* [PATCH] fexecve: implement in terms of execveat when it exists
@ 2018-09-02 4:04 Joseph Sible
2018-09-02 17:11 ` Rich Felker
0 siblings, 1 reply; 4+ messages in thread
From: Joseph Sible @ 2018-09-02 4:04 UTC (permalink / raw)
To: musl
This lets fexecve work even when /proc isn't mounted.
---
src/process/fexecve.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/src/process/fexecve.c b/src/process/fexecve.c
index 6507b42..905487e 100644
--- a/src/process/fexecve.c
+++ b/src/process/fexecve.c
@@ -1,13 +1,20 @@
+#define _GNU_SOURCE
#include <unistd.h>
#include <errno.h>
+#include <fcntl.h>
+#include "syscall.h"
void __procfdname(char *, unsigned);
int fexecve(int fd, char *const argv[], char *const envp[])
{
+#ifdef SYS_execveat
+ return syscall(SYS_execveat, fd, "", argv, envp, AT_EMPTY_PATH);
+#else
char buf[15 + 3*sizeof(int)];
__procfdname(buf, fd);
execve(buf, argv, envp);
if (errno == ENOENT) errno = EBADF;
return -1;
+#endif
}
--
2.7.4
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] fexecve: implement in terms of execveat when it exists
2018-09-02 4:04 [PATCH] fexecve: implement in terms of execveat when it exists Joseph Sible
@ 2018-09-02 17:11 ` Rich Felker
2018-09-02 17:42 ` Joseph C. Sible
0 siblings, 1 reply; 4+ messages in thread
From: Rich Felker @ 2018-09-02 17:11 UTC (permalink / raw)
To: musl
On Sun, Sep 02, 2018 at 12:04:55AM -0400, Joseph Sible wrote:
> This lets fexecve work even when /proc isn't mounted.
> ---
> src/process/fexecve.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/src/process/fexecve.c b/src/process/fexecve.c
> index 6507b42..905487e 100644
> --- a/src/process/fexecve.c
> +++ b/src/process/fexecve.c
> @@ -1,13 +1,20 @@
> +#define _GNU_SOURCE
> #include <unistd.h>
> #include <errno.h>
> +#include <fcntl.h>
> +#include "syscall.h"
>
> void __procfdname(char *, unsigned);
>
> int fexecve(int fd, char *const argv[], char *const envp[])
> {
> +#ifdef SYS_execveat
> + return syscall(SYS_execveat, fd, "", argv, envp, AT_EMPTY_PATH);
> +#else
> char buf[15 + 3*sizeof(int)];
> __procfdname(buf, fd);
> execve(buf, argv, envp);
> if (errno == ENOENT) errno = EBADF;
> return -1;
> +#endif
> }
> --
> 2.7.4
This breaks programs running on any kernel older than 3.19.
Instead it needs to be something like
int r = __syscall(SYS_execveat, fd, "", argv, envp, AT_EMPTY_PATH);
if (r!=-ENOSYS) return __syscall_ret(r);
...
with no #ifdef. #ifdef SYS_anything is only valid in musl when the
existence of the syscall is arch-specific. The defines come from musl
itself, so trying to use it for something version-specific does not
make sense; it would be unconditionally true or false.
Rich
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] fexecve: implement in terms of execveat when it exists
2018-09-02 17:11 ` Rich Felker
@ 2018-09-02 17:42 ` Joseph C. Sible
2018-09-04 23:30 ` Rich Felker
0 siblings, 1 reply; 4+ messages in thread
From: Joseph C. Sible @ 2018-09-02 17:42 UTC (permalink / raw)
To: musl
On Sun, Sep 2, 2018 at 1:11 PM Rich Felker <dalias@libc.org> wrote:
>
> On Sun, Sep 02, 2018 at 12:04:55AM -0400, Joseph Sible wrote:
> > This lets fexecve work even when /proc isn't mounted.
> > ---
> > src/process/fexecve.c | 7 +++++++
> > 1 file changed, 7 insertions(+)
> >
> > diff --git a/src/process/fexecve.c b/src/process/fexecve.c
> > index 6507b42..905487e 100644
> > --- a/src/process/fexecve.c
> > +++ b/src/process/fexecve.c
> > @@ -1,13 +1,20 @@
> > +#define _GNU_SOURCE
> > #include <unistd.h>
> > #include <errno.h>
> > +#include <fcntl.h>
> > +#include "syscall.h"
> >
> > void __procfdname(char *, unsigned);
> >
> > int fexecve(int fd, char *const argv[], char *const envp[])
> > {
> > +#ifdef SYS_execveat
> > + return syscall(SYS_execveat, fd, "", argv, envp, AT_EMPTY_PATH);
> > +#else
> > char buf[15 + 3*sizeof(int)];
> > __procfdname(buf, fd);
> > execve(buf, argv, envp);
> > if (errno == ENOENT) errno = EBADF;
> > return -1;
> > +#endif
> > }
> > --
> > 2.7.4
>
> This breaks programs running on any kernel older than 3.19.
>
> Instead it needs to be something like
>
> int r = __syscall(SYS_execveat, fd, "", argv, envp, AT_EMPTY_PATH);
> if (r!=-ENOSYS) return __syscall_ret(r);
> ...
