| Message ID | 20210924165926.752809-11-richard.henderson@linaro.org |
|---|---|
| State | Superseded |
| Headers | show |
| Series | linux-user: Move signal trampolines to new page | expand |
On 9/24/21 18:59, Richard Henderson wrote: > Create and record the two signal trampolines. > Use them when the guest does not use SA_RESTORER. > Note that x86_64 does not use this code. > > Signed-off-by: Richard Henderson <richard.henderson@linaro.org> > --- > linux-user/i386/target_signal.h | 2 ++ > linux-user/x86_64/target_signal.h | 3 ++ > linux-user/i386/signal.c | 56 +++++++++++++++++++++---------- > 3 files changed, 43 insertions(+), 18 deletions(-) > > diff --git a/linux-user/i386/target_signal.h b/linux-user/i386/target_signal.h > index 50361af874..64d09f2e75 100644 > --- a/linux-user/i386/target_signal.h > +++ b/linux-user/i386/target_signal.h > @@ -22,4 +22,6 @@ typedef struct target_sigaltstack { > #include "../generic/signal.h" > > #define TARGET_ARCH_HAS_SETUP_FRAME > +#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 1 > + > #endif /* I386_TARGET_SIGNAL_H */ > diff --git a/linux-user/x86_64/target_signal.h b/linux-user/x86_64/target_signal.h > index 4ea74f20dd..4673c5a886 100644 > --- a/linux-user/x86_64/target_signal.h > +++ b/linux-user/x86_64/target_signal.h > @@ -21,4 +21,7 @@ typedef struct target_sigaltstack { > > #include "../generic/signal.h" > > +/* For x86_64, use of SA_RESTORER is mandatory. */ > +#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 0 > + > #endif /* X86_64_TARGET_SIGNAL_H */ > diff --git a/linux-user/i386/signal.c b/linux-user/i386/signal.c > index 3b4b55fc0a..94ab6396a0 100644 > --- a/linux-user/i386/signal.c > +++ b/linux-user/i386/signal.c > @@ -310,6 +310,22 @@ get_sigframe(struct target_sigaction *ka, CPUX86State *env, size_t frame_size) > } > > #ifndef TARGET_X86_64 > +static void install_sigtramp(void *tramp) > +{ > + /* This is popl %eax ; movl $syscall,%eax ; int $0x80 */ > + __put_user(0xb858, (uint16_t *)(tramp + 0)); > + __put_user(TARGET_NR_sigreturn, (int *)(tramp + 2)); I know this is mostly code movement, but using uint32_t would make it easier to read. > + __put_user(0x80cd, (uint16_t *)(tramp + 6)); > +} > + > +static void install_rt_sigtramp(void *tramp) > +{ > + /* This is movl $syscall,%eax ; int $0x80 */ > + __put_user(0xb8, (char *)(tramp + 0)); Ditto uint8_t, > + __put_user(TARGET_NR_rt_sigreturn, (int *)(tramp + 1)); and uint32_t. > + __put_user(0x80cd, (uint16_t *)(tramp + 5)); > +} > + > /* compare linux/arch/i386/kernel/signal.c:setup_frame() */ > void setup_frame(int sig, struct target_sigaction *ka, > target_sigset_t *set, CPUX86State *env) > @@ -338,16 +354,9 @@ void setup_frame(int sig, struct target_sigaction *ka, > if (ka->sa_flags & TARGET_SA_RESTORER) { > __put_user(ka->sa_restorer, &frame->pretcode); > } else { > - uint16_t val16; > - abi_ulong retcode_addr; > - retcode_addr = frame_addr + offsetof(struct sigframe, retcode); > - __put_user(retcode_addr, &frame->pretcode); > - /* This is popl %eax ; movl $,%eax ; int $0x80 */ > - val16 = 0xb858; > - __put_user(val16, (uint16_t *)(frame->retcode+0)); > - __put_user(TARGET_NR_sigreturn, (int *)(frame->retcode+2)); > - val16 = 0x80cd; > - __put_user(val16, (uint16_t *)(frame->retcode+6)); > + /* This is no longer used, but is retained for ABI compatibility. */ > + install_sigtramp(frame->retcode); > + __put_user(default_sigreturn, &frame->pretcode); > } > > /* Set up registers for signal handler */ > @@ -416,14 +425,9 @@ void