Hi folks, sorry if messed something up, this email has never been in my inbox.
Disable the TSC Deadline timer in lapic_timer_shutdown() by writing to MSR_IA32_TSC_DEADLINE when in TSC-deadline mode. Also avoid writing to the initial-count register (APIC_TMICT) which is ignored in TSC-deadline mode.
So this commit hit stable and we now see section mismatch errors:
// stripped
WARNING: vmlinux.o(__ex_table+0x447c): Section mismatch in reference from the (unknown reference) (unknown) to the (unknown reference) .irqentry.text:(unknown) The relocation at __ex_table+0x447c references section ".irqentry.text" which is not in the list of authorized sections.
WARNING: vmlinux.o(__ex_table+0x4480): Section mismatch in reference from the (unknown reference) (unknown) to the (unknown reference) .irqentry.text:(unknown) The relocation at __ex_table+0x4480 references section ".irqentry.text" which is not in the list of authorized sections.
FATAL: modpost: Section mismatches detected.
Specifically because of wrmsrl.
I'm aware of the section mismatch errors on linux-5.4 (I know), not aware of any other stable versions (but I haven't checked). Is this something specific to linux-5.4?
On (24/11/28 20:18), Sergey Senozhatsky wrote:
Disable the TSC Deadline timer in lapic_timer_shutdown() by writing to MSR_IA32_TSC_DEADLINE when in TSC-deadline mode. Also avoid writing to the initial-count register (APIC_TMICT) which is ignored in TSC-deadline mode.
Upstream commit ffd95846c6ec6cf1f93da411ea10d504036cab42 (forgot to mention)
On Thu, Nov 28 2024 at 20:18, Sergey Senozhatsky wrote:
Disable the TSC Deadline timer in lapic_timer_shutdown() by writing to MSR_IA32_TSC_DEADLINE when in TSC-deadline mode. Also avoid writing to the initial-count register (APIC_TMICT) which is ignored in TSC-deadline mode.
So this commit hit stable and we now see section mismatch errors:
// stripped
WARNING: vmlinux.o(__ex_table+0x447c): Section mismatch in reference from the (unknown reference) (unknown) to the (unknown reference) .irqentry.text:(unknown) The relocation at __ex_table+0x447c references section ".irqentry.text" which is not in the list of authorized sections.
WARNING: vmlinux.o(__ex_table+0x4480): Section mismatch in reference from the (unknown reference) (unknown) to the (unknown reference) .irqentry.text:(unknown) The relocation at __ex_table+0x4480 references section ".irqentry.text" which is not in the list of authorized sections.
FATAL: modpost: Section mismatches detected.
Specifically because of wrmsrl.
I'm aware of the section mismatch errors on linux-5.4 (I know), not aware of any other stable versions (but I haven't checked). Is this something specific to linux-5.4?
So it seems the compiler inlines the inner guts of sysvec_apic_timer_interrupt() and local_apic_timer_interrupt().
Can you try the patch below?
Thanks,
tglx --- --- a/arch/x86/kernel/apic/apic.c +++ b/arch/x86/kernel/apic/apic.c @@ -1007,7 +1007,7 @@ void setup_secondary_APIC_clock(void) /* * The guts of the apic timer interrupt */ -static void local_apic_timer_interrupt(void) +static noinline void local_apic_timer_interrupt(void) { struct clock_event_device *evt = this_cpu_ptr(&lapic_events);
On (24/11/30 12:21), Thomas Gleixner wrote:
WARNING: vmlinux.o(__ex_table+0x447c): Section mismatch in reference from the (unknown reference) (unknown) to the (unknown reference) .irqentry.text:(unknown) The relocation at __ex_table+0x447c references section ".irqentry.text" which is not in the list of authorized sections.
WARNING: vmlinux.o(__ex_table+0x4480): Section mismatch in reference from the (unknown reference) (unknown) to the (unknown reference) .irqentry.text:(unknown) The relocation at __ex_table+0x4480 references section ".irqentry.text" which is not in the list of authorized sections.
FATAL: modpost: Section mismatches detected.
Specifically because of wrmsrl.
