diff mbox series

[PATCHv12,4/9] x86/boot/compressed: Handle unaccepted memory

Message ID 20230518231434.26080-5-kirill.shutemov@linux.intel.com
State Superseded
Headers show
Series mm, x86/cc, efi: Implement support for unaccepted memory | expand

Commit Message

Kirill A. Shutemov May 18, 2023, 11:14 p.m. UTC 
The firmware will pre-accept the memory used to run the stub. But, the
stub is responsible for accepting the memory into which it decompresses
the main kernel. Accept memory just before decompression starts.

The stub is also responsible for choosing a physical address in which to
place the decompressed kernel image. The KASLR mechanism will randomize
this physical address. Since the accepted memory region is relatively
small, KASLR would be quite ineffective if it only used the pre-accepted
area (EFI_CONVENTIONAL_MEMORY). Ensure that KASLR randomizes among the
entire physical address space by also including EFI_UNACCEPTED_MEMORY.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Liam Merwick <liam.merwick@oracle.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
---
 arch/x86/boot/compressed/efi.h   | 10 +++++++++
 arch/x86/boot/compressed/kaslr.c | 35 +++++++++++++++++++++-----------
 arch/x86/boot/compressed/mem.c   | 23 +++++++++++++++++++++
 arch/x86/boot/compressed/misc.c  |  7 +++++++
 arch/x86/boot/compressed/misc.h  |  6 ++++++
 5 files changed, 69 insertions(+), 12 deletions(-)

Comments

Kirill A. Shutemov May 19, 2023, 10:16 a.m. UTC | #1 
On Fri, May 19, 2023 at 02:14:29AM +0300, Kirill A. Shutemov wrote:
> diff --git a/arch/x86/boot/compressed/mem.c b/arch/x86/boot/compressed/mem.c
> index 67594fcb11d9..87372b96d613 100644
> --- a/arch/x86/boot/compressed/mem.c
> +++ b/arch/x86/boot/compressed/mem.c
> @@ -1,9 +1,32 @@
>  // SPDX-License-Identifier: GPL-2.0-only
>  
>  #include "error.h"
> +#include "misc.h"
>  
>  void arch_accept_memory(phys_addr_t start, phys_addr_t end)
>  {
>  	/* Platform-specific memory-acceptance call goes here */
>  	error("Cannot accept memory");
>  }
> +
> +void init_unaccepted_memory(void)
> +{
> +	guid_t guid =  LINUX_EFI_UNACCEPTED_MEM_TABLE_GUID;
> +	struct efi_unaccepted_memory *unaccepted_table;
> +	unsigned long cfg_table_pa;
> +	unsigned int cfg_table_len;
> +	int ret;
> +
> +	ret = efi_get_conf_table(boot_params, &cfg_table_pa, &cfg_table_len);
> +	if (ret)
> +		error("EFI config table not found.");
> +
> +	unaccepted_table = (void *)efi_find_vendor_table(boot_params,
> +							 cfg_table_pa,
> +							 cfg_table_len,
> +							 guid);
> +	if (unaccepted_table->version != 1)
> +		error("Unknown version of unaccepted memory table\n");
> +
> +	set_unaccepted_table(unaccepted_table);
> +}

0-day reported boot failure outdise TDX guest with CONFIG_INTEL_TDX_GUEST=y.

The fixup:

