b.eq el0_ia
cmp x24, #ESR_ELx_EC_FP_ASIMD // FP/ASIMD access
b.eq el0_fpsimd_acc
+ cmp x24, #ESR_ELx_EC_SVE // SVE access
+ b.eq el0_sve_acc
cmp x24, #ESR_ELx_EC_FP_EXC64 // FP/ASIMD exception
b.eq el0_fpsimd_exc
cmp x24, #ESR_ELx_EC_SYS64 // configurable trap
/*
* AArch32 syscall handling
*/
+ ldr x16, [tsk, #TSK_TI_FLAGS] // load thread flags
adrp stbl, compat_sys_call_table // load compat syscall table pointer
mov wscno, w7 // syscall number in w7 (r7)
mov wsc_nr, #__NR_compat_syscalls
mov x1, sp
bl do_fpsimd_acc
b ret_to_user
+el0_sve_acc:
+ /*
+ * Scalable Vector Extension access
+ */
+ enable_daif
+ ct_user_exit
+ mov x0, x25
+ mov x1, sp
+ bl do_sve_acc
+ b ret_to_user
el0_fpsimd_exc:
/*
- * Floating Point or Advanced SIMD exception
+ * Floating Point, Advanced SIMD or SVE exception
*/
enable_daif
ct_user_exit
*/
.align 6
el0_svc:
+ ldr x16, [tsk, #TSK_TI_FLAGS] // load thread flags
adrp stbl, sys_call_table // load syscall table pointer
mov wscno, w8 // syscall number in w8
mov wsc_nr, #__NR_syscalls
+
+#ifndef CONFIG_ARM64_SVE
+ b el0_svc_naked
+#else
+ tbz x16, #TIF_SVE, el0_svc_naked // Skip unless TIF_SVE set:
+ bic x16, x16, #_TIF_SVE // discard SVE state
+ str x16, [tsk, #TSK_TI_FLAGS]
+
+ /*
+ * task_fpsimd_load() won't be called to update CPACR_EL1 in
+ * ret_to_user unless TIF_FOREIGN_FPSTATE is still set, which only
+ * happens if a context switch or kernel_neon_begin() or context
+ * modification (sigreturn, ptrace) intervenes.
+ * So, ensure that CPACR_EL1 is already correct for the fast-path case:
+ */
+ mrs x9, cpacr_el1
+ bic x9, x9, #CPACR_EL1_ZEN_EL0EN // disable SVE for el0
+ msr cpacr_el1, x9 // synchronised by eret to el0
+#endif /* CONFIG_ARM64_SVE */
+
el0_svc_naked: // compat entry point
stp x0, xscno, [sp, #S_ORIG_X0] // save the original x0 and syscall number
enable_daif
ct_user_exit 1
- ldr x16, [tsk, #TSK_TI_FLAGS] // check for syscall hooks
- tst x16, #_TIF_SYSCALL_WORK
+ tst x16, #_TIF_SYSCALL_WORK // check for syscall hooks
b.ne __sys_trace
cmp wscno, wsc_nr // check upper syscall limit
b.hs ni_sys
*/
#include <linux/bottom_half.h>
+#include <linux/bug.h>
+#include <linux/compat.h>
#include <linux/cpu.h>
#include <linux/cpu_pm.h>
#include <linux/kernel.h>
#include <linux/linkage.h>
+#include <linux/irqflags.h>
#include <linux/init.h>
#include <linux/percpu.h>
#include <linux/preempt.h>
+#include <linux/ptrace.h>
#include <linux/sched/signal.h>
+#include <linux/sched/task_stack.h>
#include <linux/signal.h>
+#include <linux/slab.h>
#include <asm/fpsimd.h>
#include <asm/cputype.h>
#include <asm/simd.h>
+#include <asm/sigcontext.h>
+#include <asm/sysreg.h>
+#include <asm/traps.h>
#define FPEXC_IOF (1 << 0)
#define FPEXC_DZF (1 << 1)
#define FPEXC_IDF (1 << 7)
/*
+ * (Note: in this discussion, statements about FPSIMD apply equally to SVE.)
