Date: Thu, 5 Jun 2014 00:50:55 +0000 (UTC) From: Konstantin Belousov <kib@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-8@freebsd.org Subject: svn commit: r267085 - stable/8/sys/amd64/amd64 Message-ID: <201406050050.s550otsq017579@svn.freebsd.org>
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Author: kib Date: Thu Jun 5 00:50:55 2014 New Revision: 267085 URL: http://svnweb.freebsd.org/changeset/base/267085 Log: MFC r266846: When usermode loaded non-default segment selector into the %gs, correctly prepare KGSBASE msr to restore the user descriptor base on the last swapgs during return to usermode. Modified: stable/8/sys/amd64/amd64/exception.S Directory Properties: stable/8/sys/ (props changed) stable/8/sys/amd64/ (props changed) Modified: stable/8/sys/amd64/amd64/exception.S ============================================================================== --- stable/8/sys/amd64/amd64/exception.S Thu Jun 5 00:43:32 2014 (r267084) +++ stable/8/sys/amd64/amd64/exception.S Thu Jun 5 00:50:55 2014 (r267085) @@ -718,21 +718,38 @@ ld_fsbase: pushfq cli movl $MSR_GSBASE,%ecx + /* Save current kernel %gs base into %r12d:%r13d */ rdmsr + movl %eax,%r12d + movl %edx,%r13d .globl ld_gs ld_gs: movw %si,%gs + /* Save user %gs base into %r14d:%r15d */ + rdmsr + movl %eax,%r14d + movl %edx,%r15d + /* Restore kernel %gs base */ + movl %r12d,%eax + movl %r13d,%edx wrmsr popfq + /* + * Restore user %gs base, either from PCB if used for TLS, or + * from the previously saved msr read. + */ + movl $MSR_KGSBASE,%ecx cmpw $KUG32SEL,%si jne 1f - movl $MSR_KGSBASE,%ecx movl PCB_GSBASE(%r8),%eax movl PCB_GSBASE+4(%r8),%edx + jmp ld_gsbase +1: + movl %r14d,%eax + movl %r15d,%edx .globl ld_gsbase ld_gsbase: - wrmsr -1: + wrmsr /* May trap if non-canonical, but only for TLS. */ .globl ld_es ld_es: movw TF_ES(%rsp),%es
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