linux-stable.git/kernel/kexec_file.c, branch v4.17.3

kernel/kexec_file.c: allow archs to set purgatory load address

2018-04-14T00:10:28+00:00

For s390 new kernels are loaded to fixed addresses in memory before they
are booted.  With the current code this is a problem as it assumes the
kernel will be loaded to an 'arbitrary' address.  In particular,
kexec_locate_mem_hole searches for a large enough memory region and sets
the load address (kexec_bufer->mem) to it.

Luckily there is a simple workaround for this problem.  By returning 1
in arch_kexec_walk_mem, kexec_locate_mem_hole is turned off.  This
allows the architecture to set kbuf->mem by hand.  While the trick works
fine for the kernel it does not for the purgatory as here the
architectures don't have access to its kexec_buffer.

Give architectures access to the purgatories kexec_buffer by changing
kexec_load_purgatory to take a pointer to it.  With this change
architectures have access to the buffer and can edit it as they need.

A nice side effect of this change is that we can get rid of the
purgatory_info->purgatory_load_address field.  As now the information
stored there can directly be accessed from kbuf->mem.

Link: http://lkml.kernel.org/r/20180321112751.22196-11-prudo@linux.vnet.ibm.com
Signed-off-by: Philipp Rudo 
Reviewed-by: Martin Schwidefsky 
Acked-by: Dave Young 
Cc: AKASHI Takahiro 
Cc: Eric Biederman 
Cc: Heiko Carstens 
Cc: Ingo Molnar 
Cc: Michael Ellerman 
Cc: Thiago Jung Bauermann 
Cc: Vivek Goyal 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kernel/kexec_file.c: remove mis-use of sh_offset field during purgatory load

2018-04-14T00:10:28+00:00

The current code uses the sh_offset field in purgatory_info->sechdrs to
store a pointer to the current load address of the section.  Depending
whether the section will be loaded or not this is either a pointer into
purgatory_info->purgatory_buf or kexec_purgatory.  This is not only a
violation of the ELF standard but also makes the code very hard to
understand as you cannot tell if the memory you are using is read-only
or not.

Remove this misuse and store the offset of the section in
pugaroty_info->purgatory_buf in sh_offset.

Link: http://lkml.kernel.org/r/20180321112751.22196-10-prudo@linux.vnet.ibm.com
Signed-off-by: Philipp Rudo 
Acked-by: Dave Young 
Cc: AKASHI Takahiro 
Cc: Eric Biederman 
Cc: Heiko Carstens 
Cc: Ingo Molnar 
Cc: Martin Schwidefsky 
Cc: Michael Ellerman 
Cc: Thiago Jung Bauermann 
Cc: Vivek Goyal 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kernel/kexec_file.c: remove unneeded variables in kexec_purgatory_setup_sechdrs

2018-04-14T00:10:28+00:00

The main loop currently uses quite a lot of variables to update the
section headers.  Some of them are unnecessary.  So clean them up a
little.

Link: http://lkml.kernel.org/r/20180321112751.22196-9-prudo@linux.vnet.ibm.com
Signed-off-by: Philipp Rudo 
Acked-by: Dave Young 
Cc: AKASHI Takahiro 
Cc: Eric Biederman 
Cc: Heiko Carstens 
Cc: Ingo Molnar 
Cc: Martin Schwidefsky 
Cc: Michael Ellerman 
Cc: Thiago Jung Bauermann 
Cc: Vivek Goyal 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kernel/kexec_file.c: remove unneeded for-loop in kexec_purgatory_setup_sechdrs

2018-04-14T00:10:28+00:00

To update the entry point there is an extra loop over all section
headers although this can be done in the main loop.  So move it there
and eliminate the extra loop and variable to store the 'entry section
index'.

Also, in the main loop, move the usual case, i.e.  non-bss section, out
of the extra if-block.

Link: http://lkml.kernel.org/r/20180321112751.22196-8-prudo@linux.vnet.ibm.com
Signed-off-by: Philipp Rudo 
Reviewed-by: Martin Schwidefsky 
Acked-by: Dave Young 
Cc: AKASHI Takahiro 
Cc: Eric Biederman 
Cc: Heiko Carstens 
Cc: Ingo Molnar 
Cc: Michael Ellerman 
Cc: Thiago Jung Bauermann 
Cc: Vivek Goyal 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kernel/kexec_file.c: split up __kexec_load_puragory

2018-04-14T00:10:28+00:00

When inspecting __kexec_load_purgatory you find that it has two tasks

	1) setting up the kexec_buffer for the new kernel and,
	2) setting up pi->sechdrs for the final load address.

The two tasks are independent of each other.  To improve readability
split up __kexec_load_purgatory into two functions, one for each task,
and call them directly from kexec_load_purgatory.

