Loading...
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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 | // SPDX-License-Identifier: GPL-2.0-only
/*
* common.c - C code for kernel entry and exit
* Copyright (c) 2015 Andrew Lutomirski
*
* Based on asm and ptrace code by many authors. The code here originated
* in ptrace.c and signal.c.
*/
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/sched/task_stack.h>
#include <linux/entry-common.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/errno.h>
#include <linux/ptrace.h>
#include <linux/export.h>
#include <linux/nospec.h>
#include <linux/syscalls.h>
#include <linux/uaccess.h>
#ifdef CONFIG_XEN_PV
#include <xen/xen-ops.h>
#include <xen/events.h>
#endif
#include <asm/desc.h>
#include <asm/traps.h>
#include <asm/vdso.h>
#include <asm/cpufeature.h>
#include <asm/fpu/api.h>
#include <asm/nospec-branch.h>
#include <asm/io_bitmap.h>
#include <asm/syscall.h>
#include <asm/irq_stack.h>
#ifdef CONFIG_X86_64
static __always_inline bool do_syscall_x64(struct pt_regs *regs, int nr)
{
/*
* Convert negative numbers to very high and thus out of range
* numbers for comparisons.
*/
unsigned int unr = nr;
if (likely(unr < NR_syscalls)) {
unr = array_index_nospec(unr, NR_syscalls);
regs->ax = sys_call_table[unr](regs);
return true;
}
return false;
}
static __always_inline bool do_syscall_x32(struct pt_regs *regs, int nr)
{
/*
* Adjust the starting offset of the table, and convert numbers
* < __X32_SYSCALL_BIT to very high and thus out of range
* numbers for comparisons.
*/
unsigned int xnr = nr - __X32_SYSCALL_BIT;
if (IS_ENABLED(CONFIG_X86_X32_ABI) && likely(xnr < X32_NR_syscalls)) {
xnr = array_index_nospec(xnr, X32_NR_syscalls);
regs->ax = x32_sys_call_table[xnr](regs);
return true;
}
return false;
}
__visible noinstr void do_syscall_64(struct pt_regs *regs, int nr)
{
add_random_kstack_offset();
nr = syscall_enter_from_user_mode(regs, nr);
instrumentation_begin();
if (!do_syscall_x64(regs, nr) && !do_syscall_x32(regs, nr) && nr != -1) {
/* Invalid system call, but still a system call. */
regs->ax = __x64_sys_ni_syscall(regs);
}
instrumentation_end();
syscall_exit_to_user_mode(regs);
}
#endif
#if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
static __always_inline int syscall_32_enter(struct pt_regs *regs)
{
if (IS_ENABLED(CONFIG_IA32_EMULATION))
current_thread_info()->status |= TS_COMPAT;
return (int)regs->orig_ax;
}
/*
* Invoke a 32-bit syscall. Called with IRQs on in CONTEXT_KERNEL.
*/
static __always_inline void do_syscall_32_irqs_on(struct pt_regs *regs, int nr)
{
/*
* Convert negative numbers to very high and thus out of range
* numbers for comparisons.
*/
unsigned int unr = nr;
if (likely(unr < IA32_NR_syscalls)) {
unr = array_index_nospec(unr, IA32_NR_syscalls);
regs->ax = ia32_sys_call_table[unr](regs);
} else if (nr != -1) {
regs->ax = __ia32_sys_ni_syscall(regs);
}
}
/* Handles int $0x80 */
__visible noinstr void do_int80_syscall_32(struct pt_regs *regs)
{
int nr = syscall_32_enter(regs);
add_random_kstack_offset();
/*
* Subtlety here: if ptrace pokes something larger than 2^31-1 into
* orig_ax, the int return value truncates it. This matches
* the semantics of syscall_get_nr().
*/
nr = syscall_enter_from_user_mode(regs, nr);
instrumentation_begin();
do_syscall_32_irqs_on(regs, nr);
instrumentation_end();
syscall_exit_to_user_mode(regs);
}
static noinstr bool __do_fast_syscall_32(struct pt_regs *regs)
{
int nr = syscall_32_enter(regs);
int res;
add_random_kstack_offset();
/*
* This cannot use syscall_enter_from_user_mode() as it has to
* fetch EBP before invoking any of the syscall entry work
* functions.
*/
syscall_enter_from_user_mode_prepare(regs);
instrumentation_begin();
/* Fetch EBP from where the vDSO stashed it. */
if (IS_ENABLED(CONFIG_X86_64)) {
/*
* Micro-optimization: the pointer we're following is
* explicitly 32 bits, so it can't be out of range.
