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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v2 1/5] xen/x86: Introduce MultiBoot Data (MBD) type
On 24/09/14 18:19, Daniel Kiper wrote:
> Introduce MultiBoot Data (MBD) type. It is used to define variable
> which carry over data from multiboot protocol (any version) through
> Xen preloader stage. Later all or parts of this data is used
> to initialize boot_info structure. boot_info is introduced
> in later patches.
>
> MBD helps to break multiboot (v1) protocol dependency. Using it
> we are able to save space on trampoline (we do not allocate space
> for unused data what happens in current preloader implementation).
> Additionally, we are able to easily add new members to MBD if we
> want support for new features or protocols.
>
> There is not plan to share MBD among architectures. It will be
> nice if boot_info will be shared among architectures. Please
> check later patches for more details.
>
> Code found in xen/arch/x86/boot_info.c moves MBD data to mbi struct
> which is referenced from main Xen code. This is temporary solution
> which helps to split patches into logical parts. Later it will be
> replaced by final version of boot_info support.
>
> Signed-off-by: Daniel Kiper <daniel.kiper@xxxxxxxxxx>
Reviewing changes to ASM code is *very* hard, and this patch is still
very complicated.
Can I suggest patches split along the following lines.
* Shuffling of registers in head.S to end up with %eax and %ecx as
indended for reloc.c, and %ebx currently unclobbered, and adjusting
reloc.c for %ecx. Review for this is a simple case of verifying that
the changes are just a strict shuffling of registers.
* Whitespace and misc non-MBD cleanup to reloc.c
* Altering existing helper functions in preparation for MBD support
* Actually introduce mbd_t and use it.
In addition, I have some specific comments about the changes themselves.
> ---
> v2 - suggestions/fixes:
> - improve inline assembly
> (suggested by Andrew Cooper and Jan Beulich),
> - use __used attribute
> (suggested by Andrew Cooper),
> - patch split rearrangement
> (suggested by Andrew Cooper and Jan Beulich).
> ---
> xen/arch/x86/Makefile | 1 +
> xen/arch/x86/boot/cmdline.S | 9 +--
> xen/arch/x86/boot/head.S | 31 ++++----
> xen/arch/x86/boot/reloc.c | 147
> +++++++++++++++++++++++++------------
> xen/arch/x86/boot/x86_64.S | 10 ++-
> xen/arch/x86/boot_info.c | 58 +++++++++++++++
> xen/arch/x86/setup.c | 41 +++++++----
> xen/arch/x86/x86_64/asm-offsets.c | 5 +-
> xen/include/asm-x86/mbd.h | 70 ++++++++++++++++++
> 9 files changed, 284 insertions(+), 88 deletions(-)
> create mode 100644 xen/arch/x86/boot_info.c
> create mode 100644 xen/include/asm-x86/mbd.h
>
> diff --git a/xen/arch/x86/Makefile b/xen/arch/x86/Makefile
> index c1e244d..c465bb3 100644
> --- a/xen/arch/x86/Makefile
> +++ b/xen/arch/x86/Makefile
> @@ -42,6 +42,7 @@ obj-y += numa.o
> obj-y += pci.o
> obj-y += percpu.o
> obj-y += physdev.o
> +obj-y += boot_info.o
> obj-y += setup.o
> obj-y += shutdown.o
> obj-y += smp.o
> diff --git a/xen/arch/x86/boot/cmdline.S b/xen/arch/x86/boot/cmdline.S
> index 00687eb..7316011 100644
> --- a/xen/arch/x86/boot/cmdline.S
> +++ b/xen/arch/x86/boot/cmdline.S
> @@ -152,17 +152,14 @@ cmdline_parse_early:
> pusha
>
> /* Bail if there is no command line to parse. */
> - mov sym_phys(multiboot_ptr),%ebx
> - mov MB_flags(%ebx),%eax
> - test $4,%al
> - jz .Lcmdline_exit
> - mov MB_cmdline(%ebx),%eax
> + mov sym_phys(mbd_ptr),%ebx
As you are already changing the name of this symbol, please call it
mbd_pa or something to indicate that it genuinely is a physical address,
not a pointer in the C sense of the term.
