[PATCH v9 4/7] kexec, x86: Fix bzImage real-mode booting

[Yinghai Lu]

We need to keep space for bss, heap/stack before command line.
otherwise command_line will be cleared by kernel 16bit init code.

also need to set 32bit start in real_mode header, kernel 16bit code
need to jump there.

Also don't touch regs16 if --real-mode is not specified.

Signed-off-by: Yinghai Lu <ying...@kernel.org>
---
 kexec/arch/i386/kexec-bzImage.c |   62 +++++++++++++++++++++++++++++++--------
 1 file changed, 49 insertions(+), 13 deletions(-)

diff --git a/kexec/arch/i386/kexec-bzImage.c b/kexec/arch/i386/kexec-bzImage.c
index 35005c7..0756f23 100644
--- a/kexec/arch/i386/kexec-bzImage.c
+++ b/kexec/arch/i386/kexec-bzImage.c
@@ -117,6 +117,8 @@ int do_bzImage_load(struct kexec_info *info,
        unsigned long kernel32_load_addr;
        char *modified_cmdline;
        unsigned long cmdline_end;
+       unsigned long kern16_size_needed;
+       unsigned long heap_size = 0;
 
        /*
         * Find out about the file I am about to load.
@@ -208,8 +210,29 @@ int do_bzImage_load(struct kexec_info *info,
                elf_rel_build_load(info, &info->rhdr, purgatory, purgatory_size,
                                        0x3000, 640*1024, -1, 0);
        dbgprintf("Loaded purgatory at addr 0x%lx\n", info->rhdr.rel_addr);
+
        /* The argument/parameter segment */
-       setup_size = kern16_size + command_line_len + PURGATORY_CMDLINE_SIZE;
+       if (real_mode_entry) {
+               /* need to include size for bss and heap etc */
+               if (setup_header.protocol_version >= 0x0201)
+                       kern16_size_needed = setup_header.heap_end_ptr;
+               else
+                       kern16_size_needed = kern16_size + 8192; /* bss */
+               if (kern16_size_needed < kern16_size)
+                       kern16_size_needed = kern16_size;
+               if (kern16_size_needed > 0xfffc)
+                       die("kern16_size_needed is more then 64k\n");
+               heap_size = 0xfffc - kern16_size_needed; /* less 64k */
+               heap_size &= ~(0x200 - 1);
+               kern16_size_needed += heap_size;
+       } else {
+               kern16_size_needed = kern16_size;
+               /* need to bigger than size of struct bootparams */
+               if (kern16_size_needed < 4096)
+                       kern16_size_needed = 4096;
+       }
+       setup_size = kern16_size_needed + command_line_len +
+                        PURGATORY_CMDLINE_SIZE;
        real_mode = xmalloc(setup_size);
        memset(real_mode, 0, setup_size);
        if (!real_mode_entry) {
@@ -275,11 +298,18 @@ int do_bzImage_load(struct kexec_info *info,
 
        /* Tell the kernel what is going on */
        setup_linux_bootloader_parameters(info, real_mode, setup_base,
-               kern16_size, command_line, command_line_len,
+               kern16_size_needed, command_line, command_line_len,
                initrd, initrd_len);
 
+       if (real_mode_entry && real_mode->protocol_version >= 0x0201) {
+               real_mode->loader_flags |= 0x80; /* CAN_USE_HEAP */
+               real_mode->heap_end_ptr += heap_size - 0x200; /*stack*/
+       }
+
        /* Get the initial register values */
-       elf_rel_get_symbol(&info->rhdr, "entry16_regs", &regs16, 
sizeof(regs16));
+       if (real_mode_entry)
+               elf_rel_get_symbol(&info->rhdr, "entry16_regs",
+                                        &regs16, sizeof(regs16));
        elf_rel_get_symbol(&info->rhdr, "entry32_regs", &regs32, 
sizeof(regs32));
        /*
 
@@ -298,16 +328,18 @@ int do_bzImage_load(struct kexec_info *info,
        /*
         * Initialize the 16bit start information.
         */
-       regs16.ds = regs16.es = regs16.fs = regs16.gs = setup_base >> 4;
-       regs16.cs = regs16.ds + 0x20;
-       regs16.ip = 0;
-       /* XXX: Documentation/i386/boot.txt says 'ss' must equal 'ds' */
-       regs16.ss = (elf_rel_get_addr(&info->rhdr, "stack_end") - 64*1024) >> 4;
-       /* XXX: Documentation/i386/boot.txt says 'sp' must equal heap_end */
-       regs16.esp = 0xFFFC;
        if (real_mode_entry) {
+               regs16.ds = regs16.es = regs16.fs = regs16.gs = setup_base >> 4;
+               regs16.cs = regs16.ds + 0x20;
+               regs16.ip = 0;
+               /* XXX: Documentation/i386/boot.txt says 'ss' must equal 'ds' */
+               regs16.ss = (elf_rel_get_addr(&info->rhdr, "stack_end") - 
64*1024) >> 4;
+               /* XXX: Documentation/i386/boot.txt says 'sp' must equal 
heap_end */
+               regs16.esp = 0xFFFC;
+
                printf("Starting the kernel in real mode\n");
                regs32.eip = elf_rel_get_addr(&info->rhdr, "entry16");
+               real_mode->kernel_start = kernel32_load_addr;
        }
        if (real_mode_entry && kexec_debug) {
                unsigned long entry16_debug, pre32, first32;
@@ -327,10 +359,14 @@ int do_bzImage_load(struct kexec_info *info,
        
                regs32.eip = entry16_debug;
        }
-       elf_rel_set_symbol(&info->rhdr, "entry16_regs", &regs16, 
sizeof(regs16));
-       elf_rel_set_symbol(&info->rhdr, "entry16_debug_regs", &regs16, 
sizeof(regs16));
+       if (real_mode_entry) {
+               elf_rel_set_symbol(&info->rhdr, "entry16_regs",
+                                        &regs16, sizeof(regs16));
+               elf_rel_set_symbol(&info->rhdr, "entry16_debug_regs",
+                                        &regs16, sizeof(regs16));
+       }
        elf_rel_set_symbol(&info->rhdr, "entry32_regs", &regs32, 
sizeof(regs32));
-       cmdline_end = setup_base + kern16_size + command_line_len - 1;
+       cmdline_end = setup_base + kern16_size_needed + command_line_len - 1;
        elf_rel_set_symbol(&info->rhdr, "cmdline_end", &cmdline_end,
                           sizeof(unsigned long));
 
-- 
1.7.10.4


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