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x86: return modified setup_data only if read as memory, not as file

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If setup_data is being read into a specific memory location, then
generally the setup_data address parameter is read first, so that the
caller knows where to read it into. In that case, we should return
setup_data containing the absolute addresses that are hard coded and
determined a priori. This is the case when kernels are loaded by BIOS,
for example. In contrast, when setup_data is read as a file, then we
shouldn't modify setup_data, since the absolute address will be wrong by
definition. This is the case when OVMF loads the image.

This allows setup_data to be used like normal, without crashing when EFI
tries to use it.

(As a small development note, strangely, fw_cfg_add_file_callback() was
exported but fw_cfg_add_bytes_callback() wasn't, so this makes that
consistent.)

Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Laurent Vivier <laurent@vivier.eu>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Maydell <peter.maydell@linaro.org>
Cc: Philippe Mathieu-Daudé <f4bug@amsat.org>
Cc: Richard Henderson <richard.henderson@linaro.org>
Suggested-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Message-Id: <20220921093134.2936487-1-Jason@zx2c4.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Jason A. Donenfeld 2022-09-21 11:31:31 +02:00 committed by Paolo Bonzini
parent 99d6b11b5b
commit e935b73508
3 changed files with 64 additions and 16 deletions
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46
hw/i386/x86.c
View File

@ -37,6 +37,7 @@
#include "sysemu/whpx.h"
#include "sysemu/numa.h"
#include "sysemu/replay.h"
#include "sysemu/reset.h"
#include "sysemu/sysemu.h"
#include "sysemu/cpu-timers.h"
#include "sysemu/xen.h"
@ -764,6 +765,24 @@ 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);
}
void x86_load_linux(X86MachineState *x86ms,
FWCfgState *fw_cfg,
int acpi_data_size,
@ -1088,8 +1107,11 @@ void x86_load_linux(X86MachineState *x86ms,
qemu_guest_getrandom_nofail(setup_data->data, RNG_SEED_LENGTH);
}
/* Offset 0x250 is a pointer to the first setup_data link. */
stq_p(header + 0x250, first_setup_data);
fw_cfg_add_i32(fw_cfg, FW_CFG_KERNEL_ADDR, prot_addr);
fw_cfg_add_i32(fw_cfg, FW_CFG_KERNEL_SIZE, kernel_size);
fw_cfg_add_bytes(fw_cfg, FW_CFG_KERNEL_DATA, kernel, 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
@ -1099,16 +1121,20 @@ void x86_load_linux(X86MachineState *x86ms,
* file the user passed in.
*/
if (!sev_enabled()) {
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_KERNEL_ADDR, prot_addr);
fw_cfg_add_i32(fw_cfg, FW_CFG_KERNEL_SIZE, kernel_size);
fw_cfg_add_bytes(fw_cfg, FW_CFG_KERNEL_DATA, kernel, kernel_size);
sev_load_ctx.kernel_data = (char *)kernel;
sev_load_ctx.kernel_size = kernel_size;
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;

12
hw/nvram/fw_cfg.c
View File

@ -692,12 +692,12 @@ static const VMStateDescription vmstate_fw_cfg = {
}
};
static void fw_cfg_add_bytes_callback(FWCfgState *s, uint16_t key,
FWCfgCallback select_cb,
FWCfgWriteCallback write_cb,
void *callback_opaque,
void *data, size_t len,
bool read_only)
void fw_cfg_add_bytes_callback(FWCfgState *s, uint16_t key,
FWCfgCallback select_cb,
FWCfgWriteCallback write_cb,
void *callback_opaque,
void *data, size_t len,
bool read_only)
{
int arch = !!(key & FW_CFG_ARCH_LOCAL);

22
include/hw/nvram/fw_cfg.h
View File

@ -117,6 +117,28 @@ struct FWCfgMemState {
*/
void fw_cfg_add_bytes(FWCfgState *s, uint16_t key, void *data, size_t len);
/**
* fw_cfg_add_bytes_callback:
* @s: fw_cfg device being modified
* @key: selector key value for new fw_cfg item
* @select_cb: callback function when selecting
* @write_cb: callback function after a write
* @callback_opaque: argument to be passed into callback function
* @data: pointer to start of item data
* @len: size of item data
* @read_only: is file read only
*
* Add a new fw_cfg item, available by selecting the given key, as a raw
* "blob" of the given size. The data referenced by the starting pointer
* is only linked, NOT copied, into the data structure of the fw_cfg device.
*/
void fw_cfg_add_bytes_callback(FWCfgState *s, uint16_t key,
FWCfgCallback select_cb,
FWCfgWriteCallback write_cb,
void *callback_opaque,
void *data, size_t len,
bool read_only);
/**
* fw_cfg_add_string:
* @s: fw_cfg device being modified