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um: Stop tracking stub's PID via userspace_pid[]

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The PID of the stub process can be obtained from current_mm_id().
There is no need to track it via userspace_pid[]. Stop doing that
to simplify the code.

Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
Link: https://patch.msgid.link/20250711065021.2535362-4-tiwei.bie@linux.dev
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
This commit is contained in:
Tiwei Bie 2025-07-11 14:50:21 +08:00 • committed by Johannes Berg
parent b3fb0eb5c2
commit f7e9077a16
7 changed files with 8 additions and 26 deletions
Download patch file Download diff file Expand all files Collapse all files

9
arch/um/include/asm/mmu_context.h
View file

@ -16,11 +16,6 @@
#define activate_mm activate_mm
static inline void activate_mm(struct mm_struct *old, struct mm_struct *new)
{
/*
* This is called by fs/exec.c and sys_unshare()
* when the new ->mm is used for the first time.
*/
__switch_mm(&new->context.id);
}
static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
@ -28,11 +23,9 @@ static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
{
unsigned cpu = smp_processor_id();
if(prev != next){
if (prev != next) {
cpumask_clear_cpu(cpu, mm_cpumask(prev));
cpumask_set_cpu(cpu, mm_cpumask(next));
if(next != &init_mm)
__switch_mm(&next->context.id);
}
}

2
arch/um/include/shared/skas/mm_id.h
View file

@ -19,8 +19,6 @@ struct mm_id {
int syscall_fd_map[STUB_MAX_FDS];
};
void __switch_mm(struct mm_id *mm_idp);
void notify_mm_kill(int pid);
#endif

1
arch/um/include/shared/skas/skas.h
View file

@ -9,7 +9,6 @@
#include <sysdep/ptrace.h>
extern int using_seccomp;
extern int userspace_pid[];
extern void new_thread_handler(void);
extern void handle_syscall(struct uml_pt_regs *regs);

2
arch/um/kernel/exec.c
View file

@ -26,8 +26,6 @@ void flush_thread(void)
get_safe_registers(current_pt_regs()->regs.gp,
current_pt_regs()->regs.fp);
__switch_mm(&current->mm->context.id);
}
void start_thread(struct pt_regs *regs, unsigned long eip, unsigned long esp)

2
arch/um/kernel/skas/process.c
View file

@ -26,8 +26,6 @@ static int __init start_kernel_proc(void *unused)
return 0;
}
extern int userspace_pid[];
static char cpu0_irqstack[THREAD_SIZE] __aligned(THREAD_SIZE);
int __init start_uml(void)

16
arch/um/os-Linux/skas/process.c
View file

@ -434,7 +434,6 @@ static int __init init_stub_exe_fd(void)
__initcall(init_stub_exe_fd);
int using_seccomp;
int userspace_pid[NR_CPUS];
/**
* start_userspace() - prepare a new userspace process
@ -553,7 +552,7 @@ extern unsigned long tt_extra_sched_jiffies;
void userspace(struct uml_pt_regs *regs)
{
int err, status, op, pid = userspace_pid[0];
int err, status, op;
siginfo_t si_ptrace;
siginfo_t *si;
int sig;
@ -562,6 +561,8 @@ void userspace(struct uml_pt_regs *regs)
interrupt_end();
while (1) {
struct mm_id *mm_id = current_mm_id();
/*
* When we are in time-travel mode, userspace can theoretically
* do a *lot* of work without being scheduled. The problem with
@ -590,7 +591,6 @@ void userspace(struct uml_pt_regs *regs)
current_mm_sync();
if (using_seccomp) {
struct mm_id *mm_id = current_mm_id();
struct stub_data *proc_data = (void *) mm_id->stack;
err = set_stub_state(regs, proc_data, singlestepping());
@ -644,8 +644,10 @@ void userspace(struct uml_pt_regs *regs)
GET_FAULTINFO_FROM_MC(regs->faultinfo, mcontext);
}
} else {
int pid = mm_id->pid;
/* Flush out any pending syscalls */
err = syscall_stub_flush(current_mm_id());
err = syscall_stub_flush(mm_id);
if (err) {
if (err == -ENOMEM)
report_enomem();
@ -776,7 +778,6 @@ void userspace(struct uml_pt_regs *regs)
__func__, sig);
fatal_sigsegv();
}
pid = userspace_pid[0];
interrupt_end();
/* Avoid -ERESTARTSYS handling in host */
@ -901,8 +902,3 @@ void reboot_skas(void)
block_signals_trace();
UML_LONGJMP(&initial_jmpbuf, noreboot ? INIT_JMP_HALT : INIT_JMP_REBOOT);
}
void __switch_mm(struct mm_id *mm_idp)
{
userspace_pid[0] = mm_idp->pid;
}

2
arch/x86/um/tls_32.c
View file

@ -186,7 +186,7 @@ int arch_switch_tls(struct task_struct *to)
/*
* We have no need whatsoever to switch TLS for kernel threads; beyond
* that, that would also result in us calling os_set_thread_area with
* userspace_pid[cpu] == 0, which gives an error.
* task->mm == NULL, which would cause a crash.
*/
if (likely(to->mm))
return load_TLS(O_FORCE, to);