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powerpc/64s: early boot machine check handler

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Use the early boot interrupt fixup in the machine check handler to allow
the machine check handler to run before interrupt endian is set up.
Branch to an early boot handler that just does a basic crash, which
allows it to run before ppc_md is set up. MSR[ME] is enabled on the boot
CPU earlier, and the machine check stack is temporarily set to the
middle of the init task stack.

This allows machine checks (e.g., due to invalid data access in real
mode) to print something useful earlier in boot (as soon as udbg is set
up, if CONFIG_PPC_EARLY_DEBUG=y).

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220926055620.2676869-3-npiggin@gmail.com
This commit is contained in:
Nicholas Piggin 2022-09-26 15:56:17 +10:00 committed by Michael Ellerman
parent bf75a3258a
commit 2f5182cffa
4 changed files with 34 additions and 1 deletions
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1
arch/powerpc/include/asm/asm-prototypes.h
View File

@ -36,6 +36,7 @@ int64_t __opal_call(int64_t a0, int64_t a1, int64_t a2, int64_t a3,
int64_t opcode, uint64_t msr);
/* misc runtime */
void enable_machine_check(void);
extern u64 __bswapdi2(u64);
extern s64 __lshrdi3(s64, int);
extern s64 __ashldi3(s64, int);

6
arch/powerpc/kernel/exceptions-64s.S
View File

@ -1134,6 +1134,7 @@ INT_DEFINE_BEGIN(machine_check)
INT_DEFINE_END(machine_check)
EXC_REAL_BEGIN(machine_check, 0x200, 0x100)
EARLY_BOOT_FIXUP
GEN_INT_ENTRY machine_check_early, virt=0
EXC_REAL_END(machine_check, 0x200, 0x100)
EXC_VIRT_NONE(0x4200, 0x100)
@ -1198,6 +1199,9 @@ BEGIN_FTR_SECTION
bl enable_machine_check
END_FTR_SECTION_IFSET(CPU_FTR_HVMODE)
addi r3,r1,STACK_FRAME_OVERHEAD
BEGIN_FTR_SECTION
bl machine_check_early_boot
END_FTR_SECTION(0, 1) // nop out after boot
bl machine_check_early
std r3,RESULT(r1) /* Save result */
ld r12,_MSR(r1)
@ -3096,7 +3100,7 @@ CLOSE_FIXED_SECTION(virt_trampolines);
USE_TEXT_SECTION()
/* MSR[RI] should be clear because this uses SRR[01] */
enable_machine_check:
_GLOBAL(enable_machine_check)
mflr r0
bcl 20,31,$+4
0: mflr r3

14
arch/powerpc/kernel/setup_64.c
View File

@ -34,6 +34,7 @@
#include <linux/of.h>
#include <linux/of_fdt.h>
#include <asm/asm-prototypes.h>
#include <asm/kvm_guest.h>
#include <asm/io.h>
#include <asm/kdump.h>
@ -180,6 +181,16 @@ static void __init fixup_boot_paca(void)
{
/* The boot cpu is started */
get_paca()->cpu_start = 1;
#ifdef CONFIG_PPC_BOOK3S_64
/*
* Give the early boot machine check stack somewhere to use, use
* half of the init stack. This is a bit hacky but there should not be
* deep stack usage in early init so shouldn't overflow it or overwrite
* things.
*/
get_paca()->mc_emergency_sp = (void *)&init_thread_union +
(THREAD_SIZE/2);
#endif
/* Allow percpu accesses to work until we setup percpu data */
get_paca()->data_offset = 0;
/* Mark interrupts soft and hard disabled in PACA */
@ -357,6 +368,9 @@ void __init early_setup(unsigned long dt_ptr)
/* -------- printk is now safe to use ------- */
if (IS_ENABLED(CONFIG_PPC_BOOK3S_64) && (mfmsr() & MSR_HV))
enable_machine_check();
/* Try new device tree based feature discovery ... */
if (!dt_cpu_ftrs_init(__va(dt_ptr)))
/* Otherwise use the old style CPU table */

14
arch/powerpc/kernel/traps.c
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@ -68,6 +68,7 @@
#include <asm/stacktrace.h>
#include <asm/nmi.h>
#include <asm/disassemble.h>
#include <asm/udbg.h>
#if defined(CONFIG_DEBUGGER) || defined(CONFIG_KEXEC_CORE)
int (*__debugger)(struct pt_regs *regs) __read_mostly;
@ -850,6 +851,19 @@ bail:
}
#ifdef CONFIG_PPC_BOOK3S_64
DEFINE_INTERRUPT_HANDLER_RAW(machine_check_early_boot)
{
udbg_printf("Machine check (early boot)\n");
udbg_printf("SRR0=0x%016lx SRR1=0x%016lx\n", regs->nip, regs->msr);
udbg_printf(" DAR=0x%016lx DSISR=0x%08lx\n", regs->dar, regs->dsisr);
udbg_printf(" LR=0x%016lx R1=0x%08lx\n", regs->link, regs->gpr[1]);
udbg_printf("------\n");
die("Machine check (early boot)", regs, SIGBUS);
for (;;)
;
return 0;
}
DEFINE_INTERRUPT_HANDLER_ASYNC(machine_check_exception_async)
{
__machine_check_exception(regs);