> + mov MBD_cmdline(%ebx),%eax
> test %eax,%eax
> jz .Lcmdline_exit
>
> /* Check for 'no-real-mode' command-line option. */
> pushl $sym_phys(.Lno_rm_opt)
> - pushl MB_cmdline(%ebx)
> + pushl MBD_cmdline(%ebx)
> call .Lfind_option
> test %eax,%eax
> setnz %al
> diff --git a/xen/arch/x86/boot/head.S b/xen/arch/x86/boot/head.S
> index 10ecf51..79bce3c 100644
> --- a/xen/arch/x86/boot/head.S
> +++ b/xen/arch/x86/boot/head.S
> @@ -86,14 +86,14 @@ __start:
> jne not_multiboot
>
> /* Set up trampoline segment 64k below EBDA */
> - movzwl 0x40e,%eax /* EBDA segment */
> - cmp $0xa000,%eax /* sanity check (high) */
> + movzwl 0x40e,%ecx /* EBDA segment */
> + cmp $0xa000,%ecx /* sanity check (high) */
> jae 0f
> - cmp $0x4000,%eax /* sanity check (low) */
> + cmp $0x4000,%ecx /* sanity check (low) */
> jae 1f
> 0:
> - movzwl 0x413,%eax /* use base memory size on failure */
> - shl $10-4,%eax
> + movzwl 0x413,%ecx /* use base memory size on failure */
> + shl $10-4,%ecx
> 1:
> /*
> * Compare the value in the BDA with the information from the
> @@ -105,22 +105,23 @@ __start:
> cmp $0x100,%edx /* is the multiboot value too small? */
> jb 2f /* if so, do not use it */
> shl $10-4,%edx
> - cmp %eax,%edx /* compare with BDA value */
> - cmovb %edx,%eax /* and use the smaller */
> + cmp %ecx,%edx /* compare with BDA value */
> + cmovb %edx,%ecx /* and use the smaller */
>
> 2: /* Reserve 64kb for the trampoline */
> - sub $0x1000,%eax
> + sub $0x1000,%ecx
>
> /* From arch/x86/smpboot.c: start_eip had better be page-aligned! */
> - xor %al, %al
> - shl $4, %eax
> - mov %eax,sym_phys(trampoline_phys)
> + xor %cl, %cl
> + shl $4, %ecx
> + mov %ecx,sym_phys(trampoline_phys)
>
> - /* Save the Multiboot info struct (after relocation) for later use.
> */
> + /* Save the Multiboot data (after relocation) for later use. */
> mov $sym_phys(cpu0_stack)+1024,%esp
> - push %ebx
> - call reloc
> - mov %eax,sym_phys(multiboot_ptr)
> + push %eax /* Multiboot magic */
> + push %ebx /* Multiboot information address */
> + call reloc /* %ecx contains trampoline address */
> + mov %eax,sym_phys(mbd_ptr)
>
> /* Initialize BSS (no nasty surprises!) */
> mov $sym_phys(__bss_start),%edi
> diff --git a/xen/arch/x86/boot/reloc.c b/xen/arch/x86/boot/reloc.c
> index fa0fb6b..35a991e 100644
> --- a/xen/arch/x86/boot/reloc.c
> +++ b/xen/arch/x86/boot/reloc.c
> @@ -1,40 +1,58 @@
> -/******************************************************************************
> +/*
> * reloc.c
> - *
> + *
> * 32-bit flat memory-map routines for relocating Multiboot structures
> * and modules. This is most easily done early with paging disabled.
> - *
> + *
> * Copyright (c) 2009, Citrix Systems, Inc.
> - *
> + * Copyright (c) 2013, 2014 Oracle Co., Daniel Kiper
> + *
> * Authors:
> * Keir Fraser <keir@xxxxxxx>
> + * Daniel Kiper
> */
>
> -/* entered with %eax = BOOT_TRAMPOLINE */
> +typedef unsigned char u8;
> +typedef unsigned short u16;
> +typedef unsigned long u32;
> +typedef unsigned long long u64;
> +
> +#include "../../../include/xen/compiler.h"
> +#include "../../../include/xen/multiboot.h"
> +
> +#include "../../../include/asm/mbd.h"
How about playing with -I for this file in the Makefile to allow
#include <xen/compiler.h> and so ?
> +
> +/*
> + * __HERE__ IS ENTRY POINT!!!
I am still of the firm opinion that anyone capable of editing this file
ought to know understand the _start symbol, making this comment useless.
> + *
> + * It is entered from xen/arch/x86/boot/head.S with:
> + * - %eax = MULTIBOOT_MAGIC,
> + * - %ebx = MULTIBOOT_INFORMATION_ADDRESS,
> + * - %ecx = BOOT_TRAMPOLINE.
> + */
> asm (
> " .text \n"
> " .globl _start \n"
> "_start: \n"
> " call 1f \n"
> "1: pop %ebx \n"
> - " mov %eax,alloc-1b(%ebx) \n"
> - " jmp reloc \n"
> + " mov %ecx,alloc-1b(%ebx) \n"
> + " jmp __reloc \n"
> );
>
> -/* This is our data. Because the code must be relocatable, no BSS is
> - * allowed. All data is accessed PC-relative with inline assembly.
