On Wed, Jul 7, 2010 at 8:49 PM, Geoff Lywood <[email protected]> wrote: > This patch adds a fair amount of code size... ~300 bytes I think. Is there > some kind of script I can run that will tell me exactly how much it has > changed?
$ size bin/com32.o or $ make bin/gpxe.hd.sizes or util/diffsize.pl Take your pick! Stefan > I can see some obvious optimizations I can do to eliminate some of this added > code, and I'll send out a new patch soon. > > Thanks, > Geoff > > >> -----Original Message----- >> From: Stefan Hajnoczi [mailto:[email protected]] >> Sent: Wednesday, July 07, 2010 12:42 PM >> To: Geoff Lywood >> Cc: [email protected] >> Subject: Re: [gPXE-devel] [PATCH] Run COM32 programs with a valid IDT >> >> On Tue, Jun 29, 2010 at 2:18 AM, Geoff Lywood <[email protected]> wrote: >> > COM32 binaries generally expect to run with interrupts enabled. Syslinux >> does >> > so, and COM32 programs will execute cli/sti pairs when running a >> critical >> > section, to provide mutual exclusion against BIOS interrupt handlers. >> > Previously, under gPXE, the IDT was not valid, so any interrupt (e.g. a >> timer >> > tick) would generally cause the machine to triple fault. >> > >> > This change introduces code to: >> > - Create a valid IDT at the same location that syslinux uses >> > - Create an "interrupt jump buffer", which contains small pieces of code >> that >> > simply record the vector number and jump to a common handler >> > - Thunk down to real mode and execute the BIOS's interrupt handler >> whenever >> > an interrupt is received in a COM32 program >> > - Switch IDTs and enable/disable interrupts when context switching to >> and from >> > COM32 binaries >> > >> > Testing done: >> > - Booted VMware ESX using a COM32 multiboot loader (mboot.c32) >> > - Built with GDBSERIAL enabled, and tested breakpoints on int22 and >> com32_irq >> > - Put the following code in a COM32 program: >> > asm volatile ( "sti" ); >> > while ( 1 ); >> > Before this change, the machine would triple fault immediately. After >> this >> > change, it hangs as expected. Under Bochs, it is possible to see the >> > interrupt handler run, and the current time in the BIOS data area gets >> > incremented. >> >> I think we should merge this patch as it enables mboot.c32. Thanks >> for describing the testing you have done. >> >> I have skimmed the code but not reviewed in depth. >> >> Stefan >> >> > I have a feeling that Outlook is going to mangle this patch, so I'm >> attaching it as well. >> > >> > VMware, Inc. is providing this patch to you under the terms of the GPL >> version 2 and any later version. This patch is provided as is, with no >> warranties or support. VMware disclaims all liability in connection with >> the use/inability to use this patch. Any use of the attached is considered >> acceptance of the above. >> > >> > Signed-off-by: Geoff Lywood <[email protected]> >> > --- >> > src/arch/i386/image/com32.c | 73 >> +++++++++++++++++++++- >> > src/arch/i386/include/comboot.h | 45 +++++++++++++ >> > src/arch/i386/interface/syslinux/com32_call.c | 17 +++++ >> > src/arch/i386/interface/syslinux/com32_wrapper.S | 28 ++++++++ >> > 4 files changed, 162 insertions(+), 1 deletions(-) >> > >> > diff --git a/src/arch/i386/image/com32.c b/src/arch/i386/image/com32.c >> > index 6ab347c..0f01027 100644 >> > --- a/src/arch/i386/image/com32.c >> > +++ b/src/arch/i386/image/com32.c >> > @@ -42,6 +42,13 @@ FILE_LICENCE ( GPL2_OR_LATER ); >> > >> > struct image_type com32_image_type __image_type ( PROBE_NORMAL ); >> > >> > +struct idt_register com32_external_idtr = { >> > + .limit = COM32_NUM_IDT_ENTRIES * sizeof ( struct idt_descriptor >> ) - 1, >> > + .base = COM32_IDT >> > +}; >> > + >> > +struct idt_register com32_internal_idtr; >> > + >> > /** >> > * Execute COMBOOT image >> > * >> > @@ -89,9 +96,12 @@ static int com32_exec ( struct image *image ) { >> > unregister_image ( image ); >> > >> > __asm__ __volatile__ ( >> > + "sidt com32_internal_idtr\n\t" >> > + "lidt com32_external_idtr\n\t" /* Set up >> IDT */ >> > "movl %%esp, (com32_internal_esp)\n\t" /* Save >> internal virtual address