Link: http://lkml.kernel.org/r/20180321112751.22196-7-prudo@linux.vnet.ibm.com
Signed-off-by: Philipp Rudo 
Acked-by: Dave Young 
Cc: AKASHI Takahiro 
Cc: Eric Biederman 
Cc: Heiko Carstens 
Cc: Ingo Molnar 
Cc: Martin Schwidefsky 
Cc: Michael Ellerman 
Cc: Thiago Jung Bauermann 
Cc: Vivek Goyal 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kernel/kexec_file.c: use read-only sections in arch_kexec_apply_relocations*

2018-04-14T00:10:28+00:00

When the relocations are applied to the purgatory only the section the
relocations are applied to is writable.  The other sections, i.e.  the
symtab and .rel/.rela, are in read-only kexec_purgatory.  Highlight this
by marking the corresponding variables as 'const'.

While at it also change the signatures of arch_kexec_apply_relocations* to
take section pointers instead of just the index of the relocation section.
This removes the second lookup and sanity check of the sections in arch
code.

Link: http://lkml.kernel.org/r/20180321112751.22196-6-prudo@linux.vnet.ibm.com
Signed-off-by: Philipp Rudo 
Acked-by: Dave Young 
Cc: AKASHI Takahiro 
Cc: Eric Biederman 
Cc: Heiko Carstens 
Cc: Ingo Molnar 
Cc: Martin Schwidefsky 
Cc: Michael Ellerman 
Cc: Thiago Jung Bauermann 
Cc: Vivek Goyal 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kernel/kexec_file.c: search symbols in read-only kexec_purgatory

2018-04-14T00:10:28+00:00

The stripped purgatory does not contain a symtab.  So when looking for
symbols this is done in read-only kexec_purgatory.  Highlight this by
marking the corresponding variables as 'const'.

Link: http://lkml.kernel.org/r/20180321112751.22196-5-prudo@linux.vnet.ibm.com
Signed-off-by: Philipp Rudo 
Acked-by: Dave Young 
Cc: AKASHI Takahiro 
Cc: Eric Biederman 
Cc: Heiko Carstens 
Cc: Ingo Molnar 
Cc: Martin Schwidefsky 
Cc: Michael Ellerman 
Cc: Thiago Jung Bauermann 
Cc: Vivek Goyal 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kernel/kexec_file.c: make purgatory_info->ehdr const

2018-04-14T00:10:28+00:00

The kexec_purgatory buffer is read-only.  Thus all pointers into
kexec_purgatory are read-only, too.  Point this out by explicitly
marking purgatory_info->ehdr as 'const' and update the comments in
purgatory_info.

Link: http://lkml.kernel.org/r/20180321112751.22196-4-prudo@linux.vnet.ibm.com
Signed-off-by: Philipp Rudo 
Acked-by: Dave Young 
Cc: AKASHI Takahiro 
Cc: Eric Biederman 
Cc: Heiko Carstens 
Cc: Ingo Molnar 
Cc: Martin Schwidefsky 
Cc: Michael Ellerman 
Cc: Thiago Jung Bauermann 
Cc: Vivek Goyal 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kernel/kexec_file.c: remove checks in kexec_purgatory_load

2018-04-14T00:10:28+00:00

Before the purgatory is loaded several checks are done whether the ELF
file in kexec_purgatory is valid or not.  These checks are incomplete.
For example they don't check for the total size of the sections defined
in the section header table or if the entry point actually points into
the purgatory.

On the other hand the purgatory, although an ELF file on its own, is
part of the kernel.  Thus not trusting the purgatory means not trusting
the kernel build itself.

So remove all validity checks on the purgatory and just trust the kernel
build.

Link: http://lkml.kernel.org/r/20180321112751.22196-3-prudo@linux.vnet.ibm.com
Signed-off-by: Philipp Rudo 
Acked-by: Dave Young 
Cc: AKASHI Takahiro 
Cc: Eric Biederman 
Cc: Heiko Carstens 
Cc: Ingo Molnar 
Cc: Martin Schwidefsky 
Cc: Michael Ellerman 
Cc: Thiago Jung Bauermann 
Cc: Vivek Goyal 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kexec_file, x86: move re-factored code to generic side

2018-04-14T00:10:27+00:00

In the previous patches, commonly-used routines, exclude_mem_range() and
prepare_elf64_headers(), were carved out.  Now place them in kexec
common code.  A prefix "crash_" is given to each of their names to avoid
possible name collisions.

Link: http://lkml.kernel.org/r/20180306102303.9063-8-takahiro.akashi@linaro.org
Signed-off-by: AKASHI Takahiro 
Acked-by: Dave Young 
Tested-by: Dave Young 
Cc: Vivek Goyal 
Cc: Baoquan He 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds