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um: Drop support for hosts without SYSEMU_SINGLESTEP support

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These features have existed since Linux 2.6.14 and can be considered
widely available at this point. Also drop the backward compatibility
code for PTRACE_SETOPTIONS.

Signed-off-by: Benjamin Berg <benjamin@sipsolutions.net>

----

v2:
 * Continue to define PTRACE_SYSEMU_SINGLESTEP as glibc only added it in
   version 2.27.
Signed-off-by: Richard Weinberger <richard@nod.at>
This commit is contained in:
Benjamin Berg 2023-11-10 12:03:38 +01:00 committed by Richard Weinberger
parent a8e75902f4
commit a55719847d
12 changed files with 24 additions and 243 deletions
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1
arch/um/include/asm/processor-generic.h
View File

@ -22,7 +22,6 @@ struct mm_struct;
struct thread_struct {
struct pt_regs regs;
struct pt_regs *segv_regs;
int singlestep_syscall;
void *fault_addr;
jmp_buf *fault_catcher;
struct task_struct *prev_sched;

3
arch/um/include/shared/kern_util.h
View File

@ -34,7 +34,6 @@ extern int handle_page_fault(unsigned long address, unsigned long ip,
extern unsigned int do_IRQ(int irq, struct uml_pt_regs *regs);
extern void initial_thread_cb(void (*proc)(void *), void *arg);
extern int is_syscall(unsigned long addr);
extern void timer_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs);
@ -58,7 +57,7 @@ extern char *uml_strdup(const char *string);
extern unsigned long to_irq_stack(unsigned long *mask_out);
extern unsigned long from_irq_stack(int nested);
extern int singlestepping(void *t);
extern int singlestepping(void);
extern void segv_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs);
extern void bus_handler(int sig, struct siginfo *si, struct uml_pt_regs *regs);

41
arch/um/include/shared/ptrace_user.h
View File

@ -12,45 +12,4 @@
extern int ptrace_getregs(long pid, unsigned long *regs_out);
extern int ptrace_setregs(long pid, unsigned long *regs_in);
/* syscall emulation path in ptrace */
#ifndef PTRACE_SYSEMU
#define PTRACE_SYSEMU 31
#endif
#ifndef PTRACE_SYSEMU_SINGLESTEP
#define PTRACE_SYSEMU_SINGLESTEP 32
#endif
/* On architectures, that started to support PTRACE_O_TRACESYSGOOD
* in linux 2.4, there are two different definitions of
* PTRACE_SETOPTIONS: linux 2.4 uses 21 while linux 2.6 uses 0x4200.
* For binary compatibility, 2.6 also supports the old "21", named
* PTRACE_OLDSETOPTION. On these architectures, UML always must use
* "21", to ensure the kernel runs on 2.4 and 2.6 host without
* recompilation. So, we use PTRACE_OLDSETOPTIONS in UML.
* We also want to be able to build the kernel on 2.4, which doesn't
* have PTRACE_OLDSETOPTIONS. So, if it is missing, we declare
* PTRACE_OLDSETOPTIONS to be the same as PTRACE_SETOPTIONS.
*
* On architectures, that start to support PTRACE_O_TRACESYSGOOD on
* linux 2.6, PTRACE_OLDSETOPTIONS never is defined, and also isn't
* supported by the host kernel. In that case, our trick lets us use
* the new 0x4200 with the name PTRACE_OLDSETOPTIONS.
*/
#ifndef PTRACE_OLDSETOPTIONS
#define PTRACE_OLDSETOPTIONS PTRACE_SETOPTIONS
#endif
void set_using_sysemu(int value);
int get_using_sysemu(void);
extern int sysemu_supported;
#define SELECT_PTRACE_OPERATION(sysemu_mode, singlestep_mode) \
(((int[3][3] ) { \
{ PTRACE_SYSCALL, PTRACE_SYSCALL, PTRACE_SINGLESTEP }, \
{ PTRACE_SYSEMU, PTRACE_SYSEMU, PTRACE_SINGLESTEP }, \
{ PTRACE_SYSEMU, PTRACE_SYSEMU_SINGLESTEP, \
PTRACE_SYSEMU_SINGLESTEP } }) \
[sysemu_mode][singlestep_mode])
#endif

12
arch/um/kernel/process.c
View File

@ -332,17 +332,9 @@ int __init make_proc_sysemu(void)
late_initcall(make_proc_sysemu);
int singlestepping(void * t)
int singlestepping(void)
{
struct task_struct *task = t ? t : current;
if (!test_thread_flag(TIF_SINGLESTEP))
return 0;
if (task->thread.singlestep_syscall)
return 1;
return 2;
return test_thread_flag(TIF_SINGLESTEP);
}
/*

