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MIPS: Send proper signal and siginfo on FP emulator faults.
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We were unconditionally sending SIGBUS with an empty siginfo on FP
emulator faults.  This differs from what happens when real floating
point hardware would get a fault.

For most faults we need to send SIGSEGV with the faulting address
filled in in the struct siginfo.

Reported-by: Camm Maguire <camm@maguirefamily.org>
Signed-off-by: David Daney <ddaney@caviumnetworks.com>
To: linux-mips@linux-mips.org
Cc: Camm Maguire <camm@maguirefamily.org>
Patchwork: https://patchwork.linux-mips.org/patch/1727/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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David Daney authored and Ralf Baechle committed Dec 16, 2010
1 parent 0bc6791 commit 515b029
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Showing 2 changed files with 130 additions and 30 deletions.
44 changes: 35 additions & 9 deletions arch/mips/kernel/traps.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -83,7 +83,8 @@ extern asmlinkage void handle_mcheck(void);
extern asmlinkage void handle_reserved(void);

extern int fpu_emulator_cop1Handler(struct pt_regs *xcp,
struct mips_fpu_struct *ctx, int has_fpu);
struct mips_fpu_struct *ctx, int has_fpu,
void *__user *fault_addr);

void (*board_be_init)(void);
int (*board_be_handler)(struct pt_regs *regs, int is_fixup);
Expand Down Expand Up @@ -661,12 +662,36 @@ asmlinkage void do_ov(struct pt_regs *regs)
force_sig_info(SIGFPE, &info, current);
}

static int process_fpemu_return(int sig, void __user *fault_addr)
{
if (sig == SIGSEGV || sig == SIGBUS) {
struct siginfo si = {0};
si.si_addr = fault_addr;
si.si_signo = sig;
if (sig == SIGSEGV) {
if (find_vma(current->mm, (unsigned long)fault_addr))
si.si_code = SEGV_ACCERR;
else
si.si_code = SEGV_MAPERR;
} else {
si.si_code = BUS_ADRERR;
}
force_sig_info(sig, &si, current);
return 1;
} else if (sig) {
force_sig(sig, current);
return 1;
} else {
return 0;
}
}

/*
* XXX Delayed fp exceptions when doing a lazy ctx switch XXX
*/
asmlinkage void do_fpe(struct pt_regs *regs, unsigned long fcr31)
{
siginfo_t info;
siginfo_t info = {0};

if (notify_die(DIE_FP, "FP exception", regs, 0, regs_to_trapnr(regs), SIGFPE)
== NOTIFY_STOP)
Expand All @@ -675,6 +700,7 @@ asmlinkage void do_fpe(struct pt_regs *regs, unsigned long fcr31)

if (fcr31 & FPU_CSR_UNI_X) {
int sig;
void __user *fault_addr = NULL;

/*
* Unimplemented operation exception. If we've got the full
Expand All @@ -690,7 +716,8 @@ asmlinkage void do_fpe(struct pt_regs *regs, unsigned long fcr31)
lose_fpu(1);

/* Run the emulator */
sig = fpu_emulator_cop1Handler(regs, &current->thread.fpu, 1);
sig = fpu_emulator_cop1Handler(regs, &current->thread.fpu, 1,
&fault_addr);

/*
* We can't allow the emulated instruction to leave any of
Expand All @@ -702,8 +729,7 @@ asmlinkage void do_fpe(struct pt_regs *regs, unsigned long fcr31)
own_fpu(1); /* Using the FPU again. */

/* If something went wrong, signal */
if (sig)
force_sig(sig, current);
process_fpemu_return(sig, fault_addr);

return;
} else if (fcr31 & FPU_CSR_INV_X)
Expand Down Expand Up @@ -996,11 +1022,11 @@ asmlinkage void do_cpu(struct pt_regs *regs)

if (!raw_cpu_has_fpu) {
int sig;
void __user *fault_addr = NULL;
sig = fpu_emulator_cop1Handler(regs,
&current->thread.fpu, 0);
if (sig)
force_sig(sig, current);
else
&current->thread.fpu,
0, &fault_addr);
if (!process_fpemu_return(sig, fault_addr))
mt_ase_fp_affinity();
}

