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From:   Pavel Tatashin <pasha.tatashin@soleen.com>
To:     pasha.tatashin@soleen.com, jmorris@namei.org, sashal@kernel.org,
        ebiederm@xmission.com, kexec@lists.infradead.org,
        linux-kernel@vger.kernel.org, corbet@lwn.net,
        catalin.marinas@arm.com, will@kernel.org,
        linux-arm-kernel@lists.infradead.org, maz@kernel.org,
        james.morse@arm.com, vladimir.murzin@arm.com,
        matthias.bgg@gmail.com, linux-mm@kvack.org, mark.rutland@arm.com,
        steve.capper@arm.com, rfontana@redhat.com, tglx@linutronix.de,
        selindag@gmail.com, tyhicks@linux.microsoft.com,
        kernelfans@gmail.com, akpm@linux-foundation.org,
        madvenka@linux.microsoft.com
Subject: [PATCH v16 10/15] arm64: kexec: use ld script for relocation function
Date:   Mon,  2 Aug 2021 17:54:03 -0400
Message-Id: <20210802215408.804942-11-pasha.tatashin@soleen.com>
In-Reply-To: <20210802215408.804942-1-pasha.tatashin@soleen.com>
References: <20210802215408.804942-1-pasha.tatashin@soleen.com>
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Currently, relocation code declares start and end variables
which are used to compute its size.

The better way to do this is to use ld script incited, and put relocation
function in its own section.

Signed-off-by: Pavel Tatashin <pasha.tatashin@soleen.com>
---
 arch/arm64/include/asm/sections.h   |  1 +
 arch/arm64/kernel/machine_kexec.c   | 16 ++++++----------
 arch/arm64/kernel/relocate_kernel.S | 15 ++-------------
 arch/arm64/kernel/vmlinux.lds.S     | 19 +++++++++++++++++++
 4 files changed, 28 insertions(+), 23 deletions(-)

diff --git a/arch/arm64/include/asm/sections.h b/arch/arm64/include/asm/sections.h
index e4ad9db53af1..152cb35bf9df 100644
--- a/arch/arm64/include/asm/sections.h
+++ b/arch/arm64/include/asm/sections.h
@@ -21,5 +21,6 @@ extern char __exittext_begin[], __exittext_end[];
 extern char __irqentry_text_start[], __irqentry_text_end[];
 extern char __mmuoff_data_start[], __mmuoff_data_end[];
 extern char __entry_tramp_text_start[], __entry_tramp_text_end[];
+extern char __relocate_new_kernel_start[], __relocate_new_kernel_end[];
 
 #endif /* __ASM_SECTIONS_H */
diff --git a/arch/arm64/kernel/machine_kexec.c b/arch/arm64/kernel/machine_kexec.c
index cf5d6f22a041..83da6045cd45 100644
--- a/arch/arm64/kernel/machine_kexec.c
+++ b/arch/arm64/kernel/machine_kexec.c
@@ -21,14 +21,11 @@
 #include <asm/mmu.h>
 #include <asm/mmu_context.h>
 #include <asm/page.h>
+#include <asm/sections.h>
 #include <asm/trans_pgd.h>
 
 #include "cpu-reset.h"
 
-/* Global variables for the arm64_relocate_new_kernel routine. */
-extern const unsigned char arm64_relocate_new_kernel[];
-extern const unsigned long arm64_relocate_new_kernel_size;
-
 /**
  * kexec_image_info - For debugging output.
  */
@@ -163,6 +160,7 @@ static void *kexec_page_alloc(void *arg)
 int machine_kexec_post_load(struct kimage *kimage)
 {
 	void *reloc_code = page_to_virt(kimage->control_code_page);
+	long reloc_size;
 	struct trans_pgd_info info = {
 		.trans_alloc_page	= kexec_page_alloc,
 		.trans_alloc_arg	= kimage,
@@ -183,17 +181,15 @@ int machine_kexec_post_load(struct kimage *kimage)
 			return rc;
 	}
 
-	memcpy(reloc_code, arm64_relocate_new_kernel,
-	       arm64_relocate_new_kernel_size);
+	reloc_size = __relocate_new_kernel_end - __relocate_new_kernel_start;
+	memcpy(reloc_code, __relocate_new_kernel_start, reloc_size);
 	kimage->arch.kern_reloc = __pa(reloc_code);
 
