[tip:efi/urgent] efi: Allow the number of EFI configuration tables entries to be zero

[tip-bot for Rob Bradford]

Commit-ID:  88447c5b93d98be847f428c39ba589779a59eb83
Gitweb:     https://git.kernel.org/tip/88447c5b93d98be847f428c39ba589779a59eb83
Author:     Rob Bradford <robert.bradford@xxxxxxxxx>
AuthorDate: Sat, 25 May 2019 13:25:59 +0200
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Sat, 25 May 2019 13:48:17 +0200

efi: Allow the number of EFI configuration tables entries to be zero

Only try and access the EFI configuration tables if there there are any
reported. This allows EFI to be continued to used on systems where there
are no configuration table entries.

Signed-off-by: Rob Bradford <robert.bradford@xxxxxxxxx>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
Cc: Gen Zhang <blackgod016574@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: linux-efi@xxxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/20190525112559.7917-3-ard.biesheuvel@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 arch/x86/platform/efi/quirks.c | 3 +++
 drivers/firmware/efi/efi.c     | 3 +++
 2 files changed, 6 insertions(+)

diff --git a/arch/x86/platform/efi/quirks.c b/arch/x86/platform/efi/quirks.c
index feb77777c8b8..632b83885867 100644
--- a/arch/x86/platform/efi/quirks.c
+++ b/arch/x86/platform/efi/quirks.c
@@ -513,6 +513,9 @@ int __init efi_reuse_config(u64 tables, int nr_tables)
 	void *p, *tablep;
 	struct efi_setup_data *data;
 
+	if (nr_tables == 0)
+		return 0;
+
 	if (!efi_setup)
 		return 0;
 
diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index 55b77c576c42..521a541d02ad 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -636,6 +636,9 @@ int __init efi_config_init(efi_config_table_type_t *arch_tables)
 	void *config_tables;
 	int sz, ret;
 
+	if (efi.systab->nr_tables == 0)
+		return 0;
+
 	if (efi_enabled(EFI_64BIT))
 		sz = sizeof(efi_config_table_64_t);
 	else