issue with kexec/kdump on imx6ull

Russell King - ARM Linux
2018-03-20T10:43:02Z

On Tue, Mar 20, 2018 at 11:04:27AM +0100, Arthur LAMBERT wrote:
> Hi,
>
> I am trying to use kexec/kdump on imx6ull evaluation kit without success.
> kernel : git://git.freescale.com/imx/linux-imx.git
> kernel tag : rel_imx_4.9.x_1.0.0_ga
> defconfig : imx_v7
> device tree : imx6ull-14x14-evk

The wrong patch was merged into kexec-tools, breaking ARM support for
kexec. I think I pointed this out to the kexec-tools maintainers after
it had already taken ages to get the patches merged, but never received
any response, so I now no longer care about the allegedly maintained
kexec-tools, sorry.

I've been considering putting a working git tree on git.armlinux.org.uk
to replace the "official" kexec-tools.

The patch which fixes the mis-merge is below:

8<=====
From: Russell King <rmk@armlinux.org.uk>
Subject: [PATCH] ARM: read kernel size from zImage

Signed-off-by: Russell King <rmk@armlinux.org.uk>
---
kexec/arch/arm/kexec-zImage-arm.c | 106 ++++++++++++++++++++++++++------------
1 file changed, 74 insertions(+), 32 deletions(-)

diff --git a/kexec/arch/arm/kexec-zImage-arm.c b/kexec/arch/arm/kexec-zImage-arm.c
index a8c40cb6cd6a..76a0b5b66745 100644
--- a/kexec/arch/arm/kexec-zImage-arm.c
+++ b/kexec/arch/arm/kexec-zImage-arm.c
@@ -355,6 +355,34 @@ static int setup_dtb_prop(char **bufp, off_t *sizep, int parentoffset,
return 0;
}

+static const struct zimage_tag *find_extension_tag(const char *buf, off_t len,
+ uint32_t tag_id)
+{
+ const struct zimage_header *hdr = (const struct zimage_header *)buf;
+ const struct zimage_tag *tag;
+ uint32_t offset, size;
+ uint32_t max = len - sizeof(struct tag_header);
+
+ if (len < sizeof(*hdr) ||
+ hdr->magic != ZIMAGE_MAGIC ||
+ hdr->magic2 != ZIMAGE_MAGIC2)
+ return NULL;
+
+ for (offset = hdr->extension_tag_offset;
+ (tag = (void *)(buf + offset)) != NULL &&
+ offset < max &&
+ (size = le32_to_cpu(byte_size(tag))) != 0 &&
+ offset + size < len;
+ offset += size) {
+ dbgprintf(" offset 0x%08x tag 0x%08x size %u\n",
+ offset, le32_to_cpu(tag->hdr.tag), size);
+ if (tag->hdr.tag == tag_id)
+ return tag;
+ }
+
+ return NULL;
+}
+
int zImage_arm_load(int argc, char **argv, const char *buf, off_t len,
struct kexec_info *info)
{
@@ -362,6 +390,7 @@ int zImage_arm_load(int argc, char **argv, const char *buf, off_t len,
unsigned long base, kernel_base;
unsigned int atag_offset = 0x1000; /* 4k offset from memory start */
unsigned int extra_size = 0x8000; /* TEXT_OFFSET */
+ const struct zimage_tag *tag;
size_t kernel_mem_size;
const char *command_line;
char *modified_cmdline = NULL;
@@ -480,35 +509,6 @@ int zImage_arm_load(int argc, char **argv, const char *buf, off_t len,
if (size < len)
len = size;
}
-
- /* Do we have an extension table? */
- if (hdr->magic2 == ZIMAGE_MAGIC2 && !kexec_arm_image_size) {
- uint32_t offset = hdr->extension_tag_offset;
- uint32_t max = len - sizeof(struct tag_header);
- struct zimage_tag *tag;
-
- dbgprintf("zImage has tags\n");
-
- for (offset = hdr->extension_tag_offset;
- (tag = (void *)(buf + offset)) != NULL &&
- offset < max && byte_size(tag) &&
- offset + byte_size(tag) < len;
- offset += byte_size(tag)) {
- dbgprintf(" offset 0x%08x tag 0x%08x size %u\n",
- offset, tag->hdr.tag, byte_size(tag));
- if (tag->hdr.tag == ZIMAGE_TAG_KRNL_SIZE) {
- uint32_t *p = (void *)buf +
- tag->u.krnl_size.size_ptr;
-
- kexec_arm_image_size =
- get_unaligned(p) +
- tag->u.krnl_size.bss_size;
- }
- }
-
- dbgprintf("kernel image size: 0x%08x\n",
- kexec_arm_image_size);
- }
}

