Commit a5d2cfe7 authored by Benjamin Berg's avatar Benjamin Berg Committed by Johannes Berg
Browse files

um: remove copy_context_skas0 



The kernel flushes the memory ranges anyway for CoW and does not assume
that the userspace process has anything set up already. So, start with a
fresh process for the new mm context.

Signed-off-by: default avatarBenjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20240703134536.1161108-8-benjamin@sipsolutions.net


Signed-off-by: default avatarJohannes Berg <johannes.berg@intel.com>
parent 7911b650

arch/um/include/shared/os.h

+0 −1
Original line number Diff line number Diff line
@@ -285,7 +285,6 @@ void protect(struct mm_id *mm_idp, unsigned long addr, 
/* skas/process.c */

extern int is_skas_winch(int pid, int fd, void *data);

extern int start_userspace(unsigned long stub_stack);

extern int copy_context_skas0(unsigned long stack, int pid);

extern void userspace(struct uml_pt_regs *regs, unsigned long *aux_fp_regs);

extern void new_thread(void *stack, jmp_buf *buf, void (*handler)(void));

extern void switch_threads(jmp_buf *me, jmp_buf *you);

arch/um/include/shared/skas/stub-data.h

+0 −1
Original line number Diff line number Diff line
@@ -36,7 +36,6 @@ struct stub_syscall { 


struct stub_data {

	unsigned long offset;

	int fd;

	long err, child_err;



	int syscall_data_len;

arch/um/kernel/skas/Makefile

+3 −5
Original line number Diff line number Diff line
@@ -3,16 +3,14 @@ 
# Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)

#



obj-y := clone.o stub.o mmu.o process.o syscall.o uaccess.o

obj-y := stub.o mmu.o process.o syscall.o uaccess.o



# clone.o and stub.o are in the stub, so it can't be built with profiling

# stub.o is in the stub, so it can't be built with profiling

# GCC hardened also auto-enables -fpic, but we need %ebx so it can't work ->

# disable it



CFLAGS_clone.o := $(CFLAGS_NO_HARDENING)

CFLAGS_stub.o := $(CFLAGS_NO_HARDENING)

UNPROFILE_OBJS := clone.o stub.o



UNPROFILE_OBJS := stub.o

KCOV_INSTRUMENT := n



include $(srctree)/arch/um/scripts/Makefile.rules

arch/um/kernel/skas/clone.c

deleted100644 → 0
+0 −50
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

/*

 * Copyright (C) 2015 Thomas Meyer (thomas@m3y3r.de)

 * Copyright (C) 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)

 */



#include <signal.h>

#include <sched.h>

#include <asm/unistd.h>

#include <sys/time.h>

#include <as-layout.h>

#include <ptrace_user.h>

#include <stub-data.h>

#include <sysdep/stub.h>



/*

 * This is in a separate file because it needs to be compiled with any

 * extraneous gcc flags (-pg, -fprofile-arcs, -ftest-coverage) disabled

 *

 * Use UM_KERN_PAGE_SIZE instead of PAGE_SIZE because that calls getpagesize

 * on some systems.

 */



void __attribute__ ((__section__ (".__syscall_stub")))

stub_clone_handler(void)

{

	struct stub_data *data = get_stub_data();

	long err;



	/* syscall data as a temporary stack area (bottom half). */

	err = stub_syscall2(__NR_clone, CLONE_PARENT | CLONE_FILES | SIGCHLD,

			    (unsigned long) data->syscall_data +

					    sizeof(data->syscall_data) / 2 -

					    sizeof(void *));

	if (err) {

		data->err = err;

		goto done;

	}



	err = stub_syscall4(__NR_ptrace, PTRACE_TRACEME, 0, 0, 0);

	if (err) {

		data->child_err = err;

		goto done;

	}



	remap_stack_and_trap();



 done:

	trap_myself();

}

arch/um/kernel/skas/mmu.c

+7 −13
Original line number Diff line number Diff line
@@ -21,8 +21,7 @@ static_assert(sizeof(struct stub_data) == STUB_DATA_PAGES * UM_KERN_PAGE_SIZE); 


int init_new_context(struct task_struct *task, struct mm_struct *mm)

{

 	struct mm_context *from_mm = NULL;

	struct mm_context *to_mm = &mm->context;

	struct mm_id *new_id = &mm->context.id;

	unsigned long stack = 0;

	int ret = -ENOMEM;
@@ -30,27 +29,22 @@ int init_new_context(struct task_struct *task, struct mm_struct *mm) 
	if (stack == 0)

		goto out;



	to_mm->id.stack = stack;

	if (current->mm != NULL && current->mm != &init_mm)

		from_mm = &current->mm->context;

	new_id->stack = stack;



	block_signals_trace();

	if (from_mm)

		to_mm->id.u.pid = copy_context_skas0(stack,

						     from_mm->id.u.pid);

	else to_mm->id.u.pid = start_userspace(stack);

	new_id->u.pid = start_userspace(stack);

	unblock_signals_trace();



	if (to_mm->id.u.pid < 0) {

		ret = to_mm->id.u.pid;

	if (new_id->u.pid < 0) {

		ret = new_id->u.pid;

		goto out_free;

	}



	return 0;



 out_free:

	if (to_mm->id.stack != 0)

		free_pages(to_mm->id.stack, ilog2(STUB_DATA_PAGES));

	if (new_id->stack != 0)

		free_pages(new_id->stack, ilog2(STUB_DATA_PAGES));

 out:

	return ret;

}