From: Link Mauve <hidden> Date: 2026-02-04 03:05:28
For now only Big Endian 32-bit PowerPC is supported, as that is the only
hardware I have. This has been tested on the Nintendo Wii so far, but I
plan on also using it on the GameCube, Wii U and Apple G4.
These changes aren’t the only ones required to get the kernel to compile
and link on PowerPC, libcore will also have to be changed to not use
integer division to format u64, u128 and core::time::Duration, otherwise
__udivdi3() and __umoddi3() will have to be added. I have tested this
change by replacing the three implementations with unimplemented!() and
it linked just fine.
Signed-off-by: Link Mauve <redacted>
---
Documentation/rust/arch-support.rst | 1 +
arch/powerpc/Kconfig | 1 +
arch/powerpc/Makefile | 2 ++
arch/powerpc/include/asm/jump_label.h | 16 ++++++++++------
rust/Makefile | 4 +++-
scripts/generate_rust_target.rs | 10 ++++++++++
6 files changed, 27 insertions(+), 7 deletions(-)
From: Alice Ryhl <aliceryhl@google.com> Date: 2026-02-04 10:41:36
On Wed, Feb 04, 2026 at 04:05:04AM +0100, Link Mauve wrote:
For now only Big Endian 32-bit PowerPC is supported, as that is the only
hardware I have. This has been tested on the Nintendo Wii so far, but I
plan on also using it on the GameCube, Wii U and Apple G4.
Super cool!
These changes aren’t the only ones required to get the kernel to compile
and link on PowerPC, libcore will also have to be changed to not use
integer division to format u64, u128 and core::time::Duration, otherwise
__udivdi3() and __umoddi3() will have to be added. I have tested this
change by replacing the three implementations with unimplemented!() and
it linked just fine.
Uh oh this seems tricky. How is this not a problem on arm32 too?
Perhaps we should just be providing __udivdi3() and __umoddi3() in
general?
@@ -15,14 +15,18 @@#define JUMP_ENTRY_TYPE stringify_in_c(FTR_ENTRY_LONG)#define JUMP_LABEL_NOP_SIZE 4+/* This macro is also expanded on the Rust side. */+#define ARCH_STATIC_BRANCH_ASM(key, label) \+"1:\n\t"\+"nop # arch_static_branch\n\t"\+".pushsection __jump_table, \"aw\"\n\t"\+".long 1b - ., "label" - .\n\t"\+JUMP_ENTRY_TYPEkey" - .\n\t"\+".popsection \n\t"+static__always_inlineboolarch_static_branch(structstatic_key*key,boolbranch){-asmgoto("1:\n\t"-"nop # arch_static_branch\n\t"-".pushsection __jump_table, \"aw\"\n\t"-".long 1b - ., %l[l_yes] - .\n\t"-JUMP_ENTRY_TYPE"%c0 - .\n\t"-".popsection \n\t"+asmgoto(ARCH_STATIC_BRANCH_ASM("%c0","%l[l_yes]")::"i"(&((char*)key)[branch])::l_yes);
In case this patch takes a long time to land, it may make sense to split
this part out in a separate patch that can land now.
Also, consider pre-emptively updating arch_static_branch_jump too. We
probably need it at some point in the future.
On Wed Feb 4, 2026 at 10:41 AM GMT, Alice Ryhl wrote:
On Wed, Feb 04, 2026 at 04:05:04AM +0100, Link Mauve wrote:
quoted
For now only Big Endian 32-bit PowerPC is supported, as that is the only
hardware I have. This has been tested on the Nintendo Wii so far, but I
plan on also using it on the GameCube, Wii U and Apple G4.
Super cool!
quoted
These changes aren’t the only ones required to get the kernel to compile
and link on PowerPC, libcore will also have to be changed to not use
integer division to format u64, u128 and core::time::Duration, otherwise
__udivdi3() and __umoddi3() will have to be added. I have tested this
change by replacing the three implementations with unimplemented!() and
it linked just fine.
Uh oh this seems tricky. How is this not a problem on arm32 too?
Perhaps we should just be providing __udivdi3() and __umoddi3() in
general?
I think there is some concern that if this is provided, then C side that uses
the divide operator instead of dividing function doesn't get linker error
anymore.
However, a proper way is to do this via the hooks that we already have in
`compiler_builtins.rs`.
This can either be replace these with panics or actual implementation, but for
libcore.o only.
Best,
Gary
@@ -15,14 +15,18 @@#define JUMP_ENTRY_TYPE stringify_in_c(FTR_ENTRY_LONG)#define JUMP_LABEL_NOP_SIZE 4+/* This macro is also expanded on the Rust side. */+#define ARCH_STATIC_BRANCH_ASM(key, label) \+"1:\n\t"\+"nop # arch_static_branch\n\t"\+".pushsection __jump_table, \"aw\"\n\t"\+".long 1b - ., "label" - .\n\t"\+JUMP_ENTRY_TYPEkey" - .\n\t"\+".popsection \n\t"+static__always_inlineboolarch_static_branch(structstatic_key*key,boolbranch){-asmgoto("1:\n\t"-"nop # arch_static_branch\n\t"-".pushsection __jump_table, \"aw\"\n\t"-".long 1b - ., %l[l_yes] - .\n\t"-JUMP_ENTRY_TYPE"%c0 - .\n\t"-".popsection \n\t"+asmgoto(ARCH_STATIC_BRANCH_ASM("%c0","%l[l_yes]")::"i"(&((char*)key)[branch])::l_yes);
In case this patch takes a long time to land, it may make sense to split
this part out in a separate patch that can land now.
Also, consider pre-emptively updating arch_static_branch_jump too. We
probably need it at some point in the future.
