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Update some comments related to use of amd64 full context switch.

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In exec_linux_setregs(), use locally cached pointer to pcb to set
pcb_full_iret.
In set_regs(), note that full return is needed when code that sets
segment registers is enabled.

MFC after:	1 week
This commit is contained in:
Konstantin Belousov 2010-12-07 12:44:33 +00:00
parent 58f61ce4eb
commit 1b3c32568a
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=216255
3 changed files with 5 additions and 5 deletions
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1
sys/amd64/amd64/machdep.c
View File

@ -1906,6 +1906,7 @@ set_regs(struct thread *td, struct reg *regs)
tp->tf_fs = regs->r_fs;
tp->tf_gs = regs->r_gs;
tp->tf_flags = TF_HASSEGS;
td->td_pcb->pcb_full_iret = 1;
}
return (0);
}

5
sys/amd64/amd64/vm_machdep.c
View File

@ -339,10 +339,9 @@ cpu_set_syscall_retval(struct thread *td, int error)
* Reconstruct pc, we know that 'syscall' is 2 bytes,
* lcall $X,y is 7 bytes, int 0x80 is 2 bytes.
* We saved this in tf_err.
* We have to do a full context restore so that %r10
* (which was holding the value of %rcx) is restored
* %r10 (which was holding the value of %rcx) is restored
* for the next iteration.
* r10 restore is only required for freebsd/amd64 processes,
* %r10 restore is only required for freebsd/amd64 processes,
* but shall be innocent for any ia32 ABI.
*/
td->td_frame->tf_rip -= td->td_frame->tf_err;

4
sys/amd64/linux32/linux32_sysvec.c
View File

@ -865,13 +865,13 @@ exec_linux_setregs(struct thread *td, struct image_params *imgp, u_long stack)
regs->tf_flags = TF_HASSEGS;
regs->tf_cs = _ucode32sel;
regs->tf_rbx = imgp->ps_strings;
td->td_pcb->pcb_full_iret = 1;
load_cr0(rcr0() | CR0_MP | CR0_TS);
fpstate_drop(td);
/* Return via doreti so that we can change to a different %cs */
/* Do full restore on return so that we can change to a different %cs */
pcb->pcb_flags |= PCB_32BIT;
pcb->pcb_flags &= ~PCB_GS32BIT;
pcb->pcb_full_iret = 1;
td->td_retval[1] = 0;
}