Commit 8c89d3ad authored by Ard Biesheuvel's avatar Ard Biesheuvel Committed by Borislav Petkov (AMD)
Browse files

x86/sev: Don't emit BSS_DECRYPTED section unless it is in use 



The BSS_DECRYPTED section that gets emitted into .bss will be empty if
CONFIG_AMD_MEM_ENCRYPT is not defined. However, due to the fact that it
is injected into .bss rather than emitted as a separate section, the
2 MiB alignment that it specifies is still taken into account
unconditionally, pushing .bss out to the next 2 MiB boundary, leaving
a gap that is never freed.

So only emit a non-empty BSS_DECRYPTED section if it is going to be
used.  In that case, it would still be nice to free the padding, but
that is left for later.

Signed-off-by: default avatarArd Biesheuvel <ardb@kernel.org>
Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Link: https://patch.msgid.link/20260108092526.28586-23-ardb@kernel.org
parent af05e558

arch/x86/kernel/vmlinux.lds.S

+12 −9
Original line number Diff line number Diff line
@@ -67,7 +67,18 @@ const_cpu_current_top_of_stack = cpu_current_top_of_stack; 


#define ALIGN_ENTRY_TEXT_BEGIN	. = ALIGN(PMD_SIZE);

#define ALIGN_ENTRY_TEXT_END	. = ALIGN(PMD_SIZE);

#else



#define X86_ALIGN_RODATA_BEGIN

#define X86_ALIGN_RODATA_END					\

		. = ALIGN(PAGE_SIZE);				\

		__end_rodata_aligned = .;



#define ALIGN_ENTRY_TEXT_BEGIN

#define ALIGN_ENTRY_TEXT_END

#endif



#ifdef CONFIG_AMD_MEM_ENCRYPT

/*

 * This section contains data which will be mapped as decrypted. Memory

 * encryption operates on a page basis. Make this section PMD-aligned
@@ -88,17 +99,9 @@ const_cpu_current_top_of_stack = cpu_current_top_of_stack; 
	__pi___end_bss_decrypted = .;				\



#else



#define X86_ALIGN_RODATA_BEGIN

#define X86_ALIGN_RODATA_END					\

		. = ALIGN(PAGE_SIZE);				\

		__end_rodata_aligned = .;



#define ALIGN_ENTRY_TEXT_BEGIN

#define ALIGN_ENTRY_TEXT_END

#define BSS_DECRYPTED



#endif



#if defined(CONFIG_X86_64) && defined(CONFIG_KEXEC_CORE)

#define KEXEC_RELOCATE_KERNEL					\

	. = ALIGN(0x100);					\