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qemu/target/arm/gdbstub.c
Peter Maydell 888f470f12 target/arm: Enforce that M-profile SP low 2 bits are always zero 
For M-profile, unlike A-profile, the low 2 bits of SP are defined to be
RES0H, which is to say that they must be hardwired to zero so that
guest attempts to write non-zero values to them are ignored.

Implement this behaviour by masking out the low bits:
 * for writes to r13 by the gdbstub
 * for writes to any of the various flavours of SP via MSR
 * for writes to r13 via store_reg() in generated code

Note that all the direct uses of cpu_R[] in translate.c are in places
where the register is definitely not r13 (usually because that has
been checked for as an UNDEFINED or UNPREDICTABLE case and handled as
UNDEF).

All the other writes to regs[13] in C code are either:
 * A-profile only code
 * writes of values we can guarantee to be aligned, such as
   - writes of previous-SP-value plus or minus a 4-aligned constant
   - writes of the value in an SP limit register (which we already
     enforce to be aligned)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20210723162146.5167-2-peter.maydell@linaro.org
2021-07-27 10:57:39 +01:00

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/*
* ARM gdb server stub
*
* Copyright (c) 2003-2005 Fabrice Bellard
* Copyright (c) 2013 SUSE LINUX Products GmbH
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, see <http://www.gnu.org/licenses/>.
*/
#include "qemu/osdep.h"
#include "cpu.h"
#include "exec/gdbstub.h"
typedef struct RegisterSysregXmlParam {
CPUState *cs;
GString *s;
int n;
} RegisterSysregXmlParam;
/* Old gdb always expect FPA registers. Newer (xml-aware) gdb only expect
whatever the target description contains. Due to a historical mishap
the FPA registers appear in between core integer regs and the CPSR.
We hack round this by giving the FPA regs zero size when talking to a
newer gdb. */
int arm_cpu_gdb_read_register(CPUState *cs, GByteArray *mem_buf, int n)
{
ARMCPU *cpu = ARM_CPU(cs);
CPUARMState *env = &cpu->env;
if (n < 16) {
/* Core integer register. */
return gdb_get_reg32(mem_buf, env->regs[n]);
}
if (n < 24) {
/* FPA registers. */
if (gdb_has_xml) {
return 0;
}
return gdb_get_zeroes(mem_buf, 12);
}
switch (n) {
case 24:
/* FPA status register. */
if (gdb_has_xml) {
return 0;
}
return gdb_get_reg32(mem_buf, 0);
case 25:
/* CPSR, or XPSR for M-profile */
if (arm_feature(env, ARM_FEATURE_M)) {
return gdb_get_reg32(mem_buf, xpsr_read(env));
} else {
return gdb_get_reg32(mem_buf, cpsr_read(env));
}
}
/* Unknown register. */
return 0;
}
int arm_cpu_gdb_write_register(CPUState *cs, uint8_t *mem_buf, int n)
{
ARMCPU *cpu = ARM_CPU(cs);
CPUARMState *env = &cpu->env;
uint32_t tmp;
tmp = ldl_p(mem_buf);
/* Mask out low bit of PC to workaround gdb bugs. This will probably
cause problems if we ever implement the Jazelle DBX extensions. */
if (n == 15) {
tmp &= ~1;
}
if (n < 16) {
/* Core integer register. */
if (n == 13 && arm_feature(env, ARM_FEATURE_M)) {
/* M profile SP low bits are always 0 */
tmp &= ~3;
}
env->regs[n] = tmp;
return 4;
}
if (n < 24) { /* 16-23 */
/* FPA registers (ignored). */
if (gdb_has_xml) {
return 0;
}
return 12;
}
switch (n) {
case 24:
/* FPA status register (ignored). */
if (gdb_has_xml) {
return 0;
}
return 4;
case 25:
/* CPSR, or XPSR for M-profile */
if (arm_feature(env, ARM_FEATURE_M)) {
/*
* Don't allow writing to XPSR.Exception as it can cause
* a transition into or out of handler mode (it's not
* writeable via the MSR insn so this is a reasonable
* restriction). Other fields are safe to update.
