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linux-stable/arch/powerpc/kernel/kgdb.c
Nicholas Piggin 59dc5bfca0 powerpc/64s: avoid reloading (H)SRR registers if they are still valid 
When an interrupt is taken, the SRR registers are set to return to where
it left off. Unless they are modified in the meantime, or the return
address or MSR are modified, there is no need to reload these registers
when returning from interrupt.

Introduce per-CPU flags that track the validity of SRR and HSRR
registers. These are cleared when returning from interrupt, when
using the registers for something else (e.g., OPAL calls), when
adjusting the return address or MSR of a context, and when context
switching (which changes the return address and MSR).

This improves the performance of interrupt returns.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
[mpe: Fold in fixup patch from Nick]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210617155116.2167984-5-npiggin@gmail.com
2021-06-25 00:06:55 +10:00

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/*
* PowerPC backend to the KGDB stub.
*
* 1998 (c) Michael AK Tesch (tesch@cs.wisc.edu)
* Copyright (C) 2003 Timesys Corporation.
* Copyright (C) 2004-2006 MontaVista Software, Inc.
* PPC64 Mods (C) 2005 Frank Rowand (frowand@mvista.com)
* PPC32 support restored by Vitaly Wool <vwool@ru.mvista.com> and
* Sergei Shtylyov <sshtylyov@ru.mvista.com>
* Copyright (C) 2007-2008 Wind River Systems, Inc.
*
* This file is licensed under the terms of the GNU General Public License
* version 2. This program as licensed "as is" without any warranty of any
* kind, whether express or implied.
*/
#include <linux/kernel.h>
#include <linux/kgdb.h>
#include <linux/smp.h>
#include <linux/signal.h>
#include <linux/ptrace.h>
#include <linux/kdebug.h>
#include <asm/current.h>
#include <asm/processor.h>
#include <asm/machdep.h>
#include <asm/debug.h>
#include <asm/code-patching.h>
#include <linux/slab.h>
#include <asm/inst.h>
/*
* This table contains the mapping between PowerPC hardware trap types, and
* signals, which are primarily what GDB understands. GDB and the kernel
* don't always agree on values, so we use constants taken from gdb-6.2.
*/
static struct hard_trap_info
{
unsigned int tt; /* Trap type code for powerpc */
unsigned char signo; /* Signal that we map this trap into */
} hard_trap_info[] = {
{ 0x0100, 0x02 /* SIGINT */ }, /* system reset */
{ 0x0200, 0x0b /* SIGSEGV */ }, /* machine check */
{ 0x0300, 0x0b /* SIGSEGV */ }, /* data access */
{ 0x0400, 0x0b /* SIGSEGV */ }, /* instruction access */
{ 0x0500, 0x02 /* SIGINT */ }, /* external interrupt */
{ 0x0600, 0x0a /* SIGBUS */ }, /* alignment */
{ 0x0700, 0x05 /* SIGTRAP */ }, /* program check */
{ 0x0800, 0x08 /* SIGFPE */ }, /* fp unavailable */
{ 0x0900, 0x0e /* SIGALRM */ }, /* decrementer */
{ 0x0c00, 0x14 /* SIGCHLD */ }, /* system call */
#if defined(CONFIG_40x) || defined(CONFIG_BOOKE)
{ 0x2002, 0x05 /* SIGTRAP */ }, /* debug */
#if defined(CONFIG_FSL_BOOKE)
{ 0x2010, 0x08 /* SIGFPE */ }, /* spe unavailable */
{ 0x2020, 0x08 /* SIGFPE */ }, /* spe unavailable */
{ 0x2030, 0x08 /* SIGFPE */ }, /* spe fp data */
{ 0x2040, 0x08 /* SIGFPE */ }, /* spe fp data */
