Re: [PATCH -next v14 13/19] riscv: signal: Add sigcontext save/restore for vector

Björn Töpel
2023-03-02T12:43:06Z

Andy Chiu <andy.chiu@sifive.com> writes:

> diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
> index 376d2827e736..b9b3e03b2564 100644
> --- a/arch/riscv/kernel/setup.c
> +++ b/arch/riscv/kernel/setup.c
> @@ -262,6 +262,8 @@ static void __init parse_dtb(void)
> #endif
> }
>
> +extern void __init init_rt_signal_env(void);
> +
> void __init setup_arch(char **cmdline_p)
> {
> parse_dtb();
> @@ -299,6 +301,7 @@ void __init setup_arch(char **cmdline_p)
>
> riscv_init_cbom_blocksize();
> riscv_fill_hwcap();
> + init_rt_signal_env();
> apply_boot_alternatives();
> if (IS_ENABLED(CONFIG_RISCV_ISA_ZICBOM) &&
> riscv_isa_extension_available(NULL, ZICBOM))
> diff --git a/arch/riscv/kernel/signal.c b/arch/riscv/kernel/signal.c
> index 0c8be5404a73..76c0480ee4cd 100644
> --- a/arch/riscv/kernel/signal.c
> +++ b/arch/riscv/kernel/signal.c
> @@ -18,9 +18,11 @@
> #include <asm/signal.h>
> #include <asm/signal32.h>
> #include <asm/switch_to.h>
> +#include <asm/vector.h>
> #include <asm/csr.h>
>
> extern u32 __user_rt_sigreturn[2];
> +static size_t riscv_v_sc_size;

__ro_after_init?

>
> #define DEBUG_SIG 0
>
> @@ -62,34 +64,159 @@ static long save_fp_state(struct pt_regs *regs,
> #define restore_fp_state(task, regs) (0)
> #endif
>
> +#ifdef CONFIG_RISCV_ISA_V
> +
> +static long save_v_state(struct pt_regs *regs, void **sc_vec)
> +{
> + /*
> + * Put __sc_riscv_v_state to the user's signal context space pointed
> + * by sc_vec and the datap point the address right
> + * after __sc_riscv_v_state.
> + */
> + struct __riscv_ctx_hdr __user *hdr = (struct __riscv_ctx_hdr *)(*sc_vec);
^^^
Remove unneccery cast and parenthesis.

> + struct __sc_riscv_v_state __user *state = (struct __sc_riscv_v_state *)(hdr + 1);
> + void __user *datap = state + 1;
> + long err;
> +
> + /* datap is designed to be 16 byte aligned for better performance */
> + WARN_ON(unlikely(!IS_ALIGNED((unsigned long)datap, 16)));
> +
> + riscv_v_vstate_save(current, regs);
> + /* Copy everything of vstate but datap. */
> + err = __copy_to_user(&state->v_state, &current->thread.vstate,
> + offsetof(struct __riscv_v_ext_state, datap));
> + /* Copy the pointer datap itself. */
> + err |= __put_user(datap, &state->v_state.datap);
> + /* Copy the whole vector content to user space datap. */
> + err |= __copy_to_user(datap, current->thread.vstate.datap, riscv_v_vsize);
> + /* Copy magic to the user space after saving all vector conetext */
> + err |= __put_user(RISCV_V_MAGIC, &hdr->magic);
> + err |= __put_user(riscv_v_sc_size, &hdr->size);
> + if (unlikely(err))
> + return err;
> +
> + /* Only progress the sv_vec if everything has done successfully */
> + *sc_vec += riscv_v_sc_size;
> + return 0;
> +}
> +
> +/*
> + * Restore Vector extension context from the user's signal frame. This function
> + * assumes a valid extension header. So magic and size checking must be done by
> + * the caller.
> + */
> +static long __restore_v_state(struct pt_regs *regs, void *sc_vec)
> +{
> + long err;
> + struct __sc_riscv_v_state __user *state = (struct __sc_riscv_v_state *)(sc_vec);
^^^
Remove unneccery cast and parenthesis.

> + void __user *datap;
> +
> + /* Copy everything of __sc_riscv_v_state except datap. */
> + err = __copy_from_user(&current->thread.vstate, &state->v_state,
> + offsetof(struct __riscv_v_ext_state, datap));
> + if (unlikely(err))
> + return err;
> +
> + /* Copy the pointer datap itself. */
> + err = __get_user(datap, &state->v_state.datap);
> + if (unlikely(err))
> + return err;
> + /*
> + * Copy the whole vector content from user space datap. Use
> + * copy_from_user to prevent information leak.
> + */
> + err = copy_from_user(current->thread.vstate.datap, datap, riscv_v_vsize);
> + if (unlikely(err))
> + return err;
> +
> + riscv_v_vstate_restore(current, regs);
> +
> + return err;
> +}
> +#else
> +#define save_v_state(task, regs) (0)
> +#define __restore_v_state(task, regs) (0)
> +#endif
> +
> static long restore_sigcontext(struct pt_regs *regs,
> struct sigcontext __user *sc)

This whole function; return in favor of goto, and remove the labels at
the bottom.

