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linux/arch/arm64/kernel/kgdb.c
Alexandru Elisei 8d56e5c5a9 arm64: Treat ESR_ELx as a 64-bit register 
In the initial release of the ARM Architecture Reference Manual for
ARMv8-A, the ESR_ELx registers were defined as 32-bit registers. This
changed in 2018 with version D.a (ARM DDI 0487D.a) of the architecture,
when they became 64-bit registers, with bits [63:32] defined as RES0. In
version G.a, a new field was added to ESR_ELx, ISS2, which covers bits
[36:32].  This field is used when the Armv8.7 extension FEAT_LS64 is
implemented.

As a result of the evolution of the register width, Linux stores it as
both a 64-bit value and a 32-bit value, which hasn't affected correctness
so far as Linux only uses the lower 32 bits of the register.

Make the register type consistent and always treat it as 64-bit wide. The
register is redefined as an "unsigned long", which is an unsigned
double-word (64-bit quantity) for the LP64 machine (aapcs64 [1], Table 1,
page 14). The type was chosen because "unsigned int" is the most frequent
type for ESR_ELx and because FAR_ELx, which is used together with ESR_ELx
in exception handling, is also declared as "unsigned long". The 64-bit type
also makes adding support for architectural features that use fields above
bit 31 easier in the future.

The KVM hypervisor will receive a similar update in a subsequent patch.

[1] https://github.com/ARM-software/abi-aa/releases/download/2021Q3/aapcs64.pdf

Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220425114444.368693-4-alexandru.elisei@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2022-04-29 19:26:27 +01:00

