| Message ID | 20210918184527.408540-21-richard.henderson@linaro.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | linux-user: Streamline handling of SIGSEGV | expand |
On 9/18/21 20:45, Richard Henderson wrote: > This is a new interface to be provided by the os emulator > for raising SIGSEGV on fault. Use the new record_sigsegv > target hook. > > Signed-off-by: Richard Henderson <richard.henderson@linaro.org> > --- > include/exec/exec-all.h | 15 +++++++++++++++ > accel/tcg/user-exec.c | 33 ++++++++++++++++++--------------- > linux-user/signal.c | 30 ++++++++++++++++++++++-------- > 3 files changed, 55 insertions(+), 23 deletions(-) To the best of my knowledge: Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
On 9/18/21 11:45 AM, Richard Henderson wrote: > +/** > + * raise_sigsegv: > + * @cpu: the cpu context > + * @addr: the guest address of the fault > + * @access_type: access was read/write/execute > + * @maperr: true for invalid page, false for permission fault > + * @ra: host pc for unwinding > + * > + * Use the TCGCPUOps hook to record cpu state, do guest operating system > + * specific things to raise SIGSEGV, and jump to the main cpu loop. > + */ > +void QEMU_NORETURN raise_sigsegv(CPUState *cpu, target_ulong addr, > + MMUAccessType access_type, > + bool maperr, uintptr_t ra); FYI, something to bikeshed here is the name of the function. Should it in fact be cpu_loop_exit_raise_sigsegv? Because it can't be used outside of the running cpu context. (E.g. there are a couple of instances where it's tempting to use this from within cpu_loop itself, processing pseudo-syscalls.) r~
On 9/19/21 20:35, Richard Henderson wrote: > On 9/18/21 11:45 AM, Richard Henderson wrote: >> +/** >> + * raise_sigsegv: >> + * @cpu: the cpu context >> + * @addr: the guest address of the fault >> + * @access_type: access was read/write/execute >> + * @maperr: true for invalid page, false for permission fault >> + * @ra: host pc for unwinding >> + * >> + * Use the TCGCPUOps hook to record cpu state, do guest operating system >> + * specific things to raise SIGSEGV, and jump to the main cpu loop. >> + */ >> +void QEMU_NORETURN raise_sigsegv(CPUState *cpu, target_ulong addr, >> + MMUAccessType access_type, >> + bool maperr, uintptr_t ra); > > FYI, something to bikeshed here is the name of the function. Should it > in fact be cpu_loop_exit_raise_sigsegv? That or cpu_loop_exit_segv() which is explicit enough IMO. > Because it can't be used outside of the running cpu context. (E.g. > there are a couple of instances where it's tempting to use this from > within cpu_loop itself, processing pseudo-syscalls.) > > > r~ >
> On Sep 19, 2021, at 12:43 PM, Philippe Mathieu-Daudé <f4bug@amsat.org> wrote: > > On 9/19/21 20:35, Richard Henderson wrote: >> On 9/18/21 11:45 AM, Richard Henderson wrote: >>> +/** >>> + * raise_sigsegv: >>> + * @cpu: the cpu context >>> + * @addr: the guest address of the fault >>> + * @access_type: access was read/write/execute >>> + * @maperr: true for invalid page, false for permission fault >>> + * @ra: host pc for unwinding >>> + * >>> + * Use the TCGCPUOps hook to record cpu state, do guest operating system >>> + * specific things to raise SIGSEGV, and jump to the main cpu loop. >>> + */ >>> +void QEMU_NORETURN raise_sigsegv(CPUState *cpu, target_ulong addr, >>> + MMUAccessType access_type, >>> + bool maperr, uintptr_t ra); >> >> FYI, something to bikeshed here is the name of the function. Should it >> in fact be cpu_loop_exit_raise_sigsegv? > > That or cpu_loop_exit_segv() which is explicit enough IMO. That name works for me… Also, and this is a stretch so consider it maybe a bit weak… Reviewed by: Warner Losh <imp@bsdimp.com> > Because it can't be used outside of the running cpu context. (E.g. >> >> there are a couple of instances where it's tempting to use this from >> within cpu_loop itself, processing pseudo-syscalls.) >> >> >> r~ >> > >
diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h index 5dd663c153..2091c1bf1a 100644 --- a/include/exec/exec-all.h +++ b/include/exec/exec-all.h @@ -685,6 +685,21 @@ MMUAccessType adjust_signal_pc(uintptr_t *pc, bool is_write); bool handle_sigsegv_accerr_write(CPUState *cpu, sigset_t *old_set, uintptr_t host_pc, abi_ptr guest_addr); +/** + * raise_sigsegv: + * @cpu: the cpu context + * @addr: the guest address of the fault + * @access_type: access was read/write/execute + * @maperr: true for invalid page, false for permission fault + * @ra: host pc for unwinding + * + * Use the TCGCPUOps hook to record cpu state, do guest operating system + * specific things to raise SIGSEGV, and jump to the main cpu loop. + */ +void QEMU_NORETURN raise_sigsegv(CPUState *cpu, target_ulong addr, + MMUAccessType access_type, + bool maperr, uintptr_t ra); + #else static inline void mmap_lock(void) {} static inline void mmap_unlock(void) {} diff --git a/accel/tcg/user-exec.c b/accel/tcg/user-exec.c index 01e7e69e7f..ab9cc6686d 100644 --- a/accel/tcg/user-exec.c +++ b/accel/tcg/user-exec.c @@ -143,35 +143,38 @@ static int probe_access_internal(CPUArchState *env, target_ulong addr, int fault_size, MMUAccessType access_type, bool nonfault, uintptr_t ra) { - int flags; + bool maperr = true; + int acc_flag; switch (access_type) { case MMU_DATA_STORE: - flags = PAGE_WRITE; + acc_flag = PAGE_WRITE_ORG; break; case MMU_DATA_LOAD: - flags = PAGE_READ; + acc_flag = PAGE_READ; break; case MMU_INST_FETCH: - flags = PAGE_EXEC; + acc_flag = PAGE_EXEC; break; default: g_assert_not_reached(); } - if (!guest_addr_valid_untagged(addr) || - page_check_range(addr, 1, flags) < 0) { - if (nonfault) { - return TLB_INVALID_MASK; - } else { - CPUState *cpu = env_cpu(env); - CPUClass *cc = CPU_GET_CLASS(cpu); - cc->tcg_ops->tlb_fill(cpu, addr, fault_size, access_type, - MMU_USER_IDX, false, ra); - g_assert_not_reached(); + if (guest_addr_valid_untagged(addr)) { + int page_flags = page_get_flags(addr); + if (page_flags & acc_flag) { + return 0; /* success */ + } + if (page_flags & PAGE_VALID) { + maperr = false; } } - return 0; + + if (nonfault) { + return TLB_INVALID_MASK; + } + + raise_sigsegv(env_cpu(env), addr, access_type, maperr, ra); } int probe_access_flags(CPUArchState *env, target_ulong addr, diff --git a/linux-user/signal.c b/linux-user/signal.c index e6531fdfa0..ae31b46be0 100644 --- a/linux-user/signal.c +++ b/linux-user/signal.c @@ -681,9 +681,27 @@ void force_sigsegv(int oldsig) } force_sig(TARGET_SIGSEGV); } - #endif +void raise_sigsegv(CPUState *cpu, target_ulong addr, + MMUAccessType access_type, bool maperr, uintptr_t ra) +{ + const struct TCGCPUOps *tcg_ops = CPU_GET_CLASS(cpu)->tcg_ops; + + if (tcg_ops->record_sigsegv) { + tcg_ops->record_sigsegv(cpu, addr, access_type, maperr, ra); + } else if (tcg_ops->tlb_fill) { + tcg_ops->tlb_fill(cpu, addr, 0, access_type, MMU_USER_IDX, false, ra); + g_assert_not_reached(); + } + + force_sig_fault(TARGET_SIGSEGV, + maperr ? TARGET_SEGV_MAPERR : TARGET_SEGV_ACCERR, + addr); + cpu->exception_index = EXCP_INTERRUPT; + cpu_loop_exit_restore(cpu, ra); +} + /* abort execution with signal */ static void QEMU_NORETURN dump_core_and_abort(int target_sig) { @@ -799,7 +817,7 @@ static void host_signal_handler(int host_sig, siginfo_t *info, void *puc) access_type = adjust_signal_pc(&pc, is_write); if (host_sig == SIGSEGV) { - const struct TCGCPUOps *tcg_ops; + bool maperr = true; if (info->si_code == SEGV_ACCERR && h2g_valid(host_addr)) { /* If this was a write to a TB protected page, restart. */ @@ -814,18 +832,14 @@ static void host_signal_handler(int host_sig, siginfo_t *info, void *puc) * which means that we may get ACCERR when we want MAPERR. */ if (page_get_flags(guest_addr) & PAGE_VALID) { - /* maperr = false; */ + maperr = false; } else { info->si_code = SEGV_MAPERR; } } sigprocmask(SIG_SETMASK, &uc->uc_sigmask, NULL); - - tcg_ops = CPU_GET_CLASS(cpu)->tcg_ops; - tcg_ops->tlb_fill(cpu, guest_addr, 0, access_type, - MMU_USER_IDX, false, pc); - g_assert_not_reached(); + raise_sigsegv(cpu, guest_addr, access_type, maperr, pc); } else { sigprocmask(SIG_SETMASK, &uc->uc_sigmask, NULL); }
This is a new interface to be provided by the os emulator for raising SIGSEGV on fault. Use the new record_sigsegv target hook. Signed-off-by: Richard Henderson <richard.henderson@linaro.org> --- include/exec/exec-all.h | 15 +++++++++++++++ accel/tcg/user-exec.c | 33 ++++++++++++++++++--------------- linux-user/signal.c | 30 ++++++++++++++++++++++-------- 3 files changed, 55 insertions(+), 23 deletions(-)