The patch titled
Subject: ia64: fix ia64_syscall_get_set_arguments() for break-based syscalls
has been removed from the -mm tree. Its filename was
ia64-fix-ia64_syscall_get_set_arguments-for-break-based-syscalls.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: Sergei Trofimovich <slyfox@xxxxxxxxxx>
Subject: ia64: fix ia64_syscall_get_set_arguments() for break-based syscalls
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).
Link: https://lkml.kernel.org/r/20210221002554.333076-1-slyfox@xxxxxxxxxx
Link: https://bugs.gentoo.org/769614
Signed-off-by: Sergei Trofimovich <slyfox@xxxxxxxxxx>
Reported-by: Dmitry V. Levin <ldv@xxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: John Paul Adrian Glaubitz <glaubitz@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/ia64/kernel/ptrace.c | 24 ++++++++++++++++++------
1 file changed, 18 insertions(+), 6 deletions(-)
--- a/arch/ia64/kernel/ptrace.c~ia64-fix-ia64_syscall_get_set_arguments-for-break-based-syscalls
+++ a/arch/ia64/kernel/ptrace.c
@@ -2013,27 +2013,39 @@ static void syscall_get_set_args_cb(stru
{
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) {
_
Patches currently in -mm which might be from slyfox@xxxxxxxxxx are
