From b5e4771f20a37fdf19eac0824bf062dffb4e291f Mon Sep 17 00:00:00 2001 From: Priya Bala Govindasamy Date: Mon, 20 Jul 2026 20:50:35 +0000 Subject: rust: cpufreq: Add CPUFREQ_TABLE_END as last table entry in TableBuilder::to_table The `TableBuilder::to_table` function adds `Hertz(c_ulong::MAX).as_khz()` as the last frequency entry in the frequency table. But the C API expects the last entry to have frequency set to `CPUFREQ_TABLE_END` which is `~1u` as per include/linux/cpufreq.h. Fix this by setting the last frequency entry to `CPUFREQ_TABLE_END` instead of `Hertz(c_ulong::MAX).as_khz()`. Fixes: 2207856ff0bc8d953d6e89bda70b8978c2de8bab ("rust: cpufreq: Add initial abstractions for cpufreq framework") Reported-by: Dylan Zueck Reported-by: Yuan Tan Assisted-by: ChatGPT:gpt-5.6-terra Signed-off-by: Priya Bala Govindasamy Signed-off-by: Viresh Kumar --- rust/kernel/cpufreq.rs | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) (limited to 'rust/kernel') diff --git a/rust/kernel/cpufreq.rs b/rust/kernel/cpufreq.rs index 58ac04c650a1..f360eb9578f3 100644 --- a/rust/kernel/cpufreq.rs +++ b/rust/kernel/cpufreq.rs @@ -361,23 +361,28 @@ impl TableBuilder { } } - /// Adds a new entry to the table. - pub fn add(&mut self, freq: Hertz, flags: u32, driver_data: u32) -> Result { + /// Adds a raw frequency-table entry. + fn push(&mut self, frequency: u32, flags: u32, driver_data: u32) -> Result { // Adds the new entry at the end of the vector. Ok(self.entries.push( bindings::cpufreq_frequency_table { flags, driver_data, - frequency: freq.as_khz() as u32, + frequency, }, GFP_KERNEL, )?) } + /// Adds a new entry to the table. + pub fn add(&mut self, freq: Hertz, flags: u32, driver_data: u32) -> Result { + self.push(freq.as_khz() as u32, flags, driver_data) + } + /// Consumes the [`TableBuilder`] and returns [`TableBox`]. pub fn to_table(mut self) -> Result { // Add last entry to the table. - self.add(Hertz(c_ulong::MAX), 0, 0)?; + self.push(bindings::CPUFREQ_TABLE_END as u32, 0, 0)?; TableBox::new(self.entries) } -- cgit v1.2.3 From 19c76bdd3fc02475c73c8576f6f4a55ff07886f1 Mon Sep 17 00:00:00 2001 From: Priya Bala Govindasamy Date: Mon, 20 Jul 2026 18:00:58 +0000 Subject: rust: cpufreq: Fix temporary write in Registration::bios_limit_callback In `Registration::bios_limit_callback`, the expression `&mut (unsafe { *limit })` creates a reference to a temporary copy of the value pointed to by `limit` on the stack. Therefore, writes made by `T::bios_limit` go to this temporary instead of the memory location pointed to by `limit`. Additionally, `limit` may be uninitialized, such as when `Registration::bios_limit_callback` is invoked by `show_bios_limit` in drivers/cpufreq/cpufreq.c. Therefore creating a reference to `limit` is unsound. Fix this by changing the signature of `T::bios_limit` to return the limit value. `Registration::bios_limit_callback` can then update `limit` directly. Fixes: c6af9a1191d042839e56abff69e8b0302d117988 ("rust: cpufreq: Extend abstractions for driver registration") Reported-by: Dylan Zueck Reported-by: Yuan Tan Assisted-by: ChatGPT:gpt-5.4 Signed-off-by: Priya Bala Govindasamy [ Viresh: Fix rustfmtcheck warning ] Signed-off-by: Viresh Kumar --- rust/kernel/cpufreq.rs | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) (limited to 'rust/kernel') diff --git a/rust/kernel/cpufreq.rs b/rust/kernel/cpufreq.rs index f360eb9578f3..1158ef3a85f2 100644 --- a/rust/kernel/cpufreq.rs +++ b/rust/kernel/cpufreq.rs @@ -822,7 +822,9 @@ pub trait Driver { } /// Driver's `bios_limit` callback. - fn bios_limit(_policy: &mut Policy, _limit: &mut u32) -> Result { + /// + /// Returns HW/BIOS max frequency limitations for the CPU. + fn bios_limit(_policy: &mut Policy) -> Result { build_error!(VTABLE_DEFAULT_ERROR) } @@ -1357,9 +1359,12 @@ impl Registration { from_result(|| { let mut policy = PolicyCpu::from_cpu(cpu_id)?; - + let val = T::bios_limit(&mut policy)?; // SAFETY: `limit` is guaranteed by the C code to be valid. - T::bios_limit(&mut policy, &mut (unsafe { *limit })).map(|()| 0) + unsafe { + *limit = val; + } + Ok(0) }) } -- cgit v1.2.3