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um: make stub data pages size tweakable

Browse Source 
There's a lot of code here that hard-codes that the
data is a single page, and right now that seems to
be sufficient, but to make it easier to change this
in the future, add a new STUB_DATA_PAGES constant
and use it throughout the code.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
This commit is contained in:
Johannes Berg 2023-04-14 15:46:39 +02:00 committed by Richard Weinberger
parent fc54a4f159
commit 6032aca0de
8 changed files with 27 additions and 21 deletions
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3
arch/um/include/shared/as-layout.h
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@ -23,7 +23,8 @@
#define STUB_START stub_start #define STUB_START stub_start
#define STUB_CODE STUB_START #define STUB_CODE STUB_START
#define STUB_DATA (STUB_CODE + UM_KERN_PAGE_SIZE) #define STUB_DATA (STUB_CODE + UM_KERN_PAGE_SIZE)
#define STUB_END (STUB_DATA + UM_KERN_PAGE_SIZE) #define STUB_DATA_PAGES 1 /* must be a power of two */
#define STUB_END (STUB_DATA + STUB_DATA_PAGES * UM_KERN_PAGE_SIZE)
#ifndef __ASSEMBLY__ #ifndef __ASSEMBLY__

5
arch/um/kernel/skas/clone.c
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@ -24,11 +24,12 @@
void __attribute__ ((__section__ (".__syscall_stub"))) void __attribute__ ((__section__ (".__syscall_stub")))
stub_clone_handler(void) stub_clone_handler(void)
{ {
struct stub_data *data = get_stub_page(); struct stub_data *data = get_stub_data();
long err; long err;
err = stub_syscall2(__NR_clone, CLONE_PARENT | CLONE_FILES | SIGCHLD, err = stub_syscall2(__NR_clone, CLONE_PARENT | CLONE_FILES | SIGCHLD,
(unsigned long)data + UM_KERN_PAGE_SIZE / 2); (unsigned long)data +
STUB_DATA_PAGES * UM_KERN_PAGE_SIZE / 2);
if (err) { if (err) {
data->parent_err = err; data->parent_err = err;
goto done; goto done;

6
arch/um/kernel/skas/mmu.c
View File

@ -21,7 +21,7 @@ int init_new_context(struct task_struct *task, struct mm_struct *mm)
unsigned long stack = 0; unsigned long stack = 0;
int ret = -ENOMEM; int ret = -ENOMEM;
stack = get_zeroed_page(GFP_KERNEL); stack = __get_free_pages(GFP_KERNEL | __GFP_ZERO, ilog2(STUB_DATA_PAGES));
if (stack == 0) if (stack == 0)
goto out; goto out;
@ -52,7 +52,7 @@ int init_new_context(struct task_struct *task, struct mm_struct *mm)
out_free: out_free:
if (to_mm->id.stack != 0) if (to_mm->id.stack != 0)
free_page(to_mm->id.stack); free_pages(to_mm->id.stack, ilog2(STUB_DATA_PAGES));
out: out:
return ret; return ret;
} }
@ -74,6 +74,6 @@ void destroy_context(struct mm_struct *mm)
} }
os_kill_ptraced_process(mmu->id.u.pid, 1); os_kill_ptraced_process(mmu->id.u.pid, 1);
free_page(mmu->id.stack); free_pages(mmu->id.stack, ilog2(STUB_DATA_PAGES));
free_ldt(mmu); free_ldt(mmu);
} }

