Re: Value of eax register after BIOS interrupt call from boot(8)
On Friday, November 8, 2019, Theo de Raadt wrote: > Philip Guenther wrote: > > > No, it should be the other way, moving the “clear NT flag” block down > after > > the “save registers into save area” block > > Ah. > > Index: arch/amd64/stand/libsa/gidt.S > === > RCS file: /cvs/src/sys/arch/amd64/stand/libsa/gidt.S,v > retrieving revision 1.11 > diff -u -p -u -r1.11 gidt.S > --- arch/amd64/stand/libsa/gidt.S 27 Oct 2012 15:43:42 - > 1.11 > +++ arch/amd64/stand/libsa/gidt.S 9 Nov 2019 06:50:57 - > @@ -423,14 +423,6 @@ intno = . - 1 > movl%edx, 0x9*4(%esp) > movb%bh , 0xe*4(%esp) > > - /* clear NT flag in eflags */ > - /* Martin Fredriksson */ > - pushf > - pop %eax > - and $0xbfff, %eax > - push%eax > - popf > - > /* save registers into save area */ > movl%eax, _C_LABEL(BIOS_regs)+BIOSR_AX > movl%ecx, _C_LABEL(BIOS_regs)+BIOSR_CX > @@ -438,6 +430,13 @@ intno = . - 1 > movl%ebp, _C_LABEL(BIOS_regs)+BIOSR_BP > movl%esi, _C_LABEL(BIOS_regs)+BIOSR_SI > movl%edi, _C_LABEL(BIOS_regs)+BIOSR_DI > + > + /* clear NT flag in eflags */ > + pushf > + pop %eax > + and $0xbfff, %eax > + push%eax > + popf > > pop %gs > pop %fs > Index: arch/i386/stand/libsa/gidt.S > === > RCS file: /cvs/src/sys/arch/i386/stand/libsa/gidt.S,v > retrieving revision 1.36 > diff -u -p -u -r1.36 gidt.S > --- arch/i386/stand/libsa/gidt.S31 Oct 2012 13:55:58 - > 1.36 > +++ arch/i386/stand/libsa/gidt.S9 Nov 2019 06:51:29 - > @@ -426,14 +426,6 @@ intno = . - 1 > movl%edx, 0x9*4(%esp) > movb%bh , 0xe*4(%esp) > > - /* clear NT flag in eflags */ > - /* Martin Fredriksson */ > - pushf > - pop %eax > - and $0xbfff, %eax > - push%eax > - popf > - > /* save registers into save area */ > movl%eax, _C_LABEL(BIOS_regs)+BIOSR_AX > movl%ecx, _C_LABEL(BIOS_regs)+BIOSR_CX > @@ -441,6 +433,13 @@ intno = . - 1 > movl%ebp, _C_LABEL(BIOS_regs)+BIOSR_BP > movl%esi, _C_LABEL(BIOS_regs)+BIOSR_SI > movl%edi, _C_LABEL(BIOS_regs)+BIOSR_DI > + > + /* clear NT flag in eflags */ > + pushf > + pop %eax > + and $0xbfff, %eax > + push%eax > + popf > > pop %gs > pop %f > Ok guenther@
Re: Value of eax register after BIOS interrupt call from boot(8)
> > Index: arch/amd64/stand/libsa/gidt.S > === > RCS file: /cvs/src/sys/arch/amd64/stand/libsa/gidt.S,v > retrieving revision 1.11 > diff -u -p -u -r1.11 gidt.S > --- arch/amd64/stand/libsa/gidt.S 27 Oct 2012 15:43:42 - 1.11 > +++ arch/amd64/stand/libsa/gidt.S 9 Nov 2019 06:50:57 - > @@ -423,14 +423,6 @@ intno= . - 1 > movl%edx, 0x9*4(%esp) > movb%bh , 0xe*4(%esp) > > - /* clear NT flag in eflags */ > - /* Martin Fredriksson */ > - pushf > - pop %eax > - and $0xbfff, %eax > - push%eax > - popf > - > /* save registers into save area */ > movl%eax, _C_LABEL(BIOS_regs)+BIOSR_AX > movl%ecx, _C_LABEL(BIOS_regs)+BIOSR_CX > @@ -438,6 +430,13 @@ intno= . - 1 > movl%ebp, _C_LABEL(BIOS_regs)+BIOSR_BP > movl%esi, _C_LABEL(BIOS_regs)+BIOSR_SI > movl%edi, _C_LABEL(BIOS_regs)+BIOSR_DI > + > + /* clear NT flag in eflags */ > + pushf > + pop %eax > + and $0xbfff, %eax > + push%eax > + popf > > pop %gs > pop %fs > Index: arch/i386/stand/libsa/gidt.S > === > RCS file: /cvs/src/sys/arch/i386/stand/libsa/gidt.S,v > retrieving revision 1.36 > diff -u -p -u -r1.36 gidt.S > --- arch/i386/stand/libsa/gidt.S 31 Oct 2012 13:55:58 - 1.36 > +++ arch/i386/stand/libsa/gidt.S 9 Nov 2019 06:51:29 - > @@ -426,14 +426,6 @@ intno= . - 1 > movl%edx, 0x9*4(%esp) > movb%bh , 0xe*4(%esp) > > - /* clear NT flag in eflags */ > - /* Martin Fredriksson */ > - pushf > - pop %eax > - and $0xbfff, %eax > - push%eax > - popf > - > /* save registers into save area */ > movl%eax, _C_LABEL(BIOS_regs)+BIOSR_AX > movl%ecx, _C_LABEL(BIOS_regs)+BIOSR_CX > @@ -441,6 +433,13 @@ intno= . - 1 > movl%ebp, _C_LABEL(BIOS_regs)+BIOSR_BP > movl%esi, _C_LABEL(BIOS_regs)+BIOSR_SI > movl%edi, _C_LABEL(BIOS_regs)+BIOSR_DI > + > + /* clear NT flag in eflags */ > + pushf > + pop %eax > + and $0xbfff, %eax > + push%eax > + popf > > pop %gs > pop %fs These changes work for me. As part of my Masterthesis im working on a measured boot with OpenBSD and to communicate with the TPM from within boot (8) BIOS calls are a convenient way to do so. Thanks for the fast response Julius
Re: Value of eax register after BIOS interrupt call from boot(8)
Philip Guenther wrote: > No, it should be the other way, moving the “clear NT flag” block down after > the “save registers into save area” block Ah. Index: arch/amd64/stand/libsa/gidt.S === RCS file: /cvs/src/sys/arch/amd64/stand/libsa/gidt.S,v retrieving revision 1.11 diff -u -p -u -r1.11 gidt.S --- arch/amd64/stand/libsa/gidt.S 27 Oct 2012 15:43:42 - 1.11 +++ arch/amd64/stand/libsa/gidt.S 9 Nov 2019 06:50:57 - @@ -423,14 +423,6 @@ intno = . - 1 movl%edx, 0x9*4(%esp) movb%bh , 0xe*4(%esp) - /* clear NT flag in eflags */ - /* Martin Fredriksson */ - pushf - pop %eax - and $0xbfff, %eax - push%eax - popf - /* save registers into save area */ movl%eax, _C_LABEL(BIOS_regs)+BIOSR_AX movl%ecx, _C_LABEL(BIOS_regs)+BIOSR_CX @@ -438,6 +430,13 @@ intno = . - 1 movl%ebp, _C_LABEL(BIOS_regs)+BIOSR_BP movl%esi, _C_LABEL(BIOS_regs)+BIOSR_SI movl%edi, _C_LABEL(BIOS_regs)+BIOSR_DI + + /* clear NT flag in eflags */ + pushf + pop %eax + and $0xbfff, %eax + push%eax + popf pop %gs pop %fs Index: arch/i386/stand/libsa/gidt.S === RCS file: /cvs/src/sys/arch/i386/stand/libsa/gidt.S,v retrieving revision 1.36 diff -u -p -u -r1.36 gidt.S --- arch/i386/stand/libsa/gidt.S31 Oct 2012 13:55:58 - 1.36 +++ arch/i386/stand/libsa/gidt.S9 Nov 2019 06:51:29 - @@ -426,14 +426,6 @@ intno = . - 1 movl%edx, 0x9*4(%esp) movb%bh , 0xe*4(%esp) - /* clear NT flag in eflags */ - /* Martin Fredriksson */ - pushf - pop %eax - and $0xbfff, %eax - push%eax - popf - /* save registers into save area */ movl%eax, _C_LABEL(BIOS_regs)+BIOSR_AX movl%ecx, _C_LABEL(BIOS_regs)+BIOSR_CX @@ -441,6 +433,13 @@ intno = . - 1 movl%ebp, _C_LABEL(BIOS_regs)+BIOSR_BP movl%esi, _C_LABEL(BIOS_regs)+BIOSR_SI movl%edi, _C_LABEL(BIOS_regs)+BIOSR_DI + + /* clear NT flag in eflags */ + pushf + pop %eax + and $0xbfff, %eax + push%eax + popf pop %gs pop %fs