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// SPDX-License-Identifier: GPL-2.0-only
/*
* AArch64 KGDB support
*
* Based on arch/arm/kernel/kgdb.c
*
* Copyright (C) 2013 Cavium Inc.
* Author: Vijaya Kumar K <vijaya.kumar@caviumnetworks.com>
*/
#include <linux/bug.h>
#include <linux/irq.h>
#include <linux/kdebug.h>
#include <linux/kgdb.h>
#include <linux/kprobes.h>
#include <linux/sched/task_stack.h>
#include <asm/debug-monitors.h>
#include <asm/insn.h>
#include <asm/patching.h>
#include <asm/traps.h>
struct dbg_reg_def_t dbg_reg_def[DBG_MAX_REG_NUM] = {
{ "x0", 8, offsetof(struct pt_regs, regs[0])},
{ "x1", 8, offsetof(struct pt_regs, regs[1])},
{ "x2", 8, offsetof(struct pt_regs, regs[2])},
{ "x3", 8, offsetof(struct pt_regs, regs[3])},
{ "x4", 8, offsetof(struct pt_regs, regs[4])},
{ "x5", 8, offsetof(struct pt_regs, regs[5])},
{ "x6", 8, offsetof(struct pt_regs, regs[6])},
{ "x7", 8, offsetof(struct pt_regs, regs[7])},
{ "x8", 8, offsetof(struct pt_regs, regs[8])},
{ "x9", 8, offsetof(struct pt_regs, regs[9])},
{ "x10", 8, offsetof(struct pt_regs, regs[10])},
{ "x11", 8, offsetof(struct pt_regs, regs[11])},
{ "x12", 8, offsetof(struct pt_regs, regs[12])},
{ "x13", 8, offsetof(struct pt_regs, regs[13])},
{ "x14", 8, offsetof(struct pt_regs, regs[14])},
{ "x15", 8, offsetof(struct pt_regs, regs[15])},
{ "x16", 8, offsetof(struct pt_regs, regs[16])},
{ "x17", 8, offsetof(struct pt_regs, regs[17])},
{ "x18", 8, offsetof(struct pt_regs, regs[18])},
{ "x19", 8, offsetof(struct pt_regs, regs[19])},
{ "x20", 8, offsetof(struct pt_regs, regs[20])},
{ "x21", 8, offsetof(struct pt_regs, regs[21])},
{ "x22", 8, offsetof(struct pt_regs, regs[22])},
{ "x23", 8, offsetof(struct pt_regs, regs[23])},
{ "x24", 8, offsetof(struct pt_regs, regs[24])},
{ "x25", 8, offsetof(struct pt_regs, regs[25])},
{ "x26", 8, offsetof(struct pt_regs, regs[26])},
{ "x27", 8, offsetof(struct pt_regs, regs[27])},
{ "x28", 8, offsetof(struct pt_regs, regs[28])},
{ "x29", 8, offsetof(struct pt_regs, regs[29])},
{ "x30", 8, offsetof(struct pt_regs, regs[30])},
{ "sp", 8, offsetof(struct pt_regs, sp)},
{ "pc", 8, offsetof(struct pt_regs, pc)},
/*
* struct pt_regs thinks PSTATE is 64-bits wide but gdb remote
* protocol disagrees. Therefore we must extract only the lower
* 32-bits. Look for the big comment in asm/kgdb.h for more
* detail.
*/
{ "pstate", 4, offsetof(struct pt_regs, pstate)
#ifdef CONFIG_CPU_BIG_ENDIAN
+ 4
#endif
},
{ "v0", 16, -1 },
{ "v1", 16, -1 },
{ "v2", 16, -1 },
{ "v3", 16, -1 },
{ "v4", 16, -1 },
{ "v5", 16, -1 },
{ "v6", 16, -1 },
{ "v7", 16, -1 },
{ "v8", 16, -1 },
{ "v9", 16, -1 },
{ "v10", 16, -1 },
{ "v11", 16, -1 },
{ "v12", 16, -1 },
{ "v13", 16, -1 },
{ "v14", 16, -1 },
{ "v15", 16, -1 },
{ "v16", 16, -1 },
{ "v17", 16, -1 },
{ "v18", 16, -1 },
{ "v19", 16, -1 },
{ "v20", 16, -1 },
{ "v21", 16, -1 },
{ "v22", 16, -1 },
{ "v23", 16, -1 },
{ "v24", 16, -1 },
{ "v25", 16, -1 },
{ "v26", 16, -1 },
{ "v27", 16, -1 },
{ "v28", 16, -1 },
{ "v29", 16, -1 },
{ "v30", 16, -1 },
{ "v31", 16, -1 },
{ "fpsr", 4, -1 },
{ "fpcr", 4, -1 },
};
char *dbg_get_reg(int regno, void *mem, struct pt_regs *regs)
{
if (regno >= DBG_MAX_REG_NUM || regno < 0)
return NULL;
if (dbg_reg_def[regno].offset != -1)
memcpy(mem, (void *)regs + dbg_reg_def[regno].offset,
dbg_reg_def[regno].size);
else
memset(mem, 0, dbg_reg_def[regno].size);
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 (dbg_reg_def[regno].offset != -1)
memcpy((void *)regs + dbg_reg_def[regno].offset, mem,
dbg_reg_def[regno].size);
return 0;
}
void
sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *task)
{
struct cpu_context *cpu_context = &task->thread.cpu_context;
/* Initialize to zero */
memset((char *)gdb_regs, 0, NUMREGBYTES);
gdb_regs[19] = cpu_context->x19;
gdb_regs[20] = cpu_context->x20;
gdb_regs[21] = cpu_context->x21;
gdb_regs[22] = cpu_context->x22;
gdb_regs[23] = cpu_context->x23;
gdb_regs[24] = cpu_context->x24;
gdb_regs[25] = cpu_context->x25;
gdb_regs[26] = cpu_context->x26;
gdb_regs[27] = cpu_context->x27;
gdb_regs[28] = cpu_context->x28;
gdb_regs[29] = cpu_context->fp;
gdb_regs[31] = cpu_context->sp;
gdb_regs[32] = cpu_context->pc;
}
void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long pc)
{
regs->pc = pc;
}
static int compiled_break;
static void kgdb_arch_update_addr(struct pt_regs *regs,
char *remcom_in_buffer)
{
unsigned long addr;
