[PATCH 1/1] image: usage of value ~0UL for intrd_high
The comment for initrd_high in the coding and in README were contradicting and neither fully described what the coding does.
Clarify the usage of the special value ~0UL for the environment variable initrd_high.
Signed-off-by: Heinrich Schuchardt xypron.glpk@gmx.de --- README | 3 ++- common/image.c | 6 ++++-- 2 files changed, 6 insertions(+), 3 deletions(-)
diff --git a/README b/README index 7b73a1c973..fe58f1ab98 100644 --- a/README +++ b/README @@ -3310,7 +3310,8 @@ List of environment variables (most likely not complete):
setenv initrd_high 00c00000
- If you set initrd_high to 0xFFFFFFFF, this is an + If you set initrd_high to 0xFFFFFFFF on a 32-bit systems + or 0xFFFFFFFFFFFFFFFF on a 64-bit systems, this is an indication to U-Boot that all addresses are legal for the Linux kernel, including addresses in flash memory. In this case U-Boot will NOT COPY the diff --git a/common/image.c b/common/image.c index 451fc689a8..007e4e987a 100644 --- a/common/image.c +++ b/common/image.c @@ -1362,8 +1362,10 @@ int boot_ramdisk_high(struct lmb *lmb, ulong rd_data, ulong rd_len,
s = env_get("initrd_high"); if (s) { - /* a value of "no" or a similar string will act like 0, - * turning the "load high" feature off. This is intentional. + /* + * A value of 0xffffffffffffffff on 64-bit or 0xffffffff + * on 32-bit systems will disable the copying of the initial + * RAM disk to high memory. */ initrd_high = simple_strtoul(s, NULL, 16); if (initrd_high == ~0) -- 2.29.2
On Sat, Jan 9, 2021 at 8:06 PM Heinrich Schuchardt xypron.glpk@gmx.de wrote:
The comment for initrd_high in the coding and in README were contradicting and neither fully described what the coding does.
Clarify the usage of the special value ~0UL for the environment variable initrd_high.
All those F:s are hard to read in the comments and documentation and typo prone. I would prefer to rephrase like "all 1:s value in 32- or 64-bit format" or alike.
On Sat, Jan 09, 2021 at 08:47:07PM +0200, Andy Shevchenko wrote:
On Sat, Jan 9, 2021 at 8:06 PM Heinrich Schuchardt xypron.glpk@gmx.de wrote:
The comment for initrd_high in the coding and in README were contradicting and neither fully described what the coding does.
Clarify the usage of the special value ~0UL for the environment variable initrd_high.
All those F:s are hard to read in the comments and documentation and typo prone. I would prefer to rephrase like "all 1:s value in 32- or 64-bit format" or alike.
If we're going to improve this we should also note it's discouraged unless you know for certain there will be no overlap and it's strongly discouraged in default environments.
On 1/9/21 7:58 PM, Tom Rini wrote:
On Sat, Jan 09, 2021 at 08:47:07PM +0200, Andy Shevchenko wrote:
On Sat, Jan 9, 2021 at 8:06 PM Heinrich Schuchardt xypron.glpk@gmx.de wrote:
The comment for initrd_high in the coding and in README were contradicting and neither fully described what the coding does.
Clarify the usage of the special value ~0UL for the environment variable initrd_high.
All those F:s are hard to read in the comments and documentation and typo prone. I would prefer to rephrase like "all 1:s value in 32- or 64-bit format" or alike.
If we're going to improve this we should also note it's discouraged unless you know for certain there will be no overlap and it's strongly discouraged in default environments.
What exactly is discouraged?
* setting initrd_high to a value != ~0? Here I would agree. * setting intird_high to ~0? Why should we copy initrd to a different place? Is it for some outdated Linux release?
Best regards
Heinrich
On Sat, Jan 09, 2021 at 08:33:40PM +0100, Heinrich Schuchardt wrote:
On 1/9/21 7:58 PM, Tom Rini wrote:
On Sat, Jan 09, 2021 at 08:47:07PM +0200, Andy Shevchenko wrote:
On Sat, Jan 9, 2021 at 8:06 PM Heinrich Schuchardt xypron.glpk@gmx.de wrote:
The comment for initrd_high in the coding and in README were contradicting and neither fully described what the coding does.
