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path: root/drivers/firmware/efi/libstub/efi-stub-helper.c
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Diffstat (limited to 'drivers/firmware/efi/libstub/efi-stub-helper.c')
-rw-r--r--drivers/firmware/efi/libstub/efi-stub-helper.c62
1 files changed, 60 insertions, 2 deletions
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;