* [PATCH v5 0/2] kexec: Fix kexec_file_load for llvm16
@ 2023-03-30 9:44 Ricardo Ribalda
2023-03-30 9:44 ` [PATCH v5 1/2] kexec: Support purgatories with .text.hot sections Ricardo Ribalda
0 siblings, 1 reply; 4+ messages in thread
From: Ricardo Ribalda @ 2023-03-30 9:44 UTC (permalink / raw)
To: Eric Biederman
Cc: Baoquan He, Philipp Rudo, kexec, linux-kernel, Ross Zwisler,
Steven Rostedt, Simon Horman, Ricardo Ribalda, stable
When upreving llvm I realised that kexec stopped working on my test
platform. This patch fixes it.
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
---
Changes in v5:
- Add warning when multiple text sections are found. Thanks Simon!
- Add Fixes tag.
- Link to v4: https://lore.kernel.org/r/20230321-kexec_clang16-v4-0-1340518f98e9@chromium.org
Changes in v4:
- Add Cc: stable
- Add linker script for x86
- Add a warning when the kernel image has overlapping sections.
- Link to v3: https://lore.kernel.org/r/20230321-kexec_clang16-v3-0-5f016c8d0e87@chromium.org
Changes in v3:
- Fix initial value. Thanks Ross!
- Link to v2: https://lore.kernel.org/r/20230321-kexec_clang16-v2-0-d10e5d517869@chromium.org
Changes in v2:
- Fix if condition. Thanks Steven!.
- Update Philipp email. Thanks Baoquan.
- Link to v1: https://lore.kernel.org/r/20230321-kexec_clang16-v1-0-a768fc2c7c4d@chromium.org
---
Ricardo Ribalda (2):
kexec: Support purgatories with .text.hot sections
x86/purgatory: Add linker script
arch/x86/purgatory/.gitignore | 2 ++
arch/x86/purgatory/Makefile | 20 +++++++++----
arch/x86/purgatory/kexec-purgatory.S | 2 +-
arch/x86/purgatory/purgatory.lds.S | 57 ++++++++++++++++++++++++++++++++++++
kernel/kexec_file.c | 14 ++++++++-
5 files changed, 87 insertions(+), 8 deletions(-)
---
base-commit: 17214b70a159c6547df9ae204a6275d983146f6b
change-id: 20230321-kexec_clang16-4510c23d129c
Best regards,
--
Ricardo Ribalda <ribalda@chromium.org>
^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH v5 1/2] kexec: Support purgatories with .text.hot sections
2023-03-30 9:44 [PATCH v5 0/2] kexec: Fix kexec_file_load for llvm16 Ricardo Ribalda
@ 2023-03-30 9:44 ` Ricardo Ribalda
2023-03-30 15:03 ` Steven Rostedt
2023-04-03 14:42 ` Philipp Rudo
0 siblings, 2 replies; 4+ messages in thread
From: Ricardo Ribalda @ 2023-03-30 9:44 UTC (permalink / raw)
To: Eric Biederman
Cc: Baoquan He, Philipp Rudo, kexec, linux-kernel, Ross Zwisler,
Steven Rostedt, Simon Horman, Ricardo Ribalda, stable
Clang16 links the purgatory text in two sections:
[ 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@vger.kernel.org
Fixes: 930457057abe ("kernel/kexec_file.c: split up __kexec_load_puragory")
Reviewed-by: Ross Zwisler <zwisler@google.com>
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
---
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 f1a0e4e3fb5c..c7a0e51a6d87 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;
}
--
2.40.0.348.gf938b09366-goog
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH v5 1/2] kexec: Support purgatories with .text.hot sections
2023-03-30 9:44 ` [PATCH v5 1/2] kexec: Support purgatories with .text.hot sections Ricardo Ribalda
@ 2023-03-30 15:03 ` Steven Rostedt
2023-04-03 14:42 ` Philipp Rudo
1 sibling, 0 replies; 4+ messages in thread
From: Steven Rostedt @ 2023-03-30 15:03 UTC (permalink / raw)
To: Ricardo Ribalda
Cc: Eric Biederman, Baoquan He, Philipp Rudo, kexec, linux-kernel,
Ross Zwisler, Simon Horman, stable
On Thu, 30 Mar 2023 11:44:47 +0200
Ricardo Ribalda <ribalda@chromium.org> wrote:
> Clang16 links the purgatory text in two sections:
>
> [ 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@vger.kernel.org
> Fixes: 930457057abe ("kernel/kexec_file.c: split up __kexec_load_puragory")
> Reviewed-by: Ross Zwisler <zwisler@google.com>
> Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> ---
> 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 f1a0e4e3fb5c..c7a0e51a6d87 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;
> }
>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Thanks Ricardo!
-- Steve
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v5 1/2] kexec: Support purgatories with .text.hot sections
2023-03-30 9:44 ` [PATCH v5 1/2] kexec: Support purgatories with .text.hot sections Ricardo Ribalda
2023-03-30 15:03 ` Steven Rostedt
@ 2023-04-03 14:42 ` Philipp Rudo
1 sibling, 0 replies; 4+ messages in thread
From: Philipp Rudo @ 2023-04-03 14:42 UTC (permalink / raw)
To: Ricardo Ribalda
Cc: Eric Biederman, Baoquan He, kexec, linux-kernel, Ross Zwisler,
Steven Rostedt, Simon Horman, stable
Hi Ricardo,
On Thu, 30 Mar 2023 11:44:47 +0200
Ricardo Ribalda <ribalda@chromium.org> wrote:
> Clang16 links the purgatory text in two sections:
>
> [ 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@vger.kernel.org
> Fixes: 930457057abe ("kernel/kexec_file.c: split up __kexec_load_puragory")
> Reviewed-by: Ross Zwisler <zwisler@google.com>
> Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> ---
> 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 f1a0e4e3fb5c..c7a0e51a6d87 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)) {
Looks good to me. I'm not sure if it is better to use WARN_ON_ONCE to
avoid spamming the log when there are more than two .text sections or
when you reload the kernel. But that's only a rare corner case. So no
strong opinion from my side. Either way
Reviewed-by: Philipp Rudo <prudo@redhat.com>
> kbuf->image->start -= sechdrs[i].sh_addr;
> kbuf->image->start += kbuf->mem + offset;
> }
>
^ permalink raw reply [flat|nested] 4+ messages in thread
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2023-03-30 9:44 [PATCH v5 0/2] kexec: Fix kexec_file_load for llvm16 Ricardo Ribalda
2023-03-30 9:44 ` [PATCH v5 1/2] kexec: Support purgatories with .text.hot sections Ricardo Ribalda
2023-03-30 15:03 ` Steven Rostedt
2023-04-03 14:42 ` Philipp Rudo
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