*/
res = __get_user(*(u32 *)®s->bp,
(u32 __user __force *)(unsigned long)(u32)regs->sp);
} else {
res = get_user(*(u32 *)®s->bp,
(u32 __user __force *)(unsigned long)(u32)regs->sp);
}
if (res) {
/* User code screwed up. */
regs->ax = -EFAULT;
local_irq_disable();
instrumentation_end();
irqentry_exit_to_user_mode(regs);
return false;
}
nr = syscall_enter_from_user_mode_work(regs, nr);
/* Now this is just like a normal syscall. */
do_syscall_32_irqs_on(regs, nr);
instrumentation_end();
syscall_exit_to_user_mode(regs);
return true;
}
/* Returns 0 to return using IRET or 1 to return using SYSEXIT/SYSRETL. */
__visible noinstr long do_fast_syscall_32(struct pt_regs *regs)
{
/*
* Called using the internal vDSO SYSENTER/SYSCALL32 calling
* convention. Adjust regs so it looks like we entered using int80.
*/
unsigned long landing_pad = (unsigned long)current->mm->context.vdso +
vdso_image_32.sym_int80_landing_pad;
/*
* SYSENTER loses EIP, and even SYSCALL32 needs us to skip forward
* so that 'regs->ip -= 2' lands back on an int $0x80 instruction.
* Fix it up.
*/
regs->ip = landing_pad;
/* Invoke the syscall. If it failed, keep it simple: use IRET. */
if (!__do_fast_syscall_32(regs))
return 0;
#ifdef CONFIG_X86_64
/*
* Opportunistic SYSRETL: if possible, try to return using SYSRETL.
* SYSRETL is available on all 64-bit CPUs, so we don't need to
* bother with SYSEXIT.
*
* Unlike 64-bit opportunistic SYSRET, we can't check that CX == IP,
* because the ECX fixup above will ensure that this is essentially
* never the case.
*/
return regs->cs == __USER32_CS && regs->ss == __USER_DS &&
regs->ip == landing_pad &&
(regs->flags & (X86_EFLAGS_RF | X86_EFLAGS_TF)) == 0;
#else
/*
* Opportunistic SYSEXIT: if possible, try to return using SYSEXIT.
*
* Unlike 64-bit opportunistic SYSRET, we can't check that CX == IP,
* because the ECX fixup above will ensure that this is essentially
* never the case.
*
* We don't allow syscalls at all from VM86 mode, but we still
* need to check VM, because we might be returning from sys_vm86.
*/
return static_cpu_has(X86_FEATURE_SEP) &&
regs->cs == __USER_CS && regs->ss == __USER_DS &&
regs->ip == landing_pad &&
(regs->flags & (X86_EFLAGS_RF | X86_EFLAGS_TF | X86_EFLAGS_VM)) == 0;
#endif
}
/* Returns 0 to return using IRET or 1 to return using SYSEXIT/SYSRETL. */
__visible noinstr long do_SYSENTER_32(struct pt_regs *regs)
{
/* SYSENTER loses RSP, but the vDSO saved it in RBP. */
regs->sp = regs->bp;
/* SYSENTER clobbers EFLAGS.IF. Assume it was set in usermode. */
regs->flags |= X86_EFLAGS_IF;
return do_fast_syscall_32(regs);
}
#endif
SYSCALL_DEFINE0(ni_syscall)
{
return -ENOSYS;
}
#ifdef CONFIG_XEN_PV
#ifndef CONFIG_PREEMPTION
/*
* Some hypercalls issued by the toolstack can take many 10s of
* seconds. Allow tasks running hypercalls via the privcmd driver to
* be voluntarily preempted even if full kernel preemption is
* disabled.
*
* Such preemptible hypercalls are bracketed by
* xen_preemptible_hcall_begin() and xen_preemptible_hcall_end()
* calls.
*/
DEFINE_PER_CPU(bool, xen_in_preemptible_hcall);
EXPORT_SYMBOL_GPL(xen_in_preemptible_hcall);
/*
* In case of scheduling the flag must be cleared and restored after
* returning from schedule as the task might move to a different CPU.
*/
static __always_inline bool get_and_clear_inhcall(void)
{
bool inhcall = __this_cpu_read(xen_in_preemptible_hcall);
__this_cpu_write(xen_in_preemptible_hcall, false);
return inhcall;
}
static __always_inline void restore_inhcall(bool inhcall)
{
__this_cpu_write(xen_in_preemptible_hcall, inhcall);
}
#else
static __always_inline bool get_and_clear_inhcall(void) { return false; }
static __always_inline void restore_inhcall(bool inhcall) { }
#endif
static void __xen_pv_evtchn_do_upcall(struct pt_regs *regs)
{
struct pt_regs *old_regs = set_irq_regs(regs);
inc_irq_stat(irq_hv_callback_count);
xen_hvm_evtchn_do_upcall();
set_irq_regs(old_regs);
}
__visible noinstr void xen_pv_evtchn_do_upcall(struct pt_regs *regs)
{
irqentry_state_t state = irqentry_enter(regs);
bool inhcall;
instrumentation_begin();
run_sysvec_on_irqstack_cond(__xen_pv_evtchn_do_upcall, regs);
inhcall = get_and_clear_inhcall();
if (inhcall && !WARN_ON_ONCE(state.exit_rcu)) {
irqentry_exit_cond_resched();
instrumentation_end();
restore_inhcall(inhcall);
} else {
instrumentation_end();
irqentry_exit(regs, state);
}
}
#endif /* CONFIG_XEN_PV */
|