linux-kernel - [PATCH 08/11] ppc64/kexec_file: setup the stack for purgatory

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Date:   Sat, 27 Jun 2020 00:35:50 +0530
From:   Hari Bathini <hbathini@...ux.ibm.com>
To:     Michael Ellerman <mpe@...erman.id.au>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Pingfan Liu <piliu@...hat.com>,
        Kexec-ml <kexec@...ts.infradead.org>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        Petr Tesarik <ptesarik@...e.cz>,
        Mahesh J Salgaonkar <mahesh@...ux.ibm.com>,
        Sourabh Jain <sourabhjain@...ux.ibm.com>,
        lkml <linux-kernel@...r.kernel.org>,
        linuxppc-dev <linuxppc-dev@...abs.org>,
        Eric Biederman <ebiederm@...ssion.com>,
        Thiago Jung Bauermann <bauerman@...ux.ibm.com>,
        Dave Young <dyoung@...hat.com>, Vivek Goyal <vgoyal@...hat.com>
Subject: [PATCH 08/11] ppc64/kexec_file: setup the stack for purgatory

To avoid any weird errors, the purgatory should run with its own
stack. Set one up by adding the stack buffer to .data section of
the purgatory.

Signed-off-by: Hari Bathini <hbathini@...ux.ibm.com>
---
 arch/powerpc/include/asm/kexec.h       |    4 ++++
 arch/powerpc/kexec/file_load_64.c      |   14 +++++++++++++-
 arch/powerpc/purgatory/trampoline_64.S |   15 +++++++++++++++
 3 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/kexec.h b/arch/powerpc/include/asm/kexec.h
index bf47a01..e78cd0a 100644
--- a/arch/powerpc/include/asm/kexec.h
+++ b/arch/powerpc/include/asm/kexec.h
@@ -45,6 +45,10 @@
 #define KEXEC_ARCH KEXEC_ARCH_PPC
 #endif
 
+#ifdef CONFIG_KEXEC_FILE
+#define KEXEC_PURGATORY_STACK_SIZE	16384	/* 16KB stack size */
+#endif
+
 #define KEXEC_STATE_NONE 0
 #define KEXEC_STATE_IRQS_OFF 1
 #define KEXEC_STATE_REAL_MODE 2
diff --git a/arch/powerpc/kexec/file_load_64.c b/arch/powerpc/kexec/file_load_64.c
index 4430336..8e66c28 100644
--- a/arch/powerpc/kexec/file_load_64.c
+++ b/arch/powerpc/kexec/file_load_64.c
@@ -878,7 +878,8 @@ int setup_purgatory_ppc64(struct kimage *image, const void *slave_code,
 			  const void *fdt, unsigned long kernel_load_addr,
 			  unsigned long fdt_load_addr)
 {
-	uint64_t toc_ptr;
+	uint64_t toc_ptr, stack_top;
+	void *stack_buf;
 	int ret;
 
 	ret = setup_purgatory(image, slave_code, fdt, kernel_load_addr,
@@ -901,6 +902,17 @@ int setup_purgatory_ppc64(struct kimage *image, const void *slave_code,
 			goto out;
 	}
 
+	/* Setup the stack top */
+	stack_buf = kexec_purgatory_get_symbol_addr(image, "stack_buf");
+	if (!stack_buf)
+		goto out;
+
+	stack_top = (u64)stack_buf + KEXEC_PURGATORY_STACK_SIZE;
+	ret = kexec_purgatory_get_set_symbol(image, "stack", &stack_top,
+					     sizeof(stack_top), false);
+	if (ret)
+		goto out;
+
 	/* Setup the TOC pointer */
 	toc_ptr = get_toc_ptr(image->purgatory_info.ehdr);
 	ret = kexec_purgatory_get_set_symbol(image, "my_toc", &toc_ptr,
diff --git a/arch/powerpc/purgatory/trampoline_64.S b/arch/powerpc/purgatory/trampoline_64.S
index 7b4a5f7..80615b4 100644
--- a/arch/powerpc/purgatory/trampoline_64.S
+++ b/arch/powerpc/purgatory/trampoline_64.S
@@ -9,6 +9,7 @@
  * Copyright (C) 2013, Anton Blanchard, IBM Corporation
  */
 
+#include <asm/kexec.h>
 #include <asm/asm-compat.h>
 
 	.machine ppc64
@@ -53,6 +54,8 @@ master:
 
 	ld	%r2,(my_toc - 0b)(%r18)		/* setup toc */
 
+	ld	%r1,(stack - 0b)(%r18)		/* setup stack */
+
 	/* load device-tree address */
 	ld	%r3, (dt_offset - 0b)(%r18)
 	mr	%r16,%r3	/* save dt address in reg16 */
@@ -111,6 +114,12 @@ my_toc:
 	.8byte  0x0
 	.size my_toc, . - my_toc
 
+	.balign 8
+	.globl stack
+stack:
+	.8byte  0x0
+	.size stack, . - stack
+
 	.data
 	.balign 8
 .globl purgatory_sha256_digest
@@ -123,3 +132,9 @@ purgatory_sha256_digest:
 purgatory_sha_regions:
 	.skip	8 * 2 * 16
 	.size purgatory_sha_regions, . - purgatory_sha_regions
+
+	.balign 8
+.globl stack_buf
+stack_buf:
+	.skip	KEXEC_PURGATORY_STACK_SIZE
+	.size stack_buf, . - stack_buf