space ESP */ >> > "movl (com32_external_esp), %%esp\n\t" /* Switch >> to COM32 ESP (top of available memory) */ >> > "call _virt_to_phys\n\t" /* Switch >> to flat physical address space */ >> > + "sti\n\t" /* Enable >> interrupts */ >> > "pushl %0\n\t" /* Pointer >> to CDECL helper function */ >> > "pushl %1\n\t" /* Pointer >> to FAR call helper function */ >> > "pushl %2\n\t" /* Size of >> low memory bounce buffer */ >> > @@ -100,7 +110,9 @@ static int com32_exec ( struct image *image ) { >> > "pushl %5\n\t" /* Pointer >> to the command line arguments */ >> > "pushl $6\n\t" /* Number >> of additional arguments */ >> > "call *%6\n\t" /* Execute >> image */ >> > - "call _phys_to_virt\n\t" /* Switch >> back to internal virtual address space */ >> > + "cli\n\t" /* >> Disable interrupts */ >> > + "call _phys_to_virt\n\t" /* Switch >> back to internal virtual address space */ >> > + "lidt com32_internal_idtr\n\t" /* Switch >> back to internal IDT (for debugging) */ >> > "movl (com32_internal_esp), %%esp\n\t" /* Switch >> back to internal stack */ >> > : >> > : >> > @@ -216,6 +228,60 @@ static int comboot_load_image ( struct image *image >> ) { >> > } >> > >> > /** >> > + * Prepare COM32 Interrupt Descriptor Table and Interrupt Jump Buffer >> > + * @v image COM32 image >> > + * @ret rc Return status code >> > + */ >> > +static int comboot_prepare_idt ( struct image * image ) { >> > + struct idt_descriptor *idt; >> > + struct ijb_entry *ijb; >> > + physaddr_t com32_irq_wrapper_phys; >> > + userptr_t buffer; >> > + size_t memsz; >> > + int i, rc; >> > + >> > + buffer = phys_to_user ( COM32_IDT ); >> > + memsz = COM32_NUM_IDT_ENTRIES * sizeof ( struct idt_descriptor >> ); >> > + rc = prep_segment ( buffer, memsz, memsz ); >> > + if ( rc != 0 ) { >> > + DBGC ( image, "COM32 %p: could not prepare IDT segment: >> %s\n", >> > + image, strerror ( rc ) ); >> > + return rc; >> > + } >> > + >> > + buffer = phys_to_user ( COM32_IJB ); >> > + memsz = COM32_NUM_IDT_ENTRIES * sizeof ( struct ijb_entry ); >> > + rc = prep_segment ( buffer, memsz, memsz ); >> > + if ( rc != 0 ) { >> > + DBGC ( image, "COM32 %p: could not prepare IJB segment: >> %s\n", >> > + image, strerror ( rc ) ); >> > + return rc; >> > + } >> > + >> > + idt = phys_to_virt ( COM32_IDT ); >> > + ijb = phys_to_virt ( COM32_IJB ); >> > + com32_irq_wrapper_phys = virt_to_phys ( com32_irq_wrapper ); >> > + >> > + for ( i = 0; i < COM32_NUM_IDT_ENTRIES; i++ ) { >> > + uint32_t ijb_address = virt_to_phys ( &ijb[i] ); >> > + >> > + idt[i].offset_low = ijb_address & 0xFFFF; >> > + idt[i].selector = PHYSICAL_CS; >> > + idt[i].flags = IDT_INTERRUPT_GATE_FLAGS; >> > + idt[i].offset_high = ijb_address >> 16; >> > + >> > + ijb[i].pusha_instruction = IJB_PUSHA; >> > + ijb[i].mov_instruction = IJB_MOV_AL_IMM8; >> > + ijb[i].mov_value = i; >> > + ijb[i].jump_instruction = IJB_JMP_REL32; >> > + ijb[i].jump_destination = com32_irq_wrapper_phys - >> > + virt_to_phys ( &ijb[i + 1] ); >> > + } >> > + >> > + return 0; >> > +} >> > + >> > +/** >> > * Prepare COM32 low memory bounce buffer >> > * @v image COM32 image >> > * @ret rc Return status code >> > @@ -269,6 +335,11 @@ static int com32_load ( struct image *image ) { >> > return rc; >> > } >> > >> > + /* Set up IDT */ >> > + if ( ( rc = comboot_prepare_idt ( image ) ) != 0 ) { >> > + return rc; >> > + } >> > + >> > /* Prepare bounce buffer segment */ >> > if ( ( rc = comboot_prepare_bounce_buffer ( image ) ) != 0 ) { >> > return rc; >> > diff --git a/src/arch/i386/include/comboot.h >> b/src/arch/i386/include/comboot.h >> > index 1232f0a..ce6990d 100644 >> > --- a/src/arch/i386/include/comboot.h >> > +++ b/src/arch/i386/include/comboot.h >> > @@ -13,6 +13,50 @@ FILE_LICENCE ( GPL2_OR_LATER ); >> > #include <setjmp.h> >> > #include <gpxe/in.h> >> > >> > +/** Descriptor in a 32-bit IDT */ >> > +struct idt_descriptor { >> > + uint16_t offset_low; >> > + uint16_t selector; >> > + uint16_t flags; >> > + uint16_t offset_high; >> > +} PACKED; >> > + >> > +/** Operand for the LIDT instruction */ >> > +struct idt_register { >> > + uint16_t limit; >> > + uint32_t