While introducing new code to extract the kernel offset from the
image, commit fd0a05b ("arm64: Obtain text offset from kernel image")
introduced a regression where something such as:

  ./lkvm run -c 8 -p earlycon <(zcat 
/boot/vmlinuz-5.8.0-rc5-00172-ga161216e31ba)

now fails to load the kernel, as the file descriptor cannot be
seeked.

Let's assume the good old 0x80000 offset when the seek syscall fails,
with a warning for a good measure.

Fixes: fd0a05b ("arm64: Obtain text offset from kernel image")
Signed-off-by: Marc Zyngier <[email protected]>
---
 arm/aarch64/kvm.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/arm/aarch64/kvm.c b/arm/aarch64/kvm.c
index a46d438..49e1dd3 100644
--- a/arm/aarch64/kvm.c
+++ b/arm/aarch64/kvm.c
@@ -15,6 +15,7 @@ unsigned long long kvm__arch_get_kern_offset(struct kvm *kvm, 
int fd)
        struct arm64_image_header header;
        off_t cur_offset;
        ssize_t size;
+       const char *warn_str;
 
        /* the 32bit kernel offset is a well known value */
        if (kvm->cfg.arch.aarch32_guest)
@@ -22,8 +23,10 @@ unsigned long long kvm__arch_get_kern_offset(struct kvm 
*kvm, int fd)
 
        cur_offset = lseek(fd, 0, SEEK_CUR);
        if (cur_offset == (off_t)-1 ||
-           lseek(fd, 0, SEEK_SET) == (off_t)-1)
-               die("Failed to seek in image file");
+           lseek(fd, 0, SEEK_SET) == (off_t)-1) {
+               warn_str = "Failed to seek in kernel image file";
+               goto fail;
+       }
 
        size = xread(fd, &header, sizeof(header));
        if (size < 0 || (size_t)size < sizeof(header))
@@ -37,7 +40,9 @@ unsigned long long kvm__arch_get_kern_offset(struct kvm *kvm, 
int fd)
        if (le64_to_cpu(header.image_size))
                return le64_to_cpu(header.text_offset);
 
-       pr_warning("Image size is 0, assuming TEXT_OFFSET to be 0x80000");
+       warn_str = "Image size is 0";
+fail:
+       pr_warning("%s, assuming TEXT_OFFSET to be 0x80000", warn_str);
        return 0x80000;
 }
 
-- 
2.27.0

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