Messages in this thread | | | Date | Wed, 8 Feb 2023 15:43:14 -0500 | From | "Michael S. Tsirkin" <> | Subject | Re: [PATCH] x86: temporarily remove all attempts to provide setup_data |
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On Wed, Feb 08, 2023 at 03:08:35PM -0300, Jason A. Donenfeld wrote: > All attempts at providing setup_data have been made as an iteration on > whatever was there before, stretching back to the original > implementation used for DTBs that [mis]used the kernel image itself. > We've now had a dozen rounds of bugs and hacks, and the result is > turning into a pile of unmaintainable and increasingly brittle hacks. > > Let's just rip out all the madness and start over. We can re-architect > this based on having a separate standalone setup_data file, which is how > it should have been done in the first place. This is a larger project > with a few things to coordinate, but we can't really begin thinking > about that while trying to play whack-a-mole with the current buggy > implementation. > > So this commit removes the setup_data setting from x86_load_linux(), > while leaving intact the infrastructure we'll need in the future to try > again. > > Cc: Michael S. Tsirkin <mst@redhat.com> > Cc: Dov Murik <dovmurik@linux.ibm.com> > Cc: Tom Lendacky <thomas.lendacky@amd.com> > Cc: Gerd Hoffmann <kraxel@redhat.com> > Cc: Daniel P. Berrangé <berrange@redhat.com> > Cc: Paolo Bonzini <pbonzini@redhat.com> > Cc: Richard Henderson <richard.henderson@linaro.org> > Cc: H. Peter Anvin <hpa@zytor.com> > Cc: Philippe Mathieu-Daudé <philmd@linaro.org> > Cc: Nathan Chancellor <nathan@kernel.org> > Cc: Borislav Petkov <bp@alien8.de> > Cc: Eric Biggers <ebiggers@kernel.org> > Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
So I think we have:
Fixes: 67f7e426e5 ("hw/i386: pass RNG seed via setup_data entry") Fixes: eac7a7791b ("x86: don't let decompressed kernel image clobber setup_data") Fixes: 14b29fea74 ("x86: do not re-randomize RNG seed on snapshot load") Fixes: cc63374a5a ("x86: re-initialize RNG seed when selecting kernel") Fixes: 763a2828bf ("x86: reinitialize RNG seed on system reboot") Fixes: eebb38a563 ("x86: use typedef for SetupData struct") Fixes: e935b73508 ("x86: return modified setup_data only if read as memory, not as file")
> --- > hw/i386/microvm.c | 15 ++---- > hw/i386/x86.c | 120 +++++----------------------------------------- > 2 files changed, 17 insertions(+), 118 deletions(-) > > diff --git a/hw/i386/microvm.c b/hw/i386/microvm.c > index 29f30dd6d3..170a331e3f 100644 > --- a/hw/i386/microvm.c > +++ b/hw/i386/microvm.c > @@ -378,8 +378,7 @@ static void microvm_fix_kernel_cmdline(MachineState *machine) > MicrovmMachineState *mms = MICROVM_MACHINE(machine); > BusState *bus; > BusChild *kid; > - char *cmdline, *existing_cmdline; > - size_t len; > + char *cmdline; > > /* > * Find MMIO transports with attached devices, and add them to the kernel > @@ -388,8 +387,7 @@ static void microvm_fix_kernel_cmdline(MachineState *machine) > * Yes, this is a hack, but one that heavily improves the UX without > * introducing any significant issues. > */ > - existing_cmdline = fw_cfg_read_bytes_ptr(x86ms->fw_cfg, FW_CFG_CMDLINE_DATA); > - cmdline = g_strdup(existing_cmdline); > + cmdline = g_strdup(machine->kernel_cmdline); > bus = sysbus_get_default(); > QTAILQ_FOREACH(kid, &bus->children, sibling) { > DeviceState *dev = kid->child; > @@ -413,12 +411,9 @@ static void microvm_fix_kernel_cmdline(MachineState *machine) > } > } > > - len = strlen(cmdline); > - if (len > VIRTIO_CMDLINE_TOTAL_MAX_LEN + strlen(existing_cmdline)) { > - fprintf(stderr, "qemu: virtio mmio cmdline too large, skipping\n"); > - } else { > - memcpy(existing_cmdline, cmdline, len + 1); > - } > + fw_cfg_modify_i32(x86ms->fw_cfg, FW_CFG_CMDLINE_SIZE, strlen(cmdline) + 1); > + fw_cfg_modify_string(x86ms->fw_cfg, FW_CFG_CMDLINE_DATA, cmdline); > + > g_free(cmdline); > } > > diff --git a/hw/i386/x86.c b/hw/i386/x86.c > index eaff4227bd..6cfdca9acd 100644 > --- a/hw/i386/x86.c > +++ b/hw/i386/x86.c > @@ -50,7 +50,6 @@ > #include "hw/intc/i8259.h" > #include "hw/rtc/mc146818rtc.h" > #include "target/i386/sev.h" > -#include "hw/i386/microvm.h" > > #include "hw/acpi/cpu_hotplug.h" > #include "hw/irq.h" > @@ -770,30 +769,6 @@ static bool load_elfboot(const char *kernel_filename, > return true; > } > > -typedef struct SetupDataFixup { > - void *pos; > - hwaddr orig_val, new_val; > - uint32_t addr; > -} SetupDataFixup; > - > -static void fixup_setup_data(void *opaque) > -{ > - SetupDataFixup *fixup = opaque; > - stq_p(fixup->pos, fixup->new_val); > -} > - > -static void reset_setup_data(void *opaque) > -{ > - SetupDataFixup *fixup = opaque; > - stq_p(fixup->pos, fixup->orig_val); > -} > - > -static void reset_rng_seed(void *opaque) > -{ > - SetupData *setup_data = opaque; > - qemu_guest_getrandom_nofail(setup_data->data, le32_to_cpu(setup_data->len)); > -} > - > void x86_load_linux(X86MachineState *x86ms, > FWCfgState *fw_cfg, > int acpi_data_size, > @@ -803,29 +778,20 @@ void x86_load_linux(X86MachineState *x86ms, > bool linuxboot_dma_enabled = X86_MACHINE_GET_CLASS(x86ms)->fwcfg_dma_enabled; > uint16_t protocol; > int setup_size, kernel_size, cmdline_size; > - int dtb_size, setup_data_offset; > uint32_t initrd_max; > uint8_t header[8192], *setup, *kernel; > - hwaddr real_addr, prot_addr, cmdline_addr, initrd_addr = 0, first_setup_data = 0; > + hwaddr real_addr, prot_addr, cmdline_addr, initrd_addr = 0; > FILE *f; > char *vmode; > MachineState *machine = MACHINE(x86ms); > - SetupData *setup_data; > const char *kernel_filename = machine->kernel_filename; > const char *initrd_filename = machine->initrd_filename; > - const char *dtb_filename = machine->dtb; > - char *kernel_cmdline; > + const char *kernel_cmdline = machine->kernel_cmdline; > SevKernelLoaderContext sev_load_ctx = {}; > enum { RNG_SEED_LENGTH = 32 }; > > - /* > - * Add the NUL terminator, some padding for the microvm cmdline fiddling > - * hack, and then align to 16 bytes as a paranoia measure > - */ > - cmdline_size = (strlen(machine->kernel_cmdline) + 1 + > - VIRTIO_CMDLINE_TOTAL_MAX_LEN + 16) & ~15; > - /* Make a copy, since we might append arbitrary bytes to it later. */ > - kernel_cmdline = g_strndup(machine->kernel_cmdline, cmdline_size); > + /* Align to 16 bytes as a paranoia measure */ > + cmdline_size = (strlen(kernel_cmdline) + 16) & ~15; > > /* load the kernel header */ > f = fopen(kernel_filename, "rb"); > @@ -966,6 +932,12 @@ void x86_load_linux(X86MachineState *x86ms, > initrd_max = x86ms->below_4g_mem_size - acpi_data_size - 1; > } > > + fw_cfg_add_i32(fw_cfg, FW_CFG_CMDLINE_ADDR, cmdline_addr); > + 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); > + sev_load_ctx.cmdline_data = (char *)kernel_cmdline; > + sev_load_ctx.cmdline_size = strlen(kernel_cmdline) + 1; > + > if (protocol >= 0x202) { > stl_p(header + 0x228, cmdline_addr); > } else { > @@ -1078,81 +1050,13 @@ void x86_load_linux(X86MachineState *x86ms, > } > fclose(f); > > - /* append dtb to kernel */ > - if (dtb_filename) { > - if (protocol < 0x209) { > - fprintf(stderr, "qemu: Linux kernel too old to load a dtb\n"); > - exit(1); > - } > - > - dtb_size = get_image_size(dtb_filename); > - if (dtb_size <= 0) { > - fprintf(stderr, "qemu: error reading dtb %s: %s\n", > - dtb_filename, strerror(errno)); > - exit(1); > - } > - > - setup_data_offset = cmdline_size; > - cmdline_size += sizeof(SetupData) + dtb_size; > - kernel_cmdline = g_realloc(kernel_cmdline, cmdline_size); > - setup_data = (void *)kernel_cmdline + setup_data_offset; > - setup_data->next = cpu_to_le64(first_setup_data); > - first_setup_data = cmdline_addr + setup_data_offset; > - setup_data->type = cpu_to_le32(SETUP_DTB); > - setup_data->len = cpu_to_le32(dtb_size); > - load_image_size(dtb_filename, setup_data->data, dtb_size); > - } > - > - if (!legacy_no_rng_seed && protocol >= 0x209) { > - setup_data_offset = cmdline_size; > - cmdline_size += sizeof(SetupData) + RNG_SEED_LENGTH; > - kernel_cmdline = g_realloc(kernel_cmdline, cmdline_size); > - setup_data = (void *)kernel_cmdline + setup_data_offset; > - setup_data->next = cpu_to_le64(first_setup_data); > - first_setup_data = cmdline_addr + setup_data_offset; > - setup_data->type = cpu_to_le32(SETUP_RNG_SEED); > - setup_data->len = cpu_to_le32(RNG_SEED_LENGTH); > - qemu_guest_getrandom_nofail(setup_data->data, RNG_SEED_LENGTH); > - qemu_register_reset_nosnapshotload(reset_rng_seed, setup_data); > - fw_cfg_add_bytes_callback(fw_cfg, FW_CFG_KERNEL_DATA, reset_rng_seed, NULL, > - setup_data, kernel, kernel_size, true); > - } else { > - fw_cfg_add_bytes(fw_cfg, FW_CFG_KERNEL_DATA, kernel, kernel_size); > - } > - > - fw_cfg_add_i32(fw_cfg, FW_CFG_CMDLINE_ADDR, cmdline_addr); > - fw_cfg_add_i32(fw_cfg, FW_CFG_CMDLINE_SIZE, cmdline_size); > - fw_cfg_add_bytes(fw_cfg, FW_CFG_CMDLINE_DATA, kernel_cmdline, cmdline_size); > - sev_load_ctx.cmdline_data = (char *)kernel_cmdline; > - sev_load_ctx.cmdline_size = cmdline_size; > - > + fw_cfg_add_bytes(fw_cfg, FW_CFG_KERNEL_DATA, kernel, kernel_size); > fw_cfg_add_i32(fw_cfg, FW_CFG_KERNEL_ADDR, prot_addr); > fw_cfg_add_i32(fw_cfg, FW_CFG_KERNEL_SIZE, kernel_size); > sev_load_ctx.kernel_data = (char *)kernel; > sev_load_ctx.kernel_size = kernel_size; > > - /* > - * If we're starting an encrypted VM, it will be OVMF based, which uses the > - * efi stub for booting and doesn't require any values to be placed in the > - * kernel header. We therefore don't update the header so the hash of the > - * kernel on the other side of the fw_cfg interface matches the hash of the > - * file the user passed in. > - */ > - if (!sev_enabled() && first_setup_data) { > - SetupDataFixup *fixup = g_malloc(sizeof(*fixup)); > - > - memcpy(setup, header, MIN(sizeof(header), setup_size)); > - /* Offset 0x250 is a pointer to the first setup_data link. */ > - fixup->pos = setup + 0x250; > - fixup->orig_val = ldq_p(fixup->pos); > - fixup->new_val = first_setup_data; > - fixup->addr = cpu_to_le32(real_addr); > - fw_cfg_add_bytes_callback(fw_cfg, FW_CFG_SETUP_ADDR, fixup_setup_data, NULL, > - fixup, &fixup->addr, sizeof(fixup->addr), true); > - qemu_register_reset(reset_setup_data, fixup); > - } else { > - fw_cfg_add_i32(fw_cfg, FW_CFG_SETUP_ADDR, real_addr); > - } > + fw_cfg_add_i32(fw_cfg, FW_CFG_SETUP_ADDR, real_addr); > fw_cfg_add_i32(fw_cfg, FW_CFG_SETUP_SIZE, setup_size); > fw_cfg_add_bytes(fw_cfg, FW_CFG_SETUP_DATA, setup, setup_size); > sev_load_ctx.setup_data = (char *)setup; > -- > 2.39.1
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