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target/arm: Add v8M stack checks on ADD/SUB/MOV of SP
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Add code to insert calls to a helper function to do the stack
limit checking when we handle these forms of instruction
that write to SP:
 * ADD (SP plus immediate)
 * ADD (SP plus register)
 * SUB (SP minus immediate)
 * SUB (SP minus register)
 * MOV (register)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20181002163556.10279-5-peter.maydell@linaro.org
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@pm215
pm215 committed Oct 8, 2018
1 parent 5529bf1 commit 5520318
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Showing 4 changed files with 106 additions and 9 deletions.
2 changes: 2 additions & 0 deletions target/arm/helper.h
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Expand Up @@ -69,6 +69,8 @@ DEF_HELPER_2(v7m_blxns, void, env, i32)

DEF_HELPER_3(v7m_tt, i32, env, i32, i32)

DEF_HELPER_2(v8m_stackcheck, void, env, i32)

DEF_HELPER_4(access_check_cp_reg, void, env, ptr, i32, i32)
DEF_HELPER_3(set_cp_reg, void, env, ptr, i32)
DEF_HELPER_2(get_cp_reg, i32, env, ptr)
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14 changes: 14 additions & 0 deletions target/arm/internals.h
View file
Expand Up @@ -817,4 +817,18 @@ static inline bool v7m_using_psp(CPUARMState *env)
env->v7m.control[env->v7m.secure] & R_V7M_CONTROL_SPSEL_MASK;
}

/**
* v7m_sp_limit: Return SP limit for current CPU state
* Return the SP limit value for the current CPU security state
* and stack pointer.
*/
static inline uint32_t v7m_sp_limit(CPUARMState *env)
{
if (v7m_using_psp(env)) {
return env->v7m.psplim[env->v7m.secure];
} else {
return env->v7m.msplim[env->v7m.secure];
}
}

#endif
19 changes: 19 additions & 0 deletions target/arm/op_helper.c
View file
Expand Up @@ -238,6 +238,25 @@ void arm_cpu_do_transaction_failed(CPUState *cs, hwaddr physaddr,

#endif /* !defined(CONFIG_USER_ONLY) */

void HELPER(v8m_stackcheck)(CPUARMState *env, uint32_t newvalue)
{
/*
* Perform the v8M stack limit check for SP updates from translated code,
* raising an exception if the limit is breached.
*/
if (newvalue < v7m_sp_limit(env)) {
CPUState *cs = CPU(arm_env_get_cpu(env));

/*
* Stack limit exceptions are a rare case, so rather than syncing
* PC/condbits before the call, we use cpu_restore_state() to
* get them right before raising the exception.
*/
cpu_restore_state(cs, GETPC(), true);
raise_exception(env, EXCP_STKOF, 0, 1);
}
}

uint32_t HELPER(add_setq)(CPUARMState *env, uint32_t a, uint32_t b)
{
uint32_t res = a + b;
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80 changes: 71 additions & 9 deletions target/arm/translate.c
View file
Expand Up @@ -239,6 +239,23 @@ static void store_reg(DisasContext *s, int reg, TCGv_i32 var)
tcg_temp_free_i32(var);
}

/*
* Variant of store_reg which applies v8M stack-limit checks before updating
* SP. If the check fails this will result in an exception being taken.
* We disable the stack checks for CONFIG_USER_ONLY because we have
* no idea what the stack limits should be in that case.
* If stack checking is not being done this just acts like store_reg().
*/
static void store_sp_checked(DisasContext *s, TCGv_i32 var)
{
#ifndef CONFIG_USER_ONLY
if (s->v8m_stackcheck) {
gen_helper_v8m_stackcheck(cpu_env, var);
}
#endif
store_reg(s, 13, var);
}