{ 0x2050, 0x08 /* SIGFPE */ }, /* spe fp round */
{ 0x2060, 0x0e /* SIGILL */ }, /* performance monitor */
{ 0x2900, 0x08 /* SIGFPE */ }, /* apu unavailable */
{ 0x3100, 0x0e /* SIGALRM */ }, /* fixed interval timer */
{ 0x3200, 0x02 /* SIGINT */ }, /* watchdog */
#else /* ! CONFIG_FSL_BOOKE */
{ 0x1000, 0x0e /* SIGALRM */ }, /* prog interval timer */
{ 0x1010, 0x0e /* SIGALRM */ }, /* fixed interval timer */
{ 0x1020, 0x02 /* SIGINT */ }, /* watchdog */
{ 0x2010, 0x08 /* SIGFPE */ }, /* fp unavailable */
{ 0x2020, 0x08 /* SIGFPE */ }, /* ap unavailable */
#endif
#else /* ! (defined(CONFIG_40x) || defined(CONFIG_BOOKE)) */
{ 0x0d00, 0x05 /* SIGTRAP */ }, /* single-step */
#if defined(CONFIG_PPC_8xx)
{ 0x1000, 0x04 /* SIGILL */ }, /* software emulation */
#else /* ! CONFIG_PPC_8xx */
{ 0x0f00, 0x04 /* SIGILL */ }, /* performance monitor */
{ 0x0f20, 0x08 /* SIGFPE */ }, /* altivec unavailable */
{ 0x1300, 0x05 /* SIGTRAP */ }, /* instruction address break */
#if defined(CONFIG_PPC64)
{ 0x1200, 0x05 /* SIGILL */ }, /* system error */
{ 0x1500, 0x04 /* SIGILL */ }, /* soft patch */
{ 0x1600, 0x04 /* SIGILL */ }, /* maintenance */
{ 0x1700, 0x08 /* SIGFPE */ }, /* altivec assist */
{ 0x1800, 0x04 /* SIGILL */ }, /* thermal */
#else /* ! CONFIG_PPC64 */
{ 0x1400, 0x02 /* SIGINT */ }, /* SMI */
{ 0x1600, 0x08 /* SIGFPE */ }, /* altivec assist */
{ 0x1700, 0x04 /* SIGILL */ }, /* TAU */
{ 0x2000, 0x05 /* SIGTRAP */ }, /* run mode */
#endif
#endif
#endif
{ 0x0000, 0x00 } /* Must be last */
};
static int computeSignal(unsigned int tt)
{
struct hard_trap_info *ht;
for (ht = hard_trap_info; ht->tt && ht->signo; ht++)
if (ht->tt == tt)
return ht->signo;
return SIGHUP; /* default for things we don't know about */
}
/**
*
* kgdb_skipexception - Bail out of KGDB when we've been triggered.
* @exception: Exception vector number
* @regs: Current &struct pt_regs.
*
* On some architectures we need to skip a breakpoint exception when
* it occurs after a breakpoint has been removed.
*
*/
int kgdb_skipexception(int exception, struct pt_regs *regs)
{
return kgdb_isremovedbreak(regs->nip);
}
static int kgdb_debugger_ipi(struct pt_regs *regs)
{
kgdb_nmicallback(raw_smp_processor_id(), regs);
return 0;
}
#ifdef CONFIG_SMP
void kgdb_roundup_cpus(void)
{
smp_send_debugger_break();
}
#endif
/* KGDB functions to use existing PowerPC64 hooks. */
static int kgdb_debugger(struct pt_regs *regs)
{
return !kgdb_handle_exception(1, computeSignal(TRAP(regs)),
DIE_OOPS, regs);
}
static int kgdb_handle_breakpoint(struct pt_regs *regs)
{
if (user_mode(regs))
return 0;
if (kgdb_handle_exception(1, SIGTRAP, 0, regs) != 0)
return 0;
if (*(u32 *)regs->nip == BREAK_INSTR)
regs_add_return_ip(regs, BREAK_INSTR_SIZE);
return 1;
}
static int kgdb_singlestep(struct pt_regs *regs)
{
if (user_mode(regs))
return 0;
kgdb_handle_exception(0, SIGTRAP, 0, regs);
return 1;
}
static int kgdb_iabr_match(struct pt_regs *regs)
{
if (user_mode(regs))
return 0;
if (kgdb_handle_exception(0, computeSignal(TRAP(regs)), 0, regs) != 0)
return 0;
return 1;
}
static int kgdb_break_match(struct pt_regs *regs)
{
if (user_mode(regs))
return 0;
if (kgdb_handle_exception(0, computeSignal(TRAP(regs)), 0, regs) != 0)
return 0;
return 1;
}