I'm aware of the section mismatch errors on linux-5.4 (I know), not aware of any other stable versions (but I haven't checked). Is this something specific to linux-5.4?
So it seems the compiler inlines the inner guts of sysvec_apic_timer_interrupt() and local_apic_timer_interrupt().
Can you try the patch below?
That works, as far as I can tell, thank you!
The compiler can fully inline the actual handler function of an interrupt entry into the .irqentry.text entry point. If such a function contains an access which has an exception table entry, modpost complains about a section mismatch:
WARNING: vmlinux.o(__ex_table+0x447c): Section mismatch in reference ...
The relocation at __ex_table+0x447c references section ".irqentry.text" which is not in the list of authorized sections.
Add .irqentry.text to OTHER_SECTIONS to cure the issue.
Reported-by: Sergey Senozhatsky senozhatsky@chromium.org Signed-off-by: Thomas Gleixner tglx@linutronix.de Cc: stable@vger.kernel.org --- scripts/mod/modpost.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/scripts/mod/modpost.c +++ b/scripts/mod/modpost.c @@ -785,7 +785,7 @@ static void check_section(const char *mo ".ltext", ".ltext.*" #define OTHER_TEXT_SECTIONS ".ref.text", ".head.text", ".spinlock.text", \ ".fixup", ".entry.text", ".exception.text", \ - ".coldtext", ".softirqentry.text" + ".coldtext", ".softirqentry.text", ".irqentry.text"
#define ALL_TEXT_SECTIONS ".init.text", ".exit.text", \ TEXT_SECTIONS, OTHER_TEXT_SECTIONS
On Sun, Dec 1, 2024 at 8:17 PM Thomas Gleixner tglx@linutronix.de wrote:
The compiler can fully inline the actual handler function of an interrupt entry into the .irqentry.text entry point. If such a function contains an access which has an exception table entry, modpost complains about a section mismatch:
WARNING: vmlinux.o(__ex_table+0x447c): Section mismatch in reference ...
The relocation at __ex_table+0x447c references section ".irqentry.text" which is not in the list of authorized sections.
Add .irqentry.text to OTHER_SECTIONS to cure the issue.
Reported-by: Sergey Senozhatsky senozhatsky@chromium.org
I found the context in LKML.
Closes: https://lore.kernel.org/all/20241128111844.GE10431@google.com/
However, is this still relevant to the mainline kernel?
In Linux 5.4.y, I agree this because smp_apic_timer_interrupt() is annotated as __irq_entry:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/arch/x...
In this mainline kernel, DEFINE_IDTENTRY_SYSVEC() expands to a normal .text function which is explicitly annotated 'noinline'.
Signed-off-by: Thomas Gleixner tglx@linutronix.de Cc: stable@vger.kernel.org
scripts/mod/modpost.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/scripts/mod/modpost.c +++ b/scripts/mod/modpost.c @@ -785,7 +785,7 @@ static void check_section(const char *mo ".ltext", ".ltext.*" #define OTHER_TEXT_SECTIONS ".ref.text", ".head.text", ".spinlock.text", \ ".fixup", ".entry.text", ".exception.text", \
".coldtext", ".softirqentry.text"
".coldtext", ".softirqentry.text", ".irqentry.text"#define ALL_TEXT_SECTIONS ".init.text", ".exit.text", \ TEXT_SECTIONS, OTHER_TEXT_SECTIONS
-- Best Regards Masahiro Yamada
On Mon, Dec 02 2024 at 11:02, Masahiro Yamada wrote:
On Sun, Dec 1, 2024 at 8:17 PM Thomas Gleixner tglx@linutronix.de wrote:
The compiler can fully inline the actual handler function of an interrupt entry into the .irqentry.text entry point. If such a function contains an access which has an exception table entry, modpost complains about a section mismatch:
WARNING: vmlinux.o(__ex_table+0x447c): Section mismatch in reference ...
The relocation at __ex_table+0x447c references section ".irqentry.text" which is not in the list of authorized sections.
Add .irqentry.text to OTHER_SECTIONS to cure the issue.
Reported-by: Sergey Senozhatsky senozhatsky@chromium.org
I found the context in LKML. Closes: https://lore.kernel.org/all/20241128111844.GE10431@google.com/
However, is this still relevant to the mainline kernel?
