git: a7883464fcc4 - main - x86: Reduce code duplication in cpu_fork() and cpu_copy_thread().
John Baldwin
jhb at FreeBSD.org
Thu Mar 18 19:16:21 UTC 2021
The branch main has been updated by jhb:
URL: https://cgit.FreeBSD.org/src/commit/?id=a7883464fcc45b78e6aa01222682ae40f787a378
commit a7883464fcc45b78e6aa01222682ae40f787a378
Author: John Baldwin <jhb at FreeBSD.org>
AuthorDate: 2021-03-18 19:13:17 +0000
Commit: John Baldwin <jhb at FreeBSD.org>
CommitDate: 2021-03-18 19:13:17 +0000
x86: Reduce code duplication in cpu_fork() and cpu_copy_thread().
Add copy_thread() to hold shared code.
Reviewed by: kib
MFC after: 1 week
Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D29228
---
sys/amd64/amd64/vm_machdep.c | 167 +++++++++++++++------------------------
sys/i386/i386/vm_machdep.c | 184 +++++++++++++++++--------------------------
2 files changed, 137 insertions(+), 214 deletions(-)
diff --git a/sys/amd64/amd64/vm_machdep.c b/sys/amd64/amd64/vm_machdep.c
index a17ddd4ba6d8..0527ef95cf3b 100644
--- a/sys/amd64/amd64/vm_machdep.c
+++ b/sys/amd64/amd64/vm_machdep.c
@@ -136,6 +136,65 @@ alloc_fpusave(int flags)
return (res);
}
+/*
+ * Common code shared between cpu_fork() and cpu_copy_thread() for
+ * initializing a thread.
+ */
+static void
+copy_thread(struct thread *td1, struct thread *td2)
+{
+ struct pcb *pcb2;
+
+ pcb2 = td2->td_pcb;
+
+ /* Ensure that td1's pcb is up to date for user threads. */
+ if ((td2->td_pflags & TDP_KTHREAD) == 0) {
+ MPASS(td1 == curthread);
+ fpuexit(td1);
+ update_pcb_bases(td1->td_pcb);
+ }
+
+ /* Copy td1's pcb */
+ bcopy(td1->td_pcb, pcb2, sizeof(*pcb2));
+
+ /* Properly initialize pcb_save */
+ pcb2->pcb_save = get_pcb_user_save_pcb(pcb2);
+
+ /* Kernel threads start with clean FPU and segment bases. */
+ if ((td2->td_pflags & TDP_KTHREAD) != 0) {
+ pcb2->pcb_fsbase = 0;
+ pcb2->pcb_gsbase = 0;
+ clear_pcb_flags(pcb2, PCB_FPUINITDONE | PCB_USERFPUINITDONE |
+ PCB_KERNFPU | PCB_KERNFPU_THR);
+ } else {
+ MPASS((pcb2->pcb_flags & (PCB_KERNFPU | PCB_KERNFPU_THR)) == 0);
+ bcopy(get_pcb_user_save_td(td1), get_pcb_user_save_pcb(pcb2),
+ cpu_max_ext_state_size);
+ }
+
+ /*
+ * Set registers for trampoline to user mode. Leave space for the
+ * return address on stack. These are the kernel mode register values.
+ */
+ pcb2->pcb_r12 = (register_t)fork_return; /* fork_trampoline argument */
+ pcb2->pcb_rbp = 0;
+ pcb2->pcb_rsp = (register_t)td2->td_frame - sizeof(void *);
+ pcb2->pcb_rbx = (register_t)td2; /* fork_trampoline argument */
+ pcb2->pcb_rip = (register_t)fork_trampoline;
+ /*-
+ * pcb2->pcb_dr*: cloned above.
+ * pcb2->pcb_savefpu: cloned above.
+ * pcb2->pcb_flags: cloned above.
+ * pcb2->pcb_onfault: cloned above (always NULL here?).
+ * pcb2->pcb_[fg]sbase: cloned above
+ */
+
+ /* Setup to release spin count in fork_exit(). */
+ td2->td_md.md_spinlock_count = 1;
+ td2->td_md.md_saved_flags = PSL_KERNEL | PSL_I;
+ pmap_thread_init_invl_gen(td2);
+}
+
/*
* Finish a fork operation, with process p2 nearly set up.
