Re: [PATCH v16 11/12] powerpc: Use OF alloc and free for FDT
From: Lakshmi Ramasubramanian
Date: Thu Feb 04 2021 - 18:45:15 EST
On 2/4/21 3:36 PM, Rob Herring wrote:
On Thu, Feb 4, 2021 at 5:23 PM Lakshmi Ramasubramanian
<nramas@xxxxxxxxxxxxxxxxxxx> wrote:
On 2/4/21 11:26 AM, Rob Herring wrote:
On Thu, Feb 4, 2021 at 10:42 AM Lakshmi Ramasubramanian
<nramas@xxxxxxxxxxxxxxxxxxx> wrote:
of_alloc_and_init_fdt() and of_free_fdt() have been defined in
drivers/of/kexec.c to allocate and free memory for FDT.
Use of_alloc_and_init_fdt() and of_free_fdt() to allocate and
initialize the FDT, and to free the FDT respectively.
powerpc sets the FDT address in image_loader_data field in
"struct kimage" and the memory is freed in
kimage_file_post_load_cleanup(). This cleanup function uses kfree()
to free the memory. But since of_alloc_and_init_fdt() uses kvmalloc()
for allocation, the buffer needs to be freed using kvfree().
You could just change the kexec core to call kvfree() instead.
Define "fdt" field in "struct kimage_arch" for powerpc to store
the address of FDT, and free the memory in powerpc specific
arch_kimage_file_post_load_cleanup().
However, given all the other buffers have an explicit field in kimage
or kimage_arch, changing powerpc is to match arm64 is better IMO.
Just to be clear:
I'll leave this as is - free FDT buffer in powerpc's
arch_kimage_file_post_load_cleanup() to match arm64 behavior.
Yes.
ok
Will not change "kexec core" to call kvfree() - doing that change would
require changing all architectures to use kvmalloc() for
image_loader_data allocation.
Actually, no. AIUI, kvfree() can be used whether you used kvmalloc,
vmalloc, or kmalloc for the alloc.
That is good information. Thanks.
Signed-off-by: Lakshmi Ramasubramanian <nramas@xxxxxxxxxxxxxxxxxxx>
Suggested-by: Rob Herring <robh@xxxxxxxxxx>
Suggested-by: Thiago Jung Bauermann <bauerman@xxxxxxxxxxxxx>
---
arch/powerpc/include/asm/kexec.h | 2 ++
arch/powerpc/kexec/elf_64.c | 26 ++++++++++++++++----------
arch/powerpc/kexec/file_load_64.c | 3 +++
3 files changed, 21 insertions(+), 10 deletions(-)
diff --git a/arch/powerpc/include/asm/kexec.h b/arch/powerpc/include/asm/kexec.h
index 2c0be93d239a..d7d13cac4d31 100644
--- a/arch/powerpc/include/asm/kexec.h
+++ b/arch/powerpc/include/asm/kexec.h
@@ -111,6 +111,8 @@ struct kimage_arch {
unsigned long elf_headers_mem;
unsigned long elf_headers_sz;
void *elf_headers;
+
+ void *fdt;
};
char *setup_kdump_cmdline(struct kimage *image, char *cmdline,
diff --git a/arch/powerpc/kexec/elf_64.c b/arch/powerpc/kexec/elf_64.c
index d0e459bb2f05..51d2d8eb6c1b 100644
--- a/arch/powerpc/kexec/elf_64.c
+++ b/arch/powerpc/kexec/elf_64.c
@@ -19,6 +19,7 @@
#include <linux/kexec.h>
#include <linux/libfdt.h>
#include <linux/module.h>
+#include <linux/of.h>
#include <linux/of_fdt.h>
#include <linux/slab.h>
#include <linux/types.h>
@@ -32,7 +33,7 @@ static void *elf64_load(struct kimage *image, char *kernel_buf,
unsigned int fdt_size;
unsigned long kernel_load_addr;
unsigned long initrd_load_addr = 0, fdt_load_addr;
- void *fdt;
+ void *fdt = NULL;
const void *slave_code;
struct elfhdr ehdr;
char *modified_cmdline = NULL;
@@ -103,18 +104,12 @@ static void *elf64_load(struct kimage *image, char *kernel_buf,
}
fdt_size = fdt_totalsize(initial_boot_params) * 2;
- fdt = kmalloc(fdt_size, GFP_KERNEL);
+ fdt = of_alloc_and_init_fdt(fdt_size);
if (!fdt) {
pr_err("Not enough memory for the device tree.\n");
ret = -ENOMEM;
goto out;
}
- ret = fdt_open_into(initial_boot_params, fdt, fdt_size);
- if (ret < 0) {
- pr_err("Error setting up the new device tree.\n");
- ret = -EINVAL;
- goto out;
- }
ret = setup_new_fdt_ppc64(image, fdt, initrd_load_addr,
The first thing this function does is call setup_new_fdt() which first
calls of_kexec_setup_new_fdt(). (Note, I really don't understand the
PPC code split. It looks like there's a 32-bit and 64-bit split, but
32-bit looks broken to me. Nothing ever calls setup_new_fdt() except
setup_new_fdt_ppc64()). The arm64 version is calling
of_alloc_and_init_fdt() and then of_kexec_setup_new_fdt() directly.
So we can just make of_alloc_and_init_fdt() also call
of_kexec_setup_new_fdt() (really, just tweak of_kexec_setup_new_fdt do
the alloc and copy).
ok - will move fdt allocation into of_kexec_setup_new_fdt().
I don't think the architecture needs to pick the
size either. It's doubtful that either one is that sensitive to the
amount of extra space.
I am not clear about the above comment -
are you saying the architectures don't need to pass FDT size to the
alloc function?
arm64 is adding command line string length and some extra space to the
size computed from initial_boot_params for FDT Size:
buf_size = fdt_totalsize(initial_boot_params)
+ cmdline_len + DTB_EXTRA_SPACE;
powerpc is just using twice the size computed from initial_boot_params
fdt_size = fdt_totalsize(initial_boot_params) * 2;
I think it would be safe to let arm64 and powerpc pass the required FDT
size, along with the other params to of_kexec_setup_new_fdt() - and in
this function we allocate FDT and set it up.
It's pretty clear that someone just picked something that 'should be
enough'. The only thing I can guess for the difference is that arm
DT's tend to be a bit larger. So doubling the size would be even more
excessive. Either way, we're talking 10s kB to few 100kB. I'd go with
DTB_EXTRA_SPACE and we can bump it up if someone has problems.
ok - I'll use DTB_EXTRA_SPACE for the fdt allocation.
Also, I would like for 'initial_boot_params' to be private ultimately,
so removing any references is helpful.
ok
And, for powerpc leave the remaining code in setup_new_fdt_ppc64().
Right.
ok
thanks,
-lakshmi