[RFC][PATCH 1/1] x86, efi: EFI boot stub config file support

[Shea Levy]

Hello,

Inlined is a patch to have the kernel read its parameters from a config 
file when booted via the EFI boot stub without any parameters passed. 
This patch roughly follows the plan I discussed when proposing this 
idea, except now the file is found relative to the location of the 
bzImage and there is no additional check to see if image->parent_handle 
is NULL (despite the spec saying it will be NULL when the image was 
loaded by the firmware itself, it was never NULL on any of the systems I 
tested).

Cheers,
Shea Levy

---

From 2c12b0f49831d2d96b6bdcef931794178312c288 Mon Sep 17 00:00:00 2001
From: Shea Levy <shea@xxxxxxxxxxxx>
Date: Sun, 18 Mar 2012 16:17:04 +0100
Subject: [PATCH 1/1] x86, efi: EFI boot stub config file support

When booting via the EFI boot stub, search for a file named 'linux.conf' in
the same directory as the bzImage and read the kernel command line from it
when no load options are passed.

The file search should only be triggered when the bzImage is loaded from the
firmware's boot process. When loaded via an EFI shell, the load options 
always
contain at least one character, even if no parameters were passed at the
prompt.

Signed-off-by: Shea Levy <shea@xxxxxxxxxxxx>
---
 arch/x86/boot/compressed/eboot.c |  146 
++++++++++++++++++++++++++++++++++++--
 arch/x86/boot/compressed/eboot.h |    2 +
 2 files changed, 143 insertions(+), 5 deletions(-)

diff --git a/arch/x86/boot/compressed/eboot.c 
b/arch/x86/boot/compressed/eboot.c
index fec216f..672ecfe 100644
--- a/arch/x86/boot/compressed/eboot.c
+++ b/arch/x86/boot/compressed/eboot.c
@@ -486,14 +486,14 @@ struct initrd {
  * kernel image.
  */
 static efi_status_t handle_ramdisks(efi_loaded_image_t *image,
-                    struct setup_header *hdr)
+                    struct setup_header *hdr,
+                    efi_file_handle_t *fh)
 {
     struct initrd *initrds;
     unsigned long initrd_addr;
     efi_guid_t fs_proto = EFI_FILE_SYSTEM_GUID;
     u64 initrd_total;
     efi_file_io_interface_t *io;
-    efi_file_handle_t *fh;
     efi_status_t status;
     int nr_initrds;
     char *str;
@@ -568,7 +568,7 @@ static efi_status_t 
handle_ramdisks(efi_loaded_image_t *image,
         *p = '\0';

         /* Only open the volume once. */
-        if (!i) {
+        if (!fh) {
             efi_boot_services_t *boottime;

             boottime = sys_table->boottime;
@@ -712,6 +712,7 @@ static efi_status_t make_boot_params(struct 
boot_params *boot_params,
     u16 *s2;
     u8 *s1;
     int i;
+    efi_file_handle_t *fh = NULL;

     hdr->type_of_loader = 0x21;

@@ -743,14 +744,149 @@ static efi_status_t make_boot_params(struct 
boot_params *boot_params,

             *s1 = '\0';
         }
-    }
+    } else {
+        efi_char16_t config_file_name[
+            sizeof CONFIG_FILE_NAME * sizeof(efi_char16_t)];
+        u16 *file_path = (u16 *)image->file_path;
+        efi_char16_t config_path[256], *config_path_position;
+        efi_boot_services_t *boottime;
+        efi_file_info_t *info;
+        unsigned long info_sz = 0;
+        u64 file_sz;
+        efi_guid_t info_guid = EFI_FILE_INFO_ID;
+        efi_guid_t fs_proto = EFI_FILE_SYSTEM_GUID;
+        efi_file_io_interface_t *io;
+        efi_file_handle_t *h;
+
+        boottime = sys_table->boottime;
+
+        config_path_position = config_path;
+
+        for (i = 0; i < sizeof CONFIG_FILE_NAME; i++)
+            config_file_name[i] = CONFIG_FILE_NAME[i];
+
+        while (*file_path == 0x404) {
+            u16 node_size = *(file_path + 1)/sizeof *file_path;
+
+            if (config_path_position - config_path) {
+                if (*(file_path + 2) == '\\' &&
+                        *(file_path - 2) == '\\') {
+                    config_path_position--;
+                } else if (*(file_path + 2) != '\\' &&
+                        *(file_path - 2) != '\\') {
+                    *config_path_position++ = '\\';
+                }
+            }
+
+            if ((config_path_position - config_path) + node_size - 3
+                    + sizeof config_file_name
+                    / sizeof *config_file_name
+ > sizeof config_path
+                    / sizeof *config_path)
+                goto end;
+
+            memcpy((void *)config_path_position, file_path + 2,
+                    (node_size - 3) * sizeof *config_path);

