of/fdt: export fdt blob as /sys/firmware/fdt
PATCH v4 1/1 of/fdt: export fdt blob as /sys/firmware/fdt
Create a new /sys entry '/sys/firmware/fdt' to export the FDT blob that was passed to the kernel by the bootloader. This allows userland applications such as kexec to access the raw binary.
The fact that this node does not reside under /sys/firmware/device-tree is deliberate: FDT is also used on arm64 UEFI/ACPI systems to communicate just the UEFI and ACPI entry points, but the FDT is never unflattened and used to configure the system.
A CRC32 checksum is calculated over the entire FDT blob, and verified at late_initcall time. The sysfs entry is instantiated only if the checksum is valid, i.e., if the FDT blob has not been modified in the mean time. Otherwise, a warning is printed.
---
v4: use pr_warn() instead of WARN()
v3: keep checksum instead of copying the entire blob, and WARN on mismatch
drivers/of/Kconfig | 1 + drivers/of/fdt.c | 37 +++++++++++++++++++++++++++++++++++++ 2 files changed, 38 insertions(+)
drivers/of/Kconfig +1 -0
@@ -23,6 +23,7 @@ config OF_FLATTREE bool select DTC select LIBFDT + select CRC32 config OF_EARLY_FLATTREE bool
drivers/of/fdt.c +37 -0
@@ -9,6 +9,7 @@* version 2 as published by the Free Software Foundation. */ +#include <linux/crc32.h> #include <linux/kernel.h> #include <linux/initrd.h> #include <linux/memblock.h>
@@ -22,10 +23,20 @@#include <linux/libfdt.h> #include <linux/debugfs.h> #include <linux/serial_core.h> +#include <linux/sysfs.h> #include <asm/setup.h> /* for COMMAND_LINE_SIZE */ #include <asm/page.h> +static u32 of_fdt_crc32; + +static u32 of_fdt_get_crc32 (void *fdt) +{ +static u32 const OF_FDT_CRC32_SEED =0x04c11db7 ; + +return crc32_be (OF_FDT_CRC32_SEED , fdt,fdt_totalsize (fdt)); +} +/* * of_fdt_limit_memory - limit the number of regions in the /memory node * @limit: maximum entries
@@ -1003,6 +1014,8 @@ bool __init early_init_dt_verify(void *params)return false; } + of_fdt_crc32 =of_fdt_get_crc32 (initial_boot_params); +return true; }
@@ -1103,4 +1116,28 @@ static int __init of_flat_dt_debugfs_export_fdt(void)module_init (of_flat_dt_debugfs_export_fdt);#endif +#ifdef CONFIG_SYSFS +static ssize_t of_fdt_raw_read (struct file *filp,struct kobject *kobj, +struct bin_attribute *bin_attr, +char *buf,loff_t off,size_t count) +{ +memcpy (buf, initial_boot_params + off, count); +return count; +} + +static int __init of_fdt_raw_init (void ) +{ +static struct bin_attribute of_fdt_raw_attr = +__BIN_ATTR (fdt,S_IRUSR , of_fdt_raw_read,NULL ,0 ); + +if (of_fdt_crc32 !=of_fdt_get_crc32 (initial_boot_params)) { +pr_warn ("fdt: not creating '/sys/firmware/fdt': CRC check failed" ); +return 0 ; + } + of_fdt_raw_attr.size =fdt_totalsize (initial_boot_params); +return sysfs_create_bin_file (firmware_kobj, &of_fdt_raw_attr); +} +late_initcall (of_fdt_raw_init); +#endif +#endif /* CONFIG_OF_EARLY_FLATTREE */
Signature · 1 line
1.8.3.2
PATCH v4 1/1 of/fdt: export fdt blob as /sys/firmware/fdt
Quoted 9 lines · Ard Biesheuvel
Create a new /sys entry '
/sys/firmware/fdt' to export the FDT blob that was passed to the kernel by the bootloader. This allows userland applications such as kexec to access the raw binary.The fact that this node does not reside under
/sys/firmware/device-treeis deliberate: FDT is also used on arm64 UEFI/ACPI systems to communicate just the UEFI and ACPI entry points, but the FDT is never unflattened and used to configure the system.
Quoted 6 lines
A CRC32 checksum is calculated over the entire FDT blob, and verified at
late_initcalltime. The sysfs entry is instantiated only if the checksum is valid, i.e., if the FDT blob has not been modified in the mean time. Otherwise, a warning is printed.Signed-off-by Ard Biesheuvel <[email protected]>
Looks good to me. Merged, thanks.
g.
