| Message ID | 20240611144949.703297941@goodmis.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm/memblock: Add "reserve_mem" to reserved named memory at boot up | expand |
On Tue, Jun 11, 2024 at 10:49:13AM -0400, Steven Rostedt wrote: > From: "Steven Rostedt (Google)" <rostedt@goodmis.org> > > Add a method to find a region specified by reserve_mem=nn:align:name for > ramoops. Adding a kernel command line parameter: > > reserve_mem=12M:4096:oops ramoops.mem_name=oops > > Will use the size and location defined by the memmap parameter where it > finds the memory and labels it "oops". The "oops" in the ramoops option > is used to search for it. > > This allows for arbitrary RAM to be used for ramoops if it is known that > the memory is not cleared on kernel crashes or soft reboots. > > Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> Acked-by: Kees Cook <kees@kernel.org> Let me know if this should go via the pstore tree, if you'd rather carry it?
On Wed, 12 Jun 2024 11:45:57 -0700 Kees Cook <kees@kernel.org> wrote: > On Tue, Jun 11, 2024 at 10:49:13AM -0400, Steven Rostedt wrote: > > From: "Steven Rostedt (Google)" <rostedt@goodmis.org> > > > > Add a method to find a region specified by reserve_mem=nn:align:name for > > ramoops. Adding a kernel command line parameter: > > > > reserve_mem=12M:4096:oops ramoops.mem_name=oops > > > > Will use the size and location defined by the memmap parameter where it > > finds the memory and labels it "oops". The "oops" in the ramoops option > > is used to search for it. > > > > This allows for arbitrary RAM to be used for ramoops if it is known that > > the memory is not cleared on kernel crashes or soft reboots. > > > > Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> > > Acked-by: Kees Cook <kees@kernel.org> > > Let me know if this should go via the pstore tree, if you'd rather carry > it? > I'm going to send out another version to cover some more comments that were made, and perhaps it's best if Mike Rapoport takes it through his tree. Thanks! -- Steve
On Wed, Jun 12, 2024 at 02:52:28PM -0400, Steven Rostedt wrote: > On Wed, 12 Jun 2024 11:45:57 -0700 > Kees Cook <kees@kernel.org> wrote: > > > On Tue, Jun 11, 2024 at 10:49:13AM -0400, Steven Rostedt wrote: > > > From: "Steven Rostedt (Google)" <rostedt@goodmis.org> > > > > > > Add a method to find a region specified by reserve_mem=nn:align:name for > > > ramoops. Adding a kernel command line parameter: > > > > > > reserve_mem=12M:4096:oops ramoops.mem_name=oops > > > > > > Will use the size and location defined by the memmap parameter where it > > > finds the memory and labels it "oops". The "oops" in the ramoops option > > > is used to search for it. > > > > > > This allows for arbitrary RAM to be used for ramoops if it is known that > > > the memory is not cleared on kernel crashes or soft reboots. > > > > > > Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> > > > > Acked-by: Kees Cook <kees@kernel.org> > > > > Let me know if this should go via the pstore tree, if you'd rather carry > > it? > > > > I'm going to send out another version to cover some more comments that > were made, and perhaps it's best if Mike Rapoport takes it through his > tree. I've added one more comment to v5, with that fixed I can take this. > Thanks! > > -- Steve
On Thu, 13 Jun 2024 at 08:04, Mike Rapoport <rppt@kernel.org> wrote: > > On Wed, Jun 12, 2024 at 02:52:28PM -0400, Steven Rostedt wrote: > > On Wed, 12 Jun 2024 11:45:57 -0700 > > Kees Cook <kees@kernel.org> wrote: > > > > > On Tue, Jun 11, 2024 at 10:49:13AM -0400, Steven Rostedt wrote: > > > > From: "Steven Rostedt (Google)" <rostedt@goodmis.org> > > > > > > > > Add a method to find a region specified by reserve_mem=nn:align:name for > > > > ramoops. Adding a kernel command line parameter: > > > > > > > > reserve_mem=12M:4096:oops ramoops.mem_name=oops > > > > > > > > Will use the size and location defined by the memmap parameter where it > > > > finds the memory and labels it "oops". The "oops" in the ramoops option > > > > is used to search for it. > > > > > > > > This allows for arbitrary RAM to be used for ramoops if it is known that > > > > the memory is not cleared on kernel crashes or soft reboots. > > > > > > > > Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> > > > > > > Acked-by: Kees Cook <kees@kernel.org> > > > > > > Let me know if this should go via the pstore tree, if you'd rather carry > > > it? > > > > > > > I'm going to send out another version to cover some more comments that > > were made, and perhaps it's best if Mike Rapoport takes it through his > > tree. > > I've added one more comment to v5, with that fixed I can take this. > So how is this supposed to work wrt to the rigid 'no user visible regressions' rule, given that this whole thing is a best effort thing to begin with. This needs at least a huge disclaimer that this rule does not apply, and if this works today, there is no guarantee that it will keep working on newer kernels. Otherwise, you will be making the job of the people who work on the boot code significantly more difficult. And even then, I wonder whether Linus and #regzcop are going to honour such a disclaimer. So this belongs downstream, unless some guarantees can be provided that this functionality is exempt from the usual regression policies.