base; >> > +} PACKED; >> > + >> > +/** Entry in the interrupt jump buffer */ >> > +struct ijb_entry { >> > + uint8_t pusha_instruction; >> > + uint8_t mov_instruction; >> > + uint8_t mov_value; >> > + uint8_t jump_instruction; >> > + uint32_t jump_destination; >> > +} PACKED; >> > + >> > +/** The x86 opcode for "pushal" */ >> > +#define IJB_PUSHA 0x60 >> > + >> > +/** The x86 opcode for "movb $imm8,%al" */ >> > +#define IJB_MOV_AL_IMM8 0xB0 >> > + >> > +/** The x86 opcode for "jmp rel32" */ >> > +#define IJB_JMP_REL32 0xE9 >> > + >> > +/** Flags that specify a 32-bit interrupt gate with DPL=0 */ >> > +#define IDT_INTERRUPT_GATE_FLAGS 0x8E00 >> > + >> > +/** Address of COM32 interrupt descriptor table */ >> > +#define COM32_IDT 0x100000 >> > + >> > +/** Number of entries in a fully populated IDT */ >> > +#define COM32_NUM_IDT_ENTRIES 256 >> > + >> > +/** Address of COM32 interrupt jump buffer */ >> > +#define COM32_IJB 0x100800 >> > + >> > /** Segment used for COMBOOT PSP and image */ >> > #define COMBOOT_PSP_SEG 0x07C0 >> > >> > @@ -109,6 +153,7 @@ extern void unhook_comboot_interrupts ( ); >> > extern void com32_intcall_wrapper ( ); >> > extern void com32_farcall_wrapper ( ); >> > extern void com32_cfarcall_wrapper ( ); >> > +extern void com32_irq_wrapper ( ); >> > >> > /* Resolve a hostname to an (IPv4) address */ >> > extern int comboot_resolv ( const char *name, struct in_addr *address >> ); >> > diff --git a/src/arch/i386/interface/syslinux/com32_call.c >> b/src/arch/i386/interface/syslinux/com32_call.c >> > index d2c3f91..d271cc7 100644 >> > --- a/src/arch/i386/interface/syslinux/com32_call.c >> > +++ b/src/arch/i386/interface/syslinux/com32_call.c >> > @@ -188,3 +188,20 @@ int __asmcall com32_cfarcall ( uint32_t proc, >> physaddr_t stack, size_t stacksz ) >> > >> > return eax; >> > } >> > + >> > +/** >> > + * IRQ handler >> > + */ >> > +void __asmcall com32_irq ( uint32_t vector ) { >> > + uint32_t *ivt_entry = phys_to_virt( vector * 4 ); >> > + >> > + __asm__ __volatile__ ( >> > + REAL_CODE ( "pushfw\n\t" >> > + "pushw %%cs\n\t" >> > + "pushw $com32_irq_return\n\t" >> > + "pushl %0\n\t" >> > + "retf\n" >> > + "com32_irq_return:\n\t" ) >> > + : /* no outputs */ >> > + : "r" ( *ivt_entry ) ); >> > +} >> > diff --git a/src/arch/i386/interface/syslinux/com32_wrapper.S >> b/src/arch/i386/interface/syslinux/com32_wrapper.S >> > index 5c5bd13..84d1571 100644 >> > --- a/src/arch/i386/interface/syslinux/com32_wrapper.S >> > +++ b/src/arch/i386/interface/syslinux/com32_wrapper.S >> > @@ -22,6 +22,26 @@ FILE_LICENCE ( GPL2_OR_LATER ) >> > .arch i386 >> > .code32 >> > >> > + /* >> > + * This code is entered after running the following sequence out >> of >> > + * the interrupt jump buffer: >> > + * >> > + * pushal >> > + * movb $vector, %al >> > + * jmp com32_irq_wrapper >> > + */ >> > + >> > + .globl com32_irq_wrapper >> > +com32_irq_wrapper: >> > + >> > + movzxb %al,%eax >> > + pushl %eax >> > + movl $com32_irq, %eax >> > + call com32_wrapper >> > + popl %eax >> > + popal >> > + iret >> > + >> > .globl com32_farcall_wrapper >> > com32_farcall_wrapper: >> > >> > @@ -43,10 +63,14 @@ com32_intcall_wrapper: >> > /*jmp com32_wrapper*/ /* fall through */ >> > >> > com32_wrapper: >> > + cli >> > >> > /* Switch to internal virtual address space */ >> > call _phys_to_virt >> > >> > + /* Switch to internal IDT (if we have one for debugging) */ >> > + lidt com32_internal_idtr >> > + >> > mov %eax, (com32_helper_function) >> > >> > /* Save external COM32 stack pointer */ >> > @@ -74,9 +98,13 @@ com32_wrapper: >> > movl %esp, (com32_internal_esp) >> > movl (com32_external_esp), %esp >> > >> > + /* Switch to com32 IDT */ >> > + lidt com32_external_idtr >> > + >> > /* Switch to external flat physical address space */ >> > call _virt_to_phys >> > >> > + sti >> > ret >> > >> > >> > _______________________________________________ >> > gPXE-devel mailing list >> > [email protected] >> > http://etherboot.org/mailman/listinfo/gpxe-devel >> > >> > > _______________________________________________ gPXE-devel mailing list [email protected] http://etherboot.org/mailman/listinfo/gpxe-devel
