7f2569246c
Recent GCC compiles linuxboot_dma.c to 921 bytes, while CentOS 6 needs
1029 and clang needs 1527. Because the size of the ROM, rounded to the
next 512 bytes, must match, this causes the API to break between a <1K
ROM and one that is bigger.
We want to make the ROM 1.5 KB in size, but it's better to make clang
produce leaner ROMs, because currently it is worryingly close to the limit.
To fix this prevent clang's happy inlining (which -Os cannot prevent).
This only requires adding a noinline attribute.
Second, the patch makes sure that the ROM has enough padding to prevent
ABI breakage on different compilers. The size is now hardcoded in the file
that is passed to signrom.py, as was the case before commit 6f71b77
("scripts/signrom.py: Allow option ROM checksum script to write the size
header.", 2016-05-23); signrom.py however will still pad the input to
the requested size. This ensures that the padding goes beyond the
next multiple of 512 if necessary, and also avoids the need for
-fno-toplevel-reorder which clang doesn't support. signrom.py can then
error out if the requested size is too small for the actual size of the
compiled ROM.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
299 lines
8.0 KiB
C
299 lines
8.0 KiB
C
/*
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* Linux Boot Option ROM for fw_cfg DMA
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, see <http://www.gnu.org/licenses/>.
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*
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* Copyright (c) 2015-2016 Red Hat Inc.
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* Authors:
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* Marc Marí <marc.mari.barcelo@gmail.com>
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* Richard W.M. Jones <rjones@redhat.com>
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*/
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asm(
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".text\n"
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".global _start\n"
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"_start:\n"
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" .short 0xaa55\n"
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" .byte 3\n" /* desired size in 512 units; signrom.py adds padding */
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" .byte 0xcb\n" /* far return without prefix */
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" .org 0x18\n"
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" .short 0\n"
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" .short _pnph\n"
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"_pnph:\n"
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" .ascii \"$PnP\"\n"
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" .byte 0x01\n"
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" .byte (_pnph_len / 16)\n"
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" .short 0x0000\n"
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" .byte 0x00\n"
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" .byte 0x00\n"
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" .long 0x00000000\n"
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" .short _manufacturer\n"
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" .short _product\n"
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" .long 0x00000000\n"
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" .short 0x0000\n"
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" .short 0x0000\n"
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" .short _bev\n"
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" .short 0x0000\n"
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" .short 0x0000\n"
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" .equ _pnph_len, . - _pnph\n"
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"_manufacturer:\n"
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" .asciz \"QEMU\"\n"
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"_product:\n"
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" .asciz \"Linux loader DMA\"\n"
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" .align 4, 0\n"
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"_bev:\n"
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" cli\n"
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" cld\n"
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" jmp load_kernel\n"
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);
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#include "../../include/hw/nvram/fw_cfg_keys.h"
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/* QEMU_CFG_DMA_CONTROL bits */
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#define BIOS_CFG_DMA_CTL_ERROR 0x01
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#define BIOS_CFG_DMA_CTL_READ 0x02
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#define BIOS_CFG_DMA_CTL_SKIP 0x04
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#define BIOS_CFG_DMA_CTL_SELECT 0x08
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#define BIOS_CFG_DMA_ADDR_HIGH 0x514
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#define BIOS_CFG_DMA_ADDR_LOW 0x518
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#define uint64_t unsigned long long
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#define uint32_t unsigned int
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#define uint16_t unsigned short
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#define barrier() asm("" : : : "memory")
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typedef struct FWCfgDmaAccess {
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uint32_t control;
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uint32_t length;
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uint64_t address;
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} __attribute__((packed)) FWCfgDmaAccess;
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static inline void outl(uint32_t value, uint16_t port)
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{
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asm("outl %0, %w1" : : "a"(value), "Nd"(port));
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}
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static inline void set_es(void *addr)
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{
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uint32_t seg = (uint32_t)addr >> 4;
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asm("movl %0, %%es" : : "r"(seg));
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}
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#ifdef __clang__
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#define ADDR32
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#else
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#define ADDR32 "addr32 "
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#endif
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static inline uint16_t readw_es(uint16_t offset)
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{
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uint16_t val;
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asm(ADDR32 "movw %%es:(%1), %0" : "=r"(val) : "r"((uint32_t)offset));
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barrier();
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return val;
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}
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static inline uint32_t readl_es(uint16_t offset)
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{
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uint32_t val;
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asm(ADDR32 "movl %%es:(%1), %0" : "=r"(val) : "r"((uint32_t)offset));
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barrier();
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return val;
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}
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static inline void writel_es(uint16_t offset, uint32_t val)
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{
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barrier();
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asm(ADDR32 "movl %0, %%es:(%1)" : : "r"(val), "r"((uint32_t)offset));
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}
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static inline uint32_t bswap32(uint32_t x)
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{
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return
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((x & 0x000000ffU) << 24) |
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((x & 0x0000ff00U) << 8) |
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((x & 0x00ff0000U) >> 8) |
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((x & 0xff000000U) >> 24);
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}
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static inline uint64_t bswap64(uint64_t x)
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{
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return
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((x & 0x00000000000000ffULL) << 56) |
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((x & 0x000000000000ff00ULL) << 40) |
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((x & 0x0000000000ff0000ULL) << 24) |
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((x & 0x00000000ff000000ULL) << 8) |
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((x & 0x000000ff00000000ULL) >> 8) |
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((x & 0x0000ff0000000000ULL) >> 24) |
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((x & 0x00ff000000000000ULL) >> 40) |
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((x & 0xff00000000000000ULL) >> 56);
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}
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static inline uint64_t cpu_to_be64(uint64_t x)
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{
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return bswap64(x);
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}
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static inline uint32_t cpu_to_be32(uint32_t x)
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{
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return bswap32(x);
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}
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static inline uint32_t be32_to_cpu(uint32_t x)
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{
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return bswap32(x);
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}
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/* clang is happy to inline this function, and bloats the
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* ROM.