Quoted 94 lines
---
v4: usepr_warn()instead ofWARN()
v3: keep checksum instead of copying the entire blob, and WARN on mismatchdrivers/of/Kconfig | 1 + drivers/of/fdt.c | 37 +++++++++++++++++++++++++++++++++++++ 2 files changed, 38 insertions(+)drivers/of/Kconfig +1
-0@@ -23,6 +23,7 @@ config OF_FLATTREE bool select DTC select LIBFDT + select CRC32 config OF_EARLY_FLATTREE booldrivers/of/fdt.c +37
-0@@ -9,6 +9,7 @@* version 2 as published by the Free Software Foundation. */ +#include <linux/crc32.h> #include <linux/kernel.h> #include <linux/initrd.h> #include <linux/memblock.h> @@ -22,10 +23,20 @@#include <linux/libfdt.h> #include <linux/debugfs.h> #include <linux/serial_core.h> +#include <linux/sysfs.h> #include <asm/setup.h> /* for COMMAND_LINE_SIZE */ #include <asm/page.h> +static u32 of_fdt_crc32; + +static u32 of_fdt_get_crc32 (void *fdt) +{ +static u32 const OF_FDT_CRC32_SEED =0x04c11db7 ; + +return crc32_be (OF_FDT_CRC32_SEED , fdt,fdt_totalsize (fdt)); +} +/* * of_fdt_limit_memory - limit the number of regions in the /memory node * @limit: maximum entries @@ -1003,6 +1014,8 @@ bool __init early_init_dt_verify(void *params)return false; } + of_fdt_crc32 =of_fdt_get_crc32 (initial_boot_params); +return true; }@@ -1103,4 +1116,28 @@ static int __init of_flat_dt_debugfs_export_fdt(void)module_init (of_flat_dt_debugfs_export_fdt);#endif +#ifdef CONFIG_SYSFS +static ssize_t of_fdt_raw_read (struct file *filp,struct kobject *kobj, +struct bin_attribute *bin_attr, +char *buf,loff_t off,size_t count) +{ +memcpy (buf, initial_boot_params + off, count); +return count; +} + +static int __init of_fdt_raw_init (void ) +{ +static struct bin_attribute of_fdt_raw_attr = +__BIN_ATTR (fdt,S_IRUSR , of_fdt_raw_read,NULL ,0 ); + +if (of_fdt_crc32 !=of_fdt_get_crc32 (initial_boot_params)) { +pr_warn ("fdt: not creating '/sys/firmware/fdt': CRC check failed" ); +return 0 ; + } + of_fdt_raw_attr.size =fdt_totalsize (initial_boot_params); +return sysfs_create_bin_file (firmware_kobj, &of_fdt_raw_attr); +} +late_initcall (of_fdt_raw_init); +#endif +#endif /* CONFIG_OF_EARLY_FLATTREE */ Signature · 1 line
1.8.3.2
PATCH v4 1/1 of/fdt: export fdt blob as /sys/firmware/fdt
In reply to Ard BiesheuvelQuoted 51 lines · Ard Biesheuvel
Create a new /sys entry '
/sys/firmware/fdt' to export the FDT blob that was passed to the kernel by the bootloader. This allows userland applications such as kexec to access the raw binary.The fact that this node does not reside under
/sys/firmware/device-treeis deliberate: FDT is also used on arm64 UEFI/ACPI systems to communicate just the UEFI and ACPI entry points, but the FDT is never unflattened and used to configure the system.A CRC32 checksum is calculated over the entire FDT blob, and verified at
late_initcalltime. The sysfs entry is instantiated only if the checksum is valid, i.e., if the FDT blob has not been modified in the mean time. Otherwise, a warning is printed.Signed-off-by Ard Biesheuvel <[email protected]>---
v4: usepr_warn()instead ofWARN()
v3: keep checksum instead of copying the entire blob, and WARN on mismatchdrivers/of/Kconfig | 1 + drivers/of/fdt.c | 37 +++++++++++++++++++++++++++++++++++++ 2 files changed, 38 insertions(+)drivers/of/Kconfig +1
-0@@ -23,6 +23,7 @@ config OF_FLATTREE bool select DTC select LIBFDT + select CRC32 config OF_EARLY_FLATTREE booldrivers/of/fdt.c +1
-0@@ -9,6 +9,7 @@* version 2 as published by the Free Software Foundation. */ +#include <linux/crc32.h> #include <linux/kernel.h> #include <linux/initrd.h> #include <linux/memblock.h> @@ -22,10 +23,20 @@#include <linux/libfdt.h> #include <linux/debugfs.h> #include <linux/serial_core.h>
drivers/of/fdt.c line 35
Quoted 10 lines
drivers/of/fdt.c +6
-0+#include <linux/sysfs.h> #include <asm/setup.h> /* for COMMAND_LINE_SIZE */ #include <asm/page.h> +static u32 of_fdt_crc32; + +static u32 of_fdt_get_crc32 (void *fdt) +{ +static u32 const OF_FDT_CRC32_SEED =0x04c11db7 ;
Where did this value come from? A comment would be useful.