 	/* Flush the reloc_code in preparation for its execution. */
 	dcache_clean_inval_poc((unsigned long)reloc_code,
-			       (unsigned long)reloc_code +
-			       arm64_relocate_new_kernel_size);
+			       (unsigned long)reloc_code +  reloc_size);
 	icache_inval_pou((uintptr_t)reloc_code,
-			 (uintptr_t)reloc_code +
-			 arm64_relocate_new_kernel_size);
+			 (uintptr_t)reloc_code + reloc_size);
 	kexec_list_flush(kimage);
 	kexec_image_info(kimage);
 
diff --git a/arch/arm64/kernel/relocate_kernel.S b/arch/arm64/kernel/relocate_kernel.S
index b4fb97312a80..9d2400855ee4 100644
--- a/arch/arm64/kernel/relocate_kernel.S
+++ b/arch/arm64/kernel/relocate_kernel.S
@@ -15,6 +15,7 @@
 #include <asm/sysreg.h>
 #include <asm/virt.h>
 
+.pushsection    ".kexec_relocate.text", "ax"
 /*
  * arm64_relocate_new_kernel - Put a 2nd stage image in place and boot it.
  *
@@ -77,16 +78,4 @@ SYM_CODE_START(arm64_relocate_new_kernel)
 	mov	x3, xzr
 	br	x4				/* Jumps from el1 */
 SYM_CODE_END(arm64_relocate_new_kernel)
-
-.align 3	/* To keep the 64-bit values below naturally aligned. */
-
-.Lcopy_end:
-.org	KEXEC_CONTROL_PAGE_SIZE
-
-/*
- * arm64_relocate_new_kernel_size - Number of bytes to copy to the
- * control_code_page.
- */
-.globl arm64_relocate_new_kernel_size
-arm64_relocate_new_kernel_size:
-	.quad	.Lcopy_end - arm64_relocate_new_kernel
+.popsection
diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
index 709d2c433c5e..9479d66f03bf 100644
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S
@@ -63,6 +63,7 @@
 #include <asm-generic/vmlinux.lds.h>
 #include <asm/cache.h>
 #include <asm/kernel-pgtable.h>
+#include <asm/kexec.h>
 #include <asm/memory.h>
 #include <asm/page.h>
 
@@ -100,6 +101,16 @@ jiffies = jiffies_64;
 #define HIBERNATE_TEXT
 #endif
 
+#ifdef CONFIG_KEXEC_CORE
+#define KEXEC_TEXT					\
+	. = ALIGN(SZ_4K);				\
+	__relocate_new_kernel_start = .;		\
+	*(.kexec_relocate.text)				\
+	__relocate_new_kernel_end = .;
+#else
+#define KEXEC_TEXT
+#endif
+
 #ifdef CONFIG_UNMAP_KERNEL_AT_EL0
 #define TRAMP_TEXT					\
 	. = ALIGN(PAGE_SIZE);				\
@@ -160,6 +171,7 @@ SECTIONS
 			HYPERVISOR_TEXT
 			IDMAP_TEXT
 			HIBERNATE_TEXT
+			KEXEC_TEXT
 			TRAMP_TEXT
 			*(.fixup)
 			*(.gnu.warning)
@@ -348,3 +360,10 @@ ASSERT(swapper_pg_dir - reserved_pg_dir == RESERVED_SWAPPER_OFFSET,
 ASSERT(swapper_pg_dir - tramp_pg_dir == TRAMP_SWAPPER_OFFSET,
        "TRAMP_SWAPPER_OFFSET is wrong!")
 #endif
+
+#ifdef CONFIG_KEXEC_CORE
+/* kexec relocation code should fit into one KEXEC_CONTROL_PAGE_SIZE */
+ASSERT(__relocate_new_kernel_end - (__relocate_new_kernel_start & ~(SZ_4K - 1))
+	<= SZ_4K, "kexec relocation code is too big or misaligned")
+ASSERT(KEXEC_CONTROL_PAGE_SIZE >= SZ_4K, "KEXEC_CONTROL_PAGE_SIZE is brokern")
+#endif
-- 
2.25.1