* [PATCH v4 0/2] kexec: Fix kexec_file_load for llvm16
@ 2023-03-27 15:06 Ricardo Ribalda
2023-03-27 15:06 ` [PATCH v4 1/2] kexec: Support purgatories with .text.hot sections Ricardo Ribalda
2023-03-27 15:06 ` [PATCH v4 2/2] x86/purgatory: Add linker script Ricardo Ribalda
0 siblings, 2 replies; 6+ messages in thread
From: Ricardo Ribalda @ 2023-03-27 15:06 UTC (permalink / raw)
To: Eric Biederman
Cc: linux-kernel, Baoquan He, stable, Ross Zwisler, Ricardo Ribalda,
Philipp Rudo, Steven Rostedt, kexec
When upreving llvm I realised that kexec stopped working on my test
platform. This patch fixes it.
To: Eric Biederman <ebiederm@xmission.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Philipp Rudo <prudo@redhat.com>
Cc: kexec@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Cc: Ross Zwisler <zwisler@google.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ricardo Ribalda <ribalda@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 | 13 +++++++-
5 files changed, 86 insertions(+), 8 deletions(-)
---
base-commit: 17214b70a159c6547df9ae204a6275d983146f6b
change-id: 20230321-kexec_clang16-4510c23d129c
Best regards,
--
Ricardo Ribalda <ribalda@chromium.org>
^ permalink raw reply [flat|nested] 6+ messages in thread* [PATCH v4 1/2] kexec: Support purgatories with .text.hot sections 2023-03-27 15:06 [PATCH v4 0/2] kexec: Fix kexec_file_load for llvm16 Ricardo Ribalda @ 2023-03-27 15:06 ` Ricardo Ribalda 2023-03-30 7:48 ` Simon Horman 2023-03-27 15:06 ` [PATCH v4 2/2] x86/purgatory: Add linker script Ricardo Ribalda 1 sibling, 1 reply; 6+ messages in thread From: Ricardo Ribalda @ 2023-03-27 15:06 UTC (permalink / raw) To: Eric Biederman Cc: linux-kernel, Baoquan He, stable, Ross Zwisler, Ricardo Ribalda, Philipp Rudo, Steven Rostedt, kexec 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 inmediatly after: kexec_core: Starting new kernel Cc: stable@vger.kernel.org Reviewed-by: Ross Zwisler <zwisler@google.com> Signed-off-by: Ricardo Ribalda <ribalda@chromium.org> --- kernel/kexec_file.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c index f1a0e4e3fb5c..25a37d8f113a 100644 --- a/kernel/kexec_file.c +++ b/kernel/kexec_file.c @@ -901,10 +901,21 @@ 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 sections + * (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. + */ 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) && + 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-b4-0.11.0-dev-696ae ^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH v4 1/2] kexec: Support purgatories with .text.hot sections 2023-03-27 15:06 ` [PATCH v4 1/2] kexec: Support purgatories with .text.hot sections Ricardo Ribalda @ 2023-03-30 7:48 ` Simon Horman 2023-03-30 9:47 ` Ricardo Ribalda 0 siblings, 1 reply; 6+ messages in thread From: Simon Horman @ 2023-03-30 7:48 UTC (permalink / raw) To: Ricardo Ribalda Cc: Eric Biederman, linux-kernel, Baoquan He, stable, Ross Zwisler, Philipp Rudo, Steven Rostedt, kexec On Mon, Mar 27, 2023 at 05:06:53PM +0200, Ricardo Ribalda 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 inmediatly after: s/inmediatly/immediately/ > > kexec_core: Starting new kernel > > Cc: stable@vger.kernel.org Maybe a fixes tag is warranted here. > Reviewed-by: Ross Zwisler <zwisler@google.com> > Signed-off-by: Ricardo Ribalda <ribalda@chromium.org> > --- > kernel/kexec_file.c | 13 ++++++++++++- > 1 file changed, 12 insertions(+), 1 deletion(-) > > diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c > index f1a0e4e3fb5c..25a37d8f113a 100644 > --- a/kernel/kexec_file.c > +++ b/kernel/kexec_file.c > @@ -901,10 +901,21 @@ 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 sections nit: s/sections/section/ > + * (Eg: .text.hot), they are generally after the main .text If this is the general case, then are there cases where this doesn't hold? > + * 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. > + */ > 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) && > + 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-b4-0.11.0-dev-696ae > > _______________________________________________ > kexec mailing list > kexec@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/kexec > ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v4 1/2] kexec: Support purgatories with .text.hot sections 2023-03-30 7:48 ` Simon Horman @ 2023-03-30 9:47 ` Ricardo Ribalda 0 siblings, 0 replies; 6+ messages in thread From: Ricardo Ribalda @ 2023-03-30 9:47 UTC (permalink / raw) To: Simon Horman Cc: Eric Biederman, linux-kernel, Baoquan He, stable, Ross Zwisler, Philipp Rudo, Steven Rostedt, kexec Hi Simon Thanks for your review! On Thu, 30 Mar 2023 at 09:49, Simon Horman <horms@kernel.org> wrote: > > On Mon, Mar 27, 2023 at 05:06:53PM +0200, Ricardo Ribalda 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 inmediatly after: > > s/inmediatly/immediately/ > > > > > kexec_core: Starting new kernel > > > > Cc: stable@vger.kernel.org > > Maybe a fixes tag is warranted here. > > > Reviewed-by: Ross Zwisler <zwisler@google.com> > > Signed-off-by: Ricardo Ribalda <ribalda@chromium.org> > > --- > > kernel/kexec_file.c | 13 ++++++++++++- > > 1 file changed, 12 insertions(+), 1 deletion(-) > > > > diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c > > index f1a0e4e3fb5c..25a37d8f113a 100644 > > --- a/kernel/kexec_file.c > > +++ b/kernel/kexec_file.c > > @@ -901,10 +901,21 @@ 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 sections > > nit: s/sections/section/ > > > + * (Eg: .text.hot), they are generally after the main .text > > If this is the general case, then are there cases where this doesn't hold? When looking at this issue, I have only seen .text.hot after .text. But I cannot warantee that future versions of llvm or gcc decide to swap the order. I am going to add a WARN whenever there are two overlapping .text sections so the user has the chance to update their linker script. > > > + * 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. > > + */ > > 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) && > > + 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-b4-0.11.0-dev-696ae > > > > _______________________________________________ > > kexec mailing list > > kexec@lists.infradead.org > > http://lists.infradead.org/mailman/listinfo/kexec > > -- Ricardo Ribalda ^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH v4 2/2] x86/purgatory: Add linker script 2023-03-27 15:06 [PATCH v4 0/2] kexec: Fix kexec_file_load for llvm16 Ricardo Ribalda 2023-03-27 15:06 ` [PATCH v4 1/2] kexec: Support purgatories with .text.hot sections Ricardo Ribalda @ 2023-03-27 15:06 ` Ricardo Ribalda 2023-03-27 15:08 ` kernel test robot 1 sibling, 1 reply; 6+ messages in thread From: Ricardo Ribalda @ 2023-03-27 15:06 UTC (permalink / raw) To: Eric Biederman Cc: linux-kernel, Baoquan He, stable, Ross Zwisler, Ricardo Ribalda, Philipp Rudo, Steven Rostedt, kexec Make sure that the .text section is not divided in multiple overlapping sections. This is not supported by kexec_file. Signed-off-by: Ricardo Ribalda <ribalda@chromium.org> --- arch/x86/purgatory/.gitignore | 2 ++ arch/x86/purgatory/Makefile | 20 +++++++++---- arch/x86/purgatory/kexec-purgatory.S | 2 +- arch/x86/purgatory/purgatory.lds.S | 57 ++++++++++++++++++++++++++++++++++++ 4 files changed, 74 insertions(+), 7 deletions(-) diff --git a/arch/x86/purgatory/.gitignore b/arch/x86/purgatory/.gitignore index d2be1500671d..1fe71fe5945d 100644 --- a/arch/x86/purgatory/.gitignore +++ b/arch/x86/purgatory/.gitignore @@ -1 +1,3 @@ purgatory.chk +purgatory.lds +purgatory diff --git a/arch/x86/purgatory/Makefile b/arch/x86/purgatory/Makefile index 17f09dc26381..4dc96d409bec 100644 --- a/arch/x86/purgatory/Makefile +++ b/arch/x86/purgatory/Makefile @@ -16,10 +16,11 @@ CFLAGS_sha256.o := -D__DISABLE_EXPORTS # When linking purgatory.ro with -r unresolved symbols are not checked, # also link a purgatory.chk binary without -r to check for unresolved symbols. -PURGATORY_LDFLAGS := -e purgatory_start -z nodefaultlib -LDFLAGS_purgatory.ro := -r $(PURGATORY_LDFLAGS) -LDFLAGS_purgatory.chk := $(PURGATORY_LDFLAGS) -targets += purgatory.ro purgatory.chk +PURGATORY_LDFLAGS := -nostdlib -z nodefaultlib +LDFLAGS_purgatory := -r $(PURGATORY_LDFLAGS) -T +LDFLAGS_purgatory.chk := -e purgatory_start $(PURGATORY_LDFLAGS) + +targets += purgatory.lds purgatory.ro purgatory.chk # Sanitizer, etc. runtimes are unavailable and cannot be linked here. GCOV_PROFILE := n @@ -72,10 +73,17 @@ CFLAGS_string.o += $(PURGATORY_CFLAGS) AFLAGS_REMOVE_setup-x86_$(BITS).o += -Wa,-gdwarf-2 AFLAGS_REMOVE_entry64.o += -Wa,-gdwarf-2 -$(obj)/purgatory.ro: $(PURGATORY_OBJS) FORCE +OBJCOPYFLAGS_purgatory.ro := -O elf64-x86-64 +OBJCOPYFLAGS_purgatory.ro += --remove-section='*debug*' +OBJCOPYFLAGS_purgatory.ro += --remove-section='.comment' +OBJCOPYFLAGS_purgatory.ro += --remove-section='.note.*' +$(obj)/purgatory.ro: $(obj)/purgatory FORCE + $(call if_changed,objcopy) + +$(obj)/purgatory.chk: $(obj)/purgatory FORCE $(call if_changed,ld) -$(obj)/purgatory.chk: $(obj)/purgatory.ro FORCE +$(obj)/purgatory: $(obj)/purgatory.lds $(PURGATORY_OBJS) FORCE $(call if_changed,ld) $(obj)/kexec-purgatory.o: $(obj)/purgatory.ro $(obj)/purgatory.chk diff --git a/arch/x86/purgatory/kexec-purgatory.S b/arch/x86/purgatory/kexec-purgatory.S index 8530fe93b718..54b0d0b4dc42 100644 --- a/arch/x86/purgatory/kexec-purgatory.S +++ b/arch/x86/purgatory/kexec-purgatory.S @@ -5,7 +5,7 @@ .align 8 kexec_purgatory: .globl kexec_purgatory - .incbin "arch/x86/purgatory/purgatory.ro" + .incbin "arch/x86/purgatory/purgatory" .Lkexec_purgatory_end: .align 8 diff --git a/arch/x86/purgatory/purgatory.lds.S b/arch/x86/purgatory/purgatory.lds.S new file mode 100644 index 000000000000..610da88aafa0 --- /dev/null +++ b/arch/x86/purgatory/purgatory.lds.S @@ -0,0 +1,57 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#include <asm-generic/vmlinux.lds.h> + +OUTPUT_FORMAT(CONFIG_OUTPUT_FORMAT) + +#undef i386 + +#include <asm/cache.h> +#include <asm/page_types.h> + +ENTRY(purgatory_start) + +SECTIONS +{ + . = 0; + .head.text : { + _head = . ; + HEAD_TEXT + _ehead = . ; + } + .rodata : { + _rodata = . ; + *(.rodata) /* read-only data */ + *(.rodata.*) + _erodata = . ; + } + .text : { + _text = .; /* Text */ + *(.text) + *(.text.*) + *(.noinstr.text) + _etext = . ; + } + .data : { + _data = . ; + *(.data) + *(.data.*) + *(.bss.efistub) + _edata = . ; + } + . = ALIGN(L1_CACHE_BYTES); + .bss : { + _bss = . ; + *(.bss) + *(.bss.*) + *(COMMON) + . = ALIGN(8); /* For convenience during zeroing */ + _ebss = .; + } + + /* Sections to be discarded */ + /DISCARD/ : { + *(.eh_frame) + *(*__ksymtab*) + *(___kcrctab*) + } +} -- 2.40.0.348.gf938b09366-goog-b4-0.11.0-dev-696ae ^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH v4 2/2] x86/purgatory: Add linker script 2023-03-27 15:06 ` [PATCH v4 2/2] x86/purgatory: Add linker script Ricardo Ribalda @ 2023-03-27 15:08 ` kernel test robot 0 siblings, 0 replies; 6+ messages in thread From: kernel test robot @ 2023-03-27 15:08 UTC (permalink / raw) To: Ricardo Ribalda; +Cc: stable, oe-kbuild-all Hi, Thanks for your patch. FYI: kernel test robot notices the stable kernel rule is not satisfied. Rule: 'Cc: stable@vger.kernel.org' or 'commit <sha1> upstream.' Subject: [PATCH v4 2/2] x86/purgatory: Add linker script Link: https://lore.kernel.org/stable/20230321-kexec_clang16-v4-2-1340518f98e9%40chromium.org The check is based on https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html -- 0-DAY CI Kernel Test Service https://github.com/intel/lkp-tests ^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2023-03-30 9:49 UTC | newest] Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2023-03-27 15:06 [PATCH v4 0/2] kexec: Fix kexec_file_load for llvm16 Ricardo Ribalda 2023-03-27 15:06 ` [PATCH v4 1/2] kexec: Support purgatories with .text.hot sections Ricardo Ribalda 2023-03-30 7:48 ` Simon Horman 2023-03-30 9:47 ` Ricardo Ribalda 2023-03-27 15:06 ` [PATCH v4 2/2] x86/purgatory: Add linker script Ricardo Ribalda 2023-03-27 15:08 ` kernel test robot
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