[PATCH v2 08/12] ppc64/kexec_file: setup the stack for purgatory

From: Hari Bathini
Date: Thu Jul 02 2020 - 15:56:32 EST


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. Also, setup opal base & entry values in r8 & r9
registers to help early OPAL debugging.

Signed-off-by: Hari Bathini <hbathini@xxxxxxxxxxxxx>
---

Changes in v2:
* Setting up opal base & entry values in r8 & r9 for early OPAL debug.


arch/powerpc/include/asm/kexec.h | 4 ++++
arch/powerpc/kexec/file_load_64.c | 29 +++++++++++++++++++++++++++++
arch/powerpc/purgatory/trampoline_64.S | 32 ++++++++++++++++++++++++++++++++
3 files changed, 65 insertions(+)

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 adca9c0..f06dcf1 100644
--- a/arch/powerpc/kexec/file_load_64.c
+++ b/arch/powerpc/kexec/file_load_64.c
@@ -873,6 +873,8 @@ int setup_purgatory_ppc64(struct kimage *image, const void *slave_code,
const void *fdt, unsigned long kernel_load_addr,
unsigned long fdt_load_addr)
{
+ struct device_node *dn;
+ void *stack_buf;
uint64_t val;
int ret;

@@ -896,10 +898,37 @@ 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;
+
+ val = (u64)stack_buf + KEXEC_PURGATORY_STACK_SIZE;
+ ret = kexec_purgatory_get_set_symbol(image, "stack", &val, sizeof(val),
+ false);
+ if (ret)
+ goto out;
+
/* Setup the TOC pointer */
val = get_toc_ptr(image->purgatory_info.ehdr);
ret = kexec_purgatory_get_set_symbol(image, "my_toc", &val, sizeof(val),
false);
+ if (ret)
+ goto out;
+
+ /* Setup OPAL base & entry values */
+ dn = of_find_node_by_path("/ibm,opal");
+ if (dn) {
+ of_property_read_u64(dn, "opal-base-address", &val);
+ ret = kexec_purgatory_get_set_symbol(image, "opal_base", &val,
+ sizeof(val), false);
+ if (ret)
+ goto out;
+
+ of_property_read_u64(dn, "opal-entry-address", &val);
+ ret = kexec_purgatory_get_set_symbol(image, "opal_entry", &val,
+ sizeof(val), false);
+ }
out:
if (ret)
pr_err("Failed to setup purgatory symbols");
diff --git a/arch/powerpc/purgatory/trampoline_64.S b/arch/powerpc/purgatory/trampoline_64.S
index 7b4a5f7..83e93b7 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 */
@@ -63,6 +66,11 @@ master:
li %r4,28
STWX_BE %r17,%r3,%r4 /* Store my cpu as __be32 at byte 28 */
1:
+
+ /* Load opal base and entry values in r8 & r9 respectively */
+ ld %r8,(opal_base - 0b)(%r18)
+ ld %r9,(opal_entry - 0b)(%r18)
+
/* load the kernel address */
ld %r4,(kernel - 0b)(%r18)

@@ -111,6 +119,24 @@ my_toc:
.8byte 0x0
.size my_toc, . - my_toc

+ .balign 8
+ .globl stack
+stack:
+ .8byte 0x0
+ .size stack, . - stack
+
+ .balign 8
+ .globl opal_base
+opal_base:
+ .8byte 0x0
+ .size opal_base, . - opal_base
+
+ .balign 8
+ .globl opal_entry
+opal_entry:
+ .8byte 0x0
+ .size opal_entry, . - opal_entry
+
.data
.balign 8
.globl purgatory_sha256_digest
@@ -123,3 +149,9 @@ 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