char *ptr;
ptr = &remcom_in_buffer[1];
if (kgdb_hex2long(&ptr, &addr))
kgdb_arch_set_pc(regs, addr);
else if (compiled_break == 1)
kgdb_arch_set_pc(regs, regs->pc + 4);
compiled_break = 0;
}
int kgdb_arch_handle_exception(int exception_vector, int signo,
int err_code, char *remcom_in_buffer,
char *remcom_out_buffer,
struct pt_regs *linux_regs)
{
int err;
switch (remcom_in_buffer[0]) {
case 'D':
case 'k':
/*
* Packet D (Detach), k (kill). No special handling
* is required here. Handle same as c packet.
*/
case 'c':
/*
* Packet c (Continue) to continue executing.
* Set pc to required address.
* Try to read optional parameter and set pc.
* If this was a compiled breakpoint, we need to move
* to the next instruction else we will just breakpoint
* over and over again.
*/
kgdb_arch_update_addr(linux_regs, remcom_in_buffer);
atomic_set(&kgdb_cpu_doing_single_step, -1);
kgdb_single_step = 0;
/*
* Received continue command, disable single step
*/
if (kernel_active_single_step())
kernel_disable_single_step();
err = 0;
break;
case 's':
/*
* Update step address value with address passed
* with step packet.
* On debug exception return PC is copied to ELR
* So just update PC.
* If no step address is passed, resume from the address
* pointed by PC. Do not update PC
*/
kgdb_arch_update_addr(linux_regs, remcom_in_buffer);
atomic_set(&kgdb_cpu_doing_single_step, raw_smp_processor_id());
kgdb_single_step = 1;
/*
* Enable single step handling
*/
if (!kernel_active_single_step())
kernel_enable_single_step(linux_regs);
err = 0;
break;
default:
err = -1;
}
return err;
}
static int kgdb_brk_fn(struct pt_regs *regs, unsigned long esr)
{
kgdb_handle_exception(1, SIGTRAP, 0, regs);
return DBG_HOOK_HANDLED;
}
NOKPROBE_SYMBOL(kgdb_brk_fn)
static int kgdb_compiled_brk_fn(struct pt_regs *regs, unsigned long esr)
{
compiled_break = 1;
kgdb_handle_exception(1, SIGTRAP, 0, regs);
return DBG_HOOK_HANDLED;
}
NOKPROBE_SYMBOL(kgdb_compiled_brk_fn);
static int kgdb_step_brk_fn(struct pt_regs *regs, unsigned long esr)
{
if (!kgdb_single_step)
return DBG_HOOK_ERROR;
kgdb_handle_exception(0, SIGTRAP, 0, regs);
return DBG_HOOK_HANDLED;
}
NOKPROBE_SYMBOL(kgdb_step_brk_fn);
static struct break_hook kgdb_brkpt_hook = {
.fn = kgdb_brk_fn,
.imm = KGDB_DYN_DBG_BRK_IMM,
};
static struct break_hook kgdb_compiled_brkpt_hook = {
.fn = kgdb_compiled_brk_fn,
.imm = KGDB_COMPILED_DBG_BRK_IMM,
};
static struct step_hook kgdb_step_hook = {
.fn = kgdb_step_brk_fn
};
static int __kgdb_notify(struct die_args *args, unsigned long cmd)
{
struct pt_regs *regs = args->regs;
if (kgdb_handle_exception(1, args->signr, cmd, regs))
return NOTIFY_DONE;
return NOTIFY_STOP;
}
static int
kgdb_notify(struct notifier_block *self, unsigned long cmd, void *ptr)
{
unsigned long flags;
int ret;
local_irq_save(flags);
ret = __kgdb_notify(ptr, cmd);
local_irq_restore(flags);
return ret;
}
static struct notifier_block kgdb_notifier = {
.notifier_call = kgdb_notify,
/*
* Want to be lowest priority
*/
.priority = -INT_MAX,
};
/*
* kgdb_arch_init - Perform any architecture specific initialization.
* This function will handle the initialization of any architecture
* specific callbacks.
*/
int kgdb_arch_init(void)
{
int ret = register_die_notifier(&kgdb_notifier);
if (ret != 0)
return ret;
register_kernel_break_hook(&kgdb_brkpt_hook);
register_kernel_break_hook(&kgdb_compiled_brkpt_hook);
register_kernel_step_hook(&kgdb_step_hook);
return 0;
}
/*
* kgdb_arch_exit - Perform any architecture specific uninitalization.
* This function will handle the uninitalization of any architecture
* specific callbacks, for dynamic registration and unregistration.
*/
void kgdb_arch_exit(void)
{
unregister_kernel_break_hook(&kgdb_brkpt_hook);
unregister_kernel_break_hook(&kgdb_compiled_brkpt_hook);
unregister_kernel_step_hook(&kgdb_step_hook);
unregister_die_notifier(&kgdb_notifier);
}
const struct kgdb_arch arch_kgdb_ops;
int kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
{
int err;
BUILD_BUG_ON(AARCH64_INSN_SIZE != BREAK_INSTR_SIZE);
err = aarch64_insn_read((void *)bpt->bpt_addr, (u32 *)bpt->saved_instr);
if (err)
return err;
return aarch64_insn_write((void *)bpt->bpt_addr,
(u32)AARCH64_BREAK_KGDB_DYN_DBG);
}
int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
{
return aarch64_insn_write((void *)bpt->bpt_addr,
*(u32 *)bpt->saved_instr);
}
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