diff options
| author | Sergei Trofimovich <slyfox@gentoo.org> | 2021-03-12 21:08:23 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2021-03-13 11:27:31 -0800 |
| commit | 0ceb1ace4a2778e34a5414e5349712ae4dc41d85 (patch) | |
| tree | 67bc0a86e5d33a62555f416e31e0f322182f7952 /arch/ia64 | |
| parent | 6ce64428d62026a10cb5d80138ff2f90cc21d367 (diff) | |
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@gentoo.org
Link: https://bugs.gentoo.org/769614
Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
Reported-by: Dmitry V. Levin <ldv@altlinux.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch/ia64')
| -rw-r--r-- | arch/ia64/kernel/ptrace.c | 24 |
1 files 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) { |