This patch adds support for manipulating a task's vector length at
runtime via ptrace.
As a simplification, we turn the task back into an FPSIMD-only task
when changing the vector length. If the register data is written
too, we then turn the task back into an SVE task, with changed
task_struct layout for the SVE data, before the actual data writing
is done.
Because the vector length is now variable, sve_get() now needs to
return the real maximum for user_sve_header.max_vl, since .vl may
be less than this (that's the whole point).
Signed-off-by: Dave Martin <Dave.Martin@xxxxxxx>
---
arch/arm64/include/asm/fpsimd.h | 1 +
arch/arm64/include/uapi/asm/ptrace.h | 5 +++++
arch/arm64/kernel/ptrace.c | 25 +++++++++++++++----------
3 files changed, 21 insertions(+), 10 deletions(-)
diff --git a/arch/arm64/include/asm/fpsimd.h b/arch/arm64/include/asm/fpsimd.h
index 1ec2363..0f1b068 100644
--- a/arch/arm64/include/asm/fpsimd.h
+++ b/arch/arm64/include/asm/fpsimd.h
@@ -105,6 +105,7 @@ extern void sve_load_state(void const *state, u32 const *pfpsr,
extern unsigned int sve_get_vl(void);
extern int sve_set_vector_length(struct task_struct *task,
unsigned long vl, unsigned long flags);
+extern int sve_max_vl;
/*
* FPSIMD/SVE synchronisation helpers for ptrace:
diff --git a/arch/arm64/include/uapi/asm/ptrace.h b/arch/arm64/include/uapi/asm/ptrace.h
index 48b57a0..bcb542d 100644
--- a/arch/arm64/include/uapi/asm/ptrace.h
+++ b/arch/arm64/include/uapi/asm/ptrace.h
@@ -64,6 +64,8 @@
#ifndef __ASSEMBLY__
+#include <linux/prctl.h>
+
/*
* User structures for general purpose, floating point and debug registers.
*/
@@ -108,6 +110,9 @@ struct user_sve_header {
#define SVE_PT_REGS_FPSIMD 0
#define SVE_PT_REGS_SVE SVE_PT_REGS_MASK
+#define SVE_PT_VL_THREAD PR_SVE_SET_VL_THREAD
+#define SVE_PT_VL_INHERIT PR_SVE_SET_VL_INHERIT
+
/*
* The remainder of the SVE state follows struct user_sve_header. The
diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index 32debb8..7e40039 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -741,14 +741,15 @@ static int sve_get(struct task_struct *target,
BUG_ON(!sve_vl_valid(header.vl));
vq = sve_vq_from_vl(header.vl);
- /* Until runtime or per-task vector length changing is supported: */
- header.max_vl = header.vl;
+ BUG_ON(!sve_vl_valid(sve_max_vl));
+ header.max_vl = sve_max_vl;
header.flags = test_tsk_thread_flag(target, TIF_SVE) ?
SVE_PT_REGS_SVE : SVE_PT_REGS_FPSIMD;
header.size = SVE_PT_SIZE(vq, header.flags);
- header.max_size = SVE_PT_SIZE(vq, SVE_PT_REGS_SVE);
+ header.max_size = SVE_PT_SIZE(sve_vq_from_vl(header.max_vl),
+ SVE_PT_REGS_SVE);
ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf, &header,
0, sizeof(header));
@@ -830,14 +831,18 @@ static int sve_set(struct task_struct *target,
if (ret)
goto out;
- if (header.vl != target->thread.sve_vl)
- return -EINVAL;
-
- BUG_ON(!sve_vl_valid(header.vl));
- vq = sve_vq_from_vl(header.vl);
+ /*
+ * Apart from PT_SVE_REGS_MASK, all PT_SVE_* flags are consumed by
+ * sve_set_vector_length(), which will also validate them for us:
+ */
+ ret = sve_set_vector_length(target, header.vl,
+ header.flags & ~SVE_PT_REGS_MASK);
+ if (ret)
+ goto out;
- if (header.flags & ~SVE_PT_REGS_MASK)
- return -EINVAL;
+ /* Actual VL set may be less than the user asked for: */
+ BUG_ON(!sve_vl_valid(target->thread.sve_vl));
+ vq = sve_vq_from_vl(target->thread.sve_vl);
/* Registers: FPSIMD-only case */
--
2.1.4
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