diff options
| -rw-r--r-- | usr.sbin/bhyve/task_switch.c | 170 |
1 files changed, 94 insertions, 76 deletions
diff --git a/usr.sbin/bhyve/task_switch.c b/usr.sbin/bhyve/task_switch.c index 543c01f4536e..0002da8df8ef 100644 --- a/usr.sbin/bhyve/task_switch.c +++ b/usr.sbin/bhyve/task_switch.c @@ -48,15 +48,6 @@ __FBSDID("$FreeBSD$"); #include "bhyverun.h" /* - * Various functions in this file use 0 to denote success and VMEXIT_ABORT - * or VMEXIT_RESTART to denote failure. This assumes that the VMEXIT_xyz - * macros expand to non-zero values. Enforce this with a compile-time - * assertion. - */ -CTASSERT(VMEXIT_ABORT != 0); -CTASSERT(VMEXIT_RESTART != 0); - -/* * Using 'struct i386tss' is tempting but causes myriad sign extension * issues because all of its fields are defined as signed integers. */ @@ -175,6 +166,10 @@ sel_exception(struct vmctx *ctx, int vcpu, int vector, uint16_t sel, int ext) vm_inject_fault(ctx, vcpu, vector, 1, sel); } +/* + * Return 0 if the selector 'sel' in within the limits of the GDT/LDT + * and non-zero otherwise. + */ static int desc_table_limit_check(struct vmctx *ctx, int vcpu, uint16_t sel) { @@ -197,6 +192,14 @@ desc_table_limit_check(struct vmctx *ctx, int vcpu, uint16_t sel) return (0); } +/* + * Read/write the segment descriptor 'desc' into the GDT/LDT slot referenced + * by the selector 'sel'. + * + * Returns 0 on success. + * Returns 1 if an exception was injected into the guest. + * Returns -1 otherwise. + */ static int desc_table_rw(struct vmctx *ctx, int vcpu, struct vm_guest_paging *paging, uint16_t sel, struct user_segment_descriptor *desc, bool doread) @@ -236,6 +239,13 @@ desc_table_write(struct vmctx *ctx, int vcpu, struct vm_guest_paging *paging, return (desc_table_rw(ctx, vcpu, paging, sel, desc, false)); } +/* + * Read the TSS descriptor referenced by 'sel' into 'desc'. + * + * Returns 0 on success. + * Returns 1 if an exception was injected into the guest. + * Returns -1 otherwise. + */ static int read_tss_descriptor(struct vmctx *ctx, int vcpu, struct vm_task_switch *ts, uint16_t sel, struct user_segment_descriptor *desc) @@ -252,18 +262,13 @@ read_tss_descriptor(struct vmctx *ctx, int vcpu, struct vm_task_switch *ts, sel_exception(ctx, vcpu, IDT_TS, sel, ts->ext); else sel_exception(ctx, vcpu, IDT_GP, sel, ts->ext); - return (VMEXIT_RESTART); + return (1); } sup_paging = ts->paging; sup_paging.cpl = 0; /* implicit supervisor mode */ error = desc_table_read(ctx, vcpu, &sup_paging, sel, desc); - if (error < 0) - return (VMEXIT_ABORT); - else if (error > 0) - return (VMEXIT_RESTART); - else - return (0); + return (error); } static bool @@ -294,6 +299,13 @@ ldt_desc(int sd_type) return (sd_type == SDT_SYSLDT); } +/* + * Validate the descriptor 'seg_desc' associated with 'segment'. + * + * Returns 0 on success. + * Returns 1 if an exception was injected into the guest. + * Returns -1 otherwise. + */ static int validate_seg_desc(struct vmctx *ctx, int vcpu, struct vm_task_switch *ts, int segment, struct seg_desc *seg_desc) @@ -332,13 +344,13 @@ validate_seg_desc(struct vmctx *ctx, int vcpu, struct vm_task_switch *ts, /* LDT selector must point into the GDT */ if (ldtseg && ISLDT(sel)) { sel_exception(ctx, vcpu, IDT_TS, sel, ts->ext); - return (VMEXIT_RESTART); + return (1); } /* Descriptor table limit check */ if (desc_table_limit_check(ctx, vcpu, sel)) { sel_exception(ctx, vcpu, IDT_TS, sel, ts->ext); - return (VMEXIT_RESTART); + return (1); } /* NULL selector */ @@ -346,7 +358,7 @@ validate_seg_desc(struct vmctx *ctx, int vcpu, struct vm_task_switch *ts, /* Code and stack segment selectors cannot be NULL */ if (codeseg || stackseg) { sel_exception(ctx, vcpu, IDT_TS, sel, ts->ext); - return (VMEXIT_RESTART); + return (1); } seg_desc->base = 0; seg_desc->limit = 0; @@ -358,10 +370,8 @@ validate_seg_desc(struct vmctx *ctx, int vcpu, struct vm_task_switch *ts, sup_paging = ts->paging; sup_paging.cpl = 0; /* implicit supervisor mode */ error = desc_table_read(ctx, vcpu, &sup_paging, sel, &usd); - if (error < 0) - return (VMEXIT_ABORT); - else if (error > 0) - return (VMEXIT_RESTART); + if (error) + return (error); /* Verify that the descriptor type is compatible with the segment */ if ((ldtseg && !ldt_desc(usd.sd_type)) || @@ -369,7 +379,7 @@ validate_seg_desc(struct vmctx *ctx, int vcpu, struct vm_task_switch *ts, (dataseg && !data_desc(usd.sd_type)) || (stackseg && !stack_desc(usd.sd_type))) { sel_exception(ctx, vcpu, IDT_TS, sel, ts->ext); - return (VMEXIT_RESTART); + return (1); } /* Segment must be marked present */ @@ -381,7 +391,7 @@ validate_seg_desc(struct vmctx *ctx, int vcpu, struct vm_task_switch *ts, else idtvec = IDT_NP; sel_exception(ctx, vcpu, idtvec, sel, ts->ext); - return (VMEXIT_RESTART); + return (1); } cs = GETREG(ctx, vcpu, VM_REG_GUEST_CS); @@ -391,7 +401,7 @@ validate_seg_desc(struct vmctx *ctx, int vcpu, struct vm_task_switch *ts, if (stackseg && (rpl != cpl || dpl != cpl)) { sel_exception(ctx, vcpu, IDT_TS, sel, ts->ext); - return (VMEXIT_RESTART); + return (1); } if (codeseg) { @@ -399,7 +409,7 @@ validate_seg_desc(struct vmctx *ctx, int vcpu, struct vm_task_switch *ts, if ((conforming && (cpl < dpl)) || (!conforming && (cpl != dpl))) { sel_exception(ctx, vcpu, IDT_TS, sel, ts->ext); - return (VMEXIT_RESTART); + return (1); } } @@ -415,7 +425,7 @@ validate_seg_desc(struct vmctx *ctx, int vcpu, struct vm_task_switch *ts, if (!conforming && (rpl > dpl || cpl > dpl)) { sel_exception(ctx, vcpu, IDT_TS, sel, ts->ext); - return (VMEXIT_RESTART); + return (1); } } *seg_desc = usd_to_seg_desc(&usd); @@ -464,6 +474,13 @@ update_seg_desc(struct vmctx *ctx, int vcpu, int reg, struct seg_desc *sd) assert(error == 0); } +/* + * Update the vcpu registers to reflect the state of the new task. + * + * Returns 0 on success. + * Returns 1 if an exception was injected into the guest. + * Returns -1 otherwise. + */ static int tss32_restore(struct vmctx *ctx, int vcpu, struct vm_task_switch *ts, uint16_t ot_sel, struct tss32 *tss, struct iovec *iov) @@ -506,7 +523,7 @@ tss32_restore(struct vmctx *ctx, int vcpu, struct vm_task_switch *ts, reserved = ~maxphyaddr | 0x1E6; if (pdpte[i] & reserved) { vm_inject_gp(ctx, vcpu); - return (VMEXIT_RESTART); + return (1); } } SETREG(ctx, vcpu, VM_REG_GUEST_PDPTE0, pdpte[0]); @@ -595,6 +612,15 @@ tss32_restore(struct vmctx *ctx, int vcpu, struct vm_task_switch *ts, return (0); } +/* + * Push an error code on the stack of the new task. This is needed if the + * task switch was triggered by a hardware exception that causes an error + * code to be saved (e.g. #PF). + * + * Returns 0 on success. + * Returns 1 if an exception was injected into the guest. + * Returns -1 otherwise. + */ static int push_errcode(struct vmctx *ctx, int vcpu, struct vm_guest_paging *paging, int task_type, uint32_t errcode) @@ -640,26 +666,40 @@ push_errcode(struct vmctx *ctx, int vcpu, struct vm_guest_paging *paging, if (vie_calculate_gla(paging->cpu_mode, VM_REG_GUEST_SS, &seg_desc, esp, bytes, stacksize, PROT_WRITE, &gla)) { sel_exception(ctx, vcpu, IDT_SS, stacksel, 1); - return (VMEXIT_RESTART); + return (1); } if (vie_alignment_check(paging->cpl, bytes, cr0, rflags, gla)) { vm_inject_ac(ctx, vcpu, 1); - return (VMEXIT_RESTART); + return (1); } error = vm_copy_setup(ctx, vcpu, paging, gla, bytes, PROT_WRITE, iov, nitems(iov)); - assert(error == 0 || error == 1 || error == -1); - if (error) { - return ((error == 1) ? VMEXIT_RESTART : VMEXIT_ABORT); - } + if (error) + return (error); vm_copyout(ctx, vcpu, &errcode, iov, bytes); SETREG(ctx, vcpu, VM_REG_GUEST_RSP, esp); return (0); } +/* + * Evaluate return value from helper functions and potentially return to + * the VM run loop. + * 0: success + * +1: an exception was injected into the guest vcpu + * -1: unrecoverable/programming error + */ +#define CHKERR(x) \ + do { \ + assert(((x) == 0) || ((x) == 1) || ((x) == -1)); \ + if ((x) == -1) \ + return (VMEXIT_ABORT); \ + else if ((x) == 1) \ + return (VMEXIT_CONTINUE); \ + } while (0) + int vmexit_task_switch(struct vmctx *ctx, struct vm_exit *vmexit, int *pvcpu) { @@ -695,8 +735,7 @@ vmexit_task_switch(struct vmctx *ctx, struct vm_exit *vmexit, int *pvcpu) /* Fetch the new TSS descriptor */ error = read_tss_descriptor(ctx, vcpu, task_switch, nt_sel, &nt_desc); - if (error) - return (error); + CHKERR(error); nt = usd_to_seg_desc(&nt_desc); @@ -705,13 +744,13 @@ vmexit_task_switch(struct vmctx *ctx, struct vm_exit *vmexit, int *pvcpu) if (nt_type != SDT_SYS386BSY && nt_type != SDT_SYS386TSS && nt_type != SDT_SYS286BSY && nt_type != SDT_SYS286TSS) { sel_exception(ctx, vcpu, IDT_TS, nt_sel, ext); - return (VMEXIT_RESTART); + goto done; } /* TSS descriptor must have present bit set */ if (!SEG_DESC_PRESENT(nt.access)) { sel_exception(ctx, vcpu, IDT_NP, nt_sel, ext); - return (VMEXIT_RESTART); + goto done; } /* @@ -728,13 +767,13 @@ vmexit_task_switch(struct vmctx *ctx, struct vm_exit *vmexit, int *pvcpu) assert(minlimit > 0); if (nt.limit < minlimit) { sel_exception(ctx, vcpu, IDT_TS, nt_sel, ext); - return (VMEXIT_RESTART); + goto done; } /* TSS must be busy if task switch is due to IRET */ if (reason == TSR_IRET && !TSS_BUSY(nt_type)) { sel_exception(ctx, vcpu, IDT_TS, nt_sel, ext); - return (VMEXIT_RESTART); + goto done; } /* @@ -743,21 +782,14 @@ vmexit_task_switch(struct vmctx *ctx, struct vm_exit *vmexit, int *pvcpu) */ if (reason != TSR_IRET && TSS_BUSY(nt_type)) { sel_exception(ctx, vcpu, IDT_GP, nt_sel, ext); - return (VMEXIT_RESTART); + goto done; } /* Fetch the new TSS */ error = vm_copy_setup(ctx, vcpu, &sup_paging, nt.base, minlimit + 1, PROT_READ | PROT_WRITE, nt_iov, nitems(nt_iov)); - if (error == 1) { - /* Restart vcpu execution to handle the page fault */ - return (VMEXIT_RESTART); - } else if (error == -1) { - return (VMEXIT_ABORT); - } else { - assert(error == 0); - vm_copyin(ctx, vcpu, nt_iov, &newtss, minlimit + 1); - } + CHKERR(error); + vm_copyin(ctx, vcpu, nt_iov, &newtss, minlimit + 1); /* Get the old TSS selector from the guest's task register */ ot_sel = GETREG(ctx, vcpu, VM_REG_GUEST_TR); @@ -769,7 +801,7 @@ vmexit_task_switch(struct vmctx *ctx, struct vm_exit *vmexit, int *pvcpu) * (sel = 0, base = 0, limit = 0xffff). */ sel_exception(ctx, vcpu, IDT_TS, ot_sel, task_switch->ext); - return (VMEXIT_RESTART); + goto done; } /* Get the old TSS base and limit from the guest's task register */ @@ -781,24 +813,14 @@ vmexit_task_switch(struct vmctx *ctx, struct vm_exit *vmexit, int *pvcpu) assert(ot_type == SDT_SYS386BSY || ot_type == SDT_SYS286BSY); /* Fetch the old TSS descriptor */ - error = read_tss_descriptor(ctx, vcpu, task_switch, ot_sel, - &ot_desc); - if (error) - return (error); + error = read_tss_descriptor(ctx, vcpu, task_switch, ot_sel, &ot_desc); + CHKERR(error); /* Get the old TSS */ error = vm_copy_setup(ctx, vcpu, &sup_paging, ot_base, minlimit + 1, PROT_READ | PROT_WRITE, ot_iov, nitems(ot_iov)); - if (error == 1) { - /* Restart vcpu execution to handle the page fault */ - return (VMEXIT_RESTART); - } else if (error == -1) { - fprintf(stderr, "Error copying in old TSS: %d\n", errno); - return (VMEXIT_ABORT); - } else { - assert(error == 0); - vm_copyin(ctx, vcpu, ot_iov, &oldtss, minlimit + 1); - } + CHKERR(error); + vm_copyin(ctx, vcpu, ot_iov, &oldtss, minlimit + 1); /* * Clear the busy bit in the old TSS descriptor if the task switch @@ -808,8 +830,7 @@ vmexit_task_switch(struct vmctx *ctx, struct vm_exit *vmexit, int *pvcpu) ot_desc.sd_type &= ~0x2; error = desc_table_write(ctx, vcpu, &sup_paging, ot_sel, &ot_desc); - if (error) - return (error); + CHKERR(error); } if (nt_type == SDT_SYS286BSY || nt_type == SDT_SYS286TSS) { @@ -829,8 +850,7 @@ vmexit_task_switch(struct vmctx *ctx, struct vm_exit *vmexit, int *pvcpu) nt_desc.sd_type |= 0x2; error = desc_table_write(ctx, vcpu, &sup_paging, nt_sel, &nt_desc); - if (error) - return (error); + CHKERR(error); } /* Update task register to point at the new TSS */ @@ -854,8 +874,7 @@ vmexit_task_switch(struct vmctx *ctx, struct vm_exit *vmexit, int *pvcpu) /* Load processor state from new TSS */ error = tss32_restore(ctx, vcpu, task_switch, ot_sel, &newtss, nt_iov); - if (error) - return (error); + CHKERR(error); /* * Section "Interrupt Tasks" in Intel SDM, Vol 3: if an exception @@ -867,9 +886,7 @@ vmexit_task_switch(struct vmctx *ctx, struct vm_exit *vmexit, int *pvcpu) assert(task_switch->reason == TSR_IDT_GATE); error = push_errcode(ctx, vcpu, &task_switch->paging, nt_type, task_switch->errcode); - if (error) { - return (error); - } + CHKERR(error); } /* @@ -910,5 +927,6 @@ vmexit_task_switch(struct vmctx *ctx, struct vm_exit *vmexit, int *pvcpu) /* * XXX should inject debug exception if 'T' bit is 1 */ - return (VMEXIT_RESTART); +done: + return (VMEXIT_CONTINUE); } |