Quoted 35 lines
drivers/of/fdt.c +21
-0+ +return crc32_be (OF_FDT_CRC32_SEED , fdt,fdt_totalsize (fdt)); +} +/* * of_fdt_limit_memory - limit the number of regions in the /memory node * @limit: maximum entries @@ -1003,6 +1014,8 @@ bool __init early_init_dt_verify(void *params)return false; } + of_fdt_crc32 =of_fdt_get_crc32 (initial_boot_params); +return true; }@@ -1103,4 +1116,28 @@ static int __init of_flat_dt_debugfs_export_fdt(void)module_init (of_flat_dt_debugfs_export_fdt);#endif +#ifdef CONFIG_SYSFS +static ssize_t of_fdt_raw_read (struct file *filp,struct kobject *kobj, +struct bin_attribute *bin_attr, +char *buf,loff_t off,size_t count) +{ +memcpy (buf, initial_boot_params + off, count); +return count; +} + +static int __init of_fdt_raw_init (void ) +{ +static struct bin_attribute of_fdt_raw_attr = +__BIN_ATTR (fdt,S_IRUSR , of_fdt_raw_read,NULL ,0 ); + +if (of_fdt_crc32 !=of_fdt_get_crc32 (initial_boot_params)) {
drivers/of/fdt.c static int __init of_flat_dt_debugfs_export_fdt(void) · line 1143
Quoted 10 lines
drivers/of/fdt.c +9
-0+pr_warn ("fdt: not creating '/sys/firmware/fdt': CRC check failed" ); +return 0 ; + } + of_fdt_raw_attr.size =fdt_totalsize (initial_boot_params); +return sysfs_create_bin_file (firmware_kobj, &of_fdt_raw_attr); +} +late_initcall (of_fdt_raw_init); +#endif +#endif /* CONFIG_OF_EARLY_FLATTREE */
You have a mixture of things inside and outside of CONFIG_OF_EARLY_FLATTREE which in theory could cause warnings. However looking more closely at this, it is fine for now. Instead I think we need to get rid of CONFIG_OF_EARLY_FLATTREE (or merge with OF_FLATTREE) . Every platform selects it except Sparc.
Rob
PATCH v4 1/1 of/fdt: export fdt blob as /sys/firmware/fdt
Quoted 58 lines · Rob Herring
Quoted 56 lines · Ard Biesheuvel
Create a new /sys entry '
/sys/firmware/fdt' to export the FDT blob that was passed to the kernel by the bootloader. This allows userland applications such as kexec to access the raw binary.The fact that this node does not reside under
/sys/firmware/device-treeis deliberate: FDT is also used on arm64 UEFI/ACPI systems to communicate just the UEFI and ACPI entry points, but the FDT is never unflattened and used to configure the system.A CRC32 checksum is calculated over the entire FDT blob, and verified at
late_initcalltime. The sysfs entry is instantiated only if the checksum is valid, i.e., if the FDT blob has not been modified in the mean time. Otherwise, a warning is printed.Signed-off-by Ard Biesheuvel <[email protected]>---
v4: usepr_warn()instead ofWARN()
v3: keep checksum instead of copying the entire blob, and WARN on mismatchdrivers/of/Kconfig | 1 + drivers/of/fdt.c | 37 +++++++++++++++++++++++++++++++++++++ 2 files changed, 38 insertions(+)drivers/of/Kconfig +1
-0@@ -23,6 +23,7 @@ config OF_FLATTREE bool select DTC select LIBFDT + select CRC32 config OF_EARLY_FLATTREE booldrivers/of/fdt.c +2
-0@@ -9,6 +9,7 @@* version 2 as published by the Free Software Foundation. */ +#include <linux/crc32.h> #include <linux/kernel.h> #include <linux/initrd.h> #include <linux/memblock.h> @@ -22,10 +23,20 @@#include <linux/libfdt.h> #include <linux/debugfs.h> #include <linux/serial_core.h> +#include <linux/sysfs.h> #include <asm/setup.h> /* for COMMAND_LINE_SIZE */ #include <asm/page.h>
Quoted 8 lines
drivers/of/fdt.c line 35
Quoted 5 lines
drivers/of/fdt.c +5
-0+static u32 of_fdt_crc32; + +static u32 of_fdt_get_crc32 (void *fdt) +{ +static u32 const OF_FDT_CRC32_SEED =0x04c11db7 ;Where did this value come from? A comment would be useful.