In Linux 5.4.y, I agree this because smp_apic_timer_interrupt() is annotated as __irq_entry:
Correct.
In this mainline kernel, DEFINE_IDTENTRY_SYSVEC() expands to a normal .text function which is explicitly annotated 'noinline'.
It's not annotated noinline, it's annotated 'noinstr', which puts the code into the .noinstr.text section. That one is indeed covered.
So yes, the fix is only required for pre 5.8 kernels.
Thanks,
tglx
On Tue, Dec 3, 2024 at 6:03 AM Thomas Gleixner tglx@linutronix.de wrote:
On Mon, Dec 02 2024 at 11:02, Masahiro Yamada wrote:
On Sun, Dec 1, 2024 at 8:17 PM Thomas Gleixner tglx@linutronix.de wrote:
The compiler can fully inline the actual handler function of an interrupt entry into the .irqentry.text entry point. If such a function contains an access which has an exception table entry, modpost complains about a section mismatch:
WARNING: vmlinux.o(__ex_table+0x447c): Section mismatch in reference ...
The relocation at __ex_table+0x447c references section ".irqentry.text" which is not in the list of authorized sections.
Add .irqentry.text to OTHER_SECTIONS to cure the issue.
Reported-by: Sergey Senozhatsky senozhatsky@chromium.org
I found the context in LKML. Closes: https://lore.kernel.org/all/20241128111844.GE10431@google.com/
However, is this still relevant to the mainline kernel?
In Linux 5.4.y, I agree this because smp_apic_timer_interrupt() is annotated as __irq_entry:
Correct.
In this mainline kernel, DEFINE_IDTENTRY_SYSVEC() expands to a normal .text function which is explicitly annotated 'noinline'.
It's not annotated noinline, it's annotated 'noinstr', which puts the code into the .noinstr.text section. That one is indeed covered.
The callsite of local_apic_timer_interrupt() is annotated 'noinline' if I correctly understand this line: https://github.com/torvalds/linux/blob/v6.13-rc1/arch/x86/include/asm/idtent...
It expands to:
static noinline void __sysvec_apic_timer_interrupt(struct pt_regs *regs) { [snip] local_apic_timer_interrupt(); [snip] }
So yes, the fix is only required for pre 5.8 kernels.
This never occurs on x86 after commit f0178fc01fe46, but theoretically this may occur for other architectures.
Now applied to linux-kbuild. Thanks.
Thanks,
tglx
On Wed, Dec 04 2024 at 00:27, Masahiro Yamada wrote:
On Tue, Dec 3, 2024 at 6:03 AM Thomas Gleixner tglx@linutronix.de wrote:
In this mainline kernel, DEFINE_IDTENTRY_SYSVEC() expands to a normal .text function which is explicitly annotated 'noinline'.
It's not annotated noinline, it's annotated 'noinstr', which puts the code into the .noinstr.text section. That one is indeed covered.
The callsite of local_apic_timer_interrupt() is annotated 'noinline' if I correctly understand this line: https://github.com/torvalds/linux/blob/v6.13-rc1/arch/x86/include/asm/idtent...
You're right. I got lost in the macro maze and looked at the actual sysvec_...() part.
So yes, the fix is only required for pre 5.8 kernels.
This never occurs on x86 after commit f0178fc01fe46, but theoretically this may occur for other architectures.
Correct.
Thanks,
tglx
On (24/12/01 12:17), Thomas Gleixner wrote:
The compiler can fully inline the actual handler function of an interrupt entry into the .irqentry.text entry point. If such a function contains an access which has an exception table entry, modpost complains about a section mismatch:
WARNING: vmlinux.o(__ex_table+0x447c): Section mismatch in reference ...
The relocation at __ex_table+0x447c references section ".irqentry.text" which is not in the list of authorized sections.
Add .irqentry.text to OTHER_SECTIONS to cure the issue.
This works. In fact, this looks like a local fix which we applied here on our side, but we were very unsure. Thank you Thomas.
linux-stable-mirror@lists.linaro.org
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Masahiro Yamada -
Sergey Senozhatsky -
Thomas Gleixner