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: Nicholas Piggin <npig...@gmail.com> --- arch/powerpc/kernel/exceptions-64s.S | 15 +++++++++++++-- arch/powerpc/kernel/head_64.S | 3 +++ arch/powerpc/kernel/setup_64.c | 1 + 3 files changed, 17 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S index 9b853fdd59de..2f3b8d8a7ef6 100644 --- a/arch/powerpc/kernel/exceptions-64s.S +++ b/arch/powerpc/kernel/exceptions-64s.S @@ -724,8 +724,8 @@ 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 @@ -752,8 +752,19 @@ 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 /* diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S index cf2c08902c05..6aeba8a9814e 100644 --- a/arch/powerpc/kernel/head_64.S +++ b/arch/powerpc/kernel/head_64.S @@ -494,6 +494,9 @@ __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 diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c index 83e564564f63..4cb057e6b3aa 100644 --- a/arch/powerpc/kernel/setup_64.c +++ b/arch/powerpc/kernel/setup_64.c @@ -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 ------- */ -- 2.37.2