Clarify the usage of the special value ~0UL for the environment variable initrd_high.
All those F:s are hard to read in the comments and documentation and typo prone. I would prefer to rephrase like "all 1:s value in 32- or 64-bit format" or alike.
If we're going to improve this we should also note it's discouraged unless you know for certain there will be no overlap and it's strongly discouraged in default environments.
What exactly is discouraged?
- setting initrd_high to a value != ~0? Here I would agree.
- setting intird_high to ~0? Why should we copy initrd to a different place? Is it for some outdated Linux release?
We should always default to allowing the initrd to be relocated because we can see (in many cases) overlap that will lead to failure to boot but this forces us to ignore that. Having good default load values means we don't have a problem here.
Am 9. Januar 2021 20:40:04 MEZ schrieb Tom Rini trini@konsulko.com:
On Sat, Jan 09, 2021 at 08:33:40PM +0100, Heinrich Schuchardt wrote:
On 1/9/21 7:58 PM, Tom Rini wrote:
On Sat, Jan 09, 2021 at 08:47:07PM +0200, Andy Shevchenko wrote:
On Sat, Jan 9, 2021 at 8:06 PM Heinrich Schuchardt
xypron.glpk@gmx.de wrote:
The comment for initrd_high in the coding and in README were
contradicting
and neither fully described what the coding does.
Clarify the usage of the special value ~0UL for the environment
variable
initrd_high.
All those F:s are hard to read in the comments and documentation
and
typo prone. I would prefer to rephrase like "all 1:s value in 32-
or
64-bit format" or alike.
If we're going to improve this we should also note it's discouraged unless you know for certain there will be no overlap and it's
strongly
discouraged in default environments.
What exactly is discouraged?
- setting initrd_high to a value != ~0? Here I would agree.
- setting intird_high to ~0? Why should we copy initrd to a different place? Is it for some outdated Linux release?
We should always default to allowing the initrd to be relocated because we can see (in many cases) overlap that will lead to failure to boot but this forces us to ignore that. Having good default load values means we don't have a problem here.
We have an initrd that is already in memory. What could it overlap with that is not already overwritten?
Can you provide the text you want to see here?
On Sat, Jan 09, 2021 at 08:59:01PM +0100, Heinrich Schuchardt wrote:
Am 9. Januar 2021 20:40:04 MEZ schrieb Tom Rini trini@konsulko.com:
On Sat, Jan 09, 2021 at 08:33:40PM +0100, Heinrich Schuchardt wrote:
On 1/9/21 7:58 PM, Tom Rini wrote:
On Sat, Jan 09, 2021 at 08:47:07PM +0200, Andy Shevchenko wrote:
On Sat, Jan 9, 2021 at 8:06 PM Heinrich Schuchardt
xypron.glpk@gmx.de wrote:
The comment for initrd_high in the coding and in README were
contradicting
and neither fully described what the coding does.
Clarify the usage of the special value ~0UL for the environment
variable
initrd_high.
All those F:s are hard to read in the comments and documentation
and
typo prone. I would prefer to rephrase like "all 1:s value in 32-
or
64-bit format" or alike.
If we're going to improve this we should also note it's discouraged unless you know for certain there will be no overlap and it's
strongly
discouraged in default environments.
What exactly is discouraged?
- setting initrd_high to a value != ~0? Here I would agree.
- setting intird_high to ~0? Why should we copy initrd to a different place? Is it for some outdated Linux release?
We should always default to allowing the initrd to be relocated because we can see (in many cases) overlap that will lead to failure to boot but this forces us to ignore that. Having good default load values means we don't have a problem here.
We have an initrd that is already in memory. What could it overlap with that is not already overwritten?
Having the kernel and initrd too close in memory has the kernel BSS overwrite the initrd. This has happened time and time again before I went around making some platforms have reasonable (ie kernel early, ramdisk in lowmem but beyond where a kernel+bss can be, etc) defaults and pushing others to do the same.
Can you provide the text you want to see here?