Expand Down
116 changes: 95 additions & 21 deletions arch/mips/math-emu/cp1emu.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -64,7 +64,7 @@ static int fpu_emu(struct pt_regs *, struct mips_fpu_struct *,

#if __mips >= 4 && __mips != 32
static int fpux_emu(struct pt_regs *,
struct mips_fpu_struct *, mips_instruction);
struct mips_fpu_struct *, mips_instruction, void *__user *);
#endif

/* Further private data for which no space exists in mips_fpu_struct */
Expand Down Expand Up @@ -208,16 +208,23 @@ static inline int cop1_64bit(struct pt_regs *xcp)
* Two instructions if the instruction is in a branch delay slot.
*/

static int cop1Emulate(struct pt_regs *xcp, struct mips_fpu_struct *ctx)
static int cop1Emulate(struct pt_regs *xcp, struct mips_fpu_struct *ctx,
void *__user *fault_addr)
{
mips_instruction ir;
unsigned long emulpc, contpc;
unsigned int cond;

if (get_user(ir, (mips_instruction __user *) xcp->cp0_epc)) {
if (!access_ok(VERIFY_READ, xcp->cp0_epc, sizeof(mips_instruction))) {
MIPS_FPU_EMU_INC_STATS(errors);
*fault_addr = (mips_instruction __user *)xcp->cp0_epc;
return SIGBUS;
}
if (__get_user(ir, (mips_instruction __user *) xcp->cp0_epc)) {
MIPS_FPU_EMU_INC_STATS(errors);
*fault_addr = (mips_instruction __user *)xcp->cp0_epc;
return SIGSEGV;
}

/* XXX NEC Vr54xx bug workaround */
if ((xcp->cp0_cause & CAUSEF_BD) && !isBranchInstr(&ir))
Expand Down Expand Up @@ -245,10 +252,16 @@ static int cop1Emulate(struct pt_regs *xcp, struct mips_fpu_struct *ctx)
#endif
return SIGILL;
}
if (get_user(ir, (mips_instruction __user *) emulpc)) {
if (!access_ok(VERIFY_READ, emulpc, sizeof(mips_instruction))) {
MIPS_FPU_EMU_INC_STATS(errors);
*fault_addr = (mips_instruction __user *)emulpc;
return SIGBUS;
}
if (__get_user(ir, (mips_instruction __user *) emulpc)) {
MIPS_FPU_EMU_INC_STATS(errors);
*fault_addr = (mips_instruction __user *)emulpc;
return SIGSEGV;
}
/* __compute_return_epc() will have updated cp0_epc */
contpc = xcp->cp0_epc;
/* In order not to confuse ptrace() et al, tweak context */
Expand All @@ -269,10 +282,17 @@ static int cop1Emulate(struct pt_regs *xcp, struct mips_fpu_struct *ctx)
u64 val;

MIPS_FPU_EMU_INC_STATS(loads);
if (get_user(val, va)) {

if (!access_ok(VERIFY_READ, va, sizeof(u64))) {
MIPS_FPU_EMU_INC_STATS(errors);
*fault_addr = va;
return SIGBUS;
}
if (__get_user(val, va)) {
MIPS_FPU_EMU_INC_STATS(errors);
*fault_addr = va;
return SIGSEGV;
}
DITOREG(val, MIPSInst_RT(ir));
break;
}
Expand All @@ -284,10 +304,16 @@ static int cop1Emulate(struct pt_regs *xcp, struct mips_fpu_struct *ctx)

MIPS_FPU_EMU_INC_STATS(stores);
DIFROMREG(val, MIPSInst_RT(ir));
if (put_user(val, va)) {
if (!access_ok(VERIFY_WRITE, va, sizeof(u64))) {
MIPS_FPU_EMU_INC_STATS(errors);
*fault_addr = va;
return SIGBUS;
}
if (__put_user(val, va)) {
MIPS_FPU_EMU_INC_STATS(errors);
*fault_addr = va;
return SIGSEGV;
}
break;
}

