From 7ddcaf78e93c9282b4d92184f511b4d5bee75355 Mon Sep 17 00:00:00 2001 From: Mark Brown Date: Wed, 17 Aug 2022 19:23:21 +0100 Subject: arm64/signal: Raise limit on stack frames The signal code has a limit of 64K on the size of a stack frame that it will generate, if this limit is exceeded then a process will be killed if it receives a signal. Unfortunately with the advent of SME this limit is too small - the maximum possible size of the ZA register alone is 64K. This is not an issue for practical systems at present but is easily seen using virtual platforms. Raise the limit to 256K, this is substantially more than could be used by any current architecture extension. Signed-off-by: Mark Brown Acked-by: Catalin Marinas Link: https://lore.kernel.org/r/20220817182324.638214-2-broonie@kernel.org Signed-off-by: Will Deacon --- arch/arm64/kernel/signal.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch/arm64/kernel/signal.c') diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c index 3e6d0352d7d3..0685b8784927 100644 --- a/arch/arm64/kernel/signal.c +++ b/arch/arm64/kernel/signal.c @@ -91,7 +91,7 @@ static size_t sigframe_size(struct rt_sigframe_user_layout const *user) * not taken into account. This limit is not a guarantee and is * NOT ABI. */ -#define SIGFRAME_MAXSZ SZ_64K +#define SIGFRAME_MAXSZ SZ_256K static int __sigframe_alloc(struct rt_sigframe_user_layout *user, unsigned long *offset, size_t size, bool extend) -- cgit From ea64baacbc36a0d552aec0d87107182f40211131 Mon Sep 17 00:00:00 2001 From: Mark Brown Date: Wed, 17 Aug 2022 19:23:22 +0100 Subject: arm64/signal: Flush FPSIMD register state when disabling streaming mode When handling a signal delivered to a context with streaming mode enabled we will disable streaming mode for the signal handler, when doing so we should also flush the saved FPSIMD register state like exiting streaming mode in the hardware would do so that if that state is reloaded we get the same behaviour. Without this we will reload whatever the last FPSIMD state that was saved for the task was. Fixes: 40a8e87bb328 ("arm64/sme: Disable ZA and streaming mode when handling signals") Signed-off-by: Mark Brown Reviewed-by: Catalin Marinas Link: https://lore.kernel.org/r/20220817182324.638214-3-broonie@kernel.org Signed-off-by: Will Deacon --- arch/arm64/kernel/signal.c | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'arch/arm64/kernel/signal.c') diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c index 0685b8784927..0d28a783a69a 100644 --- a/arch/arm64/kernel/signal.c +++ b/arch/arm64/kernel/signal.c @@ -926,6 +926,16 @@ static void setup_return(struct pt_regs *regs, struct k_sigaction *ka, /* Signal handlers are invoked with ZA and streaming mode disabled */ if (system_supports_sme()) { + /* + * If we were in streaming mode the saved register + * state was SVE but we will exit SM and use the + * FPSIMD register state - flush the saved FPSIMD + * register state in case it gets loaded. + */ + if (current->thread.svcr & SVCR_SM_MASK) + memset(¤t->thread.uw.fpsimd_state, 0, + sizeof(current->thread.uw.fpsimd_state)); + current->thread.svcr &= ~(SVCR_ZA_MASK | SVCR_SM_MASK); sme_smstop(); -- cgit From 826a4fdd2ada9e5923c58bdd168f31a42e958ffc Mon Sep 17 00:00:00 2001 From: Mark Brown Date: Wed, 17 Aug 2022 19:23:23 +0100 Subject: arm64/sme: Don't flush SVE register state when allocating SME storage Currently when taking a SME access trap we allocate storage for the SVE register state in order to be able to handle storage of streaming mode SVE. Due to the original usage in a purely SVE context the SVE register state allocation this also flushes the register state for SVE if storage was already allocated but in the SME context this is not desirable. For a SME access trap to be taken the task must not be in streaming mode so either there already is SVE register state present for regular SVE mode which would be corrupted or the task does not have TIF_SVE and the flush is redundant. Fix this by adding a flag to sve_alloc() indicating if