Off-hand, it should look more like the big comment block in include/configs/ti_armv7_common.h and reference the Linux booting on arm/arm64 documents while noting that other architectures have the same fundamental issues and their exact limits may or may not be as well documented.
Am 9. Januar 2021 22:23:01 MEZ schrieb Tom Rini trini@konsulko.com:
On Sat, Jan 09, 2021 at 08:59:01PM +0100, Heinrich Schuchardt wrote:
Am 9. Januar 2021 20:40:04 MEZ schrieb Tom Rini trini@konsulko.com:
On Sat, Jan 09, 2021 at 08:33:40PM +0100, Heinrich Schuchardt wrote:
On 1/9/21 7:58 PM, Tom Rini wrote:
On Sat, Jan 09, 2021 at 08:47:07PM +0200, Andy Shevchenko wrote:
On Sat, Jan 9, 2021 at 8:06 PM Heinrich Schuchardt
xypron.glpk@gmx.de wrote:
> > The comment for initrd_high in the coding and in README were
contradicting
> and neither fully described what the coding does. > > Clarify the usage of the special value ~0UL for the
environment
variable
> initrd_high.
All those F:s are hard to read in the comments and
documentation
and
typo prone. I would prefer to rephrase like "all 1:s value in
32-
or
64-bit format" or alike.
Who would understand that?
All 1s that is 111111111?
We need something a non-developer will grasp. Copying the exact value from the readme is the easiest thing to do and the least typo prone.
Best regards
Heinrich
If we're going to improve this we should also note it's
discouraged
unless you know for certain there will be no overlap and it's
strongly
discouraged in default environments.
What exactly is discouraged?
- setting initrd_high to a value != ~0? Here I would agree.
- setting intird_high to ~0? Why should we copy initrd to a different place? Is it for some outdated Linux release?
We should always default to allowing the initrd to be relocated
because
we can see (in many cases) overlap that will lead to failure to boot but this forces us to ignore that. Having good default load values
means
we don't have a problem here.
We have an initrd that is already in memory. What could it overlap with that is not already overwritten?
Having the kernel and initrd too close in memory has the kernel BSS overwrite the initrd. This has happened time and time again before I went around making some platforms have reasonable (ie kernel early, ramdisk in lowmem but beyond where a kernel+bss can be, etc) defaults and pushing others to do the same.
Can you provide the text you want to see here?
Off-hand, it should look more like the big comment block in include/configs/ti_armv7_common.h and reference the Linux booting on arm/arm64 documents while noting that other architectures have the same fundamental issues and their exact limits may or may not be as well documented.
On Sat, Jan 9, 2021 at 5:23 PM Heinrich Schuchardt xypron.glpk@gmx.de wrote:
Am 9. Januar 2021 22:23:01 MEZ schrieb Tom Rini trini@konsulko.com:
On Sat, Jan 09, 2021 at 08:59:01PM +0100, Heinrich Schuchardt wrote:
Am 9. Januar 2021 20:40:04 MEZ schrieb Tom Rini trini@konsulko.com:
On Sat, Jan 09, 2021 at 08:33:40PM +0100, Heinrich Schuchardt wrote:
On 1/9/21 7:58 PM, Tom Rini wrote:
On Sat, Jan 09, 2021 at 08:47:07PM +0200, Andy Shevchenko wrote: > On Sat, Jan 9, 2021 at 8:06 PM Heinrich Schuchardt
xypron.glpk@gmx.de wrote:
> > > > The comment for initrd_high in the coding and in README were
contradicting
> > and neither fully described what the coding does. > > > > Clarify the usage of the special value ~0UL for the
environment
variable
> > initrd_high. > > All those F:s are hard to read in the comments and
documentation
and
> typo prone. I would prefer to rephrase like "all 1:s value in
32-
or
> 64-bit format" or alike.
Who would understand that?
All 1s that is 111111111?
We need something a non-developer will grasp. Copying the exact value from the readme is the easiest thing to do and the least typo prone.
What about -1?
adam
Best regards
Heinrich
If we're going to improve this we should also note it's
discouraged
unless you know for certain there will be no overlap and it's
strongly
discouraged in default environments.
