[BISECTED] kexec issue with v4.15-rc on N8x0
Russell King - ARM Linux
linux at armlinux.org.uk
Tue Jan 23 13:23:27 PST 2018
On Tue, Jan 23, 2018 at 08:45:44PM +0000, Russell King - ARM Linux wrote:
> On Tue, Jan 23, 2018 at 12:06:54AM +0200, Aaro Koskinen wrote:
> > Hi,
> >
> > On Mon, Jan 15, 2018 at 10:15:08AM -0800, Tony Lindgren wrote:
> > > * Aaro Koskinen <aaro.koskinen at iki.fi> [180111 11:48]:
> > > > When booting v4.15-rc kernel with kexec (kexec-tools 2.0.16) on N8x0, I get:
> > > >
> > > > Uncompressing Linux... done, booting the kernel.
> > > > no ATAGS support: can't continue
> > > >
> > > > v4.14 kernel works OK.
> > > >
> > > > I bisected this to:
> > > >
> > > > commit c772568788b5f0cbaac7c8d4111d7173bfc90673
> > > > Author: Russell King <rmk+kernel at armlinux.org.uk>
> > > > Date: Thu Sep 21 18:10:19 2017 +0100
> > > >
> > > > ARM: add additional table to compressed kernel
> > > >
> > > > If I revert the commit, kexec booting starts to work. Interesting,
> > > > the patch mentions "This is necessary for correct behaviour of kexec.",
> > > > so I wonder what could be wrong...
> > >
> > > So care to post what you get if you load with kexec -d -l options
> > > before and after this commit?
> >
> > See below. I guess the interesting part is the "zImage has tags" with the
> > bad kernel.
> >
> > Bad (plain v4.15-rc9)
> > ---------------------
> > kernel: 0xb6a25008 kernel_size: 0x3ce605
> > MEMORY RANGES
> > 0000000080000000-0000000087ffffff (0)
> > zImage header: 0x016f2818 0x00000000 0x003c59d0
> > zImage size 0x3c59d0, file size 0x3ce605
>
> This looks like you've appended a DTB blob to the zImage as the file
> is larger than the zImage says it should be.
>
> > zImage has tags
> > offset 0x00003be0 tag 0x5a534c4b size 8
>
> Right, so this says that this is a "modern" kernel that's being loaded
> with the additional tags in that tell kexec how much space the
> decompressed kernel requires.
>
> > kernel image size: 0x00c5c6ec
>
> and it requires this amount of space.
>
> > kexec_load: entry = 0x80008000 flags = 0x280000
> > nr_segments = 2
> > segment[0].buf = 0xb6a25008
> > segment[0].bufsz = 0x3c59d0
> > segment[0].mem = 0x80008000
> > segment[0].memsz = 0x3c6000
>
> This is the kernel, with the appended dtb removed.
>
> > segment[1].buf = 0x1ed52b8
> > segment[1].bufsz = 0x8c35
> > segment[1].mem = 0x80c66000
> > segment[1].memsz = 0x9000
>
> This is the DTB, placed out of the way from the kernel (the highest
> address the kernel will use while decompressing is 0x00c5c6ec +
> 0x80008000. Everything here looks correct.
>
> > [ 4.850341] kexec_core: Starting new kernel
> > [ 4.854766] Bye!
> >
> > (kernel fails to boot)
> >
> > Good (v4.15-rc9 and c772568788b5f0cbaac7c8d4111d7173bfc90673 reverted)
> > -----------------------------
> > kernel: 0xb6999008 kernel_size: 0x3ce9bd
> > MEMORY RANGES
> > 0000000080000000-0000000087ffffff (0)
> > zImage header: 0x016f2818 0x00000000 0x003c5d88
> > zImage size 0x3c5d88, file size 0x3ce9bd
> > kexec_load: entry = 0x80008000 flags = 0x280000
> > nr_segments = 2
> > segment[0].buf = 0xb6999008
> > segment[0].bufsz = 0x3c5d88
> > segment[0].mem = 0x80008000
> > segment[0].memsz = 0x3c6000
>
> Here we have the same thing for the kernel.
>
> > segment[1].buf = 0x14192b8
> > segment[1].bufsz = 0x8c35
> > segment[1].mem = 0x812e7000
> > segment[1].memsz = 0x9000
>
> Here, the DTB is placed much further away.
>
> Unfortunately, with this debug, it's still not possible to debug this.
>
> I'm rather sick of these image placement issues, there seems to be no
> solution here that works for everyone, no matter how hard I try with
> my knowledge of how the ARM kernel decompresses and places itself.
>
> It really doesn't help that it took ages for the kexec-tools patches
> to get merged, and when they did get merged, the wrong patch set was
> taken. Consequently, the debug above does not match my local source
> tree, and neither does the code.
>
> Sorry, but I'm afraid I can't debug this at the moment.
Here's the delta between what _was_ merged and what I intended to be
merged:
8<=====
From: Russell King <rmk at armlinux.org.uk>
Subject: [PATCH] ARM: read kernel size from zImage
Signed-off-by: Russell King <rmk at 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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