[PATCH v2 07/12] um: remove copy_context_skas0

benjamin
2024-04-29T13:48:39Z

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: Benjamin Berg <benjamin.berg@intel.com>
---
arch/um/include/shared/os.h | 1 -
arch/um/kernel/skas/Makefile | 8 +--
arch/um/kernel/skas/clone.c | 50 ---------------
arch/um/kernel/skas/mmu.c | 20 +++---
arch/um/os-Linux/skas/process.c | 108 --------------------------------
5 files changed, 10 insertions(+), 177 deletions(-)
delete mode 100644 arch/um/kernel/skas/clone.c

diff --git a/arch/um/include/shared/os.h b/arch/um/include/shared/os.h
index 16d726f3df84..dc341ed4724e 100644
--- a/arch/um/include/shared/os.h
+++ b/arch/um/include/shared/os.h
@@ -281,7 +281,6 @@ 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);
diff --git a/arch/um/kernel/skas/Makefile b/arch/um/kernel/skas/Makefile
index dd8bc2167e36..6f86d53e3d69 100644
--- a/arch/um/kernel/skas/Makefile
+++ b/arch/um/kernel/skas/Makefile
@@ -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
diff --git a/arch/um/kernel/skas/clone.c b/arch/um/kernel/skas/clone.c
deleted file mode 100644
index b59fa43d68ce..000000000000
--- a/arch/um/kernel/skas/clone.c
+++ /dev/null
@@ -1,50 +0,0 @@
-// 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();
-}
diff --git a/arch/um/kernel/skas/mmu.c b/arch/um/kernel/skas/mmu.c
index d6183cfd51fe..76c0c7d600a8 100644
--- a/arch/um/kernel/skas/mmu.c
+++ b/arch/um/kernel/skas/mmu.c
@@ -20,8 +20,7 @@ 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;

@@ -29,27 +28,22 @@ 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;
}
diff --git a/arch/um/os-Linux/skas/process.c b/arch/um/os-Linux/skas/process.c
index 2bf03115817c..70c43e4a9cf0 100644
--- a/arch/um/os-Linux/skas/process.c
+++ b/arch/um/os-Linux/skas/process.c
@@ -460,114 +460,6 @@ void userspace(struct uml_pt_regs *regs, unsigned long *aux_fp_regs)
}
}

-static unsigned long thread_regs[MAX_REG_NR];
-static unsigned long thread_fp_regs[FP_SIZE];
-
-static int __init init_thread_regs(void)
-{
- get_safe_registers(thread_regs, thread_fp_regs);
- /* Set parent's instruction pointer to start of clone-stub */
- thread_regs[REGS_IP_INDEX] = STUB_CODE +
- (unsigned long) stub_clone_handler -
- (unsigned long) __syscall_stub_start;
-
- /* syscall data as a temporary stack area (top half). */
- thread_regs[REGS_SP_INDEX] = STUB_DATA +
- offsetof(struct stub_data, syscall_data) +
- sizeof(((struct stub_data *) 0)->syscall_data) -
- sizeof(void *);
- return 0;
-}
-
-__initcall(init_thread_regs);
-
-int copy_context_skas0(unsigned long new_stack, int pid)
-{
- int err;
- unsigned long current_stack = current_stub_stack();
- struct stub_data *data = (struct stub_data *) current_stack;
- struct stub_data *child_data = (struct stub_data *) new_stack;
- unsigned long long new_offset;
- int new_fd = phys_mapping(uml_to_phys((void *)new_stack), &new_offset);
-
- /*
- * prepare offset and fd of child's stack as argument for parent's
- * and child's mmap2 calls
- */
- *data = ((struct stub_data) {
- .offset = MMAP_OFFSET(new_offset),
- .fd = new_fd,
- .err = -ESRCH,
- .child_err = 0,
- });
-
- *child_data = ((struct stub_data) {
- .child_err = -ESRCH,
- });
-
- err = ptrace_setregs(pid, thread_regs);
- if (err < 0) {
- err = -errno;
- printk(UM_KERN_ERR "%s : PTRACE_SETREGS failed, pid = %d, errno = %d\n",
- __func__, pid, -err);
- return err;
- }
-
- err = put_fp_registers(pid, thread_fp_regs);
- if (err < 0) {
- printk(UM_KERN_ERR "%s : put_fp_registers failed, pid = %d, err = %d\n",
- __func__, pid, err);
- return err;
- }
-
- /*
- * Wait, until parent has finished its work: read child's pid from
- * parent's stack, and check, if bad result.
- */
- err = ptrace(PTRACE_CONT, pid, 0, 0);
- if (err) {
- err = -errno;
- printk(UM_KERN_ERR "Failed to continue new process, pid = %d, errno = %d\n",
- pid, errno);
- return err;
- }
-
- wait_stub_done(pid);
-
- pid = data->err;
- if (pid < 0) {
- printk(UM_KERN_ERR "%s - stub-parent reports error %d\n",
- __func__, -pid);
- return pid;
- }
-
- /*
- * Wait, until child has finished too: read child's result from
- * child's stack and check it.
- */
- wait_stub_done(pid);
- if (child_data->child_err != STUB_DATA) {
- printk(UM_KERN_ERR "%s - stub-child %d reports error %ld\n",
- __func__, pid, data->child_err);
- err = data->child_err;
- goto out_kill;
- }
-
- if (ptrace(PTRACE_SETOPTIONS, pid, NULL,
- (void *)PTRACE_O_TRACESYSGOOD) < 0) {
- err = -errno;
- printk(UM_KERN_ERR "%s : PTRACE_SETOPTIONS failed, errno = %d\n",
- __func__, errno);
- goto out_kill;
- }
-
- return pid;
-
- out_kill:
- os_kill_ptraced_process(pid, 1);
- return err;
-}
-
void new_thread(void *stack, jmp_buf *buf, void (*handler)(void))
{
(*buf)[0].JB_IP = (unsigned long) handler;
--
2.44.0