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