> +/*
> + * This is our data. Because the code must be relocatable, no BSS is
> + * allowed. All data is accessed PC-relative with inline assembly.
> */
> asm (
> "alloc: \n"
> " .long 0 \n"
> );
>
> -typedef unsigned int u32;
> -#include "../../../include/xen/multiboot.h"
> -
> -static void *reloc_mbi_struct(void *old, unsigned int bytes)
> +static u32 alloc_struct(u32 bytes)
> {
> - void *new;
> + u32 s;
> +
> asm(
> " call 1f \n"
> "1: pop %%edx \n"
> @@ -42,58 +60,95 @@ static void *reloc_mbi_struct(void *old, unsigned int
> bytes)
> " sub %1,%0 \n"
> " and $~15,%0 \n"
> " mov %0,alloc-1b(%%edx) \n"
> - " mov %0,%%edi \n"
> + : "=&r" (s) : "r" (bytes) : "edx");
> +
> + return s;
> +}
> +
> +static void zero_struct(u32 s, u32 bytes)
> +{
> + asm volatile(
> + " rep stosb \n"
> + : "+D" (s), "+c" (bytes) : "a" (0));
> +}
> +
> +static u32 copy_struct(u32 src, u32 bytes)
> +{
> + u32 dst, dst_asm;
> +
> + dst = alloc_struct(bytes);
> + dst_asm = dst;
> +
> + asm volatile(
> " rep movsb \n"
> - : "=&r" (new), "+c" (bytes), "+S" (old)
> - : : "edx", "edi");
> - return new;
> + : "+S" (src), "+D" (dst_asm), "+c" (bytes));
> +
> + return dst;
> }
>
> -static char *reloc_mbi_string(char *old)
> +static u32 copy_string(u32 src)
> {
> char *p;
> - for ( p = old; *p != '\0'; p++ )
> +
> + if ( src == 0 )
> + return 0;
> +
> + for ( p = (char *)src; *p != '\0'; p++ )
> continue;
> - return reloc_mbi_struct(old, p - old + 1);
> +
> + return copy_struct(src, p - (char *)src + 1);
> }
>
> -multiboot_info_t *reloc(multiboot_info_t *mbi_old)
> +static mbd_t *mb_mbd(mbd_t *mbd, multiboot_info_t *mbi)
> {
> - multiboot_info_t *mbi = reloc_mbi_struct(mbi_old, sizeof(*mbi));
> - int i;
> + boot_module_t *mbd_mods;
> + module_t *mbi_mods;
> + u32 i;
> +
> + if ( mbi->flags & MBI_LOADERNAME )
> + mbd->boot_loader_name = copy_string(mbi->boot_loader_name);
>
> if ( mbi->flags & MBI_CMDLINE )
> - mbi->cmdline = (u32)reloc_mbi_string((char *)mbi->cmdline);
> + mbd->cmdline = copy_string(mbi->cmdline);
> +
> + if ( mbi->flags & MBI_MEMLIMITS )
> + {
> + mbd->mem_lower = mbi->mem_lower;
> + mbd->mem_upper = mbi->mem_upper;
> + }
> +
> + if ( mbi->flags & MBI_MEMMAP )
> + {
> + mbd->mmap_size = mbi->mmap_length;
> + mbd->mmap = copy_struct(mbi->mmap_addr, mbi->mmap_length);
> + }
>
> if ( mbi->flags & MBI_MODULES )
> {
> - module_t *mods = reloc_mbi_struct(
> - (module_t *)mbi->mods_addr, mbi->mods_count * sizeof(module_t));
> + mbd->mods_nr = mbi->mods_count;
> + mbd->mods = alloc_struct(mbi->mods_count * sizeof(boot_module_t));
>
> - mbi->mods_addr = (u32)mods;
> + mbi_mods = (module_t *)mbi->mods_addr;
> + mbd_mods = (boot_module_t *)mbd->mods;
>
> for ( i = 0; i < mbi->mods_count; i++ )
> {
> - if ( mods[i].string )
> - mods[i].string = (u32)reloc_mbi_string((char
> *)mods[i].string);
> + mbd_mods[i].start = mbi_mods[i].mod_start;
> + mbd_mods[i].end = mbi_mods[i].mod_end;
> + mbd_mods[i].cmdline = copy_string(mbi_mods[i].string);
> + mbd_mods[i].relocated = 0;
> }
> }
>
> - if ( mbi->flags & MBI_MEMMAP )
> - mbi->mmap_addr = (u32)reloc_mbi_struct(
> - (memory_map_t *)mbi->mmap_addr, mbi->mmap_length);
> + return mbd;
> +}
>
> - if ( mbi->flags & MBI_LOADERNAME )
> - mbi->boot_loader_name = (u32)reloc_mbi_string(
> - (char *)mbi->boot_loader_name);
> -
> - /* Mask features we don't understand or don't relocate. */
> - mbi->flags &= (MBI_MEMLIMITS |
> - MBI_BOOTDEV |
> - MBI_CMDLINE |
> - MBI_MODULES |
> - MBI_MEMMAP |
> - MBI_LOADERNAME);
> -
> - return mbi;
> +static mbd_t __used *__reloc(void *mbi, u32 mb_magic)
> +{
> + mbd_t *mbd;
