On Mon, Jun 18, 2018 at 01:03:01PM +0100, Mark Rutland wrote:
> Now that the syscall invocation logic is in C, we can migrate the rest
> of the syscall entry logic over, so that the entry assembly needn't look
> at the register values at all.
>
> The SVE reset across syscall logic now unconditionally clears TIF_SVE,
> but sve_user_disable() will only write back to CPACR_EL1 when SVE is
> actually enabled.
>
> Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx>
> Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> Cc: Will Deacon <will.deacon@xxxxxxx>
> ---
> arch/arm64/kernel/entry.S | 42 ++++--------------------------------------
> arch/arm64/kernel/syscall.c | 40 ++++++++++++++++++++++++++++++++++++++--
> 2 files changed, 42 insertions(+), 40 deletions(-)
>
> diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
> index 05b9f03f3e00..156c4e3fd1a4 100644
> --- a/arch/arm64/kernel/entry.S
> +++ b/arch/arm64/kernel/entry.S
> @@ -720,14 +720,9 @@ el0_sync_compat:
> b.ge el0_dbg
> b el0_inv
> el0_svc_compat:
> - /*
> - * 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
> - b el0_svc_naked
> + mov x0, sp
> + bl el0_svc_compat_handler
> + b ret_to_user
>
> .align 6
> el0_irq_compat:
> @@ -925,37 +920,8 @@ ENDPROC(ret_to_user)
> */
> .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
> -
> -#ifdef CONFIG_ARM64_SVE
> -alternative_if_not ARM64_SVE
> - b el0_svc_naked
> -alternative_else_nop_endif
> - 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
> -
> -el0_svc_naked: // compat entry point
> mov x0, sp
> - mov w1, wscno
> - mov w2, wsc_nr
> - mov x3, stbl
> - bl el0_svc_common
> + bl el0_svc_handler
> b ret_to_user
> ENDPROC(el0_svc)
>
> diff --git a/arch/arm64/kernel/syscall.c b/arch/arm64/kernel/syscall.c
> index 2adf1a073398..6a31bb2a382b 100644
> --- a/arch/arm64/kernel/syscall.c
> +++ b/arch/arm64/kernel/syscall.c
> @@ -6,7 +6,9 @@
> #include <linux/ptrace.h>
>
> #include <asm/daifflags.h>
> +#include <asm/fpsimd.h>
> #include <asm/thread_info.h>
> +#include <asm/unistd.h>
>
> long do_ni_syscall(struct pt_regs *regs);
>
> @@ -42,8 +44,8 @@ static inline bool has_syscall_work(unsigned long flags)
> int syscall_trace_enter(struct pt_regs *regs);
> void syscall_trace_exit(struct pt_regs *regs);
>
> -asmlinkage void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr,
> - syscall_fn_t syscall_table[])
> +static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr,
> + syscall_fn_t syscall_table[])
> {
> unsigned long flags = current_thread_info()->flags;
>
> @@ -80,3 +82,37 @@ asmlinkage void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr,
> trace_exit:
> syscall_trace_exit(regs);
> }
> +
> +static inline void sve_user_reset(void)
> +{
Can we call this "sve_user_discard" please?
"Reset" is a reasonable name for the concept, but the "discard"
terminology has been used elsewhere.
> + if (!system_supports_sve())
> + return;
> +
> + /*
> + * 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.
> + */
This comment should go after clear_thead_flag(), since it describes not
the purpose of this function but the presence of sve_user_disable().
> + clear_thread_flag(TIF_SVE);
> + sve_user_disable();
> +}
> +
> +extern syscall_fn_t sys_call_table[];
> +
> +asmlinkage void el0_svc_handler(struct pt_regs *regs)
> +{
> + sve_user_reset();
> + el0_svc_common(regs, regs->regs[8], __NR_syscalls, sys_call_table);
> +}
> +
> +#ifdef CONFIG_COMPAT
> +extern syscall_fn_t compat_sys_call_table[];
> +
> +asmlinkage void el0_svc_compat_handler(struct pt_regs *regs)
> +{
> + el0_svc_common(regs, regs->regs[7], __NR_compat_syscalls,
> + compat_sys_call_table);
> +}
> +#endif
> --
> 2.11.0
>
>
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