* Copy and update the pcb, set up the stack so that the child
@@ -164,36 +223,13 @@ cpu_fork(struct thread *td1, struct proc *p2, struct thread *td2, int flags)
return;
}
- /* Ensure that td1's pcb is up to date for user processes. */
- if ((td2->td_pflags & TDP_KTHREAD) == 0) {
- MPASS(td1 == curthread);
- fpuexit(td1);
- update_pcb_bases(td1->td_pcb);
- }
-
/* Point the stack and pcb to the actual location */
set_top_of_stack_td(td2);
td2->td_pcb = pcb2 = get_pcb_td(td2);
- /* Copy td1's pcb */
- bcopy(td1->td_pcb, pcb2, sizeof(*pcb2));
-
- /* Properly initialize pcb_save */
- pcb2->pcb_save = get_pcb_user_save_pcb(pcb2);
+ copy_thread(td1, td2);
- /* Kernel processes start with clean FPU and segment bases. */
- if ((td2->td_pflags & TDP_KTHREAD) != 0) {
- pcb2->pcb_fsbase = 0;
- pcb2->pcb_gsbase = 0;
- clear_pcb_flags(pcb2, PCB_FPUINITDONE | PCB_USERFPUINITDONE |
- PCB_KERNFPU | PCB_KERNFPU_THR);
- } else {
- MPASS((pcb2->pcb_flags & (PCB_KERNFPU | PCB_KERNFPU_THR)) == 0);
- bcopy(get_pcb_user_save_td(td1), get_pcb_user_save_pcb(pcb2),
- cpu_max_ext_state_size);
- }
-
- /* Point mdproc and then copy over td1's contents */
+ /* Point mdproc and then copy over p1's contents */
mdp2 = &p2->p_md;
bcopy(&p1->p_md, mdp2, sizeof(*mdp2));
@@ -215,29 +251,7 @@ cpu_fork(struct thread *td1, struct proc *p2, struct thread *td2, int flags)
*/
td2->td_frame->tf_rflags &= ~PSL_T;
- /*
- * Set registers for trampoline to user mode. Leave space for the
- * return address on stack. These are the kernel mode register values.
- */
- pcb2->pcb_r12 = (register_t)fork_return; /* fork_trampoline argument */
- pcb2->pcb_rbp = 0;
- pcb2->pcb_rsp = (register_t)td2->td_frame - sizeof(void *);
- pcb2->pcb_rbx = (register_t)td2; /* fork_trampoline argument */
- pcb2->pcb_rip = (register_t)fork_trampoline;
- /*-
- * pcb2->pcb_dr*: cloned above.
- * pcb2->pcb_savefpu: cloned above.
- * pcb2->pcb_flags: cloned above.
- * pcb2->pcb_onfault: cloned above (always NULL here?).
- * pcb2->pcb_[fg]sbase: cloned above
- */
-
- /* Setup to release spin count in fork_exit(). */
- td2->td_md.md_spinlock_count = 1;
- td2->td_md.md_saved_flags = PSL_KERNEL | PSL_I;
- pmap_thread_init_invl_gen(td2);
-
- /* As an i386, do not copy io permission bitmap. */
+ /* As on i386, do not copy io permission bitmap. */
pcb2->pcb_tssp = NULL;
/* New segment registers. */
@@ -275,7 +289,7 @@ cpu_fork(struct thread *td1, struct proc *p2, struct thread *td2, int flags)
* pcb_rsp is loaded pointing to the cpu_switch() stack frame
* containing the return address when exiting cpu_switch.
* This will normally be to fork_trampoline(), which will have
- * %ebx loaded with the new proc's pointer. fork_trampoline()
+ * %rbx loaded with the new proc's pointer. fork_trampoline()
* will set up a stack to call fork_return(p, frame); to complete
* the return to user-mode.
*/
@@ -571,38 +585,7 @@ cpu_set_syscall_retval(struct thread *td, int error)
void
cpu_copy_thread(struct thread *td, struct thread *td0)
{
- struct pcb *pcb2;
-
- pcb2 = td->td_pcb;
-
- /* Ensure that td0's pcb is up to date for user threads. */
- if ((td->td_pflags & TDP_KTHREAD) == 0) {
- MPASS(td0 == curthread);
- fpuexit(td0);
- update_pcb_bases(td0->td_pcb);
- }
-
- /*
- * Copy the upcall pcb. This loads kernel regs.