Oops, it appears I was a bit sloppy here. I misread 'seed' in the crc32 header as poly, but actually the implementation refers to this polynomial directly as CRCPOLY_BE and the seed should be 0 here (or in the verify case, the original crc, in which case the return value should be 0)
Quoted 43 lines
Quoted 43 lines
drivers/of/fdt.c +29
-0+ +return crc32_be (OF_FDT_CRC32_SEED , fdt,fdt_totalsize (fdt)); +} +/* * of_fdt_limit_memory - limit the number of regions in the /memory node * @limit: maximum entries @@ -1003,6 +1014,8 @@ bool __init early_init_dt_verify(void *params)return false; } + of_fdt_crc32 =of_fdt_get_crc32 (initial_boot_params); +return true; }@@ -1103,4 +1116,28 @@ static int __init of_flat_dt_debugfs_export_fdt(void)module_init (of_flat_dt_debugfs_export_fdt);#endif +#ifdef CONFIG_SYSFS +static ssize_t of_fdt_raw_read (struct file *filp,struct kobject *kobj, +struct bin_attribute *bin_attr, +char *buf,loff_t off,size_t count) +{ +memcpy (buf, initial_boot_params + off, count); +return count; +} + +static int __init of_fdt_raw_init (void ) +{ +static struct bin_attribute of_fdt_raw_attr = +__BIN_ATTR (fdt,S_IRUSR , of_fdt_raw_read,NULL ,0 ); + +if (of_fdt_crc32 !=of_fdt_get_crc32 (initial_boot_params)) { +pr_warn ("fdt: not creating '/sys/firmware/fdt': CRC check failed" ); +return 0 ; + } + of_fdt_raw_attr.size =fdt_totalsize (initial_boot_params); +return sysfs_create_bin_file (firmware_kobj, &of_fdt_raw_attr); +} +late_initcall (of_fdt_raw_init); +#endif
Quoted 9 lines
drivers/of/fdt.c static int __init of_flat_dt_debugfs_export_fdt(void) · line 1143
Quoted 2 lines
drivers/of/fdt.c +1
-0+#endif /* CONFIG_OF_EARLY_FLATTREE */ You have a mixture of things inside and outside of
CONFIG_OF_EARLY_FLATTREEwhich in theory could cause warnings. However looking more closely at this, it is fine for now. Instead I think we need to get rid ofCONFIG_OF_EARLY_FLATTREE(or merge withOF_FLATTREE) . Every platform selects it except Sparc.
Well, the crc will only be computed if early_init_dt_verify() was called, so it seems putting the initcall() here is not entirely inappropriate.
@Grant; I will respin based on the version you posted in this thread, and fix the crc bit.
PATCH v4 1/1 of/fdt: export fdt blob as /sys/firmware/fdt
In reply to Ard BiesheuvelQuoted 9 lines · Ard Biesheuvel
Create a new /sys entry '
/sys/firmware/fdt' to export the FDT blob that was passed to the kernel by the bootloader. This allows userland applications such as kexec to access the raw binary.The fact that this node does not reside under
/sys/firmware/device-treeis deliberate: FDT is also used on arm64 UEFI/ACPI systems to communicate just the UEFI and ACPI entry points, but the FDT is never unflattened and used to configure the system.
Quoted 6 lines
A CRC32 checksum is calculated over the entire FDT blob, and verified at
late_initcalltime. The sysfs entry is instantiated only if the checksum is valid, i.e., if the FDT blob has not been modified in the mean time. Otherwise, a warning is printed.Signed-off-by Ard Biesheuvel <[email protected]>
Actually, I made a couple of changes when I merged it. I removed the older debugfs interface since it overlaps, and I added tests for initial_boot_params to make sure it doesn't try to run on an invalid FDT:
drivers/of/Kconfig +1 -0
@@ -23,6 +23,7 @@ config OF_FLATTREE bool select DTC select LIBFDT + select CRC32 config OF_EARLY_FLATTREE bool
drivers/of/fdt.c +32 -16
81 lines not on this page · raw message
g.