What exactly is discouraged?
- setting initrd_high to a value != ~0? Here I would agree.
- setting intird_high to ~0? Why should we copy initrd to a different place? Is it for some outdated Linux release?
We should always default to allowing the initrd to be relocated
because
we can see (in many cases) overlap that will lead to failure to boot but this forces us to ignore that. Having good default load values
means
we don't have a problem here.
We have an initrd that is already in memory. What could it overlap with that is not already overwritten?
Having the kernel and initrd too close in memory has the kernel BSS overwrite the initrd. This has happened time and time again before I went around making some platforms have reasonable (ie kernel early, ramdisk in lowmem but beyond where a kernel+bss can be, etc) defaults and pushing others to do the same.
Can you provide the text you want to see here?
Off-hand, it should look more like the big comment block in include/configs/ti_armv7_common.h and reference the Linux booting on arm/arm64 documents while noting that other architectures have the same fundamental issues and their exact limits may or may not be as well documented.
On Sun, Jan 10, 2021 at 1:23 AM Heinrich Schuchardt xypron.glpk@gmx.de wrote:
Am 9. Januar 2021 22:23:01 MEZ schrieb Tom Rini trini@konsulko.com:
On Sat, Jan 09, 2021 at 08:59:01PM +0100, Heinrich Schuchardt wrote:
Am 9. Januar 2021 20:40:04 MEZ schrieb Tom Rini trini@konsulko.com:
On Sat, Jan 09, 2021 at 08:33:40PM +0100, Heinrich Schuchardt wrote:
On 1/9/21 7:58 PM, Tom Rini wrote:
On Sat, Jan 09, 2021 at 08:47:07PM +0200, Andy Shevchenko wrote: > On Sat, Jan 9, 2021 at 8:06 PM Heinrich Schuchardt
xypron.glpk@gmx.de wrote:
> > > > The comment for initrd_high in the coding and in README were
contradicting
> > and neither fully described what the coding does. > > > > Clarify the usage of the special value ~0UL for the
environment
variable
> > initrd_high. > > All those F:s are hard to read in the comments and
documentation
and
> typo prone. I would prefer to rephrase like "all 1:s value in
32-
or
> 64-bit format" or alike.
Who would understand that?
All 1s that is 111111111?
Oh, com'n. Most of the users understand that. But we could go further and be more verbose: "All bit set to 1".
We need something a non-developer will grasp. Copying the exact value from the readme is the easiest thing to do and the least typo prone.
Best regards
Heinrich
If we're going to improve this we should also note it's
discouraged
unless you know for certain there will be no overlap and it's
strongly
discouraged in default environments.
What exactly is discouraged?
- setting initrd_high to a value != ~0? Here I would agree.
- setting intird_high to ~0? Why should we copy initrd to a different place? Is it for some outdated Linux release?
We should always default to allowing the initrd to be relocated
because
we can see (in many cases) overlap that will lead to failure to boot but this forces us to ignore that. Having good default load values
means
we don't have a problem here.
We have an initrd that is already in memory. What could it overlap with that is not already overwritten?
Having the kernel and initrd too close in memory has the kernel BSS overwrite the initrd. This has happened time and time again before I went around making some platforms have reasonable (ie kernel early, ramdisk in lowmem but beyond where a kernel+bss can be, etc) defaults and pushing others to do the same.
Can you provide the text you want to see here?
Off-hand, it should look more like the big comment block in include/configs/ti_armv7_common.h and reference the Linux booting on arm/arm64 documents while noting that other architectures have the same fundamental issues and their exact limits may or may not be as well documented.
On 1/9/21 10:23 PM, Tom Rini wrote:
On Sat, Jan 09, 2021 at 08:59:01PM +0100, Heinrich Schuchardt wrote:
Am 9. Januar 2021 20:40:04 MEZ schrieb Tom Rini trini@konsulko.com:
On Sat, Jan 09, 2021 at 08:33:40PM +0100, Heinrich Schuchardt wrote:
On 1/9/21 7:58 PM, Tom Rini wrote:
On Sat, Jan 09, 2021 at 08:47:07PM +0200, Andy Shevchenko wrote:
On Sat, Jan 9, 2021 at 8:06 PM Heinrich Schuchardt
xypron.glpk@gmx.de wrote:
> > The comment for initrd_high in the coding and in README were
contradicting
> and neither fully described what the coding does. > > Clarify the usage of the special value ~0UL for the environment
variable
> initrd_high.