+ *
* In order to reduce the number of times the FPSIMD state is needlessly saved
* and restored, we need to keep track of two things:
* (a) for each task, we need to remember which CPU was the last one to have
*/
static DEFINE_PER_CPU(struct fpsimd_state *, fpsimd_last_state);
+/*
+ * Call __sve_free() directly only if you know task can't be scheduled
+ * or preempted.
+ */
+static void __sve_free(struct task_struct *task)
+{
+ kfree(task->thread.sve_state);
+ task->thread.sve_state = NULL;
+}
+
+static void sve_free(struct task_struct *task)
+{
+ WARN_ON(test_tsk_thread_flag(task, TIF_SVE));
+
+ __sve_free(task);
+}
+
+
+/* Offset of FFR in the SVE register dump */
+static size_t sve_ffr_offset(int vl)
+{
+ return SVE_SIG_FFR_OFFSET(sve_vq_from_vl(vl)) - SVE_SIG_REGS_OFFSET;
+}
+
+static void *sve_pffr(struct task_struct *task)
+{
+ return (char *)task->thread.sve_state +
+ sve_ffr_offset(task->thread.sve_vl);
+}
+
+static void change_cpacr(u64 val, u64 mask)
+{
+ u64 cpacr = read_sysreg(CPACR_EL1);
+ u64 new = (cpacr & ~mask) | val;
+
+ if (new != cpacr)
+ write_sysreg(new, CPACR_EL1);
+}
+
+static void sve_user_disable(void)
+{
+ change_cpacr(0, CPACR_EL1_ZEN_EL0EN);
+}
+
+static void sve_user_enable(void)
+{
+ change_cpacr(CPACR_EL1_ZEN_EL0EN, CPACR_EL1_ZEN_EL0EN);
+}
+
+/*
+ * TIF_SVE controls whether a task can use SVE without trapping while
+ * in userspace, and also the way a task's FPSIMD/SVE state is stored
+ * in thread_struct.
+ *
+ * The kernel uses this flag to track whether a user task is actively
+ * using SVE, and therefore whether full SVE register state needs to
+ * be tracked. If not, the cheaper FPSIMD context handling code can
+ * be used instead of the more costly SVE equivalents.
+ *
+ * * TIF_SVE set:
+ *
+ * The task can execute SVE instructions while in userspace without
+ * trapping to the kernel.
+ *
+ * When stored, Z0-Z31 (incorporating Vn in bits[127:0] or the
+ * corresponding Zn), P0-P15 and FFR are encoded in in
+ * task->thread.sve_state, formatted appropriately for vector
+ * length task->thread.sve_vl.
+ *
+ * task->thread.sve_state must point to a valid buffer at least
+ * sve_state_size(task) bytes in size.
+ *
+ * During any syscall, the kernel may optionally clear TIF_SVE and
+ * discard the vector state except for the FPSIMD subset.
+ *
+ * * TIF_SVE clear:
+ *
+ * An attempt by the user task to execute an SVE instruction causes
+ * do_sve_acc() to be called, which does some preparation and then
+ * sets TIF_SVE.
+ *
+ * When stored, FPSIMD registers V0-V31 are encoded in
+ * task->fpsimd_state; bits [max : 128] for each of Z0-Z31 are
+ * logically zero but not stored anywhere; P0-P15 and FFR are not
+ * stored and have unspecified values from userspace's point of
+ * view. For hygiene purposes, the kernel zeroes them on next use,
+ * but userspace is discouraged from relying on this.
+ *
+ * task->thread.sve_state does not need to be non-NULL, valid or any
+ * particular size: it must not be dereferenced.
+ *
+ * * FPSR and FPCR are always stored in task->fpsimd_state irrespctive of
+ * whether TIF_SVE is clear or set, since these are not vector length
+ * dependent.
+ */
+
+/*
+ * Update current's FPSIMD/SVE registers from thread_struct.
+ *
+ * This function should be called only when the FPSIMD/SVE state in
+ * thread_struct is known to be up to date, when preparing to enter
+ * userspace.
+ *
+ * Softirqs (and preemption) must be disabled.
