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Subject: [PATCH 08/11] ppc64/kexec_file: setup the stack for purgatory
From:   Hari Bathini <hbathini@linux.ibm.com>
To:     Michael Ellerman <mpe@ellerman.id.au>,
        Andrew Morton <akpm@linux-foundation.org>
Cc:     Pingfan Liu <piliu@redhat.com>,
        Kexec-ml <kexec@lists.infradead.org>,
        Mimi Zohar <zohar@linux.ibm.com>,
        Petr Tesarik <ptesarik@suse.cz>,
        Mahesh J Salgaonkar <mahesh@linux.ibm.com>,
        Sourabh Jain <sourabhjain@linux.ibm.com>,
        lkml <linux-kernel@vger.kernel.org>,
        linuxppc-dev <linuxppc-dev@ozlabs.org>,
        Eric Biederman <ebiederm@xmission.com>,
        Thiago Jung Bauermann <bauerman@linux.ibm.com>,
        Dave Young <dyoung@redhat.com>, Vivek Goyal <vgoyal@redhat.com>
Date:   Sat, 27 Jun 2020 00:35:50 +0530
Message-ID: <159319835023.16351.6771622598460231857.stgit@hbathini.in.ibm.com>
In-Reply-To: <159319825403.16351.7253978047621755765.stgit@hbathini.in.ibm.com>
References: <159319825403.16351.7253978047621755765.stgit@hbathini.in.ibm.com>
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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@linux.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