| Message ID | 20200708152435.706070-3-laurent@vivier.eu |
|---|---|
| State | New |
| Headers | show |
| Series | linux-user: fix print_syscall_err() | expand |
On 7/8/20 8:24 AM, Laurent Vivier wrote: > -static void > +static bool > print_syscall_err(abi_long ret) > { > - const char *errstr = NULL; > + const char *errstr; > > qemu_log(" = "); > if (ret < 0) { This should be a target-specific test. E.g. on most asm-generic I'm pretty sure this should be if ((abi_ulong)ret > -(abi_ulong)512) whereas for Alpha it should be /* * Syscall writes 0 to V0 to bypass error check, similar * to how this is handled internal to Linux kernel. */ if (ret < 0 && env->ir[IR_V0] != 0) r~
Le 08/07/2020 à 17:52, Richard Henderson a écrit : > On 7/8/20 8:24 AM, Laurent Vivier wrote: >> -static void >> +static bool >> print_syscall_err(abi_long ret) >> { >> - const char *errstr = NULL; >> + const char *errstr; >> >> qemu_log(" = "); >> if (ret < 0) { > > This should be a target-specific test. > > E.g. on most asm-generic I'm pretty sure this should be > > if ((abi_ulong)ret > -(abi_ulong)512) I think the test in target_strerror() gives the same result: if ((err >= ERRNO_TABLE_SIZE) || (err < 0)) { return NULL; } and it also ensures we don't overflow when we will access target_to_host_errno_table[]. It's why we rely on errstr to know if the errno is valid or not (we might also remove the "if (ret < 0)" in print_syscall_err). > whereas for Alpha it should be > > /* > * Syscall writes 0 to V0 to bypass error check, similar > * to how this is handled internal to Linux kernel. > */ > if (ret < 0 && env->ir[IR_V0] != 0) We don't have access to "env" in strace.c. it's an improvement regarding the code that has been modified. If we want it I think it should be added in a separate patch. Thanks, Laurent
Le 08/07/2020 à 17:24, Laurent Vivier a écrit : > print_syscall_err() relies on the sign of the returned value to know > if it is an errno value or not. > > But in some cases the returned value can have the most signicant bit > set without being an errno. > > This patch restores previous behaviour that was also checking if > we can decode the errno to validate it. > > This patch fixes this kind of problem (qemu-m68k): > > root@sid:/# QEMU_STRACE= ls > 3 brk(NULL) = -1 errno=21473607683 uname(0x407fff8a) = 0 > > to become: > > root@sid:/# QEMU_STRACE= ls > 3 brk(NULL) = 0x8001e000 > 3 uname(0xffffdf8a) = 0 > > Fixes: c84be71f6854 ("linux-user: Extend strace support to enable argument printing after syscall execution") > Cc: Filip.Bozuta@syrmia.com > Signed-off-by: Laurent Vivier <laurent@vivier.eu> > --- > linux-user/strace.c | 36 +++++++++++++----------------------- > 1 file changed, 13 insertions(+), 23 deletions(-) > > diff --git a/linux-user/strace.c b/linux-user/strace.c > index b42664bbd180..17f2554643f0 100644 > --- a/linux-user/strace.c > +++ b/linux-user/strace.c > @@ -724,19 +724,20 @@ print_ipc(const struct syscallname *name, > * Variants for the return value output function > */ > > -static void > +static bool > print_syscall_err(abi_long ret) > { > - const char *errstr = NULL; > + const char *errstr; > > qemu_log(" = "); > if (ret < 0) { > - qemu_log("-1 errno=%d", (int)-ret); > errstr = target_strerror(-ret); > if (errstr) { > - qemu_log(" (%s)", errstr); > + qemu_log("-1 errno=%d (%s)", (int)-ret, errstr); > + return true; > } > } > + return false; > } > > static void > @@ -744,11 +745,10 @@ print_syscall_ret_addr(const struct syscallname *name, abi_long ret, > abi_long arg0, abi_long arg1, abi_long arg2, > abi_long arg3, abi_long arg4, abi_long arg5) > { > - print_syscall_err(ret); > - > - if (ret >= 0) { > - qemu_log("0x" TARGET_ABI_FMT_lx "\n", ret); > + if (!print_syscall_err(ret)) { > + qemu_log("0x" TARGET_ABI_FMT_lx, ret); > } > + qemu_log("\n"); > } > > #if 0 /* currently unused */ > @@ -765,9 +765,7 @@ print_syscall_ret_newselect(const struct syscallname *name, abi_long ret, > abi_long arg0, abi_long arg1, abi_long arg2, > abi_long arg3, abi_long arg4, abi_long arg5) > { > - print_syscall_err(ret); > - > - if (ret >= 0) { > + if (!print_syscall_err(ret)) { > qemu_log(" = 0x" TARGET_ABI_FMT_lx " (", ret); > print_fdset(arg0, arg1); > qemu_log(","); > @@ -796,9 +794,7 @@ print_syscall_ret_adjtimex(const struct syscallname *name, abi_long ret, > abi_long arg0, abi_long arg1, abi_long arg2, > abi_long arg3, abi_long arg4, abi_long arg5) > { > - print_syscall_err(ret); > - > - if (ret >= 0) { > + if (!print_syscall_err(ret)) { > qemu_log(TARGET_ABI_FMT_ld, ret); > switch (ret) { > case TARGET_TIME_OK: > @@ -833,9 +829,7 @@ print_syscall_ret_listxattr(const struct syscallname *name, abi_long ret, > abi_long arg0, abi_long arg1, abi_long arg2, > abi_long arg3, abi_long arg4, abi_long arg5) > { > - print_syscall_err(ret); > - > - if (ret >= 0) { > + if (!print_syscall_err(ret)) { > qemu_log(TARGET_ABI_FMT_ld, ret); > qemu_log(" (list = "); > if (arg1 != 0) { > @@ -866,9 +860,7 @@ print_syscall_ret_ioctl(const struct syscallname *name, abi_long ret, > abi_long arg0, abi_long arg1, abi_long arg2, > abi_long arg3, abi_long arg4, abi_long arg5) > { > - print_syscall_err(ret); > - > - if (ret >= 0) { > + if (!print_syscall_err(ret)) { > qemu_log(TARGET_ABI_FMT_ld, ret); > > const IOCTLEntry *ie; > @@ -3189,9 +3181,7 @@ print_syscall_ret(int num, abi_long ret, > arg1, arg2, arg3, > arg4, arg5, arg6); > } else { > - print_syscall_err(ret); > - > - if (ret >= 0) { > + if (!print_syscall_err(ret)) { > qemu_log(TARGET_ABI_FMT_ld, ret); > } > qemu_log("\n"); > Applied to my linux-user-for-5.1 branch. Richard: I agree with your comment but I'd like to fix the regression before the hard freeze. Filip is currently working on some improvements in strace functions that will allow to have access to env variable. So we will be able to have a target-specific test as you suggested. Thanks, Laurent
diff --git a/linux-user/strace.c b/linux-user/strace.c index b42664bbd180..17f2554643f0 100644 --- a/linux-user/strace.c +++ b/linux-user/strace.c @@ -724,19 +724,20 @@ print_ipc(const struct syscallname *name, * Variants for the return value output function */ -static void +static bool print_syscall_err(abi_long ret) { - const char *errstr = NULL; + const char *errstr; qemu_log(" = "); if (ret < 0) { - qemu_log("-1 errno=%d", (int)-ret); errstr = target_strerror(-ret); if (errstr) { - qemu_log(" (%s)", errstr); + qemu_log("-1 errno=%d (%s)", (int)-ret, errstr); + return true; } } + return false; } static void @@ -744,11 +745,10 @@ print_syscall_ret_addr(const struct syscallname *name, abi_long ret, abi_long arg0, abi_long arg1, abi_long arg2, abi_long arg3, abi_long arg4, abi_long arg5) { - print_syscall_err(ret); - - if (ret >= 0) { - qemu_log("0x" TARGET_ABI_FMT_lx "\n", ret); + if (!print_syscall_err(ret)) { + qemu_log("0x" TARGET_ABI_FMT_lx, ret); } + qemu_log("\n"); } #if 0 /* currently unused */ @@ -765,9 +765,7 @@ print_syscall_ret_newselect(const struct syscallname *name, abi_long ret, abi_long arg0, abi_long arg1, abi_long arg2, abi_long arg3, abi_long arg4, abi_long arg5) { - print_syscall_err(ret); - - if (ret >= 0) { + if (!print_syscall_err(ret)) { qemu_log(" = 0x" TARGET_ABI_FMT_lx " (", ret); print_fdset(arg0, arg1); qemu_log(","); @@ -796,9 +794,7 @@ print_syscall_ret_adjtimex(const struct syscallname *name, abi_long ret, abi_long arg0, abi_long arg1, abi_long arg2, abi_long arg3, abi_long arg4, abi_long arg5) { - print_syscall_err(ret); - - if (ret >= 0) { + if (!print_syscall_err(ret)) { qemu_log(TARGET_ABI_FMT_ld, ret); switch (ret) { case TARGET_TIME_OK: @@ -833,9 +829,7 @@ print_syscall_ret_listxattr(const struct syscallname *name, abi_long ret, abi_long arg0, abi_long arg1, abi_long arg2, abi_long arg3, abi_long arg4, abi_long arg5) { - print_syscall_err(ret); - - if (ret >= 0) { + if (!print_syscall_err(ret)) { qemu_log(TARGET_ABI_FMT_ld, ret); qemu_log(" (list = "); if (arg1 != 0) { @@ -866,9 +860,7 @@ print_syscall_ret_ioctl(const struct syscallname *name, abi_long ret, abi_long arg0, abi_long arg1, abi_long arg2, abi_long arg3, abi_long arg4, abi_long arg5) { - print_syscall_err(ret); - - if (ret >= 0) { + if (!print_syscall_err(ret)) { qemu_log(TARGET_ABI_FMT_ld, ret); const IOCTLEntry *ie; @@ -3189,9 +3181,7 @@ print_syscall_ret(int num, abi_long ret, arg1, arg2, arg3, arg4, arg5, arg6); } else { - print_syscall_err(ret); - - if (ret >= 0) { + if (!print_syscall_err(ret)) { qemu_log(TARGET_ABI_FMT_ld, ret); } qemu_log("\n");
print_syscall_err() relies on the sign of the returned value to know if it is an errno value or not. But in some cases the returned value can have the most signicant bit set without being an errno. This patch restores previous behaviour that was also checking if we can decode the errno to validate it. This patch fixes this kind of problem (qemu-m68k): root@sid:/# QEMU_STRACE= ls 3 brk(NULL) = -1 errno=21473607683 uname(0x407fff8a) = 0 to become: root@sid:/# QEMU_STRACE= ls 3 brk(NULL) = 0x8001e000 3 uname(0xffffdf8a) = 0 Fixes: c84be71f6854 ("linux-user: Extend strace support to enable argument printing after syscall execution") Cc: Filip.Bozuta@syrmia.com Signed-off-by: Laurent Vivier <laurent@vivier.eu> --- linux-user/strace.c | 36 +++++++++++++----------------------- 1 file changed, 13 insertions(+), 23 deletions(-)