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

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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 <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220926055620.2676869-6-npiggin@gmail.com
This commit is contained in:
Nicholas Piggin 2022-09-26 15:56:20 +10:00 committed by Michael Ellerman
parent 519b2e317e
commit e1100cee05
3 changed files with 17 additions and 2 deletions
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15
arch/powerpc/kernel/exceptions-64s.S
View File

@ -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
/*

3
arch/powerpc/kernel/head_64.S
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@ -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

1
arch/powerpc/kernel/setup_64.c
View File

@ -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 ------- */