Commit c6ce7200 authored by Benjamin Berg's avatar Benjamin Berg Committed by Johannes Berg
Browse files

um: remove auxiliary FP registers 



We do not need the extra save/restore of the FP registers when getting
the fault information. This was originally added in commit 2f56debd
("uml: fix FP register corruption") but at that time the code was not
saving/restoring the FP registers when switching to userspace. This was
fixed in commit fbfe9c84 ("um: Save FPU registers between task
switches") and since then the auxiliary registers have not been useful.

Signed-off-by: default avatarBenjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20241004233821.2130874-1-benjamin@sipsolutions.net


Signed-off-by: default avatarJohannes Berg <johannes.berg@intel.com>
parent 48a858e0

arch/um/include/asm/thread_info.h

+0 −2
Original line number Diff line number Diff line
@@ -23,8 +23,6 @@ struct thread_info { 
	int			preempt_count;  /* 0 => preemptable,

						   <0 => BUG */

	struct thread_info	*real_thread;    /* Points to non-IRQ stack */

	unsigned long aux_fp_regs[FP_SIZE];	/* auxiliary fp_regs to save/restore

						   them out-of-band */

};



#define INIT_THREAD_INFO(tsk)			\

arch/um/include/shared/os.h

+1 −1
Original line number Diff line number Diff line
@@ -285,7 +285,7 @@ int 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 void userspace(struct uml_pt_regs *regs, unsigned long *aux_fp_regs);

extern void userspace(struct uml_pt_regs *regs);

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

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

extern int start_idle_thread(void *stack, jmp_buf *switch_buf);

arch/um/kernel/process.c

+2 −2
Original line number Diff line number Diff line
@@ -116,7 +116,7 @@ void new_thread_handler(void) 
	 * callback returns only if the kernel thread execs a process

	 */

	fn(arg);

	userspace(&current->thread.regs.regs, current_thread_info()->aux_fp_regs);

	userspace(&current->thread.regs.regs);

}



/* Called magically, see new_thread_handler above */
@@ -133,7 +133,7 @@ static void fork_handler(void) 


	current->thread.prev_sched = NULL;



	userspace(&current->thread.regs.regs, current_thread_info()->aux_fp_regs);

	userspace(&current->thread.regs.regs);

}



int copy_thread(struct task_struct * p, const struct kernel_clone_args *args)

arch/um/os-Linux/skas/process.c

+6 −19
Original line number Diff line number Diff line
@@ -141,16 +141,10 @@ void wait_stub_done(int pid) 


extern unsigned long current_stub_stack(void);



static void get_skas_faultinfo(int pid, struct faultinfo *fi, unsigned long *aux_fp_regs)

static void get_skas_faultinfo(int pid, struct faultinfo *fi)

{

	int err;



	err = get_fp_registers(pid, aux_fp_regs);

	if (err < 0) {

		printk(UM_KERN_ERR "save_fp_registers returned %d\n",

		       err);

		fatal_sigsegv();

	}

	err = ptrace(PTRACE_CONT, pid, 0, SIGSEGV);

	if (err) {

		printk(UM_KERN_ERR "Failed to continue stub, pid = %d, "
@@ -164,18 +158,11 @@ static void get_skas_faultinfo(int pid, struct faultinfo *fi, unsigned long *aux 
	 * the stub stack page. We just have to copy it.

	 */

	memcpy(fi, (void *)current_stub_stack(), sizeof(*fi));



	err = put_fp_registers(pid, aux_fp_regs);

	if (err < 0) {

		printk(UM_KERN_ERR "put_fp_registers returned %d\n",

		       err);

		fatal_sigsegv();

	}

}



static void handle_segv(int pid, struct uml_pt_regs *regs, unsigned long *aux_fp_regs)

static void handle_segv(int pid, struct uml_pt_regs *regs)

{

	get_skas_faultinfo(pid, &regs->faultinfo, aux_fp_regs);

	get_skas_faultinfo(pid, &regs->faultinfo);

	segv(regs->faultinfo, 0, 1, NULL);

}
@@ -336,7 +323,7 @@ int start_userspace(unsigned long stub_stack) 
	return err;

}



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

void userspace(struct uml_pt_regs *regs)

{

	int err, status, op, pid = userspace_pid[0];

	siginfo_t si;
@@ -435,11 +422,11 @@ void userspace(struct uml_pt_regs *regs, unsigned long *aux_fp_regs) 
			case SIGSEGV:

				if (PTRACE_FULL_FAULTINFO) {

					get_skas_faultinfo(pid,

							   &regs->faultinfo, aux_fp_regs);

							   &regs->faultinfo);

					(*sig_info[SIGSEGV])(SIGSEGV, (struct siginfo *)&si,

							     regs);

				}

				else handle_segv(pid, regs, aux_fp_regs);

				else handle_segv(pid, regs);

				break;

			case SIGTRAP + 0x80:

				handle_trap(pid, regs);