10
arch/um/kernel/um_arch.c
View File

@ -326,9 +326,13 @@ int __init linux_main(int argc, char **argv)
add_arg(DEFAULT_COMMAND_LINE_CONSOLE); add_arg(DEFAULT_COMMAND_LINE_CONSOLE);
host_task_size = os_get_top_address(); host_task_size = os_get_top_address();
/* reserve two pages for the stubs */ /* reserve a few pages for the stubs (taking care of data alignment) */
host_task_size -= 2 * PAGE_SIZE; /* align the data portion */
stub_start = host_task_size; BUILD_BUG_ON(!is_power_of_2(STUB_DATA_PAGES));
stub_start = (host_task_size - 1) & ~(STUB_DATA_PAGES * PAGE_SIZE - 1);
/* another page for the code portion */
stub_start -= PAGE_SIZE;
host_task_size = stub_start;
/* /*
* TASK_SIZE needs to be PGDIR_SIZE aligned or else exit_mmap craps * TASK_SIZE needs to be PGDIR_SIZE aligned or else exit_mmap craps

6
arch/um/os-Linux/skas/process.c
View File

@ -262,7 +262,7 @@ static int userspace_tramp(void *stack)
if (stack != NULL) { if (stack != NULL) {
fd = phys_mapping(uml_to_phys(stack), &offset); fd = phys_mapping(uml_to_phys(stack), &offset);
addr = mmap((void *) STUB_DATA, addr = mmap((void *) STUB_DATA,
UM_KERN_PAGE_SIZE, PROT_READ | PROT_WRITE, STUB_DATA_PAGES * UM_KERN_PAGE_SIZE, PROT_READ | PROT_WRITE,
MAP_FIXED | MAP_SHARED, fd, offset); MAP_FIXED | MAP_SHARED, fd, offset);
if (addr == MAP_FAILED) { if (addr == MAP_FAILED) {
printk(UM_KERN_ERR "mapping segfault stack at 0x%lx failed, errno = %d\n", printk(UM_KERN_ERR "mapping segfault stack at 0x%lx failed, errno = %d\n",
@ -277,7 +277,7 @@ static int userspace_tramp(void *stack)
(unsigned long) stub_segv_handler - (unsigned long) stub_segv_handler -
(unsigned long) __syscall_stub_start; (unsigned long) __syscall_stub_start;
set_sigstack((void *) STUB_DATA, UM_KERN_PAGE_SIZE); set_sigstack((void *) STUB_DATA, STUB_DATA_PAGES * UM_KERN_PAGE_SIZE);
sigemptyset(&sa.sa_mask); sigemptyset(&sa.sa_mask);
sa.sa_flags = SA_ONSTACK | SA_NODEFER | SA_SIGINFO; sa.sa_flags = SA_ONSTACK | SA_NODEFER | SA_SIGINFO;
sa.sa_sigaction = (void *) v; sa.sa_sigaction = (void *) v;
@ -515,7 +515,7 @@ static int __init init_thread_regs(void)
thread_regs[REGS_IP_INDEX] = STUB_CODE + thread_regs[REGS_IP_INDEX] = STUB_CODE +
(unsigned long) stub_clone_handler - (unsigned long) stub_clone_handler -
(unsigned long) __syscall_stub_start; (unsigned long) __syscall_stub_start;
thread_regs[REGS_SP_INDEX] = STUB_DATA + UM_KERN_PAGE_SIZE - thread_regs[REGS_SP_INDEX] = STUB_DATA + STUB_DATA_PAGES * UM_KERN_PAGE_SIZE -
sizeof(void *); sizeof(void *);
#ifdef __SIGNAL_FRAMESIZE #ifdef __SIGNAL_FRAMESIZE
thread_regs[REGS_SP_INDEX] -= __SIGNAL_FRAMESIZE; thread_regs[REGS_SP_INDEX] -= __SIGNAL_FRAMESIZE;