diff --git a/arch/x86/boot/compressed/mem.c b/arch/x86/boot/compressed/mem.c
index 0108c97399a5..8df3d988ae69 100644
--- a/arch/x86/boot/compressed/mem.c
+++ b/arch/x86/boot/compressed/mem.c
@@ -56,6 +56,9 @@ void init_unaccepted_memory(void)
 							 cfg_table_pa,
 							 cfg_table_len,
 							 guid);
+	if (!unaccepted_table)
+		return;
+
 	if (unaccepted_table->version != 1)
 		error("Unknown version of unaccepted memory table\n");
Ard Biesheuvel May 22, 2023, 11:08 a.m. UTC | #2 
On Mon, 22 May 2023 at 13:01, Kirill A. Shutemov <kirill@shutemov.name> wrote:
>
> On Fri, May 19, 2023 at 01:16:41PM +0300, Kirill A. Shutemov wrote:
> > On Fri, May 19, 2023 at 02:14:29AM +0300, Kirill A. Shutemov wrote:
> > > diff --git a/arch/x86/boot/compressed/mem.c b/arch/x86/boot/compressed/mem.c
> > > index 67594fcb11d9..87372b96d613 100644
> > > --- a/arch/x86/boot/compressed/mem.c
> > > +++ b/arch/x86/boot/compressed/mem.c
> > > @@ -1,9 +1,32 @@
> > >  // SPDX-License-Identifier: GPL-2.0-only
> > >
> > >  #include "error.h"
> > > +#include "misc.h"
> > >
> > >  void arch_accept_memory(phys_addr_t start, phys_addr_t end)
> > >  {
> > >     /* Platform-specific memory-acceptance call goes here */
> > >     error("Cannot accept memory");
> > >  }
> > > +
> > > +void init_unaccepted_memory(void)
> > > +{
> > > +   guid_t guid =  LINUX_EFI_UNACCEPTED_MEM_TABLE_GUID;
> > > +   struct efi_unaccepted_memory *unaccepted_table;
> > > +   unsigned long cfg_table_pa;
> > > +   unsigned int cfg_table_len;
> > > +   int ret;
> > > +
> > > +   ret = efi_get_conf_table(boot_params, &cfg_table_pa, &cfg_table_len);
> > > +   if (ret)
> > > +           error("EFI config table not found.");
> > > +
> > > +   unaccepted_table = (void *)efi_find_vendor_table(boot_params,
> > > +                                                    cfg_table_pa,
> > > +                                                    cfg_table_len,
> > > +                                                    guid);
> > > +   if (unaccepted_table->version != 1)
> > > +           error("Unknown version of unaccepted memory table\n");
> > > +
> > > +   set_unaccepted_table(unaccepted_table);
> > > +}
> >
> > 0-day reported boot failure outdise TDX guest with CONFIG_INTEL_TDX_GUEST=y.
>
> 0-day folks reported one more issue: booting on non-EFI system fail.
>
> Updated fixup:
>
> diff --git a/arch/x86/boot/compressed/mem.c b/arch/x86/boot/compressed/mem.c
> index 0108c97399a5..e7f7ef31e581 100644
> --- a/arch/x86/boot/compressed/mem.c
> +++ b/arch/x86/boot/compressed/mem.c
> @@ -46,8 +46,13 @@ void init_unaccepted_memory(void)
>         struct efi_unaccepted_memory *unaccepted_table;
>         unsigned long cfg_table_pa;
>         unsigned int cfg_table_len;
> +       enum efi_type et;
>         int ret;
>
> +       et = efi_get_type(boot_params);
> +       if (et == EFI_TYPE_NONE)
> +               return;
> +
>         ret = efi_get_conf_table(boot_params, &cfg_table_pa, &cfg_table_len);
>         if (ret)
>                 error("EFI config table not found.");
> @@ -56,6 +61,9 @@ void init_unaccepted_memory(void)
>                                                          cfg_table_pa,
>                                                          cfg_table_len,
>                                                          guid);
> +       if (!unaccepted_table)
> +               return;
> +
>         if (unaccepted_table->version != 1)
>                 error("Unknown version of unaccepted memory table\n");
>

With these changes applied,

Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
diff mbox series

Patch

diff --git a/arch/x86/boot/compressed/efi.h b/arch/x86/boot/compressed/efi.h
index 7db2f41b54cd..866c0af8b5b9 100644
--- a/arch/x86/boot/compressed/efi.h
+++ b/arch/x86/boot/compressed/efi.h
@@ -16,6 +16,7 @@  typedef guid_t efi_guid_t __aligned(__alignof__(u32));
 #define ACPI_TABLE_GUID				EFI_GUID(0xeb9d2d30, 0x2d88, 0x11d3,  0x9a, 0x16, 0x00, 0x90, 0x27, 0x3f, 0xc1, 0x4d)
 #define ACPI_20_TABLE_GUID			EFI_GUID(0x8868e871, 0xe4f1, 0x11d3,  0xbc, 0x22, 0x00, 0x80, 0xc7, 0x3c, 0x88, 0x81)
 #define EFI_CC_BLOB_GUID			EFI_GUID(0x067b1f5f, 0xcf26, 0x44c5, 0x85, 0x54, 0x93, 0xd7, 0x77, 0x91, 0x2d, 0x42)
+#define LINUX_EFI_UNACCEPTED_MEM_TABLE_GUID	EFI_GUID(0xd5d1de3c, 0x105c, 0x44f9,  0x9e, 0xa9, 0xbc, 0xef, 0x98, 0x12, 0x00, 0x31)
 
 #define EFI32_LOADER_SIGNATURE	"EL32"
 #define EFI64_LOADER_SIGNATURE	"EL64"
@@ -32,6 +33,7 @@  typedef	struct {
 } efi_table_hdr_t;
 
 #define EFI_CONVENTIONAL_MEMORY		 7
+#define EFI_UNACCEPTED_MEMORY		15
 
 #define EFI_MEMORY_MORE_RELIABLE \
 				((u64)0x0000000000010000ULL)	/* higher reliability */
@@ -104,6 +106,14 @@  struct efi_setup_data {
 	u64 reserved[8];
 };
 