> {
> + void *sc_ext_ptr = &sc->sc_extdesc.hdr;
> + __u32 rsvd;
> long err;
> - size_t i;
> -
> /* sc_regs is structured the same as the start of pt_regs */
> err = __copy_from_user(regs, &sc->sc_regs, sizeof(sc->sc_regs));
> if (unlikely(err))
> - return err;
> + goto done;
> /* Restore the floating-point state. */
> if (has_fpu()) {
> err = restore_fp_state(regs, &sc->sc_fpregs);
> if (unlikely(err))
> - return err;
> + goto done;
> }
>
> - /* We support no other extension state at this time. */
> - for (i = 0; i < ARRAY_SIZE(sc->sc_fpregs.q.reserved); i++) {
> - u32 value;
> -
> - err = __get_user(value, &sc->sc_fpregs.q.reserved[i]);
> - if (unlikely(err))
> + /* Check the reserved word before extensions parsing */
> + err = __get_user(rsvd, &sc->sc_extdesc.reserved);
> + if (unlikely(err))
> + goto done;
> + if (unlikely(rsvd))
> + goto invalid;
> +
> + while (1 && !err) {
> + __u32 magic, size;
> + struct __riscv_ctx_hdr *head = (struct __riscv_ctx_hdr *)sc_ext_ptr;

Remove unneccery cast.

> +
> + err |= __get_user(magic, &head->magic);
> + err |= __get_user(size, &head->size);
> + if (err)
> + goto done;
> +
> + sc_ext_ptr += sizeof(struct __riscv_ctx_hdr);

sizeof(*head);

> + switch (magic) {
> + case END_MAGIC:
> + if (size != END_HDR_SIZE)
> + goto invalid;
> + goto done;
> + case RISCV_V_MAGIC:
> + if (!has_vector() || !riscv_v_vstate_query(regs))
> + goto invalid;
> + if (size != riscv_v_sc_size)
> + goto invalid;
> + err = __restore_v_state(regs, sc_ext_ptr);
> break;
> - if (value != 0)
> - return -EINVAL;
> + default:
> + goto invalid;
> + }
> + sc_ext_ptr = ((void *)(head) + size);

Unneccery parenthesis. "(void *)head + size" is enough

> }
> +done:
> return err;
> +invalid:
> + return -EINVAL;
> +}
> +
> +static size_t cal_rt_frame_size(void)
> +{
> + struct rt_sigframe __user *frame;
> + size_t frame_size;
> + size_t total_context_size = 0;
> +
> + frame_size = sizeof(*frame);
> +
> + if (has_vector() && riscv_v_vstate_query(task_pt_regs(current)))
> + total_context_size += riscv_v_sc_size;
> + /*
> + * Preserved a __riscv_ctx_hdr for END signal context header if an
> + * extension uses __riscv_extra_ext_header
> + */
> + if (total_context_size)
> + total_context_size += sizeof(struct __riscv_ctx_hdr);
> +
> + frame_size += (total_context_size);

Remove unneccery parenthesis.

> +
> + frame_size = round_up(frame_size, 16);
> + return frame_size;
> +
> }
>
> SYSCALL_DEFINE0(rt_sigreturn)
> @@ -98,13 +225,14 @@ SYSCALL_DEFINE0(rt_sigreturn)
> struct rt_sigframe __user *frame;
> struct task_struct *task;
> sigset_t set;
> + size_t frame_size = cal_rt_frame_size();
>
> /* Always make any pending restarted system calls return -EINTR */
> current->restart_block.fn = do_no_restart_syscall;
>
> frame = (struct rt_sigframe __user *)regs->sp;
>
> - if (!access_ok(frame, sizeof(*frame)))
> + if (!access_ok(frame, frame_size))
> goto badframe;
>
> if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
> @@ -138,17 +266,22 @@ static long setup_sigcontext(struct rt_sigframe __user *frame,
> struct pt_regs *regs)
> {
> struct sigcontext __user *sc = &frame->uc.uc_mcontext;
> + void *sc_ext_ptr = &sc->sc_extdesc.hdr;

All the casts and parenthesis makes it hard to read. Change to
struct __riscv_ctx_hdr *sc_ext_ptr = &sc->sc_extdesc.hdr;

> long err;
> - size_t i;
>
> /* sc_regs is structured the same as the start of pt_regs */
> err = __copy_to_user(&sc->sc_regs, regs, sizeof(sc->sc_regs));
> /* Save the floating-point state. */
> if (has_fpu())
> err |= save_fp_state(regs, &sc->sc_fpregs);
> - /* We support no other extension state at this time. */
> - for (i = 0; i < ARRAY_SIZE(sc->sc_fpregs.q.reserved); i++)
> - err |= __put_user(0, &sc->sc_fpregs.q.reserved[i]);
> + /* Save the vector state. */
> + if (has_vector() && riscv_v_vstate_query(regs))
> + err |= save_v_state(regs, &sc_ext_ptr);

...and cast to (void **) after the change above...

> + /* Write zero to fp-reserved space and check it on restore_sigcontext */
> + err |= __put_user(0, &sc->sc_extdesc.reserved);
> + /* And put END __riscv_ctx_hdr at the end. */
> + err |= __put_user(END_MAGIC, &((struct __riscv_ctx_hdr *)sc_ext_ptr)->magic);
> + err |= __put_user(END_HDR_SIZE, &((struct __riscv_ctx_hdr *)sc_ext_ptr)->size);

...and change to:
err |= __put_user(END_MAGIC, &sc_ext_ptr->magic);
err |= __put_user(END_HDR_SIZE, &sc_ext_ptr->size);

> return err;
> }
>
> @@ -172,6 +305,13 @@ static inline void __user *get_sigframe(struct ksignal *ksig,
> /* Align the stack frame. */
> sp &= ~0xfUL;
>
> + /*
> + * Fail if the size of the altstack is not large enough for the
> + * sigframe construction.
> + */
> + if (current->sas_ss_size && sp < current->sas_ss_sp)
> + return (void __user __force *)(-1UL);

Nit: Remove unneccery parenthesis.

Björn