Expand All @@ -297,10 +323,16 @@ static int cop1Emulate(struct pt_regs *xcp, struct mips_fpu_struct *ctx)
u32 val;

MIPS_FPU_EMU_INC_STATS(loads);
if (get_user(val, va)) {
if (!access_ok(VERIFY_READ, va, sizeof(u32))) {
MIPS_FPU_EMU_INC_STATS(errors);
*fault_addr = va;
return SIGBUS;
}
if (__get_user(val, va)) {
MIPS_FPU_EMU_INC_STATS(errors);
*fault_addr = va;
return SIGSEGV;
}
SITOREG(val, MIPSInst_RT(ir));
break;
}
Expand All @@ -312,10 +344,16 @@ static int cop1Emulate(struct pt_regs *xcp, struct mips_fpu_struct *ctx)

MIPS_FPU_EMU_INC_STATS(stores);
SIFROMREG(val, MIPSInst_RT(ir));
if (put_user(val, va)) {
if (!access_ok(VERIFY_WRITE, va, sizeof(u32))) {
MIPS_FPU_EMU_INC_STATS(errors);
*fault_addr = va;
return SIGBUS;
}
if (__put_user(val, va)) {
MIPS_FPU_EMU_INC_STATS(errors);
*fault_addr = va;
return SIGSEGV;
}
break;
}

Expand Down Expand Up @@ -440,11 +478,18 @@ static int cop1Emulate(struct pt_regs *xcp, struct mips_fpu_struct *ctx)
contpc = (xcp->cp0_epc +
(MIPSInst_SIMM(ir) << 2));

if (get_user(ir,
(mips_instruction __user *) xcp->cp0_epc)) {
if (!access_ok(VERIFY_READ, xcp->cp0_epc,
sizeof(mips_instruction))) {
MIPS_FPU_EMU_INC_STATS(errors);
*fault_addr = (mips_instruction __user *)xcp->cp0_epc;
return SIGBUS;
}
if (__get_user(ir,
(mips_instruction __user *) xcp->cp0_epc)) {
MIPS_FPU_EMU_INC_STATS(errors);
*fault_addr = (mips_instruction __user *)xcp->cp0_epc;
return SIGSEGV;
}

switch (MIPSInst_OPCODE(ir)) {
case lwc1_op:
Expand Down Expand Up @@ -506,9 +551,8 @@ static int cop1Emulate(struct pt_regs *xcp, struct mips_fpu_struct *ctx)

#if __mips >= 4 && __mips != 32
case cop1x_op:{
int sig;

if ((sig = fpux_emu(xcp, ctx, ir)))
int sig = fpux_emu(xcp, ctx, ir, fault_addr);
if (sig)
return sig;
break;
}
Expand Down Expand Up @@ -604,7 +648,7 @@ DEF3OP(nmadd, dp, ieee754dp_mul, ieee754dp_add, ieee754dp_neg);
DEF3OP(nmsub, dp, ieee754dp_mul, ieee754dp_sub, ieee754dp_neg);

static int fpux_emu(struct pt_regs *xcp, struct mips_fpu_struct *ctx,
mips_instruction ir)
mips_instruction ir, void *__user *fault_addr)
{
unsigned rcsr = 0; /* resulting csr */

Expand All @@ -624,10 +668,16 @@ static int fpux_emu(struct pt_regs *xcp, struct mips_fpu_struct *ctx,
xcp->regs[MIPSInst_FT(ir)]);

MIPS_FPU_EMU_INC_STATS(loads);
if (get_user(val, va)) {
if (!access_ok(VERIFY_READ, va, sizeof(u32))) {
MIPS_FPU_EMU_INC_STATS(errors);
*fault_addr = va;
return SIGBUS;
}
if (__get_user(val, va)) {
MIPS_FPU_EMU_INC_STATS(errors);
*fault_addr = va;
return SIGSEGV;
}
SITOREG(val, MIPSInst_FD(ir));
break;

