From: Eric Snowberg <[email protected]>

Commit d64934019f6c ("x86/efi: Use efi_exit_boot_services()")
introduced a regression on systems with large memory maps
causing them to hang on boot. The first "goto get_map" that was removed
from exit_boot insured there was enough room for the memory map when
efi_call_early(exit_boot_services) was called. This happens when
(nr_desc > ARRAY_SIZE(params->e820_table).

Chain of events:
  exit_boot()
    efi_exit_boot_services()
      efi_get_memory_map <- at this point the mm can't grow over 8 desc
      priv_func()
        exit_boot_func()
          allocate_e820ext() <- new mm grows over 8 desc from e820 alloc
      efi_call_early(exit_boot_services) <- mm key doesn't match so retry
      efi_call_early(get_memory_map) <- not enough room for new mm
      system hangs

This patch allocates the e820 buffer before calling efi_exit_boot_services
and fixes the regression.

Signed-off-by: Eric Snowberg <[email protected]>
Signed-off-by: Ard Biesheuvel <[email protected]>
---
 arch/x86/boot/compressed/eboot.c | 65 ++++++++++++++++++++------------
 1 file changed, 41 insertions(+), 24 deletions(-)

diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c
index 8b4c5e001157..f7bad07bb251 100644
--- a/arch/x86/boot/compressed/eboot.c
+++ b/arch/x86/boot/compressed/eboot.c
@@ -1,3 +1,4 @@
+
 /* -----------------------------------------------------------------------
  *
  *   Copyright 2011 Intel Corporation; author Matt Fleming
@@ -634,37 +635,54 @@ static efi_status_t alloc_e820ext(u32 nr_desc, struct 
setup_data **e820ext,
        return status;
 }
 
+static efi_status_t allocate_e820(struct boot_params *params,
+                                 struct setup_data **e820ext,
+                                 u32 *e820ext_size)
+{
+       unsigned long map_size, desc_size, buff_size;
+       struct efi_boot_memmap boot_map;
+       efi_memory_desc_t *map;
+       efi_status_t status;
+       __u32 nr_desc;
+
+       boot_map.map =          &map;
+       boot_map.map_size =     &map_size;
+       boot_map.desc_size =    &desc_size;
+       boot_map.desc_ver =     NULL;
+       boot_map.key_ptr =      NULL;
+       boot_map.buff_size =    &buff_size;
+
+       status = efi_get_memory_map(sys_table, &boot_map);
+       if (status != EFI_SUCCESS)
+               return status;
+
+       nr_desc = buff_size / desc_size;
+
+       if (nr_desc > ARRAY_SIZE(params->e820_table)) {
+               u32 nr_e820ext = nr_desc - ARRAY_SIZE(params->e820_table);
+
+               status = alloc_e820ext(nr_e820ext, e820ext, e820ext_size);
+               if (status != EFI_SUCCESS)
+                       return status;
+       }
+
+       return EFI_SUCCESS;
+}
+
 struct exit_boot_struct {
        struct boot_params      *boot_params;
        struct efi_info         *efi;
-       struct setup_data       *e820ext;
-       __u32                   e820ext_size;
 };
 
 static efi_status_t exit_boot_func(efi_system_table_t *sys_table_arg,
                                   struct efi_boot_memmap *map,
                                   void *priv)
 {
-       static bool first = true;
        const char *signature;
        __u32 nr_desc;
        efi_status_t status;
        struct exit_boot_struct *p = priv;
 
-       if (first) {
-               nr_desc = *map->buff_size / *map->desc_size;
-               if (nr_desc > ARRAY_SIZE(p->boot_params->e820_table)) {
-                       u32 nr_e820ext = nr_desc -
-                                       ARRAY_SIZE(p->boot_params->e820_table);
-
-                       status = alloc_e820ext(nr_e820ext, &p->e820ext,
-                                              &p->e820ext_size);
-                       if (status != EFI_SUCCESS)
-                               return status;
-               }
-               first = false;
-       }
-
        signature = efi_is_64bit() ? EFI64_LOADER_SIGNATURE
                                   : EFI32_LOADER_SIGNATURE;
        memcpy(&p->efi->efi_loader_signature, signature, sizeof(__u32));
@@ -687,8 +705,8 @@ static efi_status_t exit_boot(struct boot_params 
*boot_params, void *handle)
 {
        unsigned long map_sz, key, desc_size, buff_size;
        efi_memory_desc_t *mem_map;
-       struct setup_data *e820ext;
-       __u32 e820ext_size;
+       struct setup_data *e820ext = NULL;
+       __u32 e820ext_size = 0;
        efi_status_t status;
        __u32 desc_version;
        struct efi_boot_memmap map;
@@ -702,8 +720,10 @@ static efi_status_t exit_boot(struct boot_params 
*boot_params, void *handle)
        map.buff_size           = &buff_size;
        priv.boot_params        = boot_params;
        priv.efi                = &boot_params->efi_info;
-       priv.e820ext            = NULL;
-       priv.e820ext_size       = 0;
+
+       status = allocate_e820(boot_params, &e820ext, &e820ext_size);
+       if (status != EFI_SUCCESS)
+               return status;
 
        /* Might as well exit boot services now */
        status = efi_exit_boot_services(sys_table, handle, &map, &priv,
@@ -711,9 +731,6 @@ static efi_status_t exit_boot(struct boot_params 
*boot_params, void *handle)
        if (status != EFI_SUCCESS)
                return status;
 
-       e820ext                 = priv.e820ext;
-       e820ext_size            = priv.e820ext_size;
-
        /* Historic? */
        boot_params->alt_mem_k  = 32 * 1024;
 
-- 
2.19.1

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