1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
|
// SPDX-License-Identifier: GPL-2.0-or-later
#include <linux/compat.h>
#include <linux/context_tracking.h>
#include <linux/randomize_kstack.h>
#include <asm/interrupt.h>
#include <asm/kup.h>
#include <asm/syscall.h>
#include <asm/time.h>
#include <asm/tm.h>
#include <asm/unistd.h>
/* Has to run notrace because it is entered not completely "reconciled" */
notrace long system_call_exception(struct pt_regs *regs, unsigned long r0)
{
long ret;
syscall_fn f;
kuap_lock();
add_random_kstack_offset();
if (IS_ENABLED(CONFIG_PPC_IRQ_SOFT_MASK_DEBUG))
BUG_ON(irq_soft_mask_return() != IRQS_ALL_DISABLED);
trace_hardirqs_off(); /* finish reconciling */
CT_WARN_ON(ct_state() == CT_STATE_KERNEL);
user_exit_irqoff();
BUG_ON(regs_is_unrecoverable(regs));
BUG_ON(!user_mode(regs));
BUG_ON(arch_irq_disabled_regs(regs));
#ifdef CONFIG_PPC_PKEY
if (mmu_has_feature(MMU_FTR_PKEY)) {
unsigned long amr, iamr;
bool flush_needed = false;
/*
* When entering from userspace we mostly have the AMR/IAMR
* different from kernel default values. Hence don't compare.
*/
amr = mfspr(SPRN_AMR);
iamr = mfspr(SPRN_IAMR);
regs->amr = amr;
regs->iamr = iamr;
if (mmu_has_feature(MMU_FTR_KUAP)) {
mtspr(SPRN_AMR, AMR_KUAP_BLOCKED);
flush_needed = true;
}
if (mmu_has_feature(MMU_FTR_BOOK3S_KUEP)) {
mtspr(SPRN_IAMR, AMR_KUEP_BLOCKED);
flush_needed = true;
}
if (flush_needed)
isync();
} else
#endif
kuap_assert_locked();
booke_restore_dbcr0();
account_cpu_user_entry();
account_stolen_time();
/*
* This is not required for the syscall exit path, but makes the
* stack frame look nicer. If this was initialised in the first stack
* frame, or if the unwinder was taught the first stack frame always
* returns to user with IRQS_ENABLED, this store could be avoided!
*/
irq_soft_mask_regs_set_state(regs, IRQS_ENABLED);
/*
* If system call is called with TM active, set _TIF_RESTOREALL to
* prevent RFSCV being used to return to userspace, because POWER9
* TM implementation has problems with this instruction returning to
* transactional state. Final register values are not relevant because
* the transaction will be aborted upon return anyway. Or in the case
* of unsupported_scv SIGILL fault, the return state does not much
* matter because it's an edge case.
*/
if (IS_ENABLED(CONFIG_PPC_TRANSACTIONAL_MEM) &&
unlikely(MSR_TM_TRANSACTIONAL(regs->msr)))
set_bits(_TIF_RESTOREALL, ¤t_thread_info()->flags);
/*
* If the system call was made with a transaction active, doom it and
* return without performing the system call. Unless it was an
* unsupported scv vector, in which case it's treated like an illegal
* instruction.
*/
#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
if (unlikely(MSR_TM_TRANSACTIONAL(regs->msr)) &&
!trap_is_unsupported_scv(regs)) {
/* Enable TM in the kernel, and disable EE (for scv) */
hard_irq_disable();
mtmsr(mfmsr() | MSR_TM);
/* tabort, this dooms the transaction, nothing else */
asm volatile(".long 0x7c00071d | ((%0) << 16)"
:: "r"(TM_CAUSE_SYSCALL|TM_CAUSE_PERSISTENT));
/*
* Userspace will never see the return value. Execution will
* resume after the tbegin. of the aborted transaction with the
* checkpointed register state. A context switch could occur
* or signal delivered to the process before resuming the
* doomed transaction context, but that should all be handled
* as expected.
*/
return -ENOSYS;
}
#endif // CONFIG_PPC_TRANSACTIONAL_MEM
local_irq_enable();
if (unlikely(read_thread_flags() & _TIF_SYSCALL_DOTRACE)) {
if (unlikely(trap_is_unsupported_scv(regs))) {
/* Unsupported scv vector */
_exception(SIGILL, regs, ILL_ILLOPC, regs->nip);
return regs->gpr[3];
}
/*
* We use the return value of do_syscall_trace_enter() as the
* syscall number. If the syscall was rejected for any reason
* do_syscall_trace_enter() returns an invalid syscall number
* and the test against NR_syscalls will fail and the return
* value to be used is in regs->gpr[3].
*/
r0 = do_syscall_trace_enter(regs);
if (unlikely(r0 >= NR_syscalls))
return regs->gpr[3];
} else if (unlikely(r0 >= NR_syscalls)) {
if (unlikely(trap_is_unsupported_scv(regs))) {
/* Unsupported scv vector */
_exception(SIGILL, regs, ILL_ILLOPC, regs->nip);
return regs->gpr[3];
}
return -ENOSYS;
}
/* May be faster to do array_index_nospec? */
barrier_nospec();
#ifdef CONFIG_ARCH_HAS_SYSCALL_WRAPPER
// No COMPAT if we have SYSCALL_WRAPPER, see Kconfig
f = (void *)sys_call_table[r0];
ret = f(regs);
#else
if (unlikely(is_compat_task())) {
unsigned long r3, r4, r5, r6, r7, r8;
f = (void *)compat_sys_call_table[r0];
r3 = regs->gpr[3] & 0x00000000ffffffffULL;
r4 = regs->gpr[4] & 0x00000000ffffffffULL;
r5 = regs->gpr[5] & 0x00000000ffffffffULL;
r6 = regs->gpr[6] & 0x00000000ffffffffULL;
r7 = regs->gpr[7] & 0x00000000ffffffffULL;
r8 = regs->gpr[8] & 0x00000000ffffffffULL;
ret = f(r3, r4, r5, r6, r7, r8);
} else {
f = (void *)sys_call_table[r0];
ret = f(regs->gpr[3], regs->gpr[4], regs->gpr[5],
regs->gpr[6], regs->gpr[7], regs->gpr[8]);
}
#endif
/*
* Ultimately, this value will get limited by KSTACK_OFFSET_MAX(),
* so the maximum stack offset is 1k bytes (10 bits).
*
* The actual entropy will be further reduced by the compiler when
* applying stack alignment constraints: the powerpc architecture
* may have two kinds of stack alignment (16-bytes and 8-bytes).
*
* So the resulting 6 or 7 bits of entropy is seen in SP[9:4] or SP[9:3].
*/
choose_random_kstack_offset(mftb());
return ret;
}
|
