[RFC,v2] PM / hibernate: Allow ACPI hardware signature to be honoured
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Message ID 2234e1693f0d8c1d1bb6b0f5c09cc82cd227eccb.camel@infradead.org
State New
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  • [RFC,v2] PM / hibernate: Allow ACPI hardware signature to be honoured
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Commit Message

David Woodhouse Feb. 27, 2019, 9 a.m. UTC
From: David Woodhouse <dwmw@amazon.co.uk>

Theoretically, when the hardware signature in FACS changes, the OS
is supposed to gracefully decline to attempt to resume from S4:

 "If the signature has changed, OSPM will not restore the system
  context and can boot from scratch"

In practice, Windows doesn't do this and many laptop vendors do allow
the signature to change especially when docking/undocking, so it would
be a bad idea to simply comply with the specification by default in the
general case.

However, there are use cases where we do want the compliant behaviour
and we know it's safe. Specifically, when resuming virtual machines where
we know the hypervisor has changed sufficiently that resume will fail.
We really want to be able to *tell* the guest kernel not to try, so it
boots cleanly and doesn't just crash. This patch provides a way to opt
in to the spec-compliant behaviour on the command line.

A follow-up patch may do this automatically for certain "known good"
machines based on a DMI match.

Still mostly untested while we conclude the bikeshedding.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
---
 Documentation/admin-guide/kernel-parameters.txt | 15 ++++++++++++---
 arch/x86/kernel/acpi/sleep.c                    |  4 +++-
 drivers/acpi/sleep.c                            | 13 ++++++++-----
 include/linux/acpi.h                            |  2 +-
 include/linux/suspend.h                         |  1 +
 kernel/power/power.h                            |  1 +
 kernel/power/swap.c                             | 16 ++++++++++++++--
 7 files changed, 40 insertions(+), 12 deletions(-)

Patch
diff mbox series

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 858b6c0b9a15..de36ef2a9cd9 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -221,14 +221,23 @@ 
 			For broken nForce2 BIOS resulting in XT-PIC timer.
 
 	acpi_sleep=	[HW,ACPI] Sleep options
-			Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
-				  old_ordering, nonvs, sci_force_enable, nobl }
+			Format: { s3_bios, s3_mode, s3_beep, s4_hwsig,
+				  s4_nohwsig, hgold_ordering, nonvs,
+				  sci_force_enable, nobl }
 			See Documentation/power/video.txt for information on
 			s3_bios and s3_mode.
 			s3_beep is for debugging; it makes the PC's speaker beep
 			as soon as the kernel's real-mode entry point is called.
+			s4_hwsig causes the kernel to check the ACPI hardware
+			signature during resume from hibernation, and gracefully
+			refuse to resume if it has changed. This complies with
+			the ACPI specification but not with reality, since
+			Windows does not do this and many laptops do change it
+			on docking. So the default behaviour is to allow resume
+			and simply warn when the signature changes, unless the
+			s4_hwsig option is enabled.
 			s4_nohwsig prevents ACPI hardware signature from being
-			used during resume from hibernation.
+			used (or even warned about) during resume.
 			old_ordering causes the ACPI 1.0 ordering of the _PTS
 			control method, with respect to putting devices into
 			low power states, to be enforced (the ACPI 2.0 ordering
diff --git a/arch/x86/kernel/acpi/sleep.c b/arch/x86/kernel/acpi/sleep.c
index ca13851f0570..c75f8a874b0a 100644
--- a/arch/x86/kernel/acpi/sleep.c
+++ b/arch/x86/kernel/acpi/sleep.c
@@ -128,8 +128,10 @@  static int __init acpi_sleep_setup(char *str)
 		if (strncmp(str, "s3_beep", 7) == 0)
 			acpi_realmode_flags |= 4;
 #ifdef CONFIG_HIBERNATION
+		if (strncmp(str, "s4_hwsig", 8) == 0)
+			acpi_check_s4_hw_signature(1);
 		if (strncmp(str, "s4_nohwsig", 10) == 0)
-			acpi_no_s4_hw_signature();
+			acpi_check_s4_hw_signature(0);
 #endif
 		if (strncmp(str, "nonvs", 5) == 0)
 			acpi_nvs_nosave();
diff --git a/drivers/acpi/sleep.c b/drivers/acpi/sleep.c
index 403c4ff15349..944aa3e1a6c0 100644
--- a/drivers/acpi/sleep.c
+++ b/drivers/acpi/sleep.c
@@ -1121,11 +1121,11 @@  static inline void acpi_sleep_syscore_init(void) {}
 #ifdef CONFIG_HIBERNATION
 static unsigned long s4_hardware_signature;
 static struct acpi_table_facs *facs;
-static bool nosigcheck;
+static int sigcheck = -1; /* Default behaviour is just to warn */
 
