Clang16 links the purgatory text in two sections when PGO is in use:
[ 1] .text PROGBITS 0000000000000000 00000040
00000000000011a1 0000000000000000 AX 0 0 16
[ 2] .rela.text RELA 0000000000000000 00003498
0000000000000648 0000000000000018 I 24 1 8
...
[17] .text.hot. PROGBITS 0000000000000000 00003220
000000000000020b 0000000000000000 AX 0 0 1
[18] .rela.text.hot. RELA 0000000000000000 00004428
0000000000000078 0000000000000018 I 24 17 8
And both of them have their range [sh_addr ... sh_addr+sh_size] on the
area pointed by `e_entry`.
This causes that image->start is calculated twice, once for .text and
another time for .text.hot. The second calculation leaves image->start
in a random location.
Because of this, the system crashes immediately after:
kexec_core: Starting new kernel
Cc: stable@xxxxxxxxxxxxxxx
Fixes: 930457057abe ("kernel/kexec_file.c: split up __kexec_load_puragory")
Reviewed-by: Ross Zwisler <zwisler@xxxxxxxxxx>
Reviewed-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
Reviewed-by: Philipp Rudo <prudo@xxxxxxxxxx>
Signed-off-by: Ricardo Ribalda <ribalda@xxxxxxxxxxxx>
---
kernel/kexec_file.c | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index f989f5f1933b..69ee4a29136f 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -901,10 +901,22 @@ static int kexec_purgatory_setup_sechdrs(struct purgatory_info *pi,
}
offset = ALIGN(offset, align);
+
+ /*
+ * Check if the segment contains the entry point, if so,
+ * calculate the value of image->start based on it.
+ * If the compiler has produced more than one .text section
+ * (Eg: .text.hot), they are generally after the main .text
+ * section, and they shall not be used to calculate
+ * image->start. So do not re-calculate image->start if it
+ * is not set to the initial value, and warn the user so they
+ * have a chance to fix their purgatory's linker script.
+ */
if (sechdrs[i].sh_flags & SHF_EXECINSTR &&
pi->ehdr->e_entry >= sechdrs[i].sh_addr &&
pi->ehdr->e_entry < (sechdrs[i].sh_addr
- + sechdrs[i].sh_size)) {
+ + sechdrs[i].sh_size) &&
+ !WARN_ON(kbuf->image->start != pi->ehdr->e_entry)) {
kbuf->image->start -= sechdrs[i].sh_addr;
kbuf->image->start += kbuf->mem + offset;
}
--
2.40.1.698.g37aff9b760-goog
