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Two more SME fixes related to ptrace(): ensure that the SME is properly

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set up for the target thread and that the thread sees the ZT registers
 set via ptrace.
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Merge tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux

Pull arm64 fixes from Catalin Marinas:
 "Two more SME fixes related to ptrace(): ensure that the SME is
  properly set up for the target thread and that the thread sees
  the ZT registers set via ptrace"

* tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux:
  arm64/ptrace: Ensure that the task sees ZT writes on first use
  arm64/ptrace: Ensure that SME is set up for target when writing SSVE state
This commit is contained in:
Linus Torvalds 2023-08-18 20:52:25 +02:00
commit d4ddefee51
4 changed files with 23 additions and 9 deletions
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4
arch/arm64/include/asm/fpsimd.h
View File

@ -356,7 +356,7 @@ static inline int sme_max_virtualisable_vl(void)
return vec_max_virtualisable_vl(ARM64_VEC_SME);
}
extern void sme_alloc(struct task_struct *task);
extern void sme_alloc(struct task_struct *task, bool flush);
extern unsigned int sme_get_vl(void);
extern int sme_set_current_vl(unsigned long arg);
extern int sme_get_current_vl(void);
@ -388,7 +388,7 @@ static inline void sme_smstart_sm(void) { }
static inline void sme_smstop_sm(void) { }
static inline void sme_smstop(void) { }
static inline void sme_alloc(struct task_struct *task) { }
static inline void sme_alloc(struct task_struct *task, bool flush) { }
static inline void sme_setup(void) { }
static inline unsigned int sme_get_vl(void) { return 0; }
static inline int sme_max_vl(void) { return 0; }

6
arch/arm64/kernel/fpsimd.c
View File

@ -1285,9 +1285,9 @@ void fpsimd_release_task(struct task_struct *dead_task)
* the interest of testability and predictability, the architecture
* guarantees that when ZA is enabled it will be zeroed.
*/
void sme_alloc(struct task_struct *task)
void sme_alloc(struct task_struct *task, bool flush)
{
if (task->thread.sme_state) {
if (task->thread.sme_state && flush) {
memset(task->thread.sme_state, 0, sme_state_size(task));
return;
}
@ -1515,7 +1515,7 @@ void do_sme_acc(unsigned long esr, struct pt_regs *regs)
}
sve_alloc(current, false);
sme_alloc(current);
sme_alloc(current, true);
if (!current->thread.sve_state || !current->thread.sme_state) {
force_sig(SIGKILL);
return;

20
arch/arm64/kernel/ptrace.c
View File

@ -881,6 +881,13 @@ static int sve_set_common(struct task_struct *target,
break;
case ARM64_VEC_SME:
target->thread.svcr |= SVCR_SM_MASK;
/*
* Disable traps and ensure there is SME storage but
* preserve any currently set values in ZA/ZT.
*/
sme_alloc(target, false);
set_tsk_thread_flag(target, TIF_SME);
break;
default:
WARN_ON_ONCE(1);
@ -1100,7 +1107,7 @@ static int za_set(struct task_struct *target,
}
/* Allocate/reinit ZA storage */
sme_alloc(target);
sme_alloc(target, true);
if (!target->thread.sme_state) {
ret = -ENOMEM;
goto out;
@ -1170,8 +1177,13 @@ static int zt_set(struct task_struct *target,
if (!system_supports_sme2())
return -EINVAL;
/* Ensure SVE storage in case this is first use of SME */
sve_alloc(target, false);
if (!target->thread.sve_state)
return -ENOMEM;
if (!thread_za_enabled(&target->thread)) {
sme_alloc(target);
sme_alloc(target, true);
if (!target->thread.sme_state)
return -ENOMEM;
}
@ -1179,8 +1191,10 @@ static int zt_set(struct task_struct *target,
ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
thread_zt_state(&target->thread),
0, ZT_SIG_REG_BYTES);
if (ret == 0)
if (ret == 0) {
target->thread.svcr |= SVCR_ZA_MASK;
set_tsk_thread_flag(target, TIF_SME);
}
fpsimd_flush_task_state(target);

2
arch/arm64/kernel/signal.c
View File

@ -475,7 +475,7 @@ static int restore_za_context(struct user_ctxs *user)
fpsimd_flush_task_state(current);
/* From now, fpsimd_thread_switch() won't touch thread.sve_state */
sme_alloc(current);
sme_alloc(current, true);
if (!current->thread.sme_state) {
current->thread.svcr &= ~SVCR_ZA_MASK;
clear_thread_flag(TIF_SME);