From ab969087da65e2f67a546cfc664901eda7029e36 Mon Sep 17 00:00:00 2001 From: Liam Merwick Date: Tue, 15 Jan 2019 12:18:06 +0000 Subject: [PATCH] pvh: Boot uncompressed kernel using direct boot ABI These changes (along with corresponding Linux kernel and qboot changes) enable a guest to be booted using the x86/HVM direct boot ABI. This commit adds a load_elfboot() routine to pass the size and location of the kernel entry point to qboot (which will fill in the start_info struct information needed to to boot the guest). Having loaded the ELF binary, load_linux() will run qboot which continues the boot. The address for the kernel entry point is read from an ELF Note in the uncompressed kernel binary by a helper routine passed to load_elf(). Co-developed-by: George Kennedy Signed-off-by: George Kennedy Signed-off-by: Liam Merwick Signed-off-by: Paolo Bonzini --- hw/i386/pc.c | 135 ++++++++++++++++++++++++++++++++++++++++++++++++++ include/elf.h | 10 ++++ 2 files changed, 145 insertions(+) diff --git a/hw/i386/pc.c b/hw/i386/pc.c index 1690b1935f..e39ef5caa1 100644 --- a/hw/i386/pc.c +++ b/hw/i386/pc.c @@ -54,6 +54,7 @@ #include "sysemu/qtest.h" #include "kvm_i386.h" #include "hw/xen/xen.h" +#include "hw/xen/start_info.h" #include "ui/qemu-spice.h" #include "exec/memory.h" #include "exec/address-spaces.h" @@ -110,6 +111,9 @@ static struct e820_entry *e820_table; static unsigned e820_entries; struct hpet_fw_config hpet_cfg = {.count = UINT8_MAX}; +/* Physical Address of PVH entry point read from kernel ELF NOTE */ +static size_t pvh_start_addr; + GlobalProperty pc_compat_3_1[] = { { "intel-iommu", "dma-drain", "off" }, { "Opteron_G3" "-" TYPE_X86_CPU, "rdtscp", "off" }, @@ -1069,6 +1073,109 @@ struct setup_data { uint8_t data[0]; } __attribute__((packed)); + +/* + * The entry point into the kernel for PVH boot is different from + * the native entry point. The PVH entry is defined by the x86/HVM + * direct boot ABI and is available in an ELFNOTE in the kernel binary. + * + * This function is passed to load_elf() when it is called from + * load_elfboot() which then additionally checks for an ELF Note of + * type XEN_ELFNOTE_PHYS32_ENTRY and passes it to this function to + * parse the PVH entry address from the ELF Note. + * + * Due to trickery in elf_opts.h, load_elf() is actually available as + * load_elf32() or load_elf64() and this routine needs to be able + * to deal with being called as 32 or 64 bit. + * + * The address of the PVH entry point is saved to the 'pvh_start_addr' + * global variable. (although the entry point is 32-bit, the kernel + * binary can be either 32-bit or 64-bit). + */ +static uint64_t read_pvh_start_addr(void *arg1, void *arg2, bool is64) +{ + size_t *elf_note_data_addr; + + /* Check if ELF Note header passed in is valid */ + if (arg1 == NULL) { + return 0; + } + + if (is64) { + struct elf64_note *nhdr64 = (struct elf64_note *)arg1; + uint64_t nhdr_size64 = sizeof(struct elf64_note); + uint64_t phdr_align = *(uint64_t *)arg2; + uint64_t nhdr_namesz = nhdr64->n_namesz; + + elf_note_data_addr = + ((void *)nhdr64) + nhdr_size64 + + QEMU_ALIGN_UP(nhdr_namesz, phdr_align); + } else { + struct elf32_note *nhdr32 = (struct elf32_note *)arg1; + uint32_t nhdr_size32 = sizeof(struct elf32_note); + uint32_t phdr_align = *(uint32_t *)arg2; + uint32_t nhdr_namesz = nhdr32->n_namesz; + + elf_note_data_addr = + ((void *)nhdr32) + nhdr_size32 + + QEMU_ALIGN_UP(nhdr_namesz, phdr_align); + } + + pvh_start_addr = *elf_note_data_addr; + + return pvh_start_addr; +} + +static bool load_elfboot(const char *kernel_filename, + int kernel_file_size, + uint8_t *header, + size_t pvh_xen_start_addr, + FWCfgState *fw_cfg) +{ + uint32_t flags = 0; + uint32_t mh_load_addr = 0; + uint32_t elf_kernel_size = 0; + uint64_t elf_entry; + uint64_t elf_low, elf_high; + int kernel_size; + + if (ldl_p(header) != 0x464c457f) { + return false; /* no elfboot */ + } + + bool elf_is64 = header[EI_CLASS] == ELFCLASS64; + flags = elf_is64 ? + ((Elf64_Ehdr *)header)->e_flags : ((Elf32_Ehdr *)header)->e_flags; + + if (flags & 0x00010004) { /* LOAD_ELF_HEADER_HAS_ADDR */ + error_report("elfboot unsupported flags = %x", flags); + exit(1); + } + + uint64_t elf_note_type = XEN_ELFNOTE_PHYS32_ENTRY; + kernel_size = load_elf(kernel_filename, read_pvh_start_addr, + NULL, &elf_note_type, &elf_entry, + &elf_low, &elf_high, 0, I386_ELF_MACHINE, + 0, 0); + + if (kernel_size < 0) { + error_report("Error while loading elf kernel"); + exit(1); + } + mh_load_addr = elf_low; + elf_kernel_size = elf_high - elf_low; + + if (pvh_start_addr == 0) { + error_report("Error loading uncompressed kernel without PVH ELF Note"); + exit(1); + } + fw_cfg_add_i32(fw_cfg, FW_CFG_KERNEL_ENTRY, pvh_start_addr); + fw_cfg_add_i32(fw_cfg, FW_CFG_KERNEL_ADDR, mh_load_addr); + fw_cfg_add_i32(fw_cfg, FW_CFG_KERNEL_SIZE, elf_kernel_size); + + return true; +} + static void load_linux(PCMachineState *pcms, FWCfgState *fw_cfg) { @@ -1108,6 +1215,34 @@ static void load_linux(PCMachineState *pcms, if (ldl_p(header+0x202) == 0x53726448) { protocol = lduw_p(header+0x206); } else { + /* + * Check if the file is an uncompressed kernel file (ELF) and load it, + * saving the PVH entry point used by the x86/HVM direct boot ABI. + * If load_elfboot() is successful, populate the fw_cfg info. + */ + if (load_elfboot(kernel_filename, kernel_size, + header, pvh_start_addr, fw_cfg)) { + struct hvm_modlist_entry ramdisk_mod = { 0 }; + + fclose(f); + + fw_cfg_add_i32(fw_cfg, FW_CFG_CMDLINE_SIZE, + strlen(kernel_cmdline) + 1); + fw_cfg_add_string(fw_cfg, FW_CFG_CMDLINE_DATA, kernel_cmdline); + + assert(machine->device_memory != NULL); + ramdisk_mod.paddr = machine->device_memory->base; + ramdisk_mod.size = + memory_region_size(&machine->device_memory->mr); + + fw_cfg_add_bytes(fw_cfg, FW_CFG_KERNEL_DATA, &ramdisk_mod, + sizeof(ramdisk_mod)); + fw_cfg_add_i32(fw_cfg, FW_CFG_SETUP_SIZE, sizeof(header)); + fw_cfg_add_bytes(fw_cfg, FW_CFG_SETUP_DATA, + header, sizeof(header)); + + return; + } /* This looks like a multiboot kernel. If it is, let's stop treating it like a Linux kernel. */ if (load_multiboot(fw_cfg, f, kernel_filename, initrd_filename, diff --git a/include/elf.h b/include/elf.h index e816fb4d76..b35347eee7 100644 --- a/include/elf.h +++ b/include/elf.h @@ -1640,6 +1640,16 @@ typedef struct elf64_shdr { #define NT_ARM_HW_WATCH 0x403 /* ARM hardware watchpoint registers */ #define NT_ARM_SYSTEM_CALL 0x404 /* ARM system call number */ +/* + * Physical entry point into the kernel. + * + * 32bit entry point into the kernel. When requested to launch the + * guest kernel, use this entry point to launch the guest in 32-bit + * protected mode with paging disabled. + * + * [ Corresponding definition in Linux kernel: include/xen/interface/elfnote.h ] + */ +#define XEN_ELFNOTE_PHYS32_ENTRY 18 /* 0x12 */ /* Note header in a PT_NOTE section */ typedef struct elf32_note { -- 2.39.2