From: Alice Ryhl <aliceryhl@google.com> Date: 2026-02-04 12:55:20
On Wed, Feb 04, 2026 at 12:36:38PM +0000, Gary Guo wrote:
On Wed Feb 4, 2026 at 10:41 AM GMT, Alice Ryhl wrote:
quoted
On Wed, Feb 04, 2026 at 04:05:04AM +0100, Link Mauve wrote:
quoted
For now only Big Endian 32-bit PowerPC is supported, as that is the only
hardware I have. This has been tested on the Nintendo Wii so far, but I
plan on also using it on the GameCube, Wii U and Apple G4.
Super cool!
quoted
These changes aren’t the only ones required to get the kernel to compile
and link on PowerPC, libcore will also have to be changed to not use
integer division to format u64, u128 and core::time::Duration, otherwise
__udivdi3() and __umoddi3() will have to be added. I have tested this
change by replacing the three implementations with unimplemented!() and
it linked just fine.
Uh oh this seems tricky. How is this not a problem on arm32 too?
Perhaps we should just be providing __udivdi3() and __umoddi3() in
general?
I think there is some concern that if this is provided, then C side that uses
the divide operator instead of dividing function doesn't get linker error
anymore.
However, a proper way is to do this via the hooks that we already have in
`compiler_builtins.rs`.
This can either be replace these with panics or actual implementation, but for
libcore.o only.
Is there any reason to not make it Rust-only but for all Rust code?
Making the / operator work seems like it would be a good idea.
Alice
From: Peter Zijlstra <peterz@infradead.org> Date: 2026-02-04 13:07:08
On Wed, Feb 04, 2026 at 12:55:17PM +0000, Alice Ryhl wrote:
Is there any reason to not make it Rust-only but for all Rust code?
Making the / operator work seems like it would be a good idea.
Why would it be a good idea to have it work on non-native types in Rust?
The reason we don't have them in C is because non-native divisions are
expensive and doing them should be a conscious choice. The very same
argument should be true for Rust code too.
From: Alice Ryhl <aliceryhl@google.com> Date: 2026-02-04 13:36:53
On Wed, Feb 04, 2026 at 02:06:53PM +0100, Peter Zijlstra wrote:
On Wed, Feb 04, 2026 at 12:55:17PM +0000, Alice Ryhl wrote:
quoted
Is there any reason to not make it Rust-only but for all Rust code?
Making the / operator work seems like it would be a good idea.
Why would it be a good idea to have it work on non-native types in Rust?
The reason we don't have them in C is because non-native divisions are
expensive and doing them should be a conscious choice. The very same
argument should be true for Rust code too.
I suppose that's fair. Perhaps one way to go about it could be to create
a clippy lint for 64-bit divisions telling you to use an explicit
division method?
This way cases such as `core` that use division can still use the slash
operator because the lint is not enabled when building core. And normal
kernel code would be told to use the explicit method instead. Or kernel
code could explicitly choose to silence the lint on a specific method if
they want to perform a lot of divisions and know what they are doing.
Alice
On Wed, Feb 04, 2026 at 04:05:04AM +0100, Link Mauve wrote:
quoted
For now only Big Endian 32-bit PowerPC is supported, as that is the only
hardware I have. This has been tested on the Nintendo Wii so far, but I
plan on also using it on the GameCube, Wii U and Apple G4.
Super cool!
quoted
These changes aren’t the only ones required to get the kernel to compile
and link on PowerPC, libcore will also have to be changed to not use
integer division to format u64, u128 and core::time::Duration, otherwise
__udivdi3() and __umoddi3() will have to be added. I have tested this
change by replacing the three implementations with unimplemented!() and
it linked just fine.
Uh oh this seems tricky. How is this not a problem on arm32 too?
Perhaps we should just be providing __udivdi3() and __umoddi3() in
general?
We don't want those functions in the kernel as they are sub-optimal and
unnecessary. Usually the kernel needs can be covered with do_div() or
other functions in include/asm-generic/div64.h. If we add those
functions people will start doing divides blindly in the kernel
forgetting the huge cost a 64 bits divide has on a 32 bits processor.
In case this patch takes a long time to land, it may make sense to split
this part out in a separate patch that can land now.
Also, consider pre-emptively updating arch_static_branch_jump too. We
probably need it at some point in the future.
On Wed, Feb 04, 2026 at 04:05:04AM +0100, Link Mauve wrote:
For now only Big Endian 32-bit PowerPC is supported, as that is the only
hardware I have. This has been tested on the Nintendo Wii so far, but I
plan on also using it on the GameCube, Wii U and Apple G4.
These changes aren’t the only ones required to get the kernel to compile
and link on PowerPC, libcore will also have to be changed to not use
integer division to format u64, u128 and core::time::Duration, otherwise
__udivdi3() and __umoddi3() will have to be added. I have tested this
change by replacing the three implementations with unimplemented!() and
it linked just fine.
Le 04/02/2026 à 18:33, Mukesh Kumar Chaurasiya a écrit :
[Vous ne recevez pas souvent de courriers de mkchauras@gmail.com. Découvrez pourquoi ceci est important à https://aka.ms/LearnAboutSenderIdentification ]
On Wed, Feb 04, 2026 at 04:05:04AM +0100, Link Mauve wrote:
quoted
For now only Big Endian 32-bit PowerPC is supported, as that is the only
hardware I have. This has been tested on the Nintendo Wii so far, but I
plan on also using it on the GameCube, Wii U and Apple G4.
These changes aren’t the only ones required to get the kernel to compile
and link on PowerPC, libcore will also have to be changed to not use
integer division to format u64, u128 and core::time::Duration, otherwise
__udivdi3() and __umoddi3() will have to be added. I have tested this
change by replacing the three implementations with unimplemented!() and
it linked just fine.