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um: Drop NULL check from start_userspace

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start_userspace is only called from exactly one location, and the passed
pointer for the userspace process stack cannot be NULL.

Remove the check, without changing the control flow.

Signed-off-by: Benjamin Berg <benjamin@sipsolutions.net>
Signed-off-by: Richard Weinberger <richard@nod.at>
This commit is contained in:
Benjamin Berg 2023-11-10 12:03:39 +01:00 committed by Richard Weinberger
parent a55719847d
commit 5713533794
1 changed files with 23 additions and 28 deletions
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51
arch/um/os-Linux/skas/process.c
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@ -189,7 +189,7 @@ extern char __syscall_stub_start[];
/**
* userspace_tramp() - userspace trampoline
* @stack: pointer to the new userspace stack page, can be NULL, if? FIXME:
* @stack: pointer to the new userspace stack page
*
* The userspace trampoline is used to setup a new userspace process in start_userspace() after it was clone()'ed.
* This function will run on a temporary stack page.
@ -204,9 +204,13 @@ extern char __syscall_stub_start[];
*/
static int userspace_tramp(void *stack)
{
struct sigaction sa;
void *addr;
int fd;
unsigned long long offset;
unsigned long segv_handler = STUB_CODE +
(unsigned long) stub_segv_handler -
(unsigned long) __syscall_stub_start;
ptrace(PTRACE_TRACEME, 0, 0, 0);
@ -222,34 +226,25 @@ static int userspace_tramp(void *stack)
exit(1);
}
if (stack != NULL) {
fd = phys_mapping(uml_to_phys(stack), &offset);
addr = mmap((void *) STUB_DATA,
STUB_DATA_PAGES * UM_KERN_PAGE_SIZE, PROT_READ | PROT_WRITE,
MAP_FIXED | MAP_SHARED, fd, offset);
if (addr == MAP_FAILED) {
printk(UM_KERN_ERR "mapping segfault stack at 0x%lx failed, errno = %d\n",
STUB_DATA, errno);
exit(1);
}
fd = phys_mapping(uml_to_phys(stack), &offset);
addr = mmap((void *) STUB_DATA,
STUB_DATA_PAGES * UM_KERN_PAGE_SIZE, PROT_READ | PROT_WRITE,
MAP_FIXED | MAP_SHARED, fd, offset);
if (addr == MAP_FAILED) {
printk(UM_KERN_ERR "mapping segfault stack at 0x%lx failed, errno = %d\n",
STUB_DATA, errno);
exit(1);
}
if (stack != NULL) {
struct sigaction sa;
unsigned long v = STUB_CODE +
(unsigned long) stub_segv_handler -
(unsigned long) __syscall_stub_start;
set_sigstack((void *) STUB_DATA, STUB_DATA_PAGES * UM_KERN_PAGE_SIZE);
sigemptyset(&sa.sa_mask);
sa.sa_flags = SA_ONSTACK | SA_NODEFER | SA_SIGINFO;
sa.sa_sigaction = (void *) v;
sa.sa_restorer = NULL;
if (sigaction(SIGSEGV, &sa, NULL) < 0) {
printk(UM_KERN_ERR "%s - setting SIGSEGV handler failed - errno = %d\n",
__func__, errno);
exit(1);
}
set_sigstack((void *) STUB_DATA, STUB_DATA_PAGES * UM_KERN_PAGE_SIZE);
sigemptyset(&sa.sa_mask);
sa.sa_flags = SA_ONSTACK | SA_NODEFER | SA_SIGINFO;
sa.sa_sigaction = (void *) segv_handler;
sa.sa_restorer = NULL;
if (sigaction(SIGSEGV, &sa, NULL) < 0) {
printk(UM_KERN_ERR "%s - setting SIGSEGV handler failed - errno = %d\n",
__func__, errno);
exit(1);
}
kill(os_getpid(), SIGSTOP);
@ -261,7 +256,7 @@ int kill_userspace_mm[NR_CPUS];
/**
* start_userspace() - prepare a new userspace process
* @stub_stack: pointer to the stub stack. Can be NULL, if? FIXME:
* @stub_stack: pointer to the stub stack.
*
* Setups a new temporary stack page that is used while userspace_tramp() runs
* Clones the kernel process into a new userspace process, with FDs only.