From: Richard Henderson <richard.henderson@linaro.org>
To: David Hildenbrand <david@redhat.com>, qemu-devel@nongnu.org
Cc: Florian Weimer <fweimer@redhat.com>,
Thomas Huth <thuth@redhat.com>, Cornelia Huck <cohuck@redhat.com>,
Stefano Brivio <sbrivio@redhat.com>,
qemu-s390x@nongnu.org, Richard Henderson <rth@twiddle.net>
Subject: Re: [Qemu-devel] [PATCH v2 04/28] s390x/tcg: MVCL: Process max 2k bytes at a time
Date: Wed, 11 Sep 2019 10:52:36 -0400 [thread overview]
Message-ID: <7788b1b6-fbf0-3370-5563-1da4f7124999@linaro.org> (raw)
In-Reply-To: <20190906075750.14791-5-david@redhat.com>
On 9/6/19 3:57 AM, David Hildenbrand wrote:
> Process max 2k bytes at a time, writing back registers between the
> accesses. The instruction is interruptible.
> "For operands longer than 2K bytes, access exceptions are not
> recognized for locations more than 2K bytes beyond the current location
> being processed."
>
> MVCL handling is quite different than MVCLE/MVCLU handling, so split up
> the handlers.
>
> We'll deal with fast_memmove() and fast_memset() not probing
> reads/writes properly later. Also, we'll defer interrupt handling, as
> that will require more thought, add a TODO for that.
>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
> target/s390x/mem_helper.c | 44 +++++++++++++++++++++++++++++++++------
> 1 file changed, 38 insertions(+), 6 deletions(-)
>
> diff --git a/target/s390x/mem_helper.c b/target/s390x/mem_helper.c
> index 2361ed6d54..2e22c183bd 100644
> --- a/target/s390x/mem_helper.c
> +++ b/target/s390x/mem_helper.c
> @@ -799,19 +799,51 @@ uint32_t HELPER(mvcl)(CPUS390XState *env, uint32_t r1, uint32_t r2)
> uint64_t srclen = env->regs[r2 + 1] & 0xffffff;
> uint64_t src = get_address(env, r2);
> uint8_t pad = env->regs[r2 + 1] >> 24;
> - uint32_t cc;
> + uint32_t cc, cur_len;
>
> if (is_destructive_overlap(env, dest, src, MIN(srclen, destlen))) {
> cc = 3;
> + } else if (srclen == destlen) {
> + cc = 0;
> + } else if (destlen < srclen) {
> + cc = 1;
> } else {
> - cc = do_mvcl(env, &dest, &destlen, &src, &srclen, pad, 1, ra);
> + cc = 2;
> }
>
> - env->regs[r1 + 1] = deposit64(env->regs[r1 + 1], 0, 24, destlen);
> - env->regs[r2 + 1] = deposit64(env->regs[r2 + 1], 0, 24, srclen);
> - set_address_zero(env, r1, dest);
> - set_address_zero(env, r2, src);
> + /* We might have to zero-out some bits even if there was no action. */
> + if (unlikely(!destlen || cc == 3)) {
> + set_address_zero(env, r2, src);
> + set_address_zero(env, r1, dest);
> + return cc;
> + } else if (!srclen) {
> + set_address_zero(env, r2, src);
> + }
>
> + /*
> + * Only perform one type of type of operation (move/pad) in one step.
> + * Process up to 2k bytes.
> + */
> + while (destlen) {
> + cur_len = MIN(destlen, 2048);
The language in the PoP is horribly written, and thus confusing. I can't
believe it really means what it appears to say, about access exceptions not
being recognized.
The code within Hercules breaks the action at every 2k address boundary -- for
both src and dest. That's the only way that actually makes sense to me, as
otherwise we end up allowing userspace to read/write into a page without
permission. Which is a security hole.
