[PATCH] powerpc/irq: Increase stack_overflow detection limit when KASAN is enabled

[Christophe Leroy]

When KASAN is enabled, as shown by the Oops below, the 2k limit is not
enough to allow stack dump after a stack overflow detection when
CONFIG_DEBUG_STACKOVERFLOW is selected:

	do_IRQ: stack overflow: 1984
	CPU: 0 PID: 126 Comm: systemd-udevd Not tainted 5.18.0-gentoo-PMacG4 #1
	Call Trace:
	Oops: Kernel stack overflow, sig: 11 [#1]
	BE PAGE_SIZE=4K MMU=Hash SMP NR_CPUS=2 PowerMac
	Modules linked in: sr_mod cdrom radeon(+) ohci_pci(+) hwmon i2c_algo_bit drm_ttm_helper ttm drm_dp_helper snd_aoa_i2sbus snd_aoa_soundbus snd_pcm ehci_pci snd_timer ohci_hcd snd ssb ehci_hcd 8250_pci soundcore drm_kms_helper pcmcia 8250 pcmcia_core syscopyarea usbcore sysfillrect 8250_base sysimgblt serial_mctrl_gpio fb_sys_fops usb_common pkcs8_key_parser fuse drm drm_panel_orientation_quirks configfs
	CPU: 0 PID: 126 Comm: systemd-udevd Not tainted 5.18.0-gentoo-PMacG4 #1
	NIP:  c02e5558 LR: c07eb3bc CTR: c07f46a8
	REGS: e7fe9f50 TRAP: 0000   Not tainted  (5.18.0-gentoo-PMacG4)
	MSR:  00001032 <ME,IR,DR,RI>  CR: 44a14824  XER: 20000000

	GPR00: c07eb3bc eaa1c000 c26baea0 eaa1c0a0 00000008 00000000 c07eb3bc eaa1c010
	GPR08: eaa1c0a8 04f3f3f3 f1f1f1f1 c07f4c84 44a14824 0080f7e4 00000005 00000010
	GPR16: 00000025 eaa1c154 eaa1c158 c0dbad64 00000020 fd543810 eaa1c0a0 eaa1c29e
	GPR24: c0dbad44 c0db8740 05ffffff fd543802 eaa1c150 c0c9a3c0 eaa1c0a0 c0c9a3c0
	NIP [c02e5558] kasan_check_range+0xc/0x2b4
	LR [c07eb3bc] format_decode+0x80/0x604
	Call Trace:
	[eaa1c000] [c07eb3bc] format_decode+0x80/0x604 (unreliable)
	[eaa1c070] [c07f4dac] vsnprintf+0x128/0x938
	[eaa1c110] [c07f5788] sprintf+0xa0/0xc0
	[eaa1c180] [c0154c1c] __sprint_symbol.constprop.0+0x170/0x198
	[eaa1c230] [c07ee71c] symbol_string+0xf8/0x260
	[eaa1c430] [c07f46d0] pointer+0x15c/0x710
	[eaa1c4b0] [c07f4fbc] vsnprintf+0x338/0x938
	[eaa1c550] [c00e8fa0] vprintk_store+0x2a8/0x678
	[eaa1c690] [c00e94e4] vprintk_emit+0x174/0x378
	[eaa1c6d0] [c00ea008] _printk+0x9c/0xc0
	[eaa1c750] [c000ca94] show_stack+0x21c/0x260
	[eaa1c7a0] [c07d0bd4] dump_stack_lvl+0x60/0x90
	[eaa1c7c0] [c0009234] __do_IRQ+0x170/0x174
	[eaa1c800] [c0009258] do_IRQ+0x20/0x34
	[eaa1c820] [c00045b4] HardwareInterrupt_virt+0x108/0x10c
...

Increase the limit to 3k when KASAN is enabled.

While at it remove the 'inline' keywork for check_stack_overflow().
This function is called only once so it will be inlined regardless.

Reported-by: Erhard Furtner <erhard_f at mailbox.org>
Cc: Arnd Bergmann <arnd at arndb.de>
Signed-off-by: Christophe Leroy <christophe.leroy at csgroup.eu>
---
 arch/powerpc/kernel/irq.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index 873e6dffb868..5ff4cf69fc2f 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -53,6 +53,7 @@
 #include <linux/vmalloc.h>
 #include <linux/pgtable.h>
 #include <linux/static_call.h>
+#include <linux/sizes.h>
 
 #include <linux/uaccess.h>
 #include <asm/interrupt.h>
@@ -184,7 +185,7 @@ u64 arch_irq_stat_cpu(unsigned int cpu)
 	return sum;
 }
 
-static inline void check_stack_overflow(void)
+static void check_stack_overflow(void)
 {
 	long sp;
 
@@ -193,11 +194,14 @@ static inline void check_stack_overflow(void)
 
 	sp = current_stack_pointer & (THREAD_SIZE - 1);
 
-	/* check for stack overflow: is there less than 2KB free? */
-	if (unlikely(sp < 2048)) {
-		pr_err("do_IRQ: stack overflow: %ld\n", sp);
-		dump_stack();
-	}
+	/* check for stack overflow: is there less than 2/3KB free? */
+	if (!IS_ENABLED(KASAN) && likely(sp >= SZ_2K))
+		return;
+	if (IS_ENABLED(KASAN) && likely(sp >= SZ_2K + SZ_1K))
+		return;
+
+	pr_err("do_IRQ: stack overflow: %ld\n", sp);
+	dump_stack();
 }
 
 static __always_inline void call_do_softirq(const void *sp)
-- 
2.35.3