[PATCH qboot] Place setup_data at location specified by host

[Jason A. Donenfeld]

QEMU places setup_data at a particular location, which cannot be
relocated due to it containing self references in absolute address
terms. For this reason, it supplies the intended location in
FW_CFG_SETUP_ADDR, which is what SeaBIOS uses. So use this too in qboot.
This also has the effect of removing the 8k limit on the copied size,
since the header is copied to the right location from the beginning.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
 fw_cfg.c            | 13 ++++++++-----
 include/linuxboot.h |  1 -
 linuxboot.c         |  4 +---
 3 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/fw_cfg.c b/fw_cfg.c
index 4b920cf..f3d9605 100644
--- a/fw_cfg.c
+++ b/fw_cfg.c
@@ -269,6 +269,7 @@ void boot_from_fwcfg(void)
 {
        struct linuxboot_args args;
        uint32_t kernel_size;
+       enum { HEADER_PEEK_SIZE = 8192 };
 
        fw_cfg_select(FW_CFG_CMDLINE_SIZE);
        args.cmdline_size = fw_cfg_readl_le();
@@ -282,15 +283,17 @@ void boot_from_fwcfg(void)
        kernel_size = fw_cfg_readl_le();
        fw_cfg_select(FW_CFG_SETUP_SIZE);
        args.vmlinuz_size = kernel_size + fw_cfg_readl_le();
+       fw_cfg_select(FW_CFG_SETUP_ADDR);
+       args.setup_addr = (void *)fw_cfg_readl_le();
 
        if (!args.vmlinuz_size)
                return;
 
        fw_cfg_select(FW_CFG_SETUP_DATA);
-       fw_cfg_read(args.header, sizeof(args.header));
+       fw_cfg_read(args.setup_addr, HEADER_PEEK_SIZE);
 
        if (!parse_bzimage(&args)) {
-               uint8_t *header = args.header;
+               uint8_t *header = args.setup_addr;
 
                if (ldl_p(header) == 0x464c457f)  /* ELF magic */
                        boot_pvh_from_fw_cfg();
@@ -298,9 +301,9 @@ void boot_from_fwcfg(void)
        }
 
        /* SETUP_DATA already selected */
-       if (args.setup_size > sizeof(args.header))
-               fw_cfg_read(args.setup_addr + sizeof(args.header),
-                           args.setup_size - sizeof(args.header));
+       if (args.setup_size > HEADER_PEEK_SIZE)
+               fw_cfg_read(args.setup_addr + HEADER_PEEK_SIZE,
+                           args.setup_size - HEADER_PEEK_SIZE);
 
        fw_cfg_select(FW_CFG_KERNEL_DATA);
        fw_cfg_read_entry(FW_CFG_KERNEL_DATA, args.kernel_addr, kernel_size);
diff --git a/include/linuxboot.h b/include/linuxboot.h
index 6e865f0..e04c234 100644
--- a/include/linuxboot.h
+++ b/include/linuxboot.h
@@ -10,7 +10,6 @@ struct linuxboot_args {
 
        /* Input */
        uint32_t cmdline_size, vmlinuz_size, initrd_size;
-       uint8_t header[8192];
 };
 
 bool parse_bzimage(struct linuxboot_args *args);
diff --git a/linuxboot.c b/linuxboot.c
index 251bcb6..bdb01ee 100644
--- a/linuxboot.c
+++ b/linuxboot.c
@@ -11,7 +11,7 @@ struct hvm_start_info start_info = {0};
 
 bool parse_bzimage(struct linuxboot_args *args)
 {
-       uint8_t *header = args->header;
+       uint8_t *header = args->setup_addr;
 
        uint32_t real_addr, cmdline_addr, prot_addr, initrd_addr;
        uint32_t setup_size;
@@ -84,7 +84,6 @@ bool parse_bzimage(struct linuxboot_args *args)
        args->setup_size = (setup_size+1)*512;
        args->kernel_size = args->vmlinuz_size - setup_size;
        args->initrd_addr = (void *)initrd_addr;
-       args->setup_addr = (void *)real_addr;
        args->kernel_addr = (void *)prot_addr;
        args->cmdline_addr = (void *)cmdline_addr;
        return true;
@@ -92,7 +91,6 @@ bool parse_bzimage(struct linuxboot_args *args)
 
 void boot_bzimage(struct linuxboot_args *args)
 {
-       memcpy(args->setup_addr, args->header, sizeof(args->header));
 #ifdef BENCHMARK_HACK
        /* Exit just before getting to vmlinuz, so that it is easy
         * to time/profile the firmware.
-- 
2.37.3