+            config_path_position += node_size - 3;
+            file_path += node_size;
+        }
+
+        while (*config_path_position != '\\' && config_path_position !=
+                config_path)
+            config_path_position--;
+
+        *config_path_position = '\\';
+
+        memcpy((void *)(config_path_position + 1),
+                config_file_name,
+                sizeof config_file_name);
+
+        status = efi_call_phys3(boottime->handle_protocol,
+                image->device_handle, &fs_proto, &io);
+
+        if (status != EFI_SUCCESS)
+            goto end;
+
+        status = efi_call_phys2(io->open_volume, io, &fh);
+
+        if (status != EFI_SUCCESS) {
+            fh = NULL;
+            goto end;
+        }
+
+        status = efi_call_phys5(fh->open,
+                fh,
+ &h,
+                config_path,
+                EFI_FILE_MODE_READ, (u64)0);
+
+        if (status != EFI_SUCCESS)
+            goto end;
+
+        status = efi_call_phys4(h->get_info, h, &info_guid,
+ &info_sz, NULL);
+
+        if (status != EFI_BUFFER_TOO_SMALL)
+            goto close_config_file;
+
+        while (status == EFI_BUFFER_TOO_SMALL) {
+            status = efi_call_phys3(boottime->allocate_pool,
+                    EFI_LOADER_DATA, info_sz, &info);
+
+            if (status != EFI_SUCCESS)
+                goto close_config_file;
+
+            status = efi_call_phys4(h->get_info, h, &info_guid,
+ &info_sz, info);
+
+            if (status == EFI_BUFFER_TOO_SMALL)
+                efi_call_phys1(boottime->free_pool, info);
+        }
+
+        if (status != EFI_SUCCESS)
+            goto free_config_file_info;
+
+        file_sz = info->file_size;
+
+        if (file_sz > hdr->cmdline_size)
+            file_sz = hdr->cmdline_size;
+
+        options_size = file_sz + 1;
+
+        status = low_alloc(options_size, 1, &cmdline);
+
+        if (status != EFI_SUCCESS)
+            goto free_config_file_info;
+
+        status = efi_call_phys3(h->read, h, &file_sz, cmdline);
+
+        if (status != EFI_SUCCESS)
+            goto free_config_file_cmdline;
+
+        *((u8 *)cmdline + file_sz) = 0;
+
+        goto free_config_file_info;
+free_config_file_cmdline:
+        low_free(options_size, cmdline);
+        cmdline = 0;
+        options_size = 0;
+free_config_file_info:
+        efi_call_phys1(boottime->free_pool, info);
+close_config_file:
+        efi_call_phys1(h->close, h);
+    }
+end:
     hdr->cmd_line_ptr = cmdline;

     hdr->ramdisk_image = 0;
     hdr->ramdisk_size = 0;

-    status = handle_ramdisks(image, hdr);
+    status = handle_ramdisks(image, hdr, fh);
+
+    if (fh)
+        efi_call_phys1(fh->close, fh);
+
     if (status != EFI_SUCCESS)
         goto free_cmdline;

diff --git a/arch/x86/boot/compressed/eboot.h 
b/arch/x86/boot/compressed/eboot.h
index 3925166..186b4c6 100644
--- a/arch/x86/boot/compressed/eboot.h
+++ b/arch/x86/boot/compressed/eboot.h
@@ -20,6 +20,8 @@
 #define PIXEL_BLT_ONLY                    3
 #define PIXEL_FORMAT_MAX                4

+#define CONFIG_FILE_NAME "linux.conf"
+
 struct efi_pixel_bitmask {
     u32 red_mask;
     u32 green_mask;
--
1.7.9.4


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