Expand All @@ -638,10 +688,16 @@ static int fpux_emu(struct pt_regs *xcp, struct mips_fpu_struct *ctx,
MIPS_FPU_EMU_INC_STATS(stores);

SIFROMREG(val, MIPSInst_FS(ir));
if (put_user(val, va)) {
if (!access_ok(VERIFY_WRITE, va, sizeof(u32))) {
MIPS_FPU_EMU_INC_STATS(errors);
*fault_addr = va;
return SIGBUS;
}
if (put_user(val, va)) {
MIPS_FPU_EMU_INC_STATS(errors);
*fault_addr = va;
return SIGSEGV;
}
break;

case madd_s_op:
Expand Down Expand Up @@ -701,10 +757,16 @@ static int fpux_emu(struct pt_regs *xcp, struct mips_fpu_struct *ctx,
xcp->regs[MIPSInst_FT(ir)]);

MIPS_FPU_EMU_INC_STATS(loads);
if (get_user(val, va)) {
if (!access_ok(VERIFY_READ, va, sizeof(u64))) {
MIPS_FPU_EMU_INC_STATS(errors);
*fault_addr = va;
return SIGBUS;
}
if (__get_user(val, va)) {
MIPS_FPU_EMU_INC_STATS(errors);
*fault_addr = va;
return SIGSEGV;
}
DITOREG(val, MIPSInst_FD(ir));
break;

Expand All @@ -714,10 +776,16 @@ static int fpux_emu(struct pt_regs *xcp, struct mips_fpu_struct *ctx,

MIPS_FPU_EMU_INC_STATS(stores);
DIFROMREG(val, MIPSInst_FS(ir));
if (put_user(val, va)) {
if (!access_ok(VERIFY_WRITE, va, sizeof(u64))) {
MIPS_FPU_EMU_INC_STATS(errors);
*fault_addr = va;
return SIGBUS;
}
if (__put_user(val, va)) {
MIPS_FPU_EMU_INC_STATS(errors);
*fault_addr = va;
return SIGSEGV;
}
break;

case madd_d_op:
Expand Down Expand Up @@ -1242,7 +1310,7 @@ static int fpu_emu(struct pt_regs *xcp, struct mips_fpu_struct *ctx,
}

int fpu_emulator_cop1Handler(struct pt_regs *xcp, struct mips_fpu_struct *ctx,
int has_fpu)
int has_fpu, void *__user *fault_addr)
{
unsigned long oldepc, prevepc;
mips_instruction insn;
Expand All @@ -1252,10 +1320,16 @@ int fpu_emulator_cop1Handler(struct pt_regs *xcp, struct mips_fpu_struct *ctx,
do {
prevepc = xcp->cp0_epc;

if (get_user(insn, (mips_instruction __user *) xcp->cp0_epc)) {
if (!access_ok(VERIFY_READ, xcp->cp0_epc, sizeof(mips_instruction))) {
MIPS_FPU_EMU_INC_STATS(errors);
*fault_addr = (mips_instruction __user *)xcp->cp0_epc;
return SIGBUS;
}
if (__get_user(insn, (mips_instruction __user *) xcp->cp0_epc)) {
MIPS_FPU_EMU_INC_STATS(errors);
*fault_addr = (mips_instruction __user *)xcp->cp0_epc;
return SIGSEGV;
}
if (insn == 0)
xcp->cp0_epc += 4; /* skip nops */
else {
Expand All @@ -1267,7 +1341,7 @@ int fpu_emulator_cop1Handler(struct pt_regs *xcp, struct mips_fpu_struct *ctx,
*/
/* convert to ieee library modes */
ieee754_csr.rm = ieee_rm[ieee754_csr.rm];
sig = cop1Emulate(xcp, ctx);
sig = cop1Emulate(xcp, ctx, fault_addr);
/* revert to mips rounding mode */
ieee754_csr.rm = mips_rm[ieee754_csr.rm];
}
Expand Down

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