On Thu, 13 Jun 2024 08:11:48 +0200 Ard Biesheuvel <ardb@kernel.org> wrote: > > > > I've added one more comment to v5, with that fixed I can take this. > > > > So how is this supposed to work wrt to the rigid 'no user visible > regressions' rule, given that this whole thing is a best effort thing This has nothing to do with user space. The kernel command line has broken in the past. If you update the kernel, you can update the command line. There's no "no user visible regressions" rule. It's "Don't break user space". This has nothing to do with user space. > to begin with. This needs at least a huge disclaimer that this rule > does not apply, and if this works today, there is no guarantee that it > will keep working on newer kernels. Otherwise, you will be making the > job of the people who work on the boot code significantly more > difficult. And even then, I wonder whether Linus and #regzcop are > going to honour such a disclaimer. Again, this has nothing to do with user space. The rule Linus talks about is breaking user space. This is about kernel debugging. Something *completely different*! > > So this belongs downstream, unless some guarantees can be provided > that this functionality is exempt from the usual regression policies. I disagree. kexec/kdump also has the same issues. -- Steve
On Thu, 13 Jun 2024 at 15:26, Steven Rostedt <rostedt@goodmis.org> wrote: > > On Thu, 13 Jun 2024 08:11:48 +0200 > Ard Biesheuvel <ardb@kernel.org> wrote: > > > > > > I've added one more comment to v5, with that fixed I can take this. > > > > > > > So how is this supposed to work wrt to the rigid 'no user visible > > regressions' rule, given that this whole thing is a best effort thing > > This has nothing to do with user space. The kernel command line has > broken in the past. If you update the kernel, you can update the > command line. There's no "no user visible regressions" rule. It's > "Don't break user space". This has nothing to do with user space. > > > to begin with. This needs at least a huge disclaimer that this rule > > does not apply, and if this works today, there is no guarantee that it > > will keep working on newer kernels. Otherwise, you will be making the > > job of the people who work on the boot code significantly more > > difficult. And even then, I wonder whether Linus and #regzcop are > > going to honour such a disclaimer. > > Again, this has nothing to do with user space. The rule Linus talks > about is breaking user space. This is about kernel debugging. Something > *completely different*! > > > > > So this belongs downstream, unless some guarantees can be provided > > that this functionality is exempt from the usual regression policies. > > I disagree. kexec/kdump also has the same issues. > Fair enough. As long as it is documented that there is no guarantee that this will keep working over a kernel upgrade, then I have no objections.
On Thu, 13 Jun 2024 16:06:47 +0200 Ard Biesheuvel <ardb@kernel.org> wrote: > Fair enough. As long as it is documented that there is no guarantee > that this will keep working over a kernel upgrade, then I have no > objections. Thanks, I'll send out v6 and even stress that this may not work for all kernel versions. -- Steve
On June 13, 2024 7:06:47 AM PDT, Ard Biesheuvel <ardb@kernel.org> wrote: >On Thu, 13 Jun 2024 at 15:26, Steven Rostedt <rostedt@goodmis.org> wrote: >> >> On Thu, 13 Jun 2024 08:11:48 +0200 >> Ard Biesheuvel <ardb@kernel.org> wrote: >> > > >> > > I've added one more comment to v5, with that fixed I can take this. >> > > >> > >> > So how is this supposed to work wrt to the rigid 'no user visible >> > regressions' rule, given that this whole thing is a best effort thing >> >> This has nothing to do with user space. The kernel command line has >> broken in the past. If you update the kernel, you can update the >> command line. There's no "no user visible regressions" rule. It's >> "Don't break user space". This has nothing to do with user space. >> >> > to begin with. This needs at least a huge disclaimer that this rule >> > does not apply, and if this works today, there is no guarantee that it >> > will keep working on newer kernels. Otherwise, you will be making the >> > job of the people who work on the boot code significantly more >> > difficult. And even then, I wonder whether Linus and #regzcop are >> > going to honour such a disclaimer. >> >> Again, this has nothing to do with user space. The rule Linus talks >> about is breaking user space. This is about kernel debugging. Something >> *completely different*! >> >> > >> > So this belongs downstream, unless some guarantees can be provided >> > that this functionality is exempt from the usual regression policies. >> >> I disagree. kexec/kdump also has the same issues. >> > >Fair enough. As long as it is documented that there is no guarantee >that this will keep working over a kernel upgrade, then I have no >objections. Yeah, I should better document this for pstore as a whole, but I've already made the call that cross-kernel-versison operation is best effort. -Kees
diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c index b1a455f42e93..0653b76c70fe 100644 --- a/fs/pstore/ram.c +++ b/fs/pstore/ram.c @@ -50,6 +50,10 @@ module_param_hw(mem_address, ullong, other, 0400); MODULE_PARM_DESC(mem_address, "start of reserved RAM used to store oops/panic logs"); +static char *mem_name; +module_param_named(mem_name, mem_name, charp, 0400); +MODULE_PARM_DESC(mem_name, "name of kernel param that holds addr"); + static ulong mem_size; module_param(mem_size, ulong, 0400); MODULE_PARM_DESC(mem_size, @@ -914,6 +918,16 @@ static void __init ramoops_register_dummy(void) { struct ramoops_platform_data pdata; + if (mem_name) { + unsigned long start; + unsigned long size; + + if (reserve_mem_find_by_name(mem_name, &start, &size)) { + mem_address = start; + mem_size = size; + } + } + /* * Prepare a dummy platform data structure to carry the module * parameters. If mem_size isn't set, then there are no module