- * Those not loaded individually below get their default
- * values here.
- */
- bcopy(td0->td_pcb, pcb2, sizeof(*pcb2));
- pcb2->pcb_save = get_pcb_user_save_pcb(pcb2);
-
- /* Kernel threads start with clean FPU and segment bases. */
- if ((td->td_pflags & TDP_KTHREAD) != 0) {
- pcb2->pcb_fsbase = 0;
- pcb2->pcb_gsbase = 0;
- clear_pcb_flags(pcb2, PCB_FPUINITDONE | PCB_USERFPUINITDONE |
- PCB_KERNFPU | PCB_KERNFPU_THR);
- } else {
- MPASS((pcb2->pcb_flags & (PCB_KERNFPU | PCB_KERNFPU_THR)) == 0);
- bcopy(get_pcb_user_save_td(td0), pcb2->pcb_save,
- cpu_max_ext_state_size);
- }
- set_pcb_flags_raw(pcb2, PCB_FULL_IRET);
-
+ copy_thread(td0, td);
/*
* Copy user general-purpose registers.
@@ -620,27 +603,7 @@ cpu_copy_thread(struct thread *td, struct thread *td0)
*/
td->td_frame->tf_rflags &= ~PSL_T;
- /*
- * Set registers for trampoline to user mode. Leave space for the
- * return address on stack. These are the kernel mode register values.
- */
- pcb2->pcb_r12 = (register_t)fork_return; /* trampoline arg */
- pcb2->pcb_rbp = 0;
- pcb2->pcb_rsp = (register_t)td->td_frame - sizeof(void *); /* trampoline arg */
- pcb2->pcb_rbx = (register_t)td; /* trampoline arg */
- pcb2->pcb_rip = (register_t)fork_trampoline;
- /*
- * If we didn't copy the pcb, we'd need to do the following registers:
- * pcb2->pcb_dr*: cloned above.
- * pcb2->pcb_savefpu: cloned above.
- * pcb2->pcb_onfault: cloned above (always NULL here?).
- * pcb2->pcb_[fg]sbase: cloned above
- */
-
- /* Setup to release spin count in fork_exit(). */
- td->td_md.md_spinlock_count = 1;
- td->td_md.md_saved_flags = PSL_KERNEL | PSL_I;
- pmap_thread_init_invl_gen(td);
+ set_pcb_flags_raw(td->td_pcb, PCB_FULL_IRET);
}
/*
diff --git a/sys/i386/i386/vm_machdep.c b/sys/i386/i386/vm_machdep.c
index 5947ae5a6d15..5bbdfdb77b2d 100644
--- a/sys/i386/i386/vm_machdep.c
+++ b/sys/i386/i386/vm_machdep.c
@@ -133,6 +133,74 @@ alloc_fpusave(int flags)
}
return (res);
}
+
+/*
+ * Common code shared between cpu_fork() and cpu_copy_thread() for
+ * initializing a thread.
+ */
+static void
+copy_thread(struct thread *td1, struct thread *td2)
+{
+ struct pcb *pcb2;
+
+ pcb2 = td2->td_pcb;
+
+ /* Ensure that td1's pcb is up to date for user threads. */
+ if ((td2->td_pflags & TDP_KTHREAD) == 0) {
+ MPASS(td1 == curthread);
+ td1->td_pcb->pcb_gs = rgs();
+ critical_enter();
+ if (PCPU_GET(fpcurthread) == td1)
+ npxsave(td1->td_pcb->pcb_save);
+ critical_exit();
+ }
+
+ /* Copy td1's pcb */
+ bcopy(td1->td_pcb, pcb2, sizeof(*pcb2));
+
+ /* Properly initialize pcb_save */
+ pcb2->pcb_save = get_pcb_user_save_pcb(pcb2);
+
+ /* Kernel threads start with clean NPX and segment bases. */
+ if ((td2->td_pflags & TDP_KTHREAD) != 0) {
+ pcb2->pcb_gs = _udatasel;
+ set_fsbase(td2, 0);
+ set_gsbase(td2, 0);
+ pcb2->pcb_flags &= ~(PCB_NPXINITDONE | PCB_NPXUSERINITDONE |
+ PCB_KERNNPX | PCB_KERNNPX_THR);
+ } else {
+ MPASS((pcb2->pcb_flags & (PCB_KERNNPX | PCB_KERNNPX_THR)) == 0);
+ bcopy(get_pcb_user_save_td(td1), get_pcb_user_save_pcb(pcb2),
+ cpu_max_ext_state_size);
+ }
+
+ /*
+ * Set registers for trampoline to user mode. Leave space for the
+ * return address on stack. These are the kernel mode register values.