r~
next prev parent reply other threads:[~2019-09-11 15:04 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-06 7:57 [Qemu-devel] [PATCH v2 00/28] s390x/tcg: mem_helper: Fault-safe handling David Hildenbrand
2019-09-06 7:57 ` [Qemu-devel] [PATCH v2 01/28] s390x/tcg: Reset exception_index to -1 instead of 0 David Hildenbrand
2019-09-11 14:38 ` Richard Henderson
2019-09-06 7:57 ` [Qemu-devel] [PATCH v2 02/28] s390x/tcg: MVCL: Zero out unused bits of address David Hildenbrand
2019-09-11 14:40 ` Richard Henderson
2019-09-11 16:10 ` David Hildenbrand
2019-09-06 7:57 ` [Qemu-devel] [PATCH v2 03/28] s390x/tcg: MVCL: Detect destructive overlaps David Hildenbrand
2019-09-11 14:42 ` Richard Henderson
2019-09-06 7:57 ` [Qemu-devel] [PATCH v2 04/28] s390x/tcg: MVCL: Process max 2k bytes at a time David Hildenbrand
2019-09-11 14:52 ` Richard Henderson [this message]
2019-09-11 15:07 ` Richard Henderson
2019-09-11 16:12 ` David Hildenbrand
2019-09-06 7:57 ` [Qemu-devel] [PATCH v2 05/28] s390x/tcg: MVC: Increment the length once David Hildenbrand
2019-09-06 7:57 ` [Qemu-devel] [PATCH v2 06/28] s390x/tcg: MVC: Use is_destructive_overlap() David Hildenbrand
2019-09-11 14:54 ` Richard Henderson
2019-09-11 16:13 ` David Hildenbrand
2019-09-06 7:57 ` [Qemu-devel] [PATCH v2 07/28] s390x/tcg: MVPG: Check for specification exceptions David Hildenbrand
2019-09-11 14:57 ` Richard Henderson
2019-09-06 7:57 ` [Qemu-devel] [PATCH v2 08/28] s390x/tcg: MVPG: Properly wrap the addresses David Hildenbrand
2019-09-11 14:58 ` Richard Henderson
2019-09-06 7:57 ` [Qemu-devel] [PATCH v2 09/28] s390x/tcg: MVCLU/MVCLE: Process max 4k bytes at a time David Hildenbrand
2019-09-11 15:05 ` Richard Henderson
2019-09-11 16:14 ` David Hildenbrand
2019-09-06 7:57 ` [Qemu-devel] [PATCH v2 10/28] s390x/tcg: MVCS/MVCP: Check for special operation exceptions David Hildenbrand
2019-09-11 15:08 ` Richard Henderson
2019-09-06 7:57 ` [Qemu-devel] [PATCH v2 11/28] s390x/tcg: MVCS/MVCP: Properly wrap the length David Hildenbrand
2019-09-11 15:11 ` Richard Henderson
2019-09-11 16:15 ` David Hildenbrand
2019-09-06 7:57 ` [Qemu-devel] [PATCH v2 12/28] s390x/tcg: MVST: Check for specification exceptions David Hildenbrand
2019-09-11 15:14 ` Richard Henderson
2019-09-06 7:57 ` [Qemu-devel] [PATCH v2 13/28] s390x/tcg: MVST: Fix storing back the addresses to registers David Hildenbrand
2019-09-11 15:18 ` Richard Henderson
2019-09-11 16:15 ` David Hildenbrand
2019-09-06 7:57 ` [Qemu-devel] [PATCH v2 14/28] s390x/tcg: Always use MMU_USER_IDX for CONFIG_USER_ONLY David Hildenbrand
2019-09-11 15:19 ` Richard Henderson
2019-09-06 7:57 ` [Qemu-devel] [PATCH v2 15/28] s390x/tcg: Fault-safe memset David Hildenbrand
2019-09-11 15:29 ` Richard Henderson
2019-09-11 16:18 ` David Hildenbrand
2019-09-06 7:57 ` [Qemu-devel] [PATCH v2 16/28] s390x/tcg: Fault-safe memmove David Hildenbrand
2019-09-11 21:11 ` Richard Henderson
2019-09-11 22:03 ` Richard Henderson
2019-09-13 12:37 ` David Hildenbrand
2019-09-06 7:57 ` [Qemu-devel] [PATCH v2 17/28] s390x/tcg: MVCS/MVCP: Use access_memmove_idx() David Hildenbrand
2019-09-11 21:13 ` Richard Henderson
2019-09-06 7:57 ` [Qemu-devel] [PATCH v2 18/28] s390x/tcg: MVC: Fault-safe handling on destructive overlaps David Hildenbrand
2019-09-11 21:20 ` Richard Henderson
2019-09-06 7:57 ` [Qemu-devel] [PATCH v2 19/28] s390x/tcg: MVCLU: Fault-safe handling David Hildenbrand
2019-09-11 21:24 ` Richard Henderson
2019-09-06 7:57 ` [Qemu-devel] [PATCH v2 20/28] s390x/tcg: OC: " David Hildenbrand
2019-09-11 21:26 ` Richard Henderson
2019-09-16 12:01 ` David Hildenbrand
2019-09-06 7:57 ` [Qemu-devel] [PATCH v2 21/28] s390x/tcg: XC: " David Hildenbrand
2019-09-11 21:29 ` Richard Henderson
2019-09-06 7:57 ` [Qemu-devel] [PATCH v2 22/28] s390x/tcg: NC: " David Hildenbrand
2019-09-11 21:32 ` Richard Henderson
2019-09-06 7:57 ` [Qemu-devel] [PATCH v2 23/28] s390x/tcg: MVCIN: " David Hildenbrand
2019-09-11 21:35 ` Richard Henderson
2019-09-06 7:57 ` [Qemu-devel] [PATCH v2 24/28] s390x/tcg: MVN: " David Hildenbrand
2019-09-11 21:37 ` Richard Henderson
2019-09-06 7:57 ` [Qemu-devel] [PATCH v2 25/28] s390x/tcg: MVZ: " David Hildenbrand
2019-09-11 21:38 ` Richard Henderson
2019-09-06 7:57 ` [Qemu-devel] [PATCH v2 26/28] s390x/tcg: MVST: " David Hildenbrand
2019-09-11 21:52 ` Richard Henderson
2019-09-16 10:39 ` David Hildenbrand
2019-09-06 7:57 ` [Qemu-devel] [PATCH v2 27/28] s390x/tcg: MVO: " David Hildenbrand
2019-09-11 22:09 ` Richard Henderson
2019-09-06 7:57 ` [Qemu-devel] [PATCH v2 28/28] tests/tcg: target/s390x: Test MVO David Hildenbrand
2019-09-11 11:11 ` [Qemu-devel] [qemu-s390x] [PATCH v2 00/28] s390x/tcg: mem_helper: Fault-safe handling David Hildenbrand
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