Additionally, to reduce debug overhead when debugging threads that
might or might not have live SVE register state, NT_ARM_SVE may be
presented in one of two different formats: the old struct
user_fpsimd_state format is embedded for describing the state of a
thread with no live SVE state, whereas a new variable-layout
structure is embedded for describing live SVE state. This avoids a
debugger needing to poll NT_PRFPREG in addition to NT_ARM_SVE, and
allows existing userspace code to handle the non-SVE case without
too much modification.
For this to work, NT_ARM_SVE is defined with a fixed-format header
of type struct user_sve_header, which the recipient can use to
figure out the content, size and layout of the reset of the regset.
Accessor macros are defined to allow the vector-length-dependent
parts of the regset to be manipulated.
Signed-off-by: Alan Hayward <alan.hayward@arm.com>
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Alex Bennée <alex.bennee@linaro.org>
Cc: Okamoto Takayuki <tokamoto@jp.fujitsu.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index 1e53115..b82d446 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -428,6 +428,66 @@ void sve_alloc(struct task_struct *task)
BUG_ON(!task->thread.sve_state);
}
+
+/*
+ * Ensure that task->thread.sve_state is up to date with respect to
+ * the user task, irrespective of when SVE is in use or not.
+ *
+ * This should only be called by ptrace. task must be non-runnable.
+ * task->thread.sve_state must point to at least sve_state_size(task)
+ * bytes of allocated kernel memory.
+ */
+void fpsimd_sync_to_sve(struct task_struct *task)
+{
+ if (!test_tsk_thread_flag(task, TIF_SVE))
+ fpsimd_to_sve(task);
+}
+
+/*
+ * Ensure that task->thread.fpsimd_state is up to date with respect to
+ * the user task, irrespective of whether SVE is in use or not.
+ *
+ * This should only be called by ptrace. task must be non-runnable.
+ * task->thread.sve_state must point to at least sve_state_size(task)
+ * bytes of allocated kernel memory.
+ */
+void sve_sync_to_fpsimd(struct task_struct *task)
+{
+ if (test_tsk_thread_flag(task, TIF_SVE))
+ sve_to_fpsimd(task);
+}
+
+/*
+ * Ensure that task->thread.sve_state is up to date with respect to
+ * the task->thread.fpsimd_state.
+ *
+ * This should only be called by ptrace to merge new FPSIMD register
+ * values into a task for which SVE is currently active.
+ * task must be non-runnable.
+ * task->thread.sve_state must point to at least sve_state_size(task)
+ * bytes of allocated kernel memory.
+ * task->thread.fpsimd_state must already have been initialised with
+ * the new FPSIMD register values to be merged in.
+ */
+void sve_sync_from_fpsimd_zeropad(struct task_struct *task)
+{
+ unsigned int vq;
+ void *sst = task->thread.sve_state;
+ struct fpsimd_state const *fst = &task->thread.fpsimd_state;
+ unsigned int i;
+
+ if (!test_tsk_thread_flag(task, TIF_SVE))
+ return;
+
+ vq = sve_vq_from_vl(task->thread.sve_vl);
+
+ memset(sst, 0, SVE_SIG_REGS_SIZE(vq));
+
+ for (i = 0; i < 32; ++i)
+ memcpy(ZREG(sst, vq, i), &fst->vregs[i],
+ sizeof(fst->vregs[i]));
+}
+
int sve_set_vector_length(struct task_struct *task,
unsigned long vl, unsigned long flags)
{