+ */
+ pcb2->pcb_edi = 0;
+ pcb2->pcb_esi = (int)fork_return; /* trampoline arg */
+ pcb2->pcb_ebp = 0;
+ pcb2->pcb_esp = (int)td2->td_frame - sizeof(void *); /* trampoline arg */
+ pcb2->pcb_ebx = (int)td2; /* trampoline arg */
+ pcb2->pcb_eip = (int)fork_trampoline + setidt_disp;
+ /*
+ * If we didn't copy the pcb, we'd need to do the following registers:
+ * pcb2->pcb_cr3: cloned above.
+ * pcb2->pcb_dr*: cloned above.
+ * pcb2->pcb_savefpu: cloned above.
+ * pcb2->pcb_flags: cloned above.
+ * pcb2->pcb_onfault: cloned above (always NULL here?).
+ * pcb2->pcb_gs: cloned above.
+ * pcb2->pcb_ext: cleared below.
+ */
+ pcb2->pcb_ext = NULL;
+
+ /* Setup to release spin count in fork_exit(). */
+ td2->td_md.md_spinlock_count = 1;
+ td2->td_md.md_saved_flags = PSL_KERNEL | PSL_I;
+}
+
/*
* Finish a fork operation, with process p2 nearly set up.
* Copy and update the pcb, set up the stack so that the child
@@ -167,38 +235,11 @@ cpu_fork(struct thread *td1, struct proc *p2, struct thread *td2, int flags)
return;
}
- /* Ensure that td1's pcb is up to date for user processes. */
- if ((td2->td_pflags & TDP_KTHREAD) == 0) {
- MPASS(td1 == curthread);
- td1->td_pcb->pcb_gs = rgs();
- critical_enter();
- if (PCPU_GET(fpcurthread) == td1)
- npxsave(td1->td_pcb->pcb_save);
- critical_exit();
- }
-
/* Point the pcb to the top of the stack */
pcb2 = get_pcb_td(td2);
td2->td_pcb = pcb2;
- /* Copy td1's pcb */
- bcopy(td1->td_pcb, pcb2, sizeof(*pcb2));
-
- /* Properly initialize pcb_save */
- pcb2->pcb_save = get_pcb_user_save_pcb(pcb2);
-
- /* Kernel processes start with clean NPX and segment bases. */
- if ((td2->td_pflags & TDP_KTHREAD) != 0) {
- pcb2->pcb_gs = _udatasel;
- set_fsbase(td2, 0);
- set_gsbase(td2, 0);
- pcb2->pcb_flags &= ~(PCB_NPXINITDONE | PCB_NPXUSERINITDONE |
- PCB_KERNNPX | PCB_KERNNPX_THR);
- } else {
- MPASS((pcb2->pcb_flags & (PCB_KERNNPX | PCB_KERNNPX_THR)) == 0);
- bcopy(get_pcb_user_save_td(td1), get_pcb_user_save_pcb(pcb2),
- cpu_max_ext_state_size);
- }
+ copy_thread(td1, td2);
/* Point mdproc and then copy over td1's contents */
mdp2 = &p2->p_md;
@@ -225,30 +266,13 @@ cpu_fork(struct thread *td1, struct proc *p2, struct thread *td2, int flags)
*/
td2->td_frame->tf_eflags &= ~PSL_T;
- /*
- * Set registers for trampoline to user mode. Leave space for the
- * return address on stack. These are the kernel mode register values.
- */
+ /* Set cr3 for the new process. */
pcb2->pcb_cr3 = pmap_get_cr3(vmspace_pmap(p2->p_vmspace));
- pcb2->pcb_edi = 0;
- pcb2->pcb_esi = (int)fork_return; /* fork_trampoline argument */
- pcb2->pcb_ebp = 0;
- pcb2->pcb_esp = (int)td2->td_frame - sizeof(void *);
- pcb2->pcb_ebx = (int)td2; /* fork_trampoline argument */
- pcb2->pcb_eip = (int)fork_trampoline + setidt_disp;
- /*-
- * pcb2->pcb_dr*: cloned above.
