powerpc/32: Remove powerpc select specialisation

Syscall #82 has been implemented for 32-bit platforms in a unique way on
powerpc systems. This hack will in effect guess whether the caller is
expecting new select semantics or old select semantics. It does so via a
guess, based off the first parameter. In new select, this parameter
represents the length of a user-memory array of file descriptors, and in
old select this is a pointer to an arguments structure.

The heuristic simply interprets sufficiently large values of its first
parameter as being a call to old select. The following is a discussion
on how this syscall should be handled.

As discussed in this thread, the existence of such a hack suggests that for
whatever powerpc binaries may predate glibc, it is most likely that they
would have taken use of the old select semantics. x86 and arm64 both
implement this syscall with oldselect semantics.

Remove the powerpc implementation, and update syscall.tbl to refer to emit
a reference to sys_old_select and compat_sys_old_select
for 32-bit binaries, in keeping with how other architectures support
syscall #82.

Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/lkml/13737de5-0eb7-e881-9af0-163b0d29a1a0@csgroup.eu/
Link: https://lore.kernel.org/r/20220921065605.1051927-12-rmclure@linux.ibm.com

diff --git a/arch/powerpc/include/asm/syscalls.h b/arch/powerpc/include/asm/syscalls.h
index 52f5e198598993d613d01d01913c116fb0495e34..565b4b1d7d415166562b26c40bd0e36af9210dad 100644 (file)
--- a/arch/powerpc/include/asm/syscalls.h
+++ b/arch/powerpc/include/asm/syscalls.h
@@ -30,8 +30,6 @@ long sys_mmap2(unsigned long addr, size_t len,
               unsigned long fd, unsigned long pgoff);
 long ppc64_personality(unsigned long personality);
 long sys_rtas(struct rtas_args __user *uargs);
-int ppc_select(int n, fd_set __user *inp, fd_set __user *outp,
-              fd_set __user *exp, struct __kernel_old_timeval __user *tvp);
 long ppc_fadvise64_64(int fd, int advice, u32 offset_high, u32 offset_low,
                      u32 len_high, u32 len_low);
 

diff --git a/arch/powerpc/kernel/syscalls.c b/arch/powerpc/kernel/syscalls.c
index abc3fbb3c4902a7c9556183e9b71c8d529aba65d..34e1ae88e15b615345cf7232be9be5e90b4fec00 100644 (file)
--- a/arch/powerpc/kernel/syscalls.c
+++ b/arch/powerpc/kernel/syscalls.c
@@ -63,23 +63,6 @@ SYSCALL_DEFINE6(mmap, unsigned long, addr, size_t, len,
        return do_mmap2(addr, len, prot, flags, fd, offset, PAGE_SHIFT);
 }
 
-#ifdef CONFIG_PPC32
-/*
- * Due to some executables calling the wrong select we sometimes
- * get wrong args.  This determines how the args are being passed
- * (a single ptr to them all args passed) then calls
- * sys_select() with the appropriate args. -- Cort
- */
-int
-ppc_select(int n, fd_set __user *inp, fd_set __user *outp, fd_set __user *exp, struct __kernel_old_timeval __user *tvp)
-{
-       if ((unsigned long)n >= 4096)
-               return sys_old_select((void __user *)n);
-
-       return sys_select(n, inp, outp, exp, tvp);
-}
-#endif
-
 #ifdef CONFIG_PPC64
 long ppc64_personality(unsigned long personality)
 {

diff --git a/arch/powerpc/kernel/syscalls/syscall.tbl b/arch/powerpc/kernel/syscalls/syscall.tbl
index 2600b4237292c78c44363159a02eaca9a2dd88c8..64f27cbbdd2cd35fe2e18b04ff5e115d5ce2c25d 100644 (file)
--- a/arch/powerpc/kernel/syscalls/syscall.tbl
+++ b/arch/powerpc/kernel/syscalls/syscall.tbl
@@ -110,7 +110,7 @@
 79     common  settimeofday                    sys_settimeofday                compat_sys_settimeofday
 80     common  getgroups                       sys_getgroups
 81     common  setgroups                       sys_setgroups
-82     32      select                          ppc_select                      sys_ni_syscall
+82     32      select                          sys_old_select                  compat_sys_old_select
 82     64      select                          sys_ni_syscall
 82     spu     select                          sys_ni_syscall
 83     common  symlink                         sys_symlink

diff --git a/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl b/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl
index 2600b4237292c78c44363159a02eaca9a2dd88c8..64f27cbbdd2cd35fe2e18b04ff5e115d5ce2c25d 100644 (file)
--- a/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl
+++ b/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl
@@ -110,7 +110,7 @@
 79     common  settimeofday                    sys_settimeofday                compat_sys_settimeofday
 80     common  getgroups                       sys_getgroups
 81     common  setgroups                       sys_setgroups
-82     32      select                          ppc_select                      sys_ni_syscall
+82     32      select                          sys_old_select                  compat_sys_old_select
 82     64      select                          sys_ni_syscall
 82     spu     select                          sys_ni_syscall
 83     common  symlink                         sys_symlink