#define PACK64(ptr, src) do { *(ptr++) = (src); } while (0)
#define PACK32(ptr, src) do { \
u32 *ptr32; \
ptr32 = (u32 *)ptr; \
*(ptr32++) = (src); \
ptr = (unsigned long *)ptr32; \
} while (0)
void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *p)
{
struct pt_regs *regs = (struct pt_regs *)(p->thread.ksp +
STACK_FRAME_OVERHEAD);
unsigned long *ptr = gdb_regs;
int reg;
memset(gdb_regs, 0, NUMREGBYTES);
/* Regs GPR0-2 */
for (reg = 0; reg < 3; reg++)
PACK64(ptr, regs->gpr[reg]);
/* Regs GPR3-13 are caller saved, not in regs->gpr[] */
ptr += 11;
/* Regs GPR14-31 */
for (reg = 14; reg < 32; reg++)
PACK64(ptr, regs->gpr[reg]);
#ifdef CONFIG_FSL_BOOKE
#ifdef CONFIG_SPE
for (reg = 0; reg < 32; reg++)
PACK64(ptr, p->thread.evr[reg]);
#else
ptr += 32;
#endif
#else
/* fp registers not used by kernel, leave zero */
ptr += 32 * 8 / sizeof(long);
#endif
PACK64(ptr, regs->nip);
PACK64(ptr, regs->msr);
PACK32(ptr, regs->ccr);
PACK64(ptr, regs->link);
PACK64(ptr, regs->ctr);
PACK32(ptr, regs->xer);
BUG_ON((unsigned long)ptr >
(unsigned long)(((void *)gdb_regs) + NUMREGBYTES));
}
#define GDB_SIZEOF_REG sizeof(unsigned long)
#define GDB_SIZEOF_REG_U32 sizeof(u32)
#ifdef CONFIG_FSL_BOOKE
#define GDB_SIZEOF_FLOAT_REG sizeof(unsigned long)
#else
#define GDB_SIZEOF_FLOAT_REG sizeof(u64)
#endif
struct dbg_reg_def_t dbg_reg_def[DBG_MAX_REG_NUM] =
{
{ "r0", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[0]) },
{ "r1", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[1]) },
{ "r2", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[2]) },
{ "r3", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[3]) },
{ "r4", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[4]) },
{ "r5", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[5]) },
{ "r6", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[6]) },
{ "r7", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[7]) },
{ "r8", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[8]) },
{ "r9", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[9]) },
{ "r10", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[10]) },
{ "r11", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[11]) },
{ "r12", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[12]) },
{ "r13", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[13]) },
{ "r14", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[14]) },
{ "r15", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[15]) },
{ "r16", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[16]) },
{ "r17", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[17]) },
{ "r18", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[18]) },
{ "r19", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[19]) },
{ "r20", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[20]) },
{ "r21", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[21]) },
{ "r22", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[22]) },
{ "r23", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[23]) },
{ "r24", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[24]) },
{ "r25", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[25]) },
{ "r26", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[26]) },