/* Handle android images, 2048 is the minimum page size */
@@ -553,9 +553,40 @@ int zImage_arm_load(int argc, char **argv, const char *buf, off_t len,
kernel_mem_size = len + 4;

/*
- * If the user didn't specify the size of the image, assume the
- * maximum kernel compression ratio is 4. Note that we must
- * include space for the compressed image here as well.
+ * Check for a kernel size extension, and set or validate the
+ * image size. This is the total space needed to avoid the
+ * boot kernel BSS, so other data (such as initrd) does not get
+ * overwritten.
+ */
+ tag = find_extension_tag(buf, len, ZIMAGE_TAG_KRNL_SIZE);
+ if (tag) {
+ uint32_t *p = (void *)buf + le32_to_cpu(tag->u.krnl_size.size_ptr);
+ uint32_t edata_size = le32_to_cpu(get_unaligned(p));
+ uint32_t bss_size = le32_to_cpu(tag->u.krnl_size.bss_size);
+ uint32_t kernel_size = edata_size + bss_size;
+
+ /*
+ * While decompressing, the zImage is placed past _edata
+ * of the decompressed kernel. Ensure we account for that.
+ */
+ if (kernel_size < edata_size + len)
+ kernel_size = edata_size + len;
+
+ if (kexec_arm_image_size == 0)
+ kexec_arm_image_size = kernel_size;
+ else if (kexec_arm_image_size < kernel_size) {
+ fprintf(stderr,
+ "Kernel size is too small, increasing to 0x%lx\n",
+ (unsigned long)kernel_size);
+ kexec_arm_image_size = kernel_size;
+ }
+ }
+
+ /*
+ * If the user didn't specify the size of the image, and we don't
+ * have the extension tables, assume the maximum kernel compression
+ * ratio is 4. Note that we must include space for the compressed
+ * image here as well.
*/
if (!kexec_arm_image_size)
kexec_arm_image_size = len * 5;
@@ -617,6 +648,10 @@ int zImage_arm_load(int argc, char **argv, const char *buf, off_t len,
*/
initrd_base = kernel_base + _ALIGN(kexec_arm_image_size, page_size);

+ dbgprintf("%-6s: address=0x%08lx size=0x%08lx\n", "Kernel",
+ (unsigned long)kernel_base,
+ (unsigned long)kexec_arm_image_size);
+
if (ramdisk_buf) {
/*
* Find a hole to place the initrd. The crash kernel use
@@ -630,6 +665,10 @@ int zImage_arm_load(int argc, char **argv, const char *buf, off_t len,
return -1;
}

+ dbgprintf("%-6s: address=0x%08lx size=0x%08lx\n", "Initrd",
+ (unsigned long)initrd_base,
+ (unsigned long)initrd_size);
+
add_segment(info, ramdisk_buf, initrd_size, initrd_base,
initrd_size);
}
@@ -708,6 +747,9 @@ int zImage_arm_load(int argc, char **argv, const char *buf, off_t len,
return -1;
}

+ dbgprintf("%-6s: address=0x%08lx size=0x%08lx\n", "DT",
+ (unsigned long)dtb_offset, (unsigned long)dtb_length);
+
add_segment(info, dtb_buf, dtb_length, dtb_offset, dtb_length);
}

--
2.7.4

--
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
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