From: Sergei Trofimovich <slyfox@gentoo.org>
To: Andrew Morton <akpm@linux-foundation.org>, linux-kernel@vger.kernel.org
Cc: Sergei Trofimovich <slyfox@gentoo.org>,
Oleg Nesterov <oleg@redhat.com>,
linux-ia64@vger.kernel.org, "Dmitry V . Levin" <ldv@altlinux.org>
Subject: [PATCH] ia64: fix ia64_syscall_get_set_arguments() for break-based syscalls
Date: Sun, 21 Feb 2021 00:25:53 +0000 [thread overview]
Message-ID: <20210221002554.333076-1-slyfox@gentoo.org> (raw)
In https://bugs.gentoo.org/769614 Dmitry noticed that
`ptrace(PTRACE_GET_SYSCALL_INFO)` does not work for syscalls called
via glibc's syscall() wrapper.
ia64 has two ways to call syscalls from userspace: via `break` and via
`eps` instructions.
The difference is in stack layout:
1. `eps` creates simple stack frame: no locals, in{0..7} == out{0..8}
2. `break` uses userspace stack frame: may be locals (glibc provides
one), in{0..7} == out{0..8}.
Both work fine in syscall handling cde itself.
But `ptrace(PTRACE_GET_SYSCALL_INFO)` uses unwind mechanism to
re-extract syscall arguments but it does not account for locals.
The change always skips locals registers. It should not change `eps`
path as kernel's handler already enforces locals=0 and fixes `break`.
Tested on v5.10 on rx3600 machine (ia64 9040 CPU).
CC: Oleg Nesterov <oleg@redhat.com>
CC: linux-ia64@vger.kernel.org
CC: linux-kernel@vger.kernel.org
CC: Andrew Morton <akpm@linux-foundation.org>
Reported-by: Dmitry V. Levin <ldv@altlinux.org>
Bug: https://bugs.gentoo.org/769614
Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
---
arch/ia64/kernel/ptrace.c | 24 ++++++++++++++++++------
1 file changed, 18 insertions(+), 6 deletions(-)
diff --git a/arch/ia64/kernel/ptrace.c b/arch/ia64/kernel/ptrace.c
index c3490ee2daa5..e14f5653393a 100644
--- a/arch/ia64/kernel/ptrace.c
+++ b/arch/ia64/kernel/ptrace.c
@@ -2013,27 +2013,39 @@ static void syscall_get_set_args_cb(struct unw_frame_info *info, void *data)
{
struct syscall_get_set_args *args = data;
struct pt_regs *pt = args->regs;
- unsigned long *krbs, cfm, ndirty;
+ unsigned long *krbs, cfm, ndirty, nlocals, nouts;
int i, count;
if (unw_unwind_to_user(info) < 0)
return;
+ /*
+ * We get here via a few paths:
+ * - break instruction: cfm is shared with caller.
+ * syscall args are in out= regs, locals are non-empty.
+ * - epsinstruction: cfm is set by br.call
+ * locals don't exist.
+ *
+ * For both cases argguments are reachable in cfm.sof - cfm.sol.
+ * CFM: [ ... | sor: 17..14 | sol : 13..7 | sof : 6..0 ]
+ */
cfm = pt->cr_ifs;
+ nlocals = (cfm >> 7) & 0x7f; /* aka sol */
+ nouts = (cfm & 0x7f) - nlocals; /* aka sof - sol */
krbs = (unsigned long *)info->task + IA64_RBS_OFFSET/8;
ndirty = ia64_rse_num_regs(krbs, krbs + (pt->loadrs >> 19));
count = 0;
if (in_syscall(pt))
- count = min_t(int, args->n, cfm & 0x7f);
+ count = min_t(int, args->n, nouts);
+ /* Iterate over outs. */
for (i = 0; i < count; i++) {
+ int j = ndirty + nlocals + i + args->i;
if (args->rw)
- *ia64_rse_skip_regs(krbs, ndirty + i + args->i) =
- args->args[i];
+ *ia64_rse_skip_regs(krbs, j) = args->args[i];
else
- args->args[i] = *ia64_rse_skip_regs(krbs,
- ndirty + i + args->i);
+ args->args[i] = *ia64_rse_skip_regs(krbs, j);
}
if (!args->rw) {
--
2.30.1
next reply other threads:[~2021-02-21 0:30 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-21 0:25 Sergei Trofimovich [this message]
2021-02-21 0:25 ` [PATCH] ia64: fix ptrace(PTRACE_SYSCALL_INFO_EXIT) sign Sergei Trofimovich
2021-02-21 9:21 ` John Paul Adrian Glaubitz
2021-02-21 13:08 ` Sergei Trofimovich
2021-03-02 23:39 ` Sergei Trofimovich
2021-03-03 14:30 ` Oleg Nesterov
2021-03-03 21:40 ` Dmitry V. Levin
2021-03-03 21:44 ` Dmitry V. Levin
2021-03-02 23:40 ` [PATCH] ia64: fix ia64_syscall_get_set_arguments() for break-based syscalls Sergei Trofimovich
2021-03-03 21:51 ` Dmitry V. Levin
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20210221002554.333076-1-slyfox@gentoo.org \
--to=slyfox@gentoo.org \
--cc=akpm@linux-foundation.org \
--cc=ldv@altlinux.org \
--cc=linux-ia64@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=oleg@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).