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linux-user: Split out host_sig{segv,bus}_handler
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Make host_signal_handler slightly easier to read.

Acked-by: Helge Deller <deller@gmx.de>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
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@rth7680
rth7680 committed Oct 18, 2023
1 parent 58c4e36 commit f4e1168
Showing 1 changed file with 85 additions and 60 deletions.
145 changes: 85 additions & 60 deletions linux-user/signal.c
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Original file line number Diff line number Diff line change
Expand Up @@ -811,6 +811,80 @@ void die_from_signal(siginfo_t *info)
die_with_signal(info->si_signo);
}

static void host_sigsegv_handler(CPUState *cpu, siginfo_t *info,
host_sigcontext *uc)
{
uintptr_t host_addr = (uintptr_t)info->si_addr;
/*
* Convert forcefully to guest address space: addresses outside
* reserved_va are still valid to report via SEGV_MAPERR.
*/
bool is_valid = h2g_valid(host_addr);
abi_ptr guest_addr = h2g_nocheck(host_addr);
uintptr_t pc = host_signal_pc(uc);
bool is_write = host_signal_write(info, uc);
MMUAccessType access_type = adjust_signal_pc(&pc, is_write);
bool maperr;

/* If this was a write to a TB protected page, restart. */
if (is_write
&& is_valid
&& info->si_code == SEGV_ACCERR
&& handle_sigsegv_accerr_write(cpu, host_signal_mask(uc),
pc, guest_addr)) {
return;
}

/*
* If the access was not on behalf of the guest, within the executable
* mapping of the generated code buffer, then it is a host bug.
*/
if (access_type != MMU_INST_FETCH
&& !in_code_gen_buffer((void *)(pc - tcg_splitwx_diff))) {
die_from_signal(info);
}

maperr = true;
if (is_valid && info->si_code == SEGV_ACCERR) {
/*
* With reserved_va, the whole address space is PROT_NONE,
* which means that we may get ACCERR when we want MAPERR.
*/
if (page_get_flags(guest_addr) & PAGE_VALID) {
maperr = false;
} else {
info->si_code = SEGV_MAPERR;
}
}

sigprocmask(SIG_SETMASK, host_signal_mask(uc), NULL);
cpu_loop_exit_sigsegv(cpu, guest_addr, access_type, maperr, pc);
}

static void host_sigbus_handler(CPUState *cpu, siginfo_t *info,
host_sigcontext *uc)
{
uintptr_t pc = host_signal_pc(uc);
bool is_write = host_signal_write(info, uc);
MMUAccessType access_type = adjust_signal_pc(&pc, is_write);

/*
* If the access was not on behalf of the guest, within the executable
* mapping of the generated code buffer, then it is a host bug.
*/
if (!in_code_gen_buffer((void *)(pc - tcg_splitwx_diff))) {
die_from_signal(info);
}

if (info->si_code == BUS_ADRALN) {
uintptr_t host_addr = (uintptr_t)info->si_addr;
abi_ptr guest_addr = h2g_nocheck(host_addr);

sigprocmask(SIG_SETMASK, host_signal_mask(uc), NULL);
cpu_loop_exit_sigbus(cpu, guest_addr, access_type, pc);
}
}

static void host_signal_handler(int host_sig, siginfo_t *info, void *puc)
{
CPUState *cpu = thread_cpu;
Expand All @@ -822,73 +896,23 @@ static void host_signal_handler(int host_sig, siginfo_t *info, void *puc)
int guest_sig;
uintptr_t pc = 0;
bool sync_sig = false;
void *sigmask = host_signal_mask(uc);
void *sigmask;

/*
* Non-spoofed SIGSEGV and SIGBUS are synchronous, and need special
* handling wrt signal blocking and unwinding.
*/
if ((host_sig == SIGSEGV || host_sig == SIGBUS) && info->si_code > 0) {
MMUAccessType access_type;
uintptr_t host_addr;
abi_ptr guest_addr;
bool is_write;

host_addr = (uintptr_t)info->si_addr;

/*
* Convert forcefully to guest address space: addresses outside
* reserved_va are still valid to report via SEGV_MAPERR.
*/
guest_addr = h2g_nocheck(host_addr);

pc = host_signal_pc(uc);
is_write = host_signal_write(info, uc);
access_type = adjust_signal_pc(&pc, is_write);

/* If this was a write to a TB protected page, restart. */
if (is_write
&& host_sig == SIGSEGV
&& info->si_code == SEGV_ACCERR
&& h2g_valid(host_addr)
&& handle_sigsegv_accerr_write(cpu, sigmask, pc, guest_addr)) {
if (info->si_code > 0) {
switch (host_sig) {
case SIGSEGV:
/* Only returns on handle_sigsegv_accerr_write success. */
host_sigsegv_handler(cpu, info, uc);
return;
case SIGBUS:
host_sigbus_handler(cpu, info, uc);
sync_sig = true;
break;
}

/*
* If the access was not on behalf of the guest, within the executable
* mapping of the generated code buffer, then it is a host bug.
*/
if (access_type != MMU_INST_FETCH
&& !in_code_gen_buffer((void *)(pc - tcg_splitwx_diff))) {
die_from_signal(info);
}

if (host_sig == SIGSEGV) {
bool maperr = true;

if (info->si_code == SEGV_ACCERR && h2g_valid(host_addr)) {
/*
* With reserved_va, the whole address space is PROT_NONE,
* which means that we may get ACCERR when we want MAPERR.
*/
if (page_get_flags(guest_addr) & PAGE_VALID) {
maperr = false;
} else {
info->si_code = SEGV_MAPERR;
}
}

sigprocmask(SIG_SETMASK, sigmask, NULL);
cpu_loop_exit_sigsegv(cpu, guest_addr, access_type, maperr, pc);
} else {
sigprocmask(SIG_SETMASK, sigmask, NULL);
if (info->si_code == BUS_ADRALN) {
cpu_loop_exit_sigbus(cpu, guest_addr, access_type, pc);
}
}

sync_sig = true;
}

/* get target signal number */
Expand Down Expand Up @@ -929,6 +953,7 @@ static void host_signal_handler(int host_sig, siginfo_t *info, void *puc)
* would write 0xff bytes off the end of the structure and trash
* data on the struct.
*/
sigmask = host_signal_mask(uc);
memset(sigmask, 0xff, SIGSET_T_SIZE);
sigdelset(sigmask, SIGSEGV);
sigdelset(sigmask, SIGBUS);
Expand Down

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