+ */
+static void task_fpsimd_load(void)
+{
+ WARN_ON(!in_softirq() && !irqs_disabled());
+
+ if (system_supports_sve() && test_thread_flag(TIF_SVE))
+ sve_load_state(sve_pffr(current),
+ ¤t->thread.fpsimd_state.fpsr,
+ sve_vq_from_vl(current->thread.sve_vl) - 1);
+ else
+ fpsimd_load_state(¤t->thread.fpsimd_state);
+
+ if (system_supports_sve()) {
+ /* Toggle SVE trapping for userspace if needed */
+ if (test_thread_flag(TIF_SVE))
+ sve_user_enable();
+ else
+ sve_user_disable();
+
+ /* Serialised by exception return to user */
+ }
+}
+
+/*
+ * Ensure current's FPSIMD/SVE storage in thread_struct is up to date
+ * with respect to the CPU registers.
+ *
+ * Softirqs (and preemption) must be disabled.
+ */
+static void task_fpsimd_save(void)
+{
+ WARN_ON(!in_softirq() && !irqs_disabled());
+
+ if (!test_thread_flag(TIF_FOREIGN_FPSTATE)) {
+ if (system_supports_sve() && test_thread_flag(TIF_SVE)) {
+ if (WARN_ON(sve_get_vl() != current->thread.sve_vl)) {
+ /*
+ * Can't save the user regs, so current would
+ * re-enter user with corrupt state.
+ * There's no way to recover, so kill it:
+ */
+ force_signal_inject(
+ SIGKILL, 0, current_pt_regs(), 0);
+ return;
+ }
+
+ sve_save_state(sve_pffr(current),
+ ¤t->thread.fpsimd_state.fpsr);
+ } else
+ fpsimd_save_state(¤t->thread.fpsimd_state);
+ }
+}
+
+#define ZREG(sve_state, vq, n) ((char *)(sve_state) + \
+ (SVE_SIG_ZREG_OFFSET(vq, n) - SVE_SIG_REGS_OFFSET))
+
+/*
+ * Transfer the FPSIMD state in task->thread.fpsimd_state to
+ * task->thread.sve_state.
+ *
+ * Task can be a non-runnable task, or current. In the latter case,
+ * softirqs (and preemption) must be disabled.
+ * task->thread.sve_state must point to at least sve_state_size(task)
+ * bytes of allocated kernel memory.
+ * task->thread.fpsimd_state must be up to date before calling this function.
+ */
+static void fpsimd_to_sve(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 (!system_supports_sve())
+ return;
+
+ vq = sve_vq_from_vl(task->thread.sve_vl);
+ for (i = 0; i < 32; ++i)
+ memcpy(ZREG(sst, vq, i), &fst->vregs[i],
+ sizeof(fst->vregs[i]));
+}
+
+#ifdef CONFIG_ARM64_SVE
+
+/*
+ * Return how many bytes of memory are required to store the full SVE
+ * state for task, given task's currently configured vector length.
+ */
+size_t sve_state_size(struct task_struct const *task)
+{
+ return SVE_SIG_REGS_SIZE(sve_vq_from_vl(task->thread.sve_vl));
+}
+
+/*
+ * Ensure that task->thread.sve_state is allocated and sufficiently large.
+ *
+ * This function should be used only in preparation for replacing
+ * task->thread.sve_state with new data. The memory is always zeroed
+ * here to prevent stale data from showing through: this is done in
+ * the interest of testability and predictability: except in the
+ * do_sve_acc() case, there is no ABI requirement to hide stale data
+ * written previously be task.
+ */
+void sve_alloc(struct task_struct *task)
+{
+ if (task->thread.sve_state) {
+ memset(task->thread.sve_state, 0, sve_state_size(current));
+ return;
+ }
+
+ /* This is a small allocation (maximum ~8KB) and Should Not Fail. */
+ task->thread.sve_state =
+ kzalloc(sve_state_size(task), GFP_KERNEL);
+
+ /*
+ * If future SVE revisions can have larger vectors though,
+ * this may cease to be true:
+ */
+ BUG_ON(!task->thread.sve_state);
+}
+
+/*
+ * Called from the put_task_struct() path, which cannot get here
+ * unless dead_task is really dead and not schedulable.