/* Value extensions. */
#define gen_uxtb(var) tcg_gen_ext8u_i32(var, var)
#define gen_uxth(var) tcg_gen_ext16u_i32(var, var)
Expand Down Expand Up @@ -10583,7 +10600,13 @@ static void disas_thumb2_insn(DisasContext *s, uint32_t insn)
if (gen_thumb2_data_op(s, op, conds, 0, tmp, tmp2))
goto illegal_op;
tcg_temp_free_i32(tmp2);
if (rd != 15) {
if (rd == 13 &&
((op == 2 && rn == 15) ||
(op == 8 && rn == 13) ||
(op == 13 && rn == 13))) {
/* MOV SP, ... or ADD SP, SP, ... or SUB SP, SP, ... */
store_sp_checked(s, tmp);
} else if (rd != 15) {
store_reg(s, rd, tmp);
} else {
tcg_temp_free_i32(tmp);
Expand Down Expand Up @@ -11267,8 +11290,15 @@ static void disas_thumb2_insn(DisasContext *s, uint32_t insn)
gen_jmp(s, s->pc + offset);
}
} else {
/* Data processing immediate. */
/*
* 0b1111_0xxx_xxxx_0xxx_xxxx_xxxx
* - Data-processing (modified immediate, plain binary immediate)
*/
if (insn & (1 << 25)) {
/*
* 0b1111_0x1x_xxxx_0xxx_xxxx_xxxx
* - Data-processing (plain binary immediate)
*/
if (insn & (1 << 24)) {
if (insn & (1 << 20))
goto illegal_op;
Expand Down Expand Up @@ -11364,6 +11394,7 @@ static void disas_thumb2_insn(DisasContext *s, uint32_t insn)
tmp = tcg_temp_new_i32();
tcg_gen_movi_i32(tmp, imm);
}
store_reg(s, rd, tmp);
} else {
/* Add/sub 12-bit immediate. */
if (rn == 15) {
Expand All @@ -11374,17 +11405,27 @@ static void disas_thumb2_insn(DisasContext *s, uint32_t insn)
offset += imm;
tmp = tcg_temp_new_i32();
tcg_gen_movi_i32(tmp, offset);
store_reg(s, rd, tmp);
} else {
tmp = load_reg(s, rn);
if (insn & (1 << 23))
tcg_gen_subi_i32(tmp, tmp, imm);
else
tcg_gen_addi_i32(tmp, tmp, imm);
if (rn == 13 && rd == 13) {
/* ADD SP, SP, imm or SUB SP, SP, imm */
store_sp_checked(s, tmp);
} else {
store_reg(s, rd, tmp);
}
}
}
store_reg(s, rd, tmp);
}
} else {
/*
* 0b1111_0x0x_xxxx_0xxx_xxxx_xxxx
* - Data-processing (modified immediate)
*/
int shifter_out = 0;
/* modified 12-bit immediate. */
shift = ((insn & 0x04000000) >> 23) | ((insn & 0x7000) >> 12);
Expand Down Expand Up @@ -11426,7 +11467,11 @@ static void disas_thumb2_insn(DisasContext *s, uint32_t insn)
goto illegal_op;
tcg_temp_free_i32(tmp2);
rd = (insn >> 8) & 0xf;
if (rd != 15) {
if (rd == 13 && rn == 13
&& (op == 8 || op == 13)) {
/* ADD(S) SP, SP, imm or SUB(S) SP, SP, imm */
store_sp_checked(s, tmp);
} else if (rd != 15) {
store_reg(s, rd, tmp);
} else {
tcg_temp_free_i32(tmp);
Expand Down Expand Up @@ -11732,7 +11777,12 @@ static void disas_thumb_insn(DisasContext *s, uint32_t insn)
tmp2 = load_reg(s, rm);
tcg_gen_add_i32(tmp, tmp, tmp2);
tcg_temp_free_i32(tmp2);
store_reg(s, rd, tmp);
if (rd == 13) {
/* ADD SP, SP, reg */
store_sp_checked(s, tmp);
} else {
store_reg(s, rd, tmp);
}
break;
case 1: /* cmp */
tmp = load_reg(s, rd);
Expand All @@ -11743,7 +11793,12 @@ static void disas_thumb_insn(DisasContext *s, uint32_t insn)
break;
case 2: /* mov/cpy */
tmp = load_reg(s, rm);
store_reg(s, rd, tmp);
if (rd == 13) {
/* MOV SP, reg */
store_sp_checked(s, tmp);
} else {
store_reg(s, rd, tmp);
}
break;
case 3:
{
Expand Down Expand Up @@ -12071,7 +12126,10 @@ static void disas_thumb_insn(DisasContext *s, uint32_t insn)
break;

case 10:
/* add to high reg */
/*
* 0b1010_xxxx_xxxx_xxxx
* - Add PC/SP (immediate)
*/
rd = (insn >> 8) & 7;
if (insn & (1 << 11)) {
/* SP */
Expand All @@ -12091,13 +12149,17 @@ static void disas_thumb_insn(DisasContext *s, uint32_t insn)
op = (insn >> 8) & 0xf;
switch (op) {
case 0:
/* adjust stack pointer */
/*
* 0b1011_0000_xxxx_xxxx
* - ADD (SP plus immediate)
* - SUB (SP minus immediate)
*/
tmp = load_reg(s, 13);
val = (insn & 0x7f) * 4;
if (insn & (1 << 7))
val = -(int32_t)val;
tcg_gen_addi_i32(tmp, tmp, val);
store_reg(s, 13, tmp);
store_sp_checked(s, tmp);
break;

case 2: /* sign/zero extend. */
Expand Down

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