> +
> + mbd = (mbd_t *)alloc_struct(sizeof(mbd_t));
> + zero_struct((u32)mbd, sizeof(mbd_t));
> +
> + return mb_mbd(mbd, mbi);
> }
> diff --git a/xen/arch/x86/boot/x86_64.S b/xen/arch/x86/boot/x86_64.S
> index bfbafd2..34243b1 100644
> --- a/xen/arch/x86/boot/x86_64.S
> +++ b/xen/arch/x86/boot/x86_64.S
> @@ -29,8 +29,12 @@
> test %ebx,%ebx
> jnz start_secondary
>
> - /* Pass off the Multiboot info structure to C land. */
> - mov multiboot_ptr(%rip),%edi
> + /* Init boot_info. */
> + mov mbd_ptr(%rip),%edi
> + call __init_boot_info
> +
> + /* Pass off the boot_info to C land. */
> + movq %rax,%rdi
> call __start_xen
> ud2 /* Force a panic (invalid opcode). */
>
> @@ -38,7 +42,7 @@
>
> .data
> .align 8
> -multiboot_ptr:
> +mbd_ptr:
> .long 0
>
> .word 0
> diff --git a/xen/arch/x86/boot_info.c b/xen/arch/x86/boot_info.c
> new file mode 100644
> index 0000000..70830c2
> --- /dev/null
> +++ b/xen/arch/x86/boot_info.c
> @@ -0,0 +1,58 @@
> +/*
> + * Copyright (c) 2013, 2014 Oracle Co., Daniel Kiper
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License along
> + * with this program. If not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#include <xen/types.h>
> +#include <xen/init.h>
> +#include <xen/multiboot.h>
> +
> +#include <asm/mbd.h>
> +#include <asm/page.h>
> +
> +static multiboot_info_t mbi = {};
"= {}" is redundant for a static declaration.
> +
> +extern void enable_exception_support(void);
> +
> +unsigned long __init __init_boot_info(u32 mbd_ptr)
> +{
> + mbd_t *mbd = __va(mbd_ptr);
> +
> + enable_exception_support();
> +
> + if ( mbd->boot_loader_name ) {
> + mbi.flags = MBI_LOADERNAME;
> + mbi.boot_loader_name = mbd->boot_loader_name;
> + }
> +
> + if ( mbd->cmdline ) {
> + mbi.flags |= MBI_CMDLINE;
> + mbi.cmdline = mbd->cmdline;
> + }
> +
> + mbi.flags |= MBI_MEMLIMITS;
> + mbi.mem_lower = mbd->mem_lower;
> + mbi.mem_upper = mbd->mem_upper;
> +
> + mbi.flags |= MBI_MEMMAP;
> + mbi.mmap_length = mbd->mmap_size;
> + mbi.mmap_addr = mbd->mmap;
> +
> + mbi.flags |= MBI_MODULES;
> + mbi.mods_count = mbd->mods_nr;
> + mbi.mods_addr = mbd->mods;
> +
> + return __pa(&mbi);
> +}
> diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
> index 6a814cd..9391efa 100644
> --- a/xen/arch/x86/setup.c
> +++ b/xen/arch/x86/setup.c
> @@ -539,6 +539,25 @@ static char * __init cmdline_cook(char *p, char
> *loader_name)
> return p;
> }
>
> +void __init enable_exception_support(void)
> +{
> + /* Critical region without IDT or TSS. Any fault is deadly! */
> +
> + set_processor_id(0);
> + set_current((struct vcpu *)0xfffff000); /* debug sanity. */
> + idle_vcpu[0] = current;
> +
> + percpu_init_areas();
> +
> + init_idt_traps();
> + load_system_tables();
> +
> + smp_prepare_boot_cpu();
> + sort_exception_tables();
> +
> + /* Full exception support from here on in. */
> +}
> +
> void __init noreturn __start_xen(unsigned long mbi_p)
> {
> char *memmap_type = NULL;
> @@ -556,21 +575,13 @@ void __init noreturn __start_xen(unsigned long mbi_p)
> .stop_bits = 1
> };
>
> - /* Critical region without IDT or TSS. Any fault is deadly! */
> -
> - set_processor_id(0);
> - set_current((struct vcpu *)0xfffff000); /* debug sanity. */
> - idle_vcpu[0] = current;
> -
> - percpu_init_areas();
> -
> - init_idt_traps();
> - load_system_tables();
> -
> - smp_prepare_boot_cpu();
> - sort_exception_tables();
> -
> - /* Full exception support from here on in. */
> + if ( !efi_enabled ) {
> + /* Exception support was enabled before __start_xen() call. */
> + }
> + else
> + {
> + enable_exception_support();
> + }
For this, absolutely not.