2
arch/um/kernel/ptrace.c
View File

@ -12,7 +12,6 @@
void user_enable_single_step(struct task_struct *child)
{
set_tsk_thread_flag(child, TIF_SINGLESTEP);
child->thread.singlestep_syscall = 0;
#ifdef SUBARCH_SET_SINGLESTEPPING
SUBARCH_SET_SINGLESTEPPING(child, 1);
@ -22,7 +21,6 @@ void user_enable_single_step(struct task_struct *child)
void user_disable_single_step(struct task_struct *child)
{
clear_tsk_thread_flag(child, TIF_SINGLESTEP);
child->thread.singlestep_syscall = 0;
#ifdef SUBARCH_SET_SINGLESTEPPING
SUBARCH_SET_SINGLESTEPPING(child, 0);

12
arch/um/kernel/signal.c
View File

@ -120,18 +120,6 @@ void do_signal(struct pt_regs *regs)
}
}
/*
* This closes a way to execute a system call on the host. If
* you set a breakpoint on a system call instruction and singlestep
* from it, the tracing thread used to PTRACE_SINGLESTEP the process
* rather than PTRACE_SYSCALL it, allowing the system call to execute
* on the host. The tracing thread will check this flag and
* PTRACE_SYSCALL if necessary.
*/
if (test_thread_flag(TIF_SINGLESTEP))
current->thread.singlestep_syscall =
is_syscall(PT_REGS_IP(&current->thread.regs));
/*
* if there's no signal to deliver, we just put the saved sigmask
* back

60
arch/um/os-Linux/skas/process.c
View File

@ -177,48 +177,11 @@ static void handle_segv(int pid, struct uml_pt_regs *regs, unsigned long *aux_fp
segv(regs->faultinfo, 0, 1, NULL);
}
/*
* To use the same value of using_sysemu as the caller, ask it that value
* (in local_using_sysemu
*/
static void handle_trap(int pid, struct uml_pt_regs *regs,
int local_using_sysemu)
static void handle_trap(int pid, struct uml_pt_regs *regs)
{
int err, status;
if ((UPT_IP(regs) >= STUB_START) && (UPT_IP(regs) < STUB_END))
fatal_sigsegv();
if (!local_using_sysemu)
{
err = ptrace(PTRACE_POKEUSER, pid, PT_SYSCALL_NR_OFFSET,
__NR_getpid);
if (err < 0) {
printk(UM_KERN_ERR "%s - nullifying syscall failed, errno = %d\n",
__func__, errno);
fatal_sigsegv();
}
err = ptrace(PTRACE_SYSCALL, pid, 0, 0);
if (err < 0) {
printk(UM_KERN_ERR "%s - continuing to end of syscall failed, errno = %d\n",
__func__, errno);
fatal_sigsegv();
}
CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED | __WALL));
if ((err < 0) || !WIFSTOPPED(status) ||
(WSTOPSIG(status) != SIGTRAP + 0x80)) {
err = ptrace_dump_regs(pid);
if (err)
printk(UM_KERN_ERR "Failed to get registers from process, errno = %d\n",
-err);
printk(UM_KERN_ERR "%s - failed to wait at end of syscall, errno = %d, status = %d\n",
__func__, errno, status);
fatal_sigsegv();
}
}
handle_syscall(regs);
}
@ -355,10 +318,10 @@ int start_userspace(unsigned long stub_stack)
goto out_kill;
}
if (ptrace(PTRACE_OLDSETOPTIONS, pid, NULL,
if (ptrace(PTRACE_SETOPTIONS, pid, NULL,
(void *) PTRACE_O_TRACESYSGOOD) < 0) {
err = -errno;
printk(UM_KERN_ERR "%s : PTRACE_OLDSETOPTIONS failed, errno = %d\n",
printk(UM_KERN_ERR "%s : PTRACE_SETOPTIONS failed, errno = %d\n",
__func__, errno);
goto out_kill;
}
@ -380,8 +343,6 @@ int start_userspace(unsigned long stub_stack)
void userspace(struct uml_pt_regs *regs, unsigned long *aux_fp_regs)
{
int err, status, op, pid = userspace_pid[0];
/* To prevent races if using_sysemu changes under us.*/
int local_using_sysemu;
siginfo_t si;
/* Handle any immediate reschedules or signals */
@ -411,11 +372,10 @@ void userspace(struct uml_pt_regs *regs, unsigned long *aux_fp_regs)
fatal_sigsegv();
}
/* Now we set local_using_sysemu to be used for one loop */
local_using_sysemu = get_using_sysemu();
op = SELECT_PTRACE_OPERATION(local_using_sysemu,
singlestepping(NULL));
if (singlestepping())
op = PTRACE_SYSEMU_SINGLESTEP;
else
op = PTRACE_SYSEMU;
if (ptrace(op, pid, 0, 0)) {
printk(UM_KERN_ERR "%s - ptrace continue failed, op = %d, errno = %d\n",
@ -474,7 +434,7 @@ void userspace(struct uml_pt_regs *regs, unsigned long *aux_fp_regs)
else handle_segv(pid, regs, aux_fp_regs);
break;
case SIGTRAP + 0x80:
handle_trap(pid, regs, local_using_sysemu);
handle_trap(pid, regs);
break;
case SIGTRAP:
relay_signal(SIGTRAP, (struct siginfo *)&si, regs);
@ -597,10 +557,10 @@ int copy_context_skas0(unsigned long new_stack, int pid)
goto out_kill;
}
if (ptrace(PTRACE_OLDSETOPTIONS, pid, NULL,
if (ptrace(PTRACE_SETOPTIONS, pid, NULL,
(void *)PTRACE_O_TRACESYSGOOD) < 0) {
err = -errno;
printk(UM_KERN_ERR "%s : PTRACE_OLDSETOPTIONS failed, errno = %d\n",
printk(UM_KERN_ERR "%s : PTRACE_SETOPTIONS failed, errno = %d\n",
__func__, errno);
goto out_kill;
}