Re: Value of eax register after BIOS interrupt call from boot(8)
On Friday, November 8, 2019, Theo de Raadt wrote: > Philip Guenther wrote: > > > Since we're unlikely to do _more_ with BIOS calls in the boot loader, my > > inclination would be to eliminate the structure value and the code that > > sets it (incorrectly). Opinions? > > I dunno, my crystal ball provides a more cynical outlook. > > How about we just repair by swapping the blocks as you propose, then > noone gets surprised down the road if they try to use the bios-interface > API's full functionality. > > The bootblocks don't shrink, but they don't grow either. > > Is this the right diff? I'm deleting the name which is in the commitlogs > since that isn't our style. ... > --- sys/arch/amd64/stand/libsa/gidt.S 27 Oct 2012 15:43:42 - > 1.11 > +++ sys/arch/amd64/stand/libsa/gidt.S 9 Nov 2019 03:57:11 - > @@ -417,19 +417,18 @@ intno = . - 1 > .byte 0xb8 > 2: .long 0x90909090 > > - /* pass BIOS return values back to caller */ > - movl%eax, 0xb*4(%esp) > - movl%ecx, 0xa*4(%esp) > - movl%edx, 0x9*4(%esp) > - movb%bh , 0xe*4(%esp) > - > /* clear NT flag in eflags */ > - /* Martin Fredriksson */ > pushf > pop %eax > and $0xbfff, %eax > push%eax > popf No, it should be the other way, moving the “clear NT flag” block down after the “save registers into save area” block Philip
Re: Value of eax register after BIOS interrupt call from boot(8)
Philip Guenther wrote: > Since we're unlikely to do _more_ with BIOS calls in the boot loader, my > inclination would be to eliminate the structure value and the code that > sets it (incorrectly). Opinions? I dunno, my crystal ball provides a more cynical outlook. How about we just repair by swapping the blocks as you propose, then noone gets surprised down the road if they try to use the bios-interface API's full functionality. The bootblocks don't shrink, but they don't grow either. Is this the right diff? I'm deleting the name which is in the commitlogs since that isn't our style. Index: sys/arch/amd64/stand/libsa/gidt.S === RCS file: /cvs/src/sys/arch/amd64/stand/libsa/gidt.S,v retrieving revision 1.11 diff -u -p -u -r1.11 gidt.S --- sys/arch/amd64/stand/libsa/gidt.S 27 Oct 2012 15:43:42 - 1.11 +++ sys/arch/amd64/stand/libsa/gidt.S 9 Nov 2019 03:57:11 - @@ -417,19 +417,18 @@ intno = . - 1 .byte 0xb8 2: .long 0x90909090 - /* pass BIOS return values back to caller */ - movl%eax, 0xb*4(%esp) - movl%ecx, 0xa*4(%esp) - movl%edx, 0x9*4(%esp) - movb%bh , 0xe*4(%esp) - /* clear NT flag in eflags */ - /* Martin Fredriksson */ pushf pop %eax and $0xbfff, %eax push%eax popf + + /* pass BIOS return values back to caller */ + movl%eax, 0xb*4(%esp) + movl%ecx, 0xa*4(%esp) + movl%edx, 0x9*4(%esp) + movb%bh , 0xe*4(%esp) /* save registers into save area */ movl%eax, _C_LABEL(BIOS_regs)+BIOSR_AX Index: sys/arch/i386/stand/libsa/gidt.S === RCS file: /cvs/src/sys/arch/i386/stand/libsa/gidt.S,v