>
> with no #ifdef. #ifdef SYS_anything is only valid in musl when the
> existence of the syscall is arch-specific. The defines come from musl
> itself, so trying to use it for something version-specific does not
> make sense; it would be unconditionally true or false.
>
> Rich
Good catch. Updated patch below.
-- >8 --
Subject: [PATCH v2] fexecve: implement in terms of execveat when it exists
This lets fexecve work even when /proc isn't mounted.
---
src/process/fexecve.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/src/process/fexecve.c b/src/process/fexecve.c
index 6507b42..5cac05e 100644
--- a/src/process/fexecve.c
+++ b/src/process/fexecve.c
@@ -1,10 +1,15 @@
+#define _GNU_SOURCE
#include <unistd.h>
#include <errno.h>
+#include <fcntl.h>
+#include "syscall.h"
void __procfdname(char *, unsigned);
int fexecve(int fd, char *const argv[], char *const envp[])
{
+ int r = __syscall(SYS_execveat, fd, "", argv, envp, AT_EMPTY_PATH);
+ if(r != -ENOSYS) return __syscall_ret(r);
char buf[15 + 3*sizeof(int)];
__procfdname(buf, fd);
execve(buf, argv, envp);
--
2.7.4
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] fexecve: implement in terms of execveat when it exists
2018-09-02 17:42 ` Joseph C. Sible
@ 2018-09-04 23:30 ` Rich Felker
0 siblings, 0 replies; 4+ messages in thread
From: Rich Felker @ 2018-09-04 23:30 UTC (permalink / raw)
To: musl
On Sun, Sep 02, 2018 at 01:42:26PM -0400, Joseph C. Sible wrote:
> On Sun, Sep 2, 2018 at 1:11 PM Rich Felker <dalias@libc.org> wrote:
> >
> > On Sun, Sep 02, 2018 at 12:04:55AM -0400, Joseph Sible wrote:
> > > This lets fexecve work even when /proc isn't mounted.
> > > ---
> > > src/process/fexecve.c | 7 +++++++
> > > 1 file changed, 7 insertions(+)
> > >
> > > diff --git a/src/process/fexecve.c b/src/process/fexecve.c
> > > index 6507b42..905487e 100644
> > > --- a/src/process/fexecve.c
> > > +++ b/src/process/fexecve.c
> > > @@ -1,13 +1,20 @@
> > > +#define _GNU_SOURCE
> > > #include <unistd.h>
> > > #include <errno.h>
> > > +#include <fcntl.h>
> > > +#include "syscall.h"
> > >
> > > void __procfdname(char *, unsigned);
> > >
> > > int fexecve(int fd, char *const argv[], char *const envp[])
> > > {
> > > +#ifdef SYS_execveat
> > > + return syscall(SYS_execveat, fd, "", argv, envp, AT_EMPTY_PATH);
> > > +#else
> > > char buf[15 + 3*sizeof(int)];
> > > __procfdname(buf, fd);
> > > execve(buf, argv, envp);
> > > if (errno == ENOENT) errno = EBADF;
> > > return -1;
> > > +#endif
> > > }
> > > --
> > > 2.7.4
> >
> > This breaks programs running on any kernel older than 3.19.
> >
> > Instead it needs to be something like
> >
> > int r = __syscall(SYS_execveat, fd, "", argv, envp, AT_EMPTY_PATH);
> > if (r!=-ENOSYS) return __syscall_ret(r);
> > ...
> >
> > with no #ifdef. #ifdef SYS_anything is only valid in musl when the
> > existence of the syscall is arch-specific. The defines come from musl
> > itself, so trying to use it for something version-specific does not
> > make sense; it would be unconditionally true or false.
> >
> > Rich
>
> Good catch. Updated patch below.
> -- >8 --
> Subject: [PATCH v2] fexecve: implement in terms of execveat when it exists
>
> This lets fexecve work even when /proc isn't mounted.
> ---
> src/process/fexecve.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/src/process/fexecve.c b/src/process/fexecve.c
> index 6507b42..5cac05e 100644
> --- a/src/process/fexecve.c
> +++ b/src/process/fexecve.c
> @@ -1,10 +1,15 @@
> +#define _GNU_SOURCE
> #include <unistd.h>
> #include <errno.h>
> +#include <fcntl.h>
> +#include "syscall.h"
>
> void __procfdname(char *, unsigned);
>
> int fexecve(int fd, char *const argv[], char *const envp[])
> {
> + int r = __syscall(SYS_execveat, fd, "", argv, envp, AT_EMPTY_PATH);
> + if(r != -ENOSYS) return __syscall_ret(r);
> char buf[15 + 3*sizeof(int)];
> __procfdname(buf, fd);
> execve(buf, argv, envp);
> --
> 2.7.4
Thanks, merging. In the future please send patches as attachments
(preferably type text/plain if it's easy to pick) unless you're sure
they'll apply correctly with git-am from the body.
Rich
^ permalink raw reply [flat|nested] 4+ messages in thread
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2018-09-02 4:04 [PATCH] fexecve: implement in terms of execveat when it exists Joseph Sible
2018-09-02 17:11 ` Rich Felker
2018-09-02 17:42 ` Joseph C. Sible
2018-09-04 23:30 ` Rich Felker
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