Pass mbi_pa into __start_xen() and have __start_xen() call
__init_boot_info() after it has set up exception support. None of the
contents of MBD are needed beforehand.
>
> loader = (mbi->flags & MBI_LOADERNAME)
> ? (char *)__va(mbi->boot_loader_name) : "unknown";
> diff --git a/xen/arch/x86/x86_64/asm-offsets.c
> b/xen/arch/x86/x86_64/asm-offsets.c
> index 3994f4d..2123eb3 100644
> --- a/xen/arch/x86/x86_64/asm-offsets.c
> +++ b/xen/arch/x86/x86_64/asm-offsets.c
> @@ -12,7 +12,7 @@
> #include <compat/xen.h>
> #include <asm/fixmap.h>
> #include <asm/hardirq.h>
> -#include <xen/multiboot.h>
> +#include <asm/mbd.h>
>
> #define DEFINE(_sym, _val) \
> asm volatile ("\n.ascii\"==>#define " #_sym " %0 /* " #_val " */<==\"" \
> @@ -163,6 +163,5 @@ void __dummy__(void)
> OFFSET(CPUINFO_features, struct cpuinfo_x86, x86_capability);
> BLANK();
>
> - OFFSET(MB_flags, multiboot_info_t, flags);
> - OFFSET(MB_cmdline, multiboot_info_t, cmdline);
> + OFFSET(MBD_cmdline, mbd_t, cmdline);
> }
> diff --git a/xen/include/asm-x86/mbd.h b/xen/include/asm-x86/mbd.h
> new file mode 100644
> index 0000000..96e3044
> --- /dev/null
> +++ b/xen/include/asm-x86/mbd.h
> @@ -0,0 +1,70 @@
> +/*
> + * Copyright (c) 2013, 2014 Oracle Co., Daniel Kiper
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License along
> + * with this program. If not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#ifndef __MBD_H__
> +#define __MBD_H__
#include <xen/types.h>
Do not rely on the translation using including this file to make u32
available for you.
> +
> +/* Module type. */
> +typedef struct {
> + u32 start;
> + u32 end;
> +
> + /* Pointer to a module command line. */
> + u32 cmdline;
> +
> + /* If relocated != 0 then a given module was relocated. */
> + u32 relocated;
> +} boot_module_t;
> +
> +/*
> + * MultiBoot Data (MBD) type. It is used to define variable which
> + * carry over data from multiboot protocol (any version) through
> + * Xen preloader stage. Later all or parts of this data is used
> + * to initialize boot_info structure.
> + */
> +typedef struct {
> + /* Pointer to boot loader name. */
> + u32 boot_loader_name;
> +
> + /* Pointer to Xen command line. */
> + u32 cmdline;
These need to be very clear about being physical addresses rather than
pointers.
~Andrew
> +
> + /*
> + * Amount of lower memory (in KiB) accordingly to The Multiboot
> + * Specification version 0.6.96.
> + */
> + u32 mem_lower;
> +
> + /*
> + * Amount of upper memory (in KiB) accordingly to The Multiboot
> + * Specification version 0.6.96.
> + */
> + u32 mem_upper;
> +
> + /* Size (in bytes) of memory map provided by bootloader. */
> + u32 mmap_size;
> +
> + /* Pointer to memory map provided by bootloader. */
> + u32 mmap;
> +
> + /* Number of modules. */
> + u32 mods_nr;
> +
> + /* Pointer to modules description (boot_module_t *). */
> + u32 mods;
> +} mbd_t;
> +#endif /* __MBD_H__ */
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