*/
xpsr_write(env, tmp, ~XPSR_EXCP);
} else {
cpsr_write(env, tmp, 0xffffffff, CPSRWriteByGDBStub);
}
return 4;
}
/* Unknown register. */
return 0;
}
static void arm_gen_one_xml_sysreg_tag(GString *s, DynamicGDBXMLInfo *dyn_xml,
ARMCPRegInfo *ri, uint32_t ri_key,
int bitsize, int regnum)
{
g_string_append_printf(s, "<reg name=\"%s\"", ri->name);
g_string_append_printf(s, " bitsize=\"%d\"", bitsize);
g_string_append_printf(s, " regnum=\"%d\"", regnum);
g_string_append_printf(s, " group=\"cp_regs\"/>");
dyn_xml->data.cpregs.keys[dyn_xml->num] = ri_key;
dyn_xml->num++;
}
static void arm_register_sysreg_for_xml(gpointer key, gpointer value,
gpointer p)
{
uint32_t ri_key = *(uint32_t *)key;
ARMCPRegInfo *ri = value;
RegisterSysregXmlParam *param = (RegisterSysregXmlParam *)p;
GString *s = param->s;
ARMCPU *cpu = ARM_CPU(param->cs);
CPUARMState *env = &cpu->env;
DynamicGDBXMLInfo *dyn_xml = &cpu->dyn_sysreg_xml;
if (!(ri->type & (ARM_CP_NO_RAW | ARM_CP_NO_GDB))) {
if (arm_feature(env, ARM_FEATURE_AARCH64)) {
if (ri->state == ARM_CP_STATE_AA64) {
arm_gen_one_xml_sysreg_tag(s , dyn_xml, ri, ri_key, 64,
param->n++);
}
} else {
if (ri->state == ARM_CP_STATE_AA32) {
if (!arm_feature(env, ARM_FEATURE_EL3) &&
(ri->secure & ARM_CP_SECSTATE_S)) {
return;
}
if (ri->type & ARM_CP_64BIT) {
arm_gen_one_xml_sysreg_tag(s , dyn_xml, ri, ri_key, 64,
param->n++);
} else {
arm_gen_one_xml_sysreg_tag(s , dyn_xml, ri, ri_key, 32,
param->n++);
}
}
}
}
}
int arm_gen_dynamic_sysreg_xml(CPUState *cs, int base_reg)
{
ARMCPU *cpu = ARM_CPU(cs);
GString *s = g_string_new(NULL);
RegisterSysregXmlParam param = {cs, s, base_reg};
cpu->dyn_sysreg_xml.num = 0;
cpu->dyn_sysreg_xml.data.cpregs.keys = g_new(uint32_t, g_hash_table_size(cpu->cp_regs));
g_string_printf(s, "<?xml version=\"1.0\"?>");
g_string_append_printf(s, "<!DOCTYPE target SYSTEM \"gdb-target.dtd\">");
g_string_append_printf(s, "<feature name=\"org.qemu.gdb.arm.sys.regs\">");
g_hash_table_foreach(cpu->cp_regs, arm_register_sysreg_for_xml, &param);
g_string_append_printf(s, "</feature>");
cpu->dyn_sysreg_xml.desc = g_string_free(s, false);
return cpu->dyn_sysreg_xml.num;
}
struct TypeSize {
const char *gdb_type;
int size;
const char sz, suffix;
};
static const struct TypeSize vec_lanes[] = {
/* quads */
{ "uint128", 128, 'q', 'u' },
{ "int128", 128, 'q', 's' },
/* 64 bit */
{ "ieee_double", 64, 'd', 'f' },
{ "uint64", 64, 'd', 'u' },
{ "int64", 64, 'd', 's' },
/* 32 bit */
{ "ieee_single", 32, 's', 'f' },
{ "uint32", 32, 's', 'u' },
{ "int32", 32, 's', 's' },
/* 16 bit */
{ "ieee_half", 16, 'h', 'f' },
{ "uint16", 16, 'h', 'u' },
{ "int16", 16, 'h', 's' },
/* bytes */
{ "uint8", 8, 'b', 'u' },
{ "int8", 8, 'b', 's' },
};
int arm_gen_dynamic_svereg_xml(CPUState *cs, int base_reg)
{
ARMCPU *cpu = ARM_CPU(cs);
GString *s = g_string_new(NULL);
DynamicGDBXMLInfo *info = &cpu->dyn_svereg_xml;
g_autoptr(GString) ts = g_string_new("");
int i, j, bits, reg_width = (cpu->sve_max_vq * 128);
info->num = 0;
g_string_printf(s, "<?xml version=\"1.0\"?>");
g_string_append_printf(s, "<!DOCTYPE target SYSTEM \"gdb-target.dtd\">");
g_string_append_printf(s, "<feature name=\"org.gnu.gdb.aarch64.sve\">");
/* First define types and totals in a whole VL */
for (i = 0; i < ARRAY_SIZE(vec_lanes); i++) {
int count = reg_width / vec_lanes[i].size;
g_string_printf(ts, "svev%c%c", vec_lanes[i].sz, vec_lanes[i].suffix);
g_string_append_printf(s,
"<vector id=\"%s\" type=\"%s\" count=\"%d\"/>",
ts->str, vec_lanes[i].gdb_type, count);
}
/*
* Now define a union for each size group containing unsigned and
* signed and potentially float versions of each size from 128 to
* 8 bits.
