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. Link: https://lore.kernel.org/lkml/13737de5-0eb7-e881-9af0-163b0d29a...@csgroup.eu/ 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 <rmcl...@linux.ibm.com> Reviewed-by: Nicholas Piggin <npig...@gmail.com> --- V2: Remove arch-specific select handler V3: Remove ppc_old_select prototype in <asm/syscalls.h>. Move to earlier in patch series V5: Use compat_sys_old_select on 64-bit systems. --- arch/powerpc/include/asm/syscalls.h | 2 -- arch/powerpc/kernel/syscalls.c | 17 ----------------- arch/powerpc/kernel/syscalls/syscall.tbl | 2 +- .../arch/powerpc/entry/syscalls/syscall.tbl | 2 +- 4 files changed, 2 insertions(+), 21 deletions(-) diff --git a/arch/powerpc/include/asm/syscalls.h b/arch/powerpc/include/asm/syscalls.h index 960b3871db72..20cbd29b1228 100644 --- 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 abc3fbb3c490..34e1ae88e15b 100644 --- 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 2600b4237292..64f27cbbdd2c 100644 --- 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 2600b4237292..64f27cbbdd2c 100644 --- 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 -- 2.34.1