- * pcb2->pcb_savefpu: cloned above.
- * pcb2->pcb_flags: cloned above.
- * pcb2->pcb_onfault: cloned above (always NULL here?).
- * pcb2->pcb_gs: cloned above.
- * pcb2->pcb_ext: cleared below.
- */
/*
* XXX don't copy the i/o pages. this should probably be fixed.
*/
- pcb2->pcb_ext = 0;
+ pcb2->pcb_ext = NULL;
/* Copy the LDT, if necessary. */
mtx_lock_spin(&dt_lock);
@@ -264,10 +288,6 @@ cpu_fork(struct thread *td1, struct proc *p2, struct thread *td2, int flags)
}
mtx_unlock_spin(&dt_lock);
- /* Setup to release spin count in fork_exit(). */
- td2->td_md.md_spinlock_count = 1;
- td2->td_md.md_saved_flags = PSL_KERNEL | PSL_I;
-
/*
* Now, cpu_switch() can schedule the new process.
* pcb_esp is loaded pointing to the cpu_switch() stack frame
@@ -435,41 +455,7 @@ cpu_set_syscall_retval(struct thread *td, int error)
void
cpu_copy_thread(struct thread *td, struct thread *td0)
{
- struct pcb *pcb2;
-
- /* Point the pcb to the top of the stack. */
- pcb2 = td->td_pcb;
-
- /* Ensure that td0's pcb is up to date for user threads. */
- if ((td->td_pflags & TDP_KTHREAD) == 0) {
- MPASS(td0 == curthread);
- td0->td_pcb->pcb_gs = rgs();
- critical_enter();
- if (PCPU_GET(fpcurthread) == td0)
- npxsave(td0->td_pcb->pcb_save);
- critical_exit();
- }
-
- /*
- * Copy the upcall pcb. This loads kernel regs.
- * Those not loaded individually below get their default
- * values here.
- */
- bcopy(td0->td_pcb, pcb2, sizeof(*pcb2));
- pcb2->pcb_save = get_pcb_user_save_pcb(pcb2);
-
- /* Kernel threads start with clean NPX and segment bases. */
- if ((td->td_pflags & TDP_KTHREAD) != 0) {
- pcb2->pcb_gs = _udatasel;
- set_fsbase(td, 0);
- set_gsbase(td, 0);
- pcb2->pcb_flags &= ~(PCB_NPXINITDONE | PCB_NPXUSERINITDONE |
- PCB_KERNNPX | PCB_KERNNPX_THR);
- } else {
- MPASS((pcb2->pcb_flags & (PCB_KERNNPX | PCB_KERNNPX_THR)) == 0);
- bcopy(get_pcb_user_save_td(td0), pcb2->pcb_save,
- cpu_max_ext_state_size);
- }
+ copy_thread(td0, td);
/*
* Copy user general-purpose registers.
@@ -486,32 +472,6 @@ cpu_copy_thread(struct thread *td, struct thread *td0)
* instruction after returning to userland.
*/
td->td_frame->tf_eflags &= ~PSL_T;
-
- /*
- * Set registers for trampoline to user mode. Leave space for the
- * return address on stack. These are the kernel mode register values.
- */
- pcb2->pcb_edi = 0;
- pcb2->pcb_esi = (int)fork_return; /* trampoline arg */
- pcb2->pcb_ebp = 0;
- pcb2->pcb_esp = (int)td->td_frame - sizeof(void *); /* trampoline arg */
- pcb2->pcb_ebx = (int)td; /* trampoline arg */
- pcb2->pcb_eip = (int)fork_trampoline + setidt_disp;
- /*
- * If we didn't copy the pcb, we'd need to do the following registers:
- * pcb2->pcb_cr3: cloned above.
- * pcb2->pcb_dr*: cloned above.
- * pcb2->pcb_savefpu: cloned above.
- * pcb2->pcb_flags: cloned above.
- * pcb2->pcb_onfault: cloned above (always NULL here?).
- * pcb2->pcb_gs: cloned above.
- * pcb2->pcb_ext: cleared below.
- */
- pcb2->pcb_ext = NULL;
-
- /* Setup to release spin count in fork_exit(). */
- td->td_md.md_spinlock_count = 1;
- td->td_md.md_saved_flags = PSL_KERNEL | PSL_I;
}
/*
More information about the dev-commits-src-main
mailing list