we are in a SVE context and need to flush the state. Freshly allocated storage is always zeroed either way. Fixes: 8bd7f91c03d8 ("arm64/sme: Implement traps and syscall handling for SME") Signed-off-by: Mark Brown Reviewed-by: Catalin Marinas Link: https://lore.kernel.org/r/20220817182324.638214-4-broonie@kernel.org Signed-off-by: Will Deacon --- arch/arm64/include/asm/fpsimd.h | 4 ++-- arch/arm64/kernel/fpsimd.c | 10 ++++++---- arch/arm64/kernel/ptrace.c | 6 +++--- arch/arm64/kernel/signal.c | 2 +- 4 files changed, 12 insertions(+), 10 deletions(-) (limited to 'arch/arm64/kernel/signal.c') diff --git a/arch/arm64/include/asm/fpsimd.h b/arch/arm64/include/asm/fpsimd.h index 9bb1873f5295..6f86b7ab6c28 100644 --- a/arch/arm64/include/asm/fpsimd.h +++ b/arch/arm64/include/asm/fpsimd.h @@ -153,7 +153,7 @@ struct vl_info { #ifdef CONFIG_ARM64_SVE -extern void sve_alloc(struct task_struct *task); +extern void sve_alloc(struct task_struct *task, bool flush); extern void fpsimd_release_task(struct task_struct *task); extern void fpsimd_sync_to_sve(struct task_struct *task); extern void fpsimd_force_sync_to_sve(struct task_struct *task); @@ -256,7 +256,7 @@ size_t sve_state_size(struct task_struct const *task); #else /* ! CONFIG_ARM64_SVE */ -static inline void sve_alloc(struct task_struct *task) { } +static inline void sve_alloc(struct task_struct *task, bool flush) { } static inline void fpsimd_release_task(struct task_struct *task) { } static inline void sve_sync_to_fpsimd(struct task_struct *task) { } static inline void sve_sync_from_fpsimd_zeropad(struct task_struct *task) { } diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c index dd63ffc3a2fa..b9ae9827e6e8 100644 --- a/arch/arm64/kernel/fpsimd.c +++ b/arch/arm64/kernel/fpsimd.c @@ -715,10 +715,12 @@ size_t sve_state_size(struct task_struct const *task) * do_sve_acc() case, there is no ABI requirement to hide stale data * written previously be task. */ -void sve_alloc(struct task_struct *task) +void sve_alloc(struct task_struct *task, bool flush) { if (task->thread.sve_state) { - memset(task->thread.sve_state, 0, sve_state_size(task)); + if (flush) + memset(task->thread.sve_state, 0, + sve_state_size(task)); return; } @@ -1388,7 +1390,7 @@ void do_sve_acc(unsigned long esr, struct pt_regs *regs) return; } - sve_alloc(current); + sve_alloc(current, true); if (!current->thread.sve_state) { force_sig(SIGKILL); return; @@ -1439,7 +1441,7 @@ void do_sme_acc(unsigned long esr, struct pt_regs *regs) return; } - sve_alloc(current); + sve_alloc(current, false); sme_alloc(current); if (!current->thread.sve_state || !current->thread.za_state) { force_sig(SIGKILL); diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c index 21da83187a60..eb7c08dfb834 100644 --- a/arch/arm64/kernel/ptrace.c +++ b/arch/arm64/kernel/ptrace.c @@ -882,7 +882,7 @@ static int sve_set_common(struct task_struct *target, * state and ensure there's storage. */ if (target->thread.svcr != old_svcr) - sve_alloc(target); + sve_alloc(target, true); } /* Registers: FPSIMD-only case */ @@ -912,7 +912,7 @@ static int sve_set_common(struct task_struct *target, goto out; } - sve_alloc(target); + sve_alloc(target, true); if (!target->thread.sve_state) { ret = -ENOMEM; clear_tsk_thread_flag(target, TIF_SVE); @@ -1082,7 +1082,7 @@ static int za_set(struct task_struct *target, /* Ensure there is some SVE storage for streaming mode */ if (!target->thread.sve_state) { - sve_alloc(target); + sve_alloc(target, false); if (!target->thread.sve_state) { clear_thread_flag(TIF_SME); ret = -ENOMEM; diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c index 0d28a783a69a..9ad911f1647c 100644 --- a/arch/arm64/kernel/signal.c +++ b/arch/arm64/kernel/signal.c @@ -310,7 +310,7 @@ static int restore_sve_fpsimd_context(struct user_ctxs *user) fpsimd_flush_task_state(current); /* From now, fpsimd_thread_switch() won't touch thread.sve_state */ - sve_alloc(current); + sve_alloc(current, true); if (!current->thread.sve_state) { clear_thread_flag(TIF_SVE); return -ENOMEM; -- cgit