setup_rt_frame(int sig, struct target_sigaction *ka, > if (ka->sa_flags & TARGET_SA_RESTORER) { > __put_user(ka->sa_restorer, &frame->pretcode); > } else { > - uint16_t val16; > - addr = frame_addr + offsetof(struct rt_sigframe, retcode); > - __put_user(addr, &frame->pretcode); > - /* This is movl $,%eax ; int $0x80 */ > - __put_user(0xb8, (char *)(frame->retcode+0)); > - __put_user(TARGET_NR_rt_sigreturn, (int *)(frame->retcode+1)); > - val16 = 0x80cd; > - __put_user(val16, (uint16_t *)(frame->retcode+5)); > + /* This is no longer used, but is retained for ABI compatibility. */ > + install_rt_sigtramp(frame->retcode); > + __put_user(default_rt_sigreturn, &frame->pretcode); > } > #else > /* XXX: Would be slightly better to return -EFAULT here if test fails > @@ -592,3 +596,19 @@ badframe: > force_sig(TARGET_SIGSEGV); > return -TARGET_QEMU_ESIGRETURN; > } > + > +#ifndef TARGET_X86_64 > +void setup_sigtramp(abi_ulong sigtramp_page) > +{ > + uint16_t *tramp = lock_user(VERIFY_WRITE, sigtramp_page, 2 * 8, 0); Shouldn't this be 8 + 7? > + assert(tramp != NULL); > + > + default_sigreturn = sigtramp_page; > + install_sigtramp(tramp); > + > + default_rt_sigreturn = sigtramp_page + 8; > + install_rt_sigtramp(tramp + 8); > + > + unlock_user(tramp, sigtramp_page, 2 * 8); > +} > +#endif >
On 9/24/21 2:01 PM, Philippe Mathieu-Daudé wrote: >> +static void install_sigtramp(void *tramp) >> +{ >> + /* This is popl %eax ; movl $syscall,%eax ; int $0x80 */ >> + __put_user(0xb858, (uint16_t *)(tramp + 0)); >> + __put_user(TARGET_NR_sigreturn, (int *)(tramp + 2)); > > I know this is mostly code movement, but using uint32_t would > make it easier to read. I'll give you int32_t here, since the value is signed. >> + __put_user(TARGET_NR_rt_sigreturn, (int *)(tramp + 1)); > > and uint32_t. Likewise. >> + uint16_t *tramp = lock_user(VERIFY_WRITE, sigtramp_page, 2 * 8, 0); > > Shouldn't this be 8 + 7? Does it really matter if we write 15 or 16 bytes of this page? r~
On Tue, Sep 28, 2021 at 3:42 AM Richard Henderson <richard.henderson@linaro.org> wrote: > On 9/24/21 2:01 PM, Philippe Mathieu-Daudé wrote: > >> +static void install_sigtramp(void *tramp) > >> +{ > >> + /* This is popl %eax ; movl $syscall,%eax ; int $0x80 */ > >> + __put_user(0xb858, (uint16_t *)(tramp + 0)); > >> + __put_user(TARGET_NR_sigreturn, (int *)(tramp + 2)); > > > > I know this is mostly code movement, but using uint32_t would > > make it easier to read. > > I'll give you int32_t here, since the value is signed. Better, thanks. > > >> + __put_user(TARGET_NR_rt_sigreturn, (int *)(tramp + 1)); > > > > and uint32_t. > > Likewise. > > >> + uint16_t *tramp = lock_user(VERIFY_WRITE, sigtramp_page, 2 * 8, 0); > > > > Shouldn't this be 8 + 7? > > Does it really matter if we write 15 or 16 bytes of this page? Certainly not :)
diff --git a/linux-user/i386/target_signal.h b/linux-user/i386/target_signal.h index 50361af874..64d09f2e75 100644 --- a/linux-user/i386/target_signal.h +++ b/linux-user/i386/target_signal.h @@ -22,4 +22,6 @@ typedef struct target_sigaltstack { #include "../generic/signal.h" #define TARGET_ARCH_HAS_SETUP_FRAME +#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 1 + #endif /* I386_TARGET_SIGNAL_H */ diff --git a/linux-user/x86_64/target_signal.h b/linux-user/x86_64/target_signal.h index 4ea74f20dd..4673c5a886 100644 --- a/linux-user/x86_64/target_signal.h +++ b/linux-user/x86_64/target_signal.h @@ -21,4 +21,7 @@ typedef struct target_sigaltstack { #include "../generic/signal.h" +/* For