70
arch/um/os-Linux/start_up.c
View File

@ -143,71 +143,16 @@ static int stop_ptraced_child(int pid, int exitcode, int mustexit)
return ret;
}
/* Changed only during early boot */
static int force_sysemu_disabled = 0;
static int __init nosysemu_cmd_param(char *str, int* add)
{
force_sysemu_disabled = 1;
return 0;
}
__uml_setup("nosysemu", nosysemu_cmd_param,
"nosysemu\n"
" Turns off syscall emulation patch for ptrace (SYSEMU).\n"
" SYSEMU is a performance-patch introduced by Laurent Vivier. It changes\n"
" behaviour of ptrace() and helps reduce host context switch rates.\n"
" To make it work, you need a kernel patch for your host, too.\n"
" See http://perso.wanadoo.fr/laurent.vivier/UML/ for further \n"
" information.\n\n");
static void __init check_sysemu(void)
{
unsigned long regs[MAX_REG_NR];
int pid, n, status, count=0;
os_info("Checking syscall emulation patch for ptrace...");
sysemu_supported = 0;
os_info("Checking syscall emulation for ptrace...");
pid = start_ptraced_child();
if (ptrace(PTRACE_SYSEMU, pid, 0, 0) < 0)
goto fail;
CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
if (n < 0)
fatal_perror("check_sysemu : wait failed");
if (!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGTRAP))
fatal("check_sysemu : expected SIGTRAP, got status = %d\n",
status);
if (ptrace(PTRACE_GETREGS, pid, 0, regs) < 0)
fatal_perror("check_sysemu : PTRACE_GETREGS failed");
if (PT_SYSCALL_NR(regs) != __NR_getpid) {
non_fatal("check_sysemu got system call number %d, "
"expected %d...", PT_SYSCALL_NR(regs), __NR_getpid);
goto fail;
}
n = ptrace(PTRACE_POKEUSER, pid, PT_SYSCALL_RET_OFFSET, os_getpid());
if (n < 0) {
non_fatal("check_sysemu : failed to modify system call "
"return");
goto fail;
}
if (stop_ptraced_child(pid, 0, 0) < 0)
goto fail_stopped;
sysemu_supported = 1;
os_info("OK\n");
set_using_sysemu(!force_sysemu_disabled);
os_info("Checking advanced syscall emulation patch for ptrace...");
pid = start_ptraced_child();
if ((ptrace(PTRACE_OLDSETOPTIONS, pid, 0,
if ((ptrace(PTRACE_SETOPTIONS, pid, 0,
(void *) PTRACE_O_TRACESYSGOOD) < 0))
fatal_perror("check_sysemu: PTRACE_OLDSETOPTIONS failed");
fatal_perror("check_sysemu: PTRACE_SETOPTIONS failed");
while (1) {
count++;
@ -243,17 +188,14 @@ static void __init check_sysemu(void)
if (stop_ptraced_child(pid, 0, 0) < 0)
goto fail_stopped;
sysemu_supported = 2;
os_info("OK\n");
if (!force_sysemu_disabled)
set_using_sysemu(sysemu_supported);
return;
fail:
stop_ptraced_child(pid, 1, 0);
fail_stopped:
non_fatal("missing\n");
fatal("missing\n");
}
static void __init check_ptrace(void)
@ -263,9 +205,9 @@ static void __init check_ptrace(void)
os_info("Checking that ptrace can change system call numbers...");
pid = start_ptraced_child();
if ((ptrace(PTRACE_OLDSETOPTIONS, pid, 0,
if ((ptrace(PTRACE_SETOPTIONS, pid, 0,
(void *) PTRACE_O_TRACESYSGOOD) < 0))
fatal_perror("check_ptrace: PTRACE_OLDSETOPTIONS failed");
fatal_perror("check_ptrace: PTRACE_SETOPTIONS failed");
while (1) {
if (ptrace(PTRACE_SYSCALL, pid, 0, 0) < 0)

