The patch titled
Subject: kexec: support purgatories with .text.hot sections
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
kexec-support-purgatories-with-texthot-sections.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/kexec-support-purgatories-with-texthot-sections.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Ricardo Ribalda <ribalda@xxxxxxxxxxxx>
Subject: kexec: support purgatories with .text.hot sections
Date: Fri, 19 May 2023 16:47:36 +0200
Patch series "kexec: Fix kexec_file_load for llvm16 with PGO", v7.
When upreving llvm I realised that kexec stopped working on my test
platform.
The reason seems to be that due to PGO there are multiple .text sections
on the purgatory, and kexec does not supports that.
This patch (of 4):
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
Link: https://lkml.kernel.org/r/20230321-kexec_clang16-v7-0-b05c520b7296@xxxxxxxxxxxx
Link: https://lkml.kernel.org/r/20230321-kexec_clang16-v7-1-b05c520b7296@xxxxxxxxxxxx
Fixes: 930457057abe ("kernel/kexec_file.c: split up __kexec_load_puragory")
Signed-off-by: Ricardo Ribalda <ribalda@xxxxxxxxxxxx>
Reviewed-by: Ross Zwisler <zwisler@xxxxxxxxxx>
Reviewed-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
Reviewed-by: Philipp Rudo <prudo@xxxxxxxxxx>
Cc: Albert Ou <aou@xxxxxxxxxxxxxxxxx>
Cc: Baoquan He <bhe@xxxxxxxxxx>
Cc: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Cc: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Dave Young <dyoung@xxxxxxxxxx>
Cc: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Nathan Chancellor <nathan@xxxxxxxxxx>
Cc: Nicholas Piggin <npiggin@xxxxxxxxx>
Cc: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Cc: Palmer Dabbelt <palmer@xxxxxxxxxxx>
Cc: Palmer Dabbelt <palmer@xxxxxxxxxxxx>
Cc: Paul Walmsley <paul.walmsley@xxxxxxxxxx>
Cc: Simon Horman <horms@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Tom Rix <trix@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/kexec_file.c | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)
--- a/kernel/kexec_file.c~kexec-support-purgatories-with-texthot-sections
+++ a/kernel/kexec_file.c
@@ -901,10 +901,22 @@ static int kexec_purgatory_setup_sechdrs
}
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;
}
_
Patches currently in -mm which might be from ribalda@xxxxxxxxxxxx are
kexec-support-purgatories-with-texthot-sections.patch
x86-purgatory-remove-pgo-flags.patch
powerpc-purgatory-remove-pgo-flags.patch
riscv-purgatory-remove-pgo-flags.patch