+struct efi_unaccepted_memory {
+	u32 version;
+	u32 unit_size;
+	u64 phys_base;
+	u64 size;
+	unsigned long bitmap[];
+};
+
 static inline int efi_guidcmp (efi_guid_t left, efi_guid_t right)
 {
 	return memcmp(&left, &right, sizeof (efi_guid_t));
diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index 454757fbdfe5..749f0fe7e446 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -672,6 +672,28 @@  static bool process_mem_region(struct mem_vector *region,
 }
 
 #ifdef CONFIG_EFI
+
+/*
+ * Only EFI_CONVENTIONAL_MEMORY and EFI_UNACCEPTED_MEMORY (if supported) are
+ * guaranteed to be free.
+ *
+ * It is more conservative in picking free memory than the EFI spec allows:
+ *
+ * According to the spec, EFI_BOOT_SERVICES_{CODE|DATA} are also free memory
+ * and thus available to place the kernel image into, but in practice there's
+ * firmware where using that memory leads to crashes.
+ */
+static inline bool memory_type_is_free(efi_memory_desc_t *md)
+{
+	if (md->type == EFI_CONVENTIONAL_MEMORY)
+		return true;
+
+	if (md->type == EFI_UNACCEPTED_MEMORY)
+		return IS_ENABLED(CONFIG_UNACCEPTED_MEMORY);
+
+	return false;
+}
+
 /*
  * Returns true if we processed the EFI memmap, which we prefer over the E820
  * table if it is available.
@@ -716,18 +738,7 @@  process_efi_entries(unsigned long minimum, unsigned long image_size)
 	for (i = 0; i < nr_desc; i++) {
 		md = efi_early_memdesc_ptr(pmap, e->efi_memdesc_size, i);
 
-		/*
-		 * Here we are more conservative in picking free memory than
-		 * the EFI spec allows:
-		 *
-		 * According to the spec, EFI_BOOT_SERVICES_{CODE|DATA} are also
-		 * free memory and thus available to place the kernel image into,
-		 * but in practice there's firmware where using that memory leads
-		 * to crashes.
-		 *
-		 * Only EFI_CONVENTIONAL_MEMORY is guaranteed to be free.
-		 */
-		if (md->type != EFI_CONVENTIONAL_MEMORY)
+		if (!memory_type_is_free(md))
 			continue;
 
 		if (efi_soft_reserve_enabled() &&
diff --git a/arch/x86/boot/compressed/mem.c b/arch/x86/boot/compressed/mem.c
index 67594fcb11d9..87372b96d613 100644
--- a/arch/x86/boot/compressed/mem.c
+++ b/arch/x86/boot/compressed/mem.c
@@ -1,9 +1,32 @@ 
 // SPDX-License-Identifier: GPL-2.0-only
 
 #include "error.h"
+#include "misc.h"
 
 void arch_accept_memory(phys_addr_t start, phys_addr_t end)
 {
 	/* Platform-specific memory-acceptance call goes here */
 	error("Cannot accept memory");
 }
+
+void init_unaccepted_memory(void)
+{
+	guid_t guid =  LINUX_EFI_UNACCEPTED_MEM_TABLE_GUID;
+	struct efi_unaccepted_memory *unaccepted_table;
+	unsigned long cfg_table_pa;
+	unsigned int cfg_table_len;
+	int ret;
+
+	ret = efi_get_conf_table(boot_params, &cfg_table_pa, &cfg_table_len);
+	if (ret)
+		error("EFI config table not found.");
+
+	unaccepted_table = (void *)efi_find_vendor_table(boot_params,
+							 cfg_table_pa,
+							 cfg_table_len,
+							 guid);
+	if (unaccepted_table->version != 1)
+		error("Unknown version of unaccepted memory table\n");
+
+	set_unaccepted_table(unaccepted_table);
+}
diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index 014ff222bf4b..36535a3753f5 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -455,6 +455,13 @@  asmlinkage __visible void *extract_kernel(void *rmode, memptr heap,
 #endif
 
 	debug_putstr("\nDecompressing Linux... ");
+
+	if (IS_ENABLED(CONFIG_UNACCEPTED_MEMORY)) {
+		debug_putstr("Accepting memory... ");
+		init_unaccepted_memory();
+		accept_memory(__pa(output), __pa(output) + needed_size);
+	}
+
 	__decompress(input_data, input_len, NULL, NULL, output, output_len,
 			NULL, error);
 	entry_offset = parse_elf(output);
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index 2f155a0e3041..e1a0b49e0ed2 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -247,4 +247,10 @@  static inline unsigned long efi_find_vendor_table(struct boot_params *bp,
 }
 #endif /* CONFIG_EFI */
 
+void init_unaccepted_memory(void);
+
+/* Implemented in EFI stub */
+void set_unaccepted_table(struct efi_unaccepted_memory *table);
+void accept_memory(phys_addr_t start, phys_addr_t end);
+
 #endif /* BOOT_COMPRESSED_MISC_H */