{ "r27", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[27]) },
{ "r28", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[28]) },
{ "r29", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[29]) },
{ "r30", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[30]) },
{ "r31", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[31]) },
{ "f0", GDB_SIZEOF_FLOAT_REG, 0 },
{ "f1", GDB_SIZEOF_FLOAT_REG, 1 },
{ "f2", GDB_SIZEOF_FLOAT_REG, 2 },
{ "f3", GDB_SIZEOF_FLOAT_REG, 3 },
{ "f4", GDB_SIZEOF_FLOAT_REG, 4 },
{ "f5", GDB_SIZEOF_FLOAT_REG, 5 },
{ "f6", GDB_SIZEOF_FLOAT_REG, 6 },
{ "f7", GDB_SIZEOF_FLOAT_REG, 7 },
{ "f8", GDB_SIZEOF_FLOAT_REG, 8 },
{ "f9", GDB_SIZEOF_FLOAT_REG, 9 },
{ "f10", GDB_SIZEOF_FLOAT_REG, 10 },
{ "f11", GDB_SIZEOF_FLOAT_REG, 11 },
{ "f12", GDB_SIZEOF_FLOAT_REG, 12 },
{ "f13", GDB_SIZEOF_FLOAT_REG, 13 },
{ "f14", GDB_SIZEOF_FLOAT_REG, 14 },
{ "f15", GDB_SIZEOF_FLOAT_REG, 15 },
{ "f16", GDB_SIZEOF_FLOAT_REG, 16 },
{ "f17", GDB_SIZEOF_FLOAT_REG, 17 },
{ "f18", GDB_SIZEOF_FLOAT_REG, 18 },
{ "f19", GDB_SIZEOF_FLOAT_REG, 19 },
{ "f20", GDB_SIZEOF_FLOAT_REG, 20 },
{ "f21", GDB_SIZEOF_FLOAT_REG, 21 },
{ "f22", GDB_SIZEOF_FLOAT_REG, 22 },
{ "f23", GDB_SIZEOF_FLOAT_REG, 23 },
{ "f24", GDB_SIZEOF_FLOAT_REG, 24 },
{ "f25", GDB_SIZEOF_FLOAT_REG, 25 },
{ "f26", GDB_SIZEOF_FLOAT_REG, 26 },
{ "f27", GDB_SIZEOF_FLOAT_REG, 27 },
{ "f28", GDB_SIZEOF_FLOAT_REG, 28 },
{ "f29", GDB_SIZEOF_FLOAT_REG, 29 },
{ "f30", GDB_SIZEOF_FLOAT_REG, 30 },
{ "f31", GDB_SIZEOF_FLOAT_REG, 31 },
{ "pc", GDB_SIZEOF_REG, offsetof(struct pt_regs, nip) },
{ "msr", GDB_SIZEOF_REG, offsetof(struct pt_regs, msr) },
{ "cr", GDB_SIZEOF_REG_U32, offsetof(struct pt_regs, ccr) },
{ "lr", GDB_SIZEOF_REG, offsetof(struct pt_regs, link) },
{ "ctr", GDB_SIZEOF_REG_U32, offsetof(struct pt_regs, ctr) },
{ "xer", GDB_SIZEOF_REG, offsetof(struct pt_regs, xer) },
};
char *dbg_get_reg(int regno, void *mem, struct pt_regs *regs)
{
if (regno >= DBG_MAX_REG_NUM || regno < 0)
return NULL;
if (regno < 32 || regno >= 64)
/* First 0 -> 31 gpr registers*/
/* pc, msr, ls... registers 64 -> 69 */
memcpy(mem, (void *)regs + dbg_reg_def[regno].offset,
dbg_reg_def[regno].size);
if (regno >= 32 && regno < 64) {
/* FP registers 32 -> 63 */
#if defined(CONFIG_FSL_BOOKE) && defined(CONFIG_SPE)
if (current)
memcpy(mem, &current->thread.evr[regno-32],
dbg_reg_def[regno].size);
#else
/* fp registers not used by kernel, leave zero */
memset(mem, 0, dbg_reg_def[regno].size);
#endif
}
return dbg_reg_def[regno].name;
}
int dbg_set_reg(int regno, void *mem, struct pt_regs *regs)
{
if (regno >= DBG_MAX_REG_NUM || regno < 0)
return -EINVAL;
if (regno < 32 || regno >= 64)
/* First 0 -> 31 gpr registers*/
/* pc, msr, ls... registers 64 -> 69 */
memcpy((void *)regs + dbg_reg_def[regno].offset, mem,
dbg_reg_def[regno].size);
if (regno >= 32 && regno < 64) {
/* FP registers 32 -> 63 */
#if defined(CONFIG_FSL_BOOKE) && defined(CONFIG_SPE)
memcpy(&current->thread.evr[regno-32], mem,
dbg_reg_def[regno].size);
#else
/* fp registers not used by kernel, leave zero */
return 0;
#endif
}
return 0;
}
void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long pc)
{
regs_set_return_ip(regs, pc);
}
/*
* This function does PowerPC specific processing for interfacing to gdb.