All those F:s are hard to read in the comments and documentation
and
typo prone. I would prefer to rephrase like "all 1:s value in 32-
or
64-bit format" or alike.
If we're going to improve this we should also note it's discouraged unless you know for certain there will be no overlap and it's
strongly
discouraged in default environments.
What exactly is discouraged?
- setting initrd_high to a value != ~0? Here I would agree.
- setting intird_high to ~0? Why should we copy initrd to a different place? Is it for some outdated Linux release?
We should always default to allowing the initrd to be relocated because we can see (in many cases) overlap that will lead to failure to boot but this forces us to ignore that. Having good default load values means we don't have a problem here.
We have an initrd that is already in memory. What could it overlap with that is not already overwritten?
Having the kernel and initrd too close in memory has the kernel BSS overwrite the initrd. This has happened time and time again before I went around making some platforms have reasonable (ie kernel early, ramdisk in lowmem but beyond where a kernel+bss can be, etc) defaults and pushing others to do the same.
Can you provide the text you want to see here?
Off-hand, it should look more like the big comment block in include/configs/ti_armv7_common.h and reference the Linux booting on arm/arm64 documents while noting that other architectures have the same fundamental issues and their exact limits may or may not be as well documented.
There is nothing in the include/configs/ti_armv7_common.h comments requiring to relocate initrd.
Best regards
Heinrich
On Sun, Jan 10, 2021 at 01:05:14PM +0100, Heinrich Schuchardt wrote:
On 1/9/21 10:23 PM, Tom Rini wrote:
On Sat, Jan 09, 2021 at 08:59:01PM +0100, Heinrich Schuchardt wrote:
Am 9. Januar 2021 20:40:04 MEZ schrieb Tom Rini trini@konsulko.com:
On Sat, Jan 09, 2021 at 08:33:40PM +0100, Heinrich Schuchardt wrote:
On 1/9/21 7:58 PM, Tom Rini wrote:
On Sat, Jan 09, 2021 at 08:47:07PM +0200, Andy Shevchenko wrote: > On Sat, Jan 9, 2021 at 8:06 PM Heinrich Schuchardt
xypron.glpk@gmx.de wrote:
> > > > The comment for initrd_high in the coding and in README were
contradicting
> > and neither fully described what the coding does. > > > > Clarify the usage of the special value ~0UL for the environment
variable
> > initrd_high. > > All those F:s are hard to read in the comments and documentation
and
> typo prone. I would prefer to rephrase like "all 1:s value in 32-
or
> 64-bit format" or alike.
If we're going to improve this we should also note it's discouraged unless you know for certain there will be no overlap and it's
strongly
discouraged in default environments.
What exactly is discouraged?
- setting initrd_high to a value != ~0? Here I would agree.
- setting intird_high to ~0? Why should we copy initrd to a different place? Is it for some outdated Linux release?
We should always default to allowing the initrd to be relocated because we can see (in many cases) overlap that will lead to failure to boot but this forces us to ignore that. Having good default load values means we don't have a problem here.
We have an initrd that is already in memory. What could it overlap with that is not already overwritten?
Having the kernel and initrd too close in memory has the kernel BSS overwrite the initrd. This has happened time and time again before I went around making some platforms have reasonable (ie kernel early, ramdisk in lowmem but beyond where a kernel+bss can be, etc) defaults and pushing others to do the same.
Can you provide the text you want to see here?
Off-hand, it should look more like the big comment block in include/configs/ti_armv7_common.h and reference the Linux booting on arm/arm64 documents while noting that other architectures have the same fundamental issues and their exact limits may or may not be as well documented.
There is nothing in the include/configs/ti_armv7_common.h comments requiring to relocate initrd.