*/
for (bits = 128, i = 0; bits >= 8; bits /= 2, i++) {
const char suf[] = { 'q', 'd', 's', 'h', 'b' };
g_string_append_printf(s, "<union id=\"svevn%c\">", suf[i]);
for (j = 0; j < ARRAY_SIZE(vec_lanes); j++) {
if (vec_lanes[j].size == bits) {
g_string_append_printf(s, "<field name=\"%c\" type=\"svev%c%c\"/>",
vec_lanes[j].suffix,
vec_lanes[j].sz, vec_lanes[j].suffix);
}
}
g_string_append(s, "</union>");
}
/* And now the final union of unions */
g_string_append(s, "<union id=\"svev\">");
for (bits = 128, i = 0; bits >= 8; bits /= 2, i++) {
const char suf[] = { 'q', 'd', 's', 'h', 'b' };
g_string_append_printf(s, "<field name=\"%c\" type=\"svevn%c\"/>",
suf[i], suf[i]);
}
g_string_append(s, "</union>");
/* Finally the sve prefix type */
g_string_append_printf(s,
"<vector id=\"svep\" type=\"uint8\" count=\"%d\"/>",
reg_width / 8);
/* Then define each register in parts for each vq */
for (i = 0; i < 32; i++) {
g_string_append_printf(s,
"<reg name=\"z%d\" bitsize=\"%d\""
" regnum=\"%d\" type=\"svev\"/>",
i, reg_width, base_reg++);
info->num++;
}
/* fpscr & status registers */
g_string_append_printf(s, "<reg name=\"fpsr\" bitsize=\"32\""
" regnum=\"%d\" group=\"float\""
" type=\"int\"/>", base_reg++);
g_string_append_printf(s, "<reg name=\"fpcr\" bitsize=\"32\""
" regnum=\"%d\" group=\"float\""
" type=\"int\"/>", base_reg++);
info->num += 2;
for (i = 0; i < 16; i++) {
g_string_append_printf(s,
"<reg name=\"p%d\" bitsize=\"%d\""
" regnum=\"%d\" type=\"svep\"/>",
i, cpu->sve_max_vq * 16, base_reg++);
info->num++;
}
g_string_append_printf(s,
"<reg name=\"ffr\" bitsize=\"%d\""
" regnum=\"%d\" group=\"vector\""
" type=\"svep\"/>",
cpu->sve_max_vq * 16, base_reg++);
g_string_append_printf(s,
"<reg name=\"vg\" bitsize=\"64\""
" regnum=\"%d\" type=\"int\"/>",
base_reg++);
info->num += 2;
g_string_append_printf(s, "</feature>");
cpu->dyn_svereg_xml.desc = g_string_free(s, false);
return cpu->dyn_svereg_xml.num;
}
const char *arm_gdb_get_dynamic_xml(CPUState *cs, const char *xmlname)
{
ARMCPU *cpu = ARM_CPU(cs);
if (strcmp(xmlname, "system-registers.xml") == 0) {
return cpu->dyn_sysreg_xml.desc;
} else if (strcmp(xmlname, "sve-registers.xml") == 0) {
return cpu->dyn_svereg_xml.desc;
}
return NULL;
}
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