*/
int kgdb_arch_handle_exception(int vector, int signo, int err_code,
char *remcom_in_buffer, char *remcom_out_buffer,
struct pt_regs *linux_regs)
{
char *ptr = &remcom_in_buffer[1];
unsigned long addr;
switch (remcom_in_buffer[0]) {
/*
* sAA..AA Step one instruction from AA..AA
* This will return an error to gdb ..
*/
case 's':
case 'c':
/* handle the optional parameter */
if (kgdb_hex2long(&ptr, &addr))
regs_set_return_ip(linux_regs, addr);
atomic_set(&kgdb_cpu_doing_single_step, -1);
/* set the trace bit if we're stepping */
if (remcom_in_buffer[0] == 's') {
#ifdef CONFIG_PPC_ADV_DEBUG_REGS
mtspr(SPRN_DBCR0,
mfspr(SPRN_DBCR0) | DBCR0_IC | DBCR0_IDM);
regs_set_return_msr(linux_regs, linux_regs->msr | MSR_DE);
#else
regs_set_return_msr(linux_regs, linux_regs->msr | MSR_SE);
#endif
atomic_set(&kgdb_cpu_doing_single_step,
raw_smp_processor_id());
}
return 0;
}
return -1;
}
int kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
{
u32 instr, *addr = (u32 *)bpt->bpt_addr;
int err;
err = get_kernel_nofault(instr, addr);
if (err)
return err;
err = patch_instruction(addr, ppc_inst(BREAK_INSTR));
if (err)
return -EFAULT;
*(u32 *)bpt->saved_instr = instr;
return 0;
}
int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
{
int err;
unsigned int instr = *(unsigned int *)bpt->saved_instr;
u32 *addr = (u32 *)bpt->bpt_addr;
err = patch_instruction(addr, ppc_inst(instr));
if (err)
return -EFAULT;
return 0;
}
/*
* Global data
*/
const struct kgdb_arch arch_kgdb_ops;
static int kgdb_not_implemented(struct pt_regs *regs)
{
return 0;
}
static void *old__debugger_ipi;
static void *old__debugger;
static void *old__debugger_bpt;
static void *old__debugger_sstep;
static void *old__debugger_iabr_match;
static void *old__debugger_break_match;
static void *old__debugger_fault_handler;
int kgdb_arch_init(void)
{
old__debugger_ipi = __debugger_ipi;
old__debugger = __debugger;
old__debugger_bpt = __debugger_bpt;
old__debugger_sstep = __debugger_sstep;
old__debugger_iabr_match = __debugger_iabr_match;
old__debugger_break_match = __debugger_break_match;
old__debugger_fault_handler = __debugger_fault_handler;
__debugger_ipi = kgdb_debugger_ipi;
__debugger = kgdb_debugger;
__debugger_bpt = kgdb_handle_breakpoint;
__debugger_sstep = kgdb_singlestep;
__debugger_iabr_match = kgdb_iabr_match;
__debugger_break_match = kgdb_break_match;
__debugger_fault_handler = kgdb_not_implemented;
return 0;
}
void kgdb_arch_exit(void)
{
__debugger_ipi = old__debugger_ipi;
__debugger = old__debugger;
__debugger_bpt = old__debugger_bpt;
__debugger_sstep = old__debugger_sstep;
__debugger_iabr_match = old__debugger_iabr_match;
__debugger_break_match = old__debugger_break_match;
__debugger_fault_handler = old__debugger_fault_handler;
}
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