24
arch/x86/um/ptrace_32.c
View File

@ -25,30 +25,6 @@ void arch_switch_to(struct task_struct *to)
printk(KERN_WARNING "arch_switch_tls failed, errno = EINVAL\n");
}
int is_syscall(unsigned long addr)
{
unsigned short instr;
int n;
n = copy_from_user(&instr, (void __user *) addr, sizeof(instr));
if (n) {
/* access_process_vm() grants access to vsyscall and stub,
* while copy_from_user doesn't. Maybe access_process_vm is
* slow, but that doesn't matter, since it will be called only
* in case of singlestepping, if copy_from_user failed.
*/
n = access_process_vm(current, addr, &instr, sizeof(instr),
FOLL_FORCE);
if (n != sizeof(instr)) {
printk(KERN_ERR "is_syscall : failed to read "
"instruction from 0x%lx\n", addr);
return 1;
}
}
/* int 0x80 or sysenter */
return (instr == 0x80cd) || (instr == 0x340f);
}
/* determines which flags the user has access to. */
/* 1 = access 0 = no access */
#define FLAG_MASK 0x00044dd5

26
arch/x86/um/ptrace_64.c
View File

@ -188,32 +188,6 @@ int peek_user(struct task_struct *child, long addr, long data)
return put_user(tmp, (unsigned long *) data);
}
/* XXX Mostly copied from sys-i386 */
int is_syscall(unsigned long addr)
{
unsigned short instr;
int n;
n = copy_from_user(&instr, (void __user *) addr, sizeof(instr));
if (n) {
/*
* access_process_vm() grants access to vsyscall and stub,
* while copy_from_user doesn't. Maybe access_process_vm is
* slow, but that doesn't matter, since it will be called only
* in case of singlestepping, if copy_from_user failed.
*/
n = access_process_vm(current, addr, &instr, sizeof(instr),
FOLL_FORCE);
if (n != sizeof(instr)) {
printk("is_syscall : failed to read instruction from "
"0x%lx\n", addr);
return 1;
}
}
/* sysenter */
return instr == 0x050f;
}
static int get_fpregs(struct user_i387_struct __user *buf, struct task_struct *child)
{
int err, n, cpu = ((struct thread_info *) child->stack)->cpu;

4
arch/x86/um/shared/sysdep/ptrace_32.h
View File

@ -8,10 +8,6 @@
#define MAX_FP_NR HOST_FPX_SIZE
void set_using_sysemu(int value);
int get_using_sysemu(void);
extern int sysemu_supported;
#define UPT_SYSCALL_ARG1(r) UPT_BX(r)
#define UPT_SYSCALL_ARG2(r) UPT_CX(r)
#define UPT_SYSCALL_ARG3(r) UPT_DX(r)

12
arch/x86/um/shared/sysdep/ptrace_user.h
View File

@ -15,14 +15,12 @@
#define FP_SIZE ((HOST_FPX_SIZE > HOST_FP_SIZE) ? HOST_FPX_SIZE : HOST_FP_SIZE)
#else
#define FP_SIZE HOST_FP_SIZE
#endif
/*
* x86_64 FC3 doesn't define this in /usr/include/linux/ptrace.h even though
* it's defined in the kernel's include/linux/ptrace.h. Additionally, use the
* 2.4 name and value for 2.4 host compatibility.
* glibc before 2.27 does not include PTRACE_SYSEMU_SINGLESTEP in its enum,
* ensure we have a definition by (re-)defining it here.
*/
#ifndef PTRACE_OLDSETOPTIONS
#define PTRACE_OLDSETOPTIONS 21
#endif
#ifndef PTRACE_SYSEMU_SINGLESTEP
#define PTRACE_SYSEMU_SINGLESTEP 32
#endif