6 files changed, 91 insertions, 5 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 5ae8608ca9f5..67d79597d9d6 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -992,10 +992,13 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                         Format: {"off" | "on" | "skip[mbr]"}
 
         efi=            [EFI]
-                        Format: { "old_map" }
+                        Format: { "old_map", "nochunk" }
                         old_map [X86-64]: switch to the old ioremap-based EFI
                         runtime services mapping. 32-bit still uses this one by
                         default.
+                        nochunk: disable reading files in "chunks" in the EFI
+                        boot stub, as chunking can cause problems with some
+                        firmware implementations.
 
         efi_no_storage_paranoia [EFI; X86]
                         Using this parameter you can use more than 50% of
diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c
index f277184e2ac1..f4bdab1dbf66 100644
--- a/arch/x86/boot/compressed/eboot.c
+++ b/arch/x86/boot/compressed/eboot.c
@@ -1100,6 +1100,10 @@ struct boot_params *make_boot_params(struct efi_config *c)
         else
                 initrd_addr_max = hdr->initrd_addr_max;
 
+        status = efi_parse_options(cmdline_ptr);
+        if (status != EFI_SUCCESS)
+                goto fail2;
+
         status = handle_cmdline_files(sys_table, image,
                                       (char *)(unsigned long)hdr->cmd_line_ptr,
                                       "initrd=", initrd_addr_max,
diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index 850da94fef30..a1f745b0bf1d 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -943,8 +943,23 @@ static int __init parse_efi_cmdline(char *str)
         if (*str == '=')
                 str++;
 
-        if (!strncmp(str, "old_map", 7))
-                set_bit(EFI_OLD_MEMMAP, &efi.flags);
+        while (*str) {
+                if (!strncmp(str, "old_map", 7)) {
+                        set_bit(EFI_OLD_MEMMAP, &efi.flags);
+                        str += strlen("old_map");
+                }
+
+                /*
+                 * Skip any options we don't understand. Presumably
+                 * they apply to the EFI boot stub.
+                 */
+                while (*str && *str != ',')
+                        str++;
+
+                /* If we hit a delimiter, skip it */
+                if (*str == ',')
+                        str++;
+        }
 
         return 0;
 }
diff --git a/drivers/firmware/efi/libstub/arm-stub.c b/drivers/firmware/efi/libstub/arm-stub.c
index 480339b6b110..75ee05964cbc 100644
--- a/drivers/firmware/efi/libstub/arm-stub.c
+++ b/drivers/firmware/efi/libstub/arm-stub.c
@@ -226,6 +226,10 @@ unsigned long __init efi_entry(void *handle, efi_system_table_t *sys_table,
                 goto fail_free_image;
         }
 
+        status = efi_parse_options(cmdline_ptr);
+        if (status != EFI_SUCCESS)
+                pr_efi_err(sys_table, "Failed to parse EFI cmdline options\n");
+
         /*
          * Unauthenticated device tree data is a security hazard, so
          * ignore 'dtb=' unless UEFI Secure Boot is disabled.
diff --git a/drivers/firmware/efi/libstub/efi-stub-helper.c b/drivers/firmware/efi/libstub/efi-stub-helper.c
index 32d5cca30f49..a920fec8fe88 100644
--- a/drivers/firmware/efi/libstub/efi-stub-helper.c
+++ b/drivers/firmware/efi/libstub/efi-stub-helper.c
@@ -15,8 +15,23 @@
 
 #include "efistub.h"
 
+/*
+ * Some firmware implementations have problems reading files in one go.
+ * A read chunk size of 1MB seems to work for most platforms.
+ *
+ * Unfortunately, reading files in chunks triggers *other* bugs on some
+ * platforms, so we provide a way to disable this workaround, which can
+ * be done by passing "efi=nochunk" on the EFI boot stub command line.
+ *
+ * If you experience issues with initrd images being corrupt it's worth
+ * trying efi=nochunk, but chunking is enabled by default because there
+ * are far more machines that require the workaround than those that
+ * break with it enabled.
+ */
 #define EFI_READ_CHUNK_SIZE     (1024 * 1024)
 
+static unsigned long __chunk_size = EFI_READ_CHUNK_SIZE;
+
 struct file_info {
         efi_file_handle_t *handle;
         u64 size;
@@ -281,6 +296,49 @@ void efi_free(efi_system_table_t *sys_table_arg, unsigned long size,
         efi_call_early(free_pages, addr, nr_pages);
 }
 
+/*
+ * Parse the ASCII string 'cmdline' for EFI options, denoted by the efi=
+ * option, e.g. efi=nochunk.
+ *
+ * It should be noted that efi= is parsed in two very different
+ * environments, first in the early boot environment of the EFI boot
+ * stub, and subsequently during the kernel boot.
+ */
+efi_status_t efi_parse_options(char *cmdline)
+{
+        char *str;
+
+        /*
+         * If no EFI parameters were specified on the cmdline we've got
+         * nothing to do.
+         */
+        str = strstr(cmdline, "efi=");
+        if (!str)
+                return EFI_SUCCESS;
+
+        /* Skip ahead to first argument */
+        str += strlen("efi=");
+
+        /*
+         * Remember, because efi= is also used by the kernel we need to
+         * skip over arguments we don't understand.
+         */
+        while (*str) {
+                if (!strncmp(str, "nochunk", 7)) {
+                        str += strlen("nochunk");
+                        __chunk_size = -1UL;
+                }
+
+                /* Group words together, delimited by "," */
+                while (*str && *str != ',')
+                        str++;
+
+                if (*str == ',')
+                        str++;
+        }
+
+        return EFI_SUCCESS;
+}
 
 /*
  * Check the cmdline for a LILO-style file= arguments.
@@ -423,8 +481,8 @@ efi_status_t handle_cmdline_files(efi_system_table_t *sys_table_arg,
                         size = files[j].size;
                         while (size) {
                                 unsigned long chunksize;
-                                if (size > EFI_READ_CHUNK_SIZE)
-                                        chunksize = EFI_READ_CHUNK_SIZE;
+                                if (size > __chunk_size)
+                                        chunksize = __chunk_size;
                                 else
                                         chunksize = size;
 
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 45cb4ffdea62..518779fb5e90 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -1227,4 +1227,6 @@ efi_status_t handle_cmdline_files(efi_system_table_t *sys_table_arg,
                                   unsigned long *load_addr,
                                   unsigned long *load_size);
 
+efi_status_t efi_parse_options(char *cmdline);
+
 #endif /* _LINUX_EFI_H */