+ */
+void fpsimd_release_task(struct task_struct *dead_task)
+{
+ __sve_free(dead_task);
+}
+
+#endif /* CONFIG_ARM64_SVE */
+
+/*
+ * Trapped SVE access
+ *
+ * Storage is allocated for the full SVE state, the current FPSIMD
+ * register contents are migrated across, and TIF_SVE is set so that
+ * the SVE access trap will be disabled the next time this task
+ * reaches ret_to_user.
+ *
+ * TIF_SVE should be clear on entry: otherwise, task_fpsimd_load()
+ * would have disabled the SVE access trap for userspace during
+ * ret_to_user, making an SVE access trap impossible in that case.
+ */
+asmlinkage void do_sve_acc(unsigned int esr, struct pt_regs *regs)
+{
+ /* Even if we chose not to use SVE, the hardware could still trap: */
+ if (unlikely(!system_supports_sve()) || WARN_ON(is_compat_task())) {
+ force_signal_inject(SIGILL, ILL_ILLOPC, regs, 0);
+ return;
+ }
+
+ sve_alloc(current);
+
+ local_bh_disable();
+
+ task_fpsimd_save();
+ fpsimd_to_sve(current);
+
+ /* Force ret_to_user to reload the registers: */
+ fpsimd_flush_task_state(current);
+ set_thread_flag(TIF_FOREIGN_FPSTATE);
+
+ if (test_and_set_thread_flag(TIF_SVE))
+ WARN_ON(1); /* SVE access shouldn't have trapped */
+
+ local_bh_enable();
+}
+
/*
* Trapped FP/ASIMD access.
*/
* the registers is in fact the most recent userland FPSIMD state of
* 'current'.
*/
- if (current->mm && !test_thread_flag(TIF_FOREIGN_FPSTATE))
- fpsimd_save_state(¤t->thread.fpsimd_state);
+ if (current->mm)
+ task_fpsimd_save();
if (next->mm) {
/*
void fpsimd_flush_thread(void)
{
+ int vl;
+
if (!system_supports_fpsimd())
return;
memset(¤t->thread.fpsimd_state, 0, sizeof(struct fpsimd_state));
fpsimd_flush_task_state(current);
+
+ if (system_supports_sve()) {
+ clear_thread_flag(TIF_SVE);
+ sve_free(current);
+
+ /*
+ * Reset the task vector length as required.
+ * This is where we ensure that all user tasks have a valid
+ * vector length configured: no kernel task can become a user
+ * task without an exec and hence a call to this function.
+ * If a bug causes this to go wrong, we make some noise and
+ * try to fudge thread.sve_vl to a safe value here.
+ */
+ vl = current->thread.sve_vl;
+
+ if (vl == 0)
+ vl = SVE_VL_MIN;
+
+ if (WARN_ON(!sve_vl_valid(vl)))
+ vl = SVE_VL_MIN;
+
+ current->thread.sve_vl = vl;
+ }
+
set_thread_flag(TIF_FOREIGN_FPSTATE);
local_bh_enable();
/*
* Save the userland FPSIMD state of 'current' to memory, but only if the state
* currently held in the registers does in fact belong to 'current'
+ *
+ * Currently, SVE tasks can't exist, so just WARN in that case.
+ * Subsequent patches will add full SVE support here.
*/
void fpsimd_preserve_current_state(void)
{
if (!test_thread_flag(TIF_FOREIGN_FPSTATE))
fpsimd_save_state(¤t->thread.fpsimd_state);
+ WARN_ON_ONCE(test_and_clear_thread_flag(TIF_SVE));
+
local_bh_enable();
}
if (test_and_clear_thread_flag(TIF_FOREIGN_FPSTATE)) {
struct fpsimd_state *st = ¤t->thread.fpsimd_state;
- fpsimd_load_state(st);
+ task_fpsimd_load();
__this_cpu_write(fpsimd_last_state, st);
st->cpu = smp_processor_id();
}
{
switch (cmd) {
case CPU_PM_ENTER:
- if (current->mm && !test_thread_flag(TIF_FOREIGN_FPSTATE))
- fpsimd_save_state(¤t->thread.fpsimd_state);
+ if (current->mm)
+ task_fpsimd_save();
this_cpu_write(fpsimd_last_state, NULL);
break;
case CPU_PM_EXIT:
projects / users / willy / xarray.git / commitdiff