-void __init acpi_no_s4_hw_signature(void)
+void __init acpi_check_s4_hw_signature(int check)
 {
-	nosigcheck = true;
+	sigcheck = check;
 }
 
 static int acpi_hibernation_begin(void)
@@ -1244,12 +1244,15 @@  static void acpi_sleep_hibernate_setup(void)
 	hibernation_set_ops(old_suspend_ordering ?
 			&acpi_hibernation_ops_old : &acpi_hibernation_ops);
 	sleep_states[ACPI_STATE_S4] = 1;
-	if (nosigcheck)
+	if (!sigcheck)
 		return;
 
 	acpi_get_table(ACPI_SIG_FACS, 1, (struct acpi_table_header **)&facs);
-	if (facs)
+	if (facs) {
 		s4_hardware_signature = facs->hardware_signature;
+		if (sigcheck > 0)
+			swsusp_hardware_signature = facs->hardware_signature;
+	}
 }
 #else /* !CONFIG_HIBERNATION */
 static inline void acpi_sleep_hibernate_setup(void) {}
diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index 87715f20b69a..a354ad5930a1 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -456,7 +456,7 @@  acpi_status acpi_release_memory(acpi_handle handle, struct resource *res,
 int acpi_resources_are_enforced(void);
 
 #ifdef CONFIG_HIBERNATION
-void __init acpi_no_s4_hw_signature(void);
+void __init acpi_check_s4_hw_signature(int check);
 #endif
 
 #ifdef CONFIG_PM_SLEEP
diff --git a/include/linux/suspend.h b/include/linux/suspend.h
index 3f529ad9a9d2..0e830ccd67dc 100644
--- a/include/linux/suspend.h
+++ b/include/linux/suspend.h
@@ -389,6 +389,7 @@  extern unsigned long get_safe_page(gfp_t gfp_mask);
 extern asmlinkage int swsusp_arch_suspend(void);
 extern asmlinkage int swsusp_arch_resume(void);
 
+extern u32 swsusp_hardware_signature;
 extern void hibernation_set_ops(const struct platform_hibernation_ops *ops);
 extern int hibernate(void);
 extern bool system_entering_hibernation(void);
diff --git a/kernel/power/power.h b/kernel/power/power.h
index 9e58bdc8a562..d447571484e9 100644
--- a/kernel/power/power.h
+++ b/kernel/power/power.h
@@ -170,6 +170,7 @@  extern int swsusp_swap_in_use(void);
 #define SF_PLATFORM_MODE	1
 #define SF_NOCOMPRESS_MODE	2
 #define SF_CRC32_MODE	        4
+#define SF_HW_SIG		8
 
 /* kernel/power/hibernate.c */
 extern int swsusp_check(void);
diff --git a/kernel/power/swap.c b/kernel/power/swap.c
index d7f6c1a288d3..bd37784b522f 100644
--- a/kernel/power/swap.c
+++ b/kernel/power/swap.c
@@ -38,6 +38,8 @@ 
 
 #define HIBERNATE_SIG	"S1SUSPEND"
 
+u32 swsusp_hardware_signature;
+
 /*
  * When reading an {un,}compressed image, we may restore pages in place,
  * in which case some architectures need these pages cleaning before they
@@ -106,7 +108,8 @@  struct swap_map_handle {
 
 struct swsusp_header {
 	char reserved[PAGE_SIZE - 20 - sizeof(sector_t) - sizeof(int) -
-	              sizeof(u32)];
+	              sizeof(u32) - sizeof(u32)];
+	u32	hw_sig;
 	u32	crc32;
 	sector_t image;
 	unsigned int flags;	/* Flags to pass to the "boot" kernel */
@@ -303,7 +306,6 @@  static blk_status_t hib_wait_io(struct hib_bio_batch *hb)
 /*
  * Saving part
  */
-
 static int mark_swapfiles(struct swap_map_handle *handle, unsigned int flags)
 {
 	int error;
@@ -315,6 +317,10 @@  static int mark_swapfiles(struct swap_map_handle *handle, unsigned int flags)
 		memcpy(swsusp_header->orig_sig,swsusp_header->sig, 10);
 		memcpy(swsusp_header->sig, HIBERNATE_SIG, 10);
 		swsusp_header->image = handle->first_sector;
+		if (swsusp_hardware_signature) {
+			swsusp_header->hw_sig = swsusp_hardware_signature;
+			flags |= SF_HW_SIG;
+		}
 		swsusp_header->flags = flags;
 		if (flags & SF_CRC32_MODE)
 			swsusp_header->crc32 = handle->crc32;
@@ -1533,6 +1539,12 @@  int swsusp_check(void)
 		} else {
 			error = -EINVAL;
 		}
+		if (!error && swsusp_header->flags & SF_HW_SIG &&
+		    swsusp_header->hw_sig != swsusp_hardware_signature) {
+			pr_info("Suspend image hardware signature mismatch (%08x now %08x); aborting resume.\n",
+				swsusp_header->hw_sig, swsusp_hardware_signature);
+			error = -EINVAL;
+		}
 
 put:
 		if (error)