x86_64, use of SA_RESTORER is mandatory. */ +#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 0 + #endif /* X86_64_TARGET_SIGNAL_H */ diff --git a/linux-user/i386/signal.c b/linux-user/i386/signal.c index 3b4b55fc0a..94ab6396a0 100644 --- a/linux-user/i386/signal.c +++ b/linux-user/i386/signal.c @@ -310,6 +310,22 @@ get_sigframe(struct target_sigaction *ka, CPUX86State *env, size_t frame_size) } #ifndef TARGET_X86_64 +static void install_sigtramp(void *tramp) +{ + /* This is popl %eax ; movl $syscall,%eax ; int $0x80 */ + __put_user(0xb858, (uint16_t *)(tramp + 0)); + __put_user(TARGET_NR_sigreturn, (int *)(tramp + 2)); + __put_user(0x80cd, (uint16_t *)(tramp + 6)); +} + +static void install_rt_sigtramp(void *tramp) +{ + /* This is movl $syscall,%eax ; int $0x80 */ + __put_user(0xb8, (char *)(tramp + 0)); + __put_user(TARGET_NR_rt_sigreturn, (int *)(tramp + 1)); + __put_user(0x80cd, (uint16_t *)(tramp + 5)); +} + /* compare linux/arch/i386/kernel/signal.c:setup_frame() */ void setup_frame(int sig, struct target_sigaction *ka, target_sigset_t *set, CPUX86State *env) @@ -338,16 +354,9 @@ void setup_frame(int sig, struct target_sigaction *ka, if (ka->sa_flags & TARGET_SA_RESTORER) { __put_user(ka->sa_restorer, &frame->pretcode); } else { - uint16_t val16; - abi_ulong retcode_addr; - retcode_addr = frame_addr + offsetof(struct sigframe, retcode); - __put_user(retcode_addr, &frame->pretcode); - /* This is popl %eax ; movl $,%eax ; int $0x80 */ - val16 = 0xb858; - __put_user(val16, (uint16_t *)(frame->retcode+0)); - __put_user(TARGET_NR_sigreturn, (int *)(frame->retcode+2)); - val16 = 0x80cd; - __put_user(val16, (uint16_t *)(frame->retcode+6)); + /* This is no longer used, but is retained for ABI compatibility. */ + install_sigtramp(frame->retcode); + __put_user(default_sigreturn, &frame->pretcode); } /* Set up registers for signal handler */ @@ -416,14 +425,9 @@ void setup_rt_frame(int sig, struct target_sigaction *ka, if (ka->sa_flags & TARGET_SA_RESTORER) { __put_user(ka->sa_restorer, &frame->pretcode); } else { - uint16_t val16; - addr = frame_addr + offsetof(struct rt_sigframe, retcode); - __put_user(addr, &frame->pretcode); - /* This is movl $,%eax ; int $0x80 */ - __put_user(0xb8, (char *)(frame->retcode+0)); - __put_user(TARGET_NR_rt_sigreturn, (int *)(frame->retcode+1)); - val16 = 0x80cd; - __put_user(val16, (uint16_t *)(frame->retcode+5)); + /* This is no longer used, but is retained for ABI compatibility. */ + install_rt_sigtramp(frame->retcode); + __put_user(default_rt_sigreturn, &frame->pretcode); } #else /* XXX: Would be slightly better to return -EFAULT here if test fails @@ -592,3 +596,19 @@ badframe: force_sig(TARGET_SIGSEGV); return -TARGET_QEMU_ESIGRETURN; } + +#ifndef TARGET_X86_64 +void setup_sigtramp(abi_ulong sigtramp_page) +{ + uint16_t *tramp = lock_user(VERIFY_WRITE, sigtramp_page, 2 * 8, 0); + assert(tramp != NULL); + + default_sigreturn = sigtramp_page; + install_sigtramp(tramp); + + default_rt_sigreturn = sigtramp_page + 8; + install_rt_sigtramp(tramp + 8); + + unlock_user(tramp, sigtramp_page, 2 * 8); +} +#endif
Create and record the two signal trampolines. Use them when the guest does not use SA_RESTORER. Note that x86_64 does not use this code. Signed-off-by: Richard Henderson <richard.henderson@linaro.org> --- linux-user/i386/target_signal.h | 2 ++ linux-user/x86_64/target_signal.h | 3 ++ linux-user/i386/signal.c | 56 +++++++++++++++++++++---------- 3 files changed, 43 insertions(+), 18 deletions(-) -- 2.25.1