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*/
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static __attribute__((__noinline__))
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void bios_cfg_read_entry(void *buf, uint16_t entry, uint32_t len)
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{
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FWCfgDmaAccess access;
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uint32_t control = (entry << 16) | BIOS_CFG_DMA_CTL_SELECT
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| BIOS_CFG_DMA_CTL_READ;
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access.address = cpu_to_be64((uint64_t)(uint32_t)buf);
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access.length = cpu_to_be32(len);
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access.control = cpu_to_be32(control);
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barrier();
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outl(cpu_to_be32((uint32_t)&access), BIOS_CFG_DMA_ADDR_LOW);
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while (be32_to_cpu(access.control) & ~BIOS_CFG_DMA_CTL_ERROR) {
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barrier();
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}
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}
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/* Return top of memory using BIOS function E801. */
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static uint32_t get_e801_addr(void)
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{
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uint16_t ax, bx, cx, dx;
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uint32_t ret;
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asm("int $0x15\n"
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: "=a"(ax), "=b"(bx), "=c"(cx), "=d"(dx)
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: "a"(0xe801), "b"(0), "c"(0), "d"(0));
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/* Not SeaBIOS, but in theory a BIOS could return CX=DX=0 in which
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* case we need to use the result from AX & BX instead.
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*/
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if (cx == 0 && dx == 0) {
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cx = ax;
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dx = bx;
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}
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if (dx) {
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/* DX = extended memory above 16M, in 64K units.
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* Convert it to bytes and return.
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*/
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ret = ((uint32_t)dx + 256 /* 16M in 64K units */) << 16;
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} else {
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/* This is a fallback path for machines with <= 16MB of RAM,
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* which probably would never be the case, but deal with it
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* anyway.
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*
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* CX = extended memory between 1M and 16M, in kilobytes
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* Convert it to bytes and return.
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*/
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ret = ((uint32_t)cx + 1024 /* 1M in K */) << 10;
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}
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return ret;
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}
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/* Force the asm name without leading underscore, even on Win32. */
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extern void load_kernel(void) asm("load_kernel");
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void load_kernel(void)
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{
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void *setup_addr;
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void *initrd_addr;
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void *kernel_addr;
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void *cmdline_addr;
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uint32_t setup_size;
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uint32_t initrd_size;
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uint32_t kernel_size;
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uint32_t cmdline_size;
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uint32_t initrd_end_page, max_allowed_page;
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uint32_t segment_addr, stack_addr;
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bios_cfg_read_entry(&setup_addr, FW_CFG_SETUP_ADDR, 4);
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bios_cfg_read_entry(&setup_size, FW_CFG_SETUP_SIZE, 4);
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bios_cfg_read_entry(setup_addr, FW_CFG_SETUP_DATA, setup_size);
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set_es(setup_addr);
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/* For protocol < 0x203 we don't have initrd_max ... */
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if (readw_es(0x206) < 0x203) {
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/* ... so we assume initrd_max = 0x37ffffff. */
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writel_es(0x22c, 0x37ffffff);
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}
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bios_cfg_read_entry(&initrd_addr, FW_CFG_INITRD_ADDR, 4);
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bios_cfg_read_entry(&initrd_size, FW_CFG_INITRD_SIZE, 4);
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initrd_end_page = ((uint32_t)(initrd_addr + initrd_size) & -4096);
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max_allowed_page = (readl_es(0x22c) & -4096);
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if (initrd_end_page != 0 && max_allowed_page != 0 &&
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initrd_end_page != max_allowed_page) {
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/* Initrd at the end of memory. Compute better initrd address
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* based on e801 data
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*/
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initrd_addr = (void *)((get_e801_addr() - initrd_size) & -4096);
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writel_es(0x218, (uint32_t)initrd_addr);
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}
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bios_cfg_read_entry(initrd_addr, FW_CFG_INITRD_DATA, initrd_size);
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bios_cfg_read_entry(&kernel_addr, FW_CFG_KERNEL_ADDR, 4);
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bios_cfg_read_entry(&kernel_size, FW_CFG_KERNEL_SIZE, 4);
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bios_cfg_read_entry(kernel_addr, FW_CFG_KERNEL_DATA, kernel_size);
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bios_cfg_read_entry(&cmdline_addr, FW_CFG_CMDLINE_ADDR, 4);
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bios_cfg_read_entry(&cmdline_size, FW_CFG_CMDLINE_SIZE, 4);
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bios_cfg_read_entry(cmdline_addr, FW_CFG_CMDLINE_DATA, cmdline_size);
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/* Boot linux */
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segment_addr = ((uint32_t)setup_addr >> 4);
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stack_addr = (uint32_t)(cmdline_addr - setup_addr - 16);
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/* As we are changing critical registers, we cannot leave freedom to the
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* compiler.
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*/
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asm("movw %%ax, %%ds\n"
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"movw %%ax, %%es\n"
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"movw %%ax, %%fs\n"
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"movw %%ax, %%gs\n"
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"movw %%ax, %%ss\n"
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"movl %%ebx, %%esp\n"
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"addw $0x20, %%ax\n"
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"pushw %%ax\n" /* CS */
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"pushw $0\n" /* IP */
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/* Clear registers and jump to Linux */
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"xor %%ebx, %%ebx\n"
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"xor %%ecx, %%ecx\n"
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"xor %%edx, %%edx\n"
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"xor %%edi, %%edi\n"
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"xor %%ebp, %%ebp\n"
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"lretw\n"
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: : "a"(segment_addr), "b"(stack_addr));
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}
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