/* * We setup defaults based on constraints from the Linux kernel, which should * also be safe elsewhere. We have the default load at 32MB into DDR (for * the kernel), FDT above 128MB (the maximum location for the end of the * kernel), and the ramdisk 512KB above that (allowing for hopefully never * seen large trees). We say all of this must be within the first 256MB * as that will normally be within the kernel lowmem and thus visible via * bootm_size and we only run on platforms with 256MB or more of memory. * * As a temporary storage for DTBO blobs (which should be applied into DTB * blob), we use the location 15.5 MB above the ramdisk. If someone wants to * use ramdisk bigger than 15.5 MB, then DTBO can be loaded and applied to DTB * blob before loading the ramdisk, as DTBO location is only used as a temporary * storage, and can be re-used after 'fdt apply' command is done. */
Now, it's I gather not clear that we're NOT setting initrd_high here (nor fdt_high) because we're setting reasonable defaults for everyone to use, so long as they have enough memory.
On 1/10/21 2:43 PM, Tom Rini wrote:
On Sun, Jan 10, 2021 at 01:05:14PM +0100, Heinrich Schuchardt wrote:
On 1/9/21 10:23 PM, Tom Rini wrote:
On Sat, Jan 09, 2021 at 08:59:01PM +0100, Heinrich Schuchardt wrote:
Am 9. Januar 2021 20:40:04 MEZ schrieb Tom Rini trini@konsulko.com:
On Sat, Jan 09, 2021 at 08:33:40PM +0100, Heinrich Schuchardt wrote:
On 1/9/21 7:58 PM, Tom Rini wrote: > On Sat, Jan 09, 2021 at 08:47:07PM +0200, Andy Shevchenko wrote: >> On Sat, Jan 9, 2021 at 8:06 PM Heinrich Schuchardt
xypron.glpk@gmx.de wrote:
>>> >>> The comment for initrd_high in the coding and in README were
contradicting
>>> and neither fully described what the coding does. >>> >>> Clarify the usage of the special value ~0UL for the environment
variable
>>> initrd_high. >> >> All those F:s are hard to read in the comments and documentation
and
>> typo prone. I would prefer to rephrase like "all 1:s value in 32-
or
>> 64-bit format" or alike. > > If we're going to improve this we should also note it's discouraged > unless you know for certain there will be no overlap and it's
strongly
> discouraged in default environments.
What exactly is discouraged?
- setting initrd_high to a value != ~0? Here I would agree.
- setting intird_high to ~0? Why should we copy initrd to a different place? Is it for some outdated Linux release?
We should always default to allowing the initrd to be relocated because we can see (in many cases) overlap that will lead to failure to boot but this forces us to ignore that. Having good default load values means we don't have a problem here.
We have an initrd that is already in memory. What could it overlap with that is not already overwritten?
Having the kernel and initrd too close in memory has the kernel BSS overwrite the initrd. This has happened time and time again before I went around making some platforms have reasonable (ie kernel early, ramdisk in lowmem but beyond where a kernel+bss can be, etc) defaults and pushing others to do the same.
Can you provide the text you want to see here?
Off-hand, it should look more like the big comment block in include/configs/ti_armv7_common.h and reference the Linux booting on arm/arm64 documents while noting that other architectures have the same fundamental issues and their exact limits may or may not be as well documented.
There is nothing in the include/configs/ti_armv7_common.h comments requiring to relocate initrd.
/*
- We setup defaults based on constraints from the Linux kernel, which should
- also be safe elsewhere. We have the default load at 32MB into DDR (for
- the kernel), FDT above 128MB (the maximum location for the end of the
- kernel), and the ramdisk 512KB above that (allowing for hopefully never
- seen large trees). We say all of this must be within the first 256MB
- as that will normally be within the kernel lowmem and thus visible via
- bootm_size and we only run on platforms with 256MB or more of memory.
- As a temporary storage for DTBO blobs (which should be applied into DTB
- blob), we use the location 15.5 MB above the ramdisk. If someone wants to
- use ramdisk bigger than 15.5 MB, then DTBO can be loaded and applied to DTB
- blob before loading the ramdisk, as DTBO location is only used as a temporary
- storage, and can be re-used after 'fdt apply' command is done.