8
arch/x86/um/shared/sysdep/stub_32.h
View File

@ -89,19 +89,19 @@ static inline void remap_stack_and_trap(void)
"addl %4,%%ebx ; movl %%eax, (%%ebx) ;" "addl %4,%%ebx ; movl %%eax, (%%ebx) ;"
"int $3" "int $3"
: : : :
"g" (~(UM_KERN_PAGE_SIZE - 1)), "g" (~(STUB_DATA_PAGES * UM_KERN_PAGE_SIZE - 1)),
"g" (STUB_MMAP_NR), "g" (STUB_MMAP_NR),
"g" (UML_STUB_FIELD_FD), "g" (UML_STUB_FIELD_FD),
"g" (UML_STUB_FIELD_OFFSET), "g" (UML_STUB_FIELD_OFFSET),
"g" (UML_STUB_FIELD_CHILD_ERR), "g" (UML_STUB_FIELD_CHILD_ERR),
"c" (UM_KERN_PAGE_SIZE), "c" (STUB_DATA_PAGES * UM_KERN_PAGE_SIZE),
"d" (PROT_READ | PROT_WRITE), "d" (PROT_READ | PROT_WRITE),
"S" (MAP_FIXED | MAP_SHARED) "S" (MAP_FIXED | MAP_SHARED)
: :
"memory"); "memory");
} }
static __always_inline void *get_stub_page(void) static __always_inline void *get_stub_data(void)
{ {
unsigned long ret; unsigned long ret;
@ -109,7 +109,7 @@ static __always_inline void *get_stub_page(void)
"movl %%esp,%0 ;" "movl %%esp,%0 ;"
"andl %1,%0" "andl %1,%0"
: "=a" (ret) : "=a" (ret)
: "g" (~(UM_KERN_PAGE_SIZE - 1))); : "g" (~(STUB_DATA_PAGES * UM_KERN_PAGE_SIZE - 1)));
return (void *)ret; return (void *)ret;
} }

8
arch/x86/um/shared/sysdep/stub_64.h
View File

@ -98,18 +98,18 @@ static inline void remap_stack_and_trap(void)
"int3" "int3"
: : : :
"g" (STUB_MMAP_NR), "g" (STUB_MMAP_NR),
"g" (~(UM_KERN_PAGE_SIZE - 1)), "g" (~(STUB_DATA_PAGES * UM_KERN_PAGE_SIZE - 1)),
"g" (MAP_FIXED | MAP_SHARED), "g" (MAP_FIXED | MAP_SHARED),
"g" (UML_STUB_FIELD_FD), "g" (UML_STUB_FIELD_FD),
"g" (UML_STUB_FIELD_OFFSET), "g" (UML_STUB_FIELD_OFFSET),
"g" (UML_STUB_FIELD_CHILD_ERR), "g" (UML_STUB_FIELD_CHILD_ERR),
"S" (UM_KERN_PAGE_SIZE), "S" (STUB_DATA_PAGES * UM_KERN_PAGE_SIZE),
"d" (PROT_READ | PROT_WRITE) "d" (PROT_READ | PROT_WRITE)
: :
__syscall_clobber, "r10", "r8", "r9"); __syscall_clobber, "r10", "r8", "r9");
} }
static __always_inline void *get_stub_page(void) static __always_inline void *get_stub_data(void)
{ {
unsigned long ret; unsigned long ret;
@ -117,7 +117,7 @@ static __always_inline void *get_stub_page(void)
"movq %%rsp,%0 ;" "movq %%rsp,%0 ;"
"andq %1,%0" "andq %1,%0"
: "=a" (ret) : "=a" (ret)
: "g" (~(UM_KERN_PAGE_SIZE - 1))); : "g" (~(STUB_DATA_PAGES * UM_KERN_PAGE_SIZE - 1)));
return (void *)ret; return (void *)ret;
} }

2
arch/x86/um/stub_segv.c
View File

@ -11,7 +11,7 @@
void __attribute__ ((__section__ (".__syscall_stub"))) void __attribute__ ((__section__ (".__syscall_stub")))
stub_segv_handler(int sig, siginfo_t *info, void *p) stub_segv_handler(int sig, siginfo_t *info, void *p)
{ {
struct faultinfo *f = get_stub_page(); struct faultinfo *f = get_stub_data();
ucontext_t *uc = p; ucontext_t *uc = p;
GET_FAULTINFO_FROM_MC(*f, &uc->uc_mcontext); GET_FAULTINFO_FROM_MC(*f, &uc->uc_mcontext);