retrieving revision 1.36 diff -u -p -u -r1.36 gidt.S --- sys/arch/i386/stand/libsa/gidt.S31 Oct 2012 13:55:58 - 1.36 +++ sys/arch/i386/stand/libsa/gidt.S9 Nov 2019 03:56:56 - @@ -420,19 +420,18 @@ intno = . - 1 .byte 0xb8 2: .long 0x90909090 - /* pass BIOS return values back to caller */ - movl%eax, 0xb*4(%esp) - movl%ecx, 0xa*4(%esp) - movl%edx, 0x9*4(%esp) - movb%bh , 0xe*4(%esp) - /* clear NT flag in eflags */ - /* Martin Fredriksson */ pushf pop %eax and $0xbfff, %eax push%eax popf + + /* pass BIOS return values back to caller */ + movl%eax, 0xb*4(%esp) + movl%ecx, 0xa*4(%esp) + movl%edx, 0x9*4(%esp) + movb%bh , 0xe*4(%esp) /* save registers into save area */ movl%eax, _C_LABEL(BIOS_regs)+BIOSR_AX
Re: Value of eax register after BIOS interrupt call from boot(8)
On Thu, Nov 7, 2019 at 9:31 AM Julius Zint wrote: > the following code snipped is from sys/arch/amd64/stand/libsa/gidt.S > > /* pass BIOS return values back to caller */ > movl%eax, 0xb*4(%esp) > movl%ecx, 0xa*4(%esp) > movl%edx, 0x9*4(%esp) > movb%bh , 0xe*4(%esp) > > /* clear NT flag in eflags */ > /* Martin Fredriksson */ > pushf > pop %eax > and $0xbfff, %eax > push%eax > popf > > /* save registers into save area */ > movl%eax, _C_LABEL(BIOS_regs)+BIOSR_AX > movl%ecx, _C_LABEL(BIOS_regs)+BIOSR_CX > movl%edx, _C_LABEL(BIOS_regs)+BIOSR_DX > movl%ebp, _C_LABEL(BIOS_regs)+BIOSR_BP > movl%esi, _C_LABEL(BIOS_regs)+BIOSR_SI > movl%edi, _C_LABEL(BIOS_regs)+BIOSR_DI > > These instructions are being executed after a BIOS interrupt. If i read > correctly, than (BIOS_regs)+BIOSR_AX contains the contents of the eflags > processor register and not of %eax. Is this intended or should it contain > the value of %eax? > Yeah, it looks like it's in the wrong order. The trick, of course, is that nothing actually examines BIOS_regs.biosr_ax, so the fact that the wrong value is saved there hasn't mattered. Since we're unlikely to do _more_ with BIOS calls in the boot loader, my inclination would be to eliminate the structure value and the code that sets it (incorrectly). Opinions? Philip Guenther
Value of eax register after BIOS interrupt call from boot(8)
Hi misc, the following code snipped is from sys/arch/amd64/stand/libsa/gidt.S /* pass BIOS return values back to caller */ movl%eax, 0xb*4(%esp) movl%ecx, 0xa*4(%esp) movl%edx, 0x9*4(%esp) movb%bh , 0xe*4(%esp) /* clear NT flag in eflags */ /* Martin Fredriksson */ pushf pop %eax and $0xbfff, %eax push%eax popf /* save registers into save area */ movl%eax, _C_LABEL(BIOS_regs)+BIOSR_AX movl%ecx, _C_LABEL(BIOS_regs)+BIOSR_CX movl%edx, _C_LABEL(BIOS_regs)+BIOSR_DX movl%ebp, _C_LABEL(BIOS_regs)+BIOSR_BP movl%esi, _C_LABEL(BIOS_regs)+BIOSR_SI movl%edi, _C_LABEL(BIOS_regs)+BIOSR_DI These instructions are being executed after a BIOS interrupt. If i read correctly, than (BIOS_regs)+BIOSR_AX contains the contents of the eflags processor register and not of %eax. Is this intended or should it contain the value of %eax? Kind regards Julius