*/
I cannot see how this relates to initrd relocation.
Best regards
Heinrich
Now, it's I gather not clear that we're NOT setting initrd_high here (nor fdt_high) because we're setting reasonable defaults for everyone to use, so long as they have enough memory.
On Sun, Jan 10, 2021 at 05:20:50PM +0100, Heinrich Schuchardt wrote:
On 1/10/21 2:43 PM, Tom Rini wrote:
On Sun, Jan 10, 2021 at 01:05:14PM +0100, Heinrich Schuchardt wrote:
On 1/9/21 10:23 PM, Tom Rini wrote:
On Sat, Jan 09, 2021 at 08:59:01PM +0100, Heinrich Schuchardt wrote:
Am 9. Januar 2021 20:40:04 MEZ schrieb Tom Rini trini@konsulko.com:
On Sat, Jan 09, 2021 at 08:33:40PM +0100, Heinrich Schuchardt wrote: > On 1/9/21 7:58 PM, Tom Rini wrote: > > On Sat, Jan 09, 2021 at 08:47:07PM +0200, Andy Shevchenko wrote: > > > On Sat, Jan 9, 2021 at 8:06 PM Heinrich Schuchardt xypron.glpk@gmx.de wrote: > > > > > > > > The comment for initrd_high in the coding and in README were contradicting > > > > and neither fully described what the coding does. > > > > > > > > Clarify the usage of the special value ~0UL for the environment variable > > > > initrd_high. > > > > > > All those F:s are hard to read in the comments and documentation and > > > typo prone. I would prefer to rephrase like "all 1:s value in 32- or > > > 64-bit format" or alike. > > > > If we're going to improve this we should also note it's discouraged > > unless you know for certain there will be no overlap and it's strongly > > discouraged in default environments. > > What exactly is discouraged? > > * setting initrd_high to a value != ~0? Here I would agree. > * setting intird_high to ~0? Why should we copy initrd to a > different place? Is it for some outdated Linux release?
We should always default to allowing the initrd to be relocated because we can see (in many cases) overlap that will lead to failure to boot but this forces us to ignore that. Having good default load values means we don't have a problem here.
We have an initrd that is already in memory. What could it overlap with that is not already overwritten?
Having the kernel and initrd too close in memory has the kernel BSS overwrite the initrd. This has happened time and time again before I went around making some platforms have reasonable (ie kernel early, ramdisk in lowmem but beyond where a kernel+bss can be, etc) defaults and pushing others to do the same.
Can you provide the text you want to see here?
Off-hand, it should look more like the big comment block in include/configs/ti_armv7_common.h and reference the Linux booting on arm/arm64 documents while noting that other architectures have the same fundamental issues and their exact limits may or may not be as well documented.
There is nothing in the include/configs/ti_armv7_common.h comments requiring to relocate initrd.
/*
- We setup defaults based on constraints from the Linux kernel, which should
- also be safe elsewhere. We have the default load at 32MB into DDR (for
- the kernel), FDT above 128MB (the maximum location for the end of the
- kernel), and the ramdisk 512KB above that (allowing for hopefully never
- seen large trees). We say all of this must be within the first 256MB
- as that will normally be within the kernel lowmem and thus visible via
- bootm_size and we only run on platforms with 256MB or more of memory.
- As a temporary storage for DTBO blobs (which should be applied into DTB
- blob), we use the location 15.5 MB above the ramdisk. If someone wants to
- use ramdisk bigger than 15.5 MB, then DTBO can be loaded and applied to DTB
- blob before loading the ramdisk, as DTBO location is only used as a temporary
- storage, and can be re-used after 'fdt apply' command is done.
*/
I cannot see how this relates to initrd relocation.
You cannot safely disable initrd relocation without ensuring it won't be locked in an unsafe location first. It's also _generally_ going to be noise in the boot sequence and not an advisable default. It should be documented as part of how to tune a system for optimal boot times. But given how often defaults are copy/pasted to the next platform without fully understanding why those values were picked is why what we use as default in one platform needs to be very carefully done.
participants (4)
-
Adam Ford -
Andy Shevchenko -
Heinrich Schuchardt -
Tom Rini