Commit e1100cee authored by Nicholas Piggin's avatar Nicholas Piggin Committed by Michael Ellerman
Browse files

powerpc/64s/interrupt: halt early boot interrupts if paca is not set up 



Ensure r13 is zero from very early in boot until it gets set to the
boot paca pointer. This allows early program and mce handlers to halt
if there is no valid paca, rather than potentially run off into the
weeds. This preserves register and memory contents for low level
debugging tools.

Nothing could be printed to console at this point in any case because
even udbg is only set up after the boot paca is set, so this shouldn't
be missed.

Signed-off-by: default avatarNicholas Piggin <npiggin@gmail.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220926055620.2676869-6-npiggin@gmail.com
parent 519b2e31

arch/powerpc/kernel/exceptions-64s.S

+13 −2
Original line number Diff line number Diff line
@@ -725,8 +725,8 @@ END_FTR_SECTION_IFSET(CPU_FTR_CFAR) 
 * userspace starts.

 */

.macro EARLY_BOOT_FIXUP

#ifdef CONFIG_CPU_LITTLE_ENDIAN

BEGIN_FTR_SECTION

#ifdef CONFIG_CPU_LITTLE_ENDIAN

	tdi   0,0,0x48    // Trap never, or in reverse endian: b . + 8

	b     2f          // Skip trampoline if endian is correct

	.long 0xa643707d  // mtsprg  0, r11      Backup r11
@@ -753,8 +753,19 @@ BEGIN_FTR_SECTION 
	mtsrr0 r11        // Restore SRR0

	mfsprg r11, 0     // Restore r11

2:

END_FTR_SECTION(0, 1)     // nop out after boot

#endif

	/*

	 * program check could hit at any time, and pseries can not block

	 * MSR[ME] in early boot. So check if there is anything useful in r13

	 * yet, and spin forever if not.

	 */

	mtsprg	0, r11

	mfcr	r11

	cmpdi	r13, 0

	beq	.

	mtcr	r11

	mfsprg	r11, 0

END_FTR_SECTION(0, 1)     // nop out after boot

.endm



/*

arch/powerpc/kernel/head_64.S

+3 −0
Original line number Diff line number Diff line
@@ -487,6 +487,9 @@ __start_initialization_multiplatform: 
	/* Make sure we are running in 64 bits mode */

	bl	enable_64b_mode



	/* Zero r13 (paca) so early program check / mce don't use it */

	li	r13,0



	/* Get TOC pointer (current runtime address) */

	bl	relative_toc

arch/powerpc/kernel/setup_64.c

+1 −0
Original line number Diff line number Diff line
@@ -364,6 +364,7 @@ void __init early_setup(unsigned long dt_ptr) 
	 */

	initialise_paca(&boot_paca, 0);

	fixup_boot_paca(&boot_paca);

	WARN_ON(local_paca != 0);

	setup_paca(&boot_paca); /* install the paca into registers */



	/* -------- printk is now safe to use ------- */