Re: [PATCH v2 3/4] powerpc/64: make buildable without CONFIG_COMPAT

From: Christophe Leroy <hidden>
Date: 2019-08-28 12:49:20
Also in: linux-fsdevel, lkml


Le 28/08/2019 à 12:30, Michal Suchanek a écrit :

There are numerous references to 32bit functions in generic and 64bit
code so ifdef them out.

As far as possible, avoid opting things out with ifdefs. Ref 
https://www.kernel.org/doc/html/latest/process/coding-style.html#conditional-compilation

See comment below.

quoted hunk ↗ jump to hunk

Signed-off-by: Michal Suchanek <redacted>
---
v2:
- fix 32bit ifdef condition in signal.c
- simplify the compat ifdef condition in vdso.c - 64bit is redundant
- simplify the compat ifdef condition in callchain.c - 64bit is redundant
---
  arch/powerpc/include/asm/syscall.h |  2 ++
  arch/powerpc/kernel/Makefile       | 15 ++++++++++++---
  arch/powerpc/kernel/entry_64.S     |  2 ++
  arch/powerpc/kernel/signal.c       |  5 +++--
  arch/powerpc/kernel/syscall_64.c   |  5 +++--
  arch/powerpc/kernel/vdso.c         |  4 +++-
  arch/powerpc/perf/callchain.c      | 14 ++++++++++----
  7 files changed, 35 insertions(+), 12 deletions(-)

diff --git a/arch/powerpc/include/asm/syscall.h b/arch/powerpc/include/asm/syscall.h
index 38d62acfdce7..3ed3b75541a1 100644
--- a/arch/powerpc/include/asm/syscall.h
+++ b/arch/powerpc/include/asm/syscall.h

@@ -16,7 +16,9 @@
  
  /* ftrace syscalls requires exporting the sys_call_table */
  extern const unsigned long sys_call_table[];
+#ifdef CONFIG_COMPAT
  extern const unsigned long compat_sys_call_table[];
+#endif

Leaving the declaration should be harmless.

quoted hunk ↗ jump to hunk

  
  static inline int syscall_get_nr(struct task_struct *task, struct pt_regs *regs)
  {

diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index 1d646a94d96c..b0db365b83d8 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile

@@ -44,16 +44,25 @@ CFLAGS_btext.o += -DDISABLE_BRANCH_PROFILING
  endif
  
  obj-y				:= cputable.o ptrace.o syscalls.o \
-				   irq.o align.o signal_32.o pmc.o vdso.o \
+				   irq.o align.o pmc.o vdso.o \
  				   process.o systbl.o idle.o \
  				   signal.o sysfs.o cacheinfo.o time.o \
  				   prom.o traps.o setup-common.o \
  				   udbg.o misc.o io.o misc_$(BITS).o \
  				   of_platform.o prom_parse.o
-obj-$(CONFIG_PPC64)		+= setup_64.o sys_ppc32.o \
-				   signal_64.o ptrace32.o \
+ifndef CONFIG_PPC64
+obj-y				+= signal_32.o
+else
+ifdef CONFIG_COMPAT
+obj-y				+= signal_32.o
+endif
+endif
+obj-$(CONFIG_PPC64)		+= setup_64.o signal_64.o \
  				   paca.o nvram_64.o firmware.o \
  				   syscall_64.o

That's still a bit messy. You could have:

obj-y = +=signal_$(BITS).o
obj-$(CONFIG_COMPAT) += signal_32.o

+ifdef CONFIG_COMPAT
+obj-$(CONFIG_PPC64)		+= sys_ppc32.o ptrace32.o
+endif

AFAIK, CONFIG_COMPAT is only defined when CONFIG_PP64 is defined, so 
could be:

obj-$(CONFIG_COMPAT)		+= sys_ppc32.o ptrace32.o

And could be grouped with the above signal_32.o

quoted hunk ↗ jump to hunk

  obj-$(CONFIG_VDSO32)		+= vdso32/
  obj-$(CONFIG_PPC_WATCHDOG)	+= watchdog.o
  obj-$(CONFIG_HAVE_HW_BREAKPOINT)	+= hw_breakpoint.o

diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index 2ec825a85f5b..a2dbf216f607 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S

@@ -51,8 +51,10 @@
  SYS_CALL_TABLE:
  	.tc sys_call_table[TC],sys_call_table
  
+#ifdef CONFIG_COMPAT
  COMPAT_SYS_CALL_TABLE:
  	.tc compat_sys_call_table[TC],compat_sys_call_table
+#endif

Can we avoid this ifdef ?

quoted hunk ↗ jump to hunk

  
  /* This value is used to mark exception frames on the stack. */
  exception_marker:

diff --git a/arch/powerpc/kernel/signal.c b/arch/powerpc/kernel/signal.c
index 60436432399f..ffd045e9fb57 100644
--- a/arch/powerpc/kernel/signal.c
+++ b/arch/powerpc/kernel/signal.c

@@ -277,14 +277,15 @@ static void do_signal(struct task_struct *tsk)
  
  	rseq_signal_deliver(&ksig, tsk->thread.regs);
  
+#if !defined(CONFIG_PPC64) || defined(CONFIG_COMPAT)
  	if (is32) {
          	if (ksig.ka.sa.sa_flags & SA_SIGINFO)
  			ret = handle_rt_signal32(&ksig, oldset, tsk);
  		else
  			ret = handle_signal32(&ksig, oldset, tsk);
-	} else {
+	} else

" if only one branch of a conditional statement is a single statement 
[...] use braces in both branches"

Ref 
https://www.kernel.org/doc/html/latest/process/coding-style.html#placing-braces-and-spaces

+#endif /* 32bit */

Having an #ifdef in a middle of a if/else is gross.

Check what are the possible values for is32. It will be always true 
which CONFIG_PPC32.
If you can make sure it is always false without CONFIG_COMPAT, you are 
done. If not, then combine the if(is32) with something involving 
IS_ENABLED(CONFIG_COMPAT).

quoted hunk ↗ jump to hunk

  		ret = handle_rt_signal64(&ksig, oldset, tsk);
-	}
  
  	tsk->thread.regs->trap = 0;
  	signal_setup_done(ret, &ksig, test_thread_flag(TIF_SINGLESTEP));

diff --git a/arch/powerpc/kernel/syscall_64.c b/arch/powerpc/kernel/syscall_64.c
index 98ed970796d5..3f48262b512d 100644
--- a/arch/powerpc/kernel/syscall_64.c
+++ b/arch/powerpc/kernel/syscall_64.c

@@ -100,6 +100,7 @@ long system_call_exception(long r3, long r4, long r5, long r6, long r7, long r8,
  	/* May be faster to do array_index_nospec? */
  	barrier_nospec();
  
+#ifdef CONFIG_COMPAT
  	if (unlikely(ti_flags & _TIF_32BIT)) {
  		f = (void *)compat_sys_call_table[r0];

Don't opt out compat_sys_call_table[] declaration in .h file, and use:

	if (IS_ENABLED(CONFIG_COMPAT) && unlikely(ti_flags & _TIF_32BIT)) {

quoted hunk ↗ jump to hunk

@@ -110,9 +111,9 @@ long system_call_exception(long r3, long r4, long r5, long r6, long r7, long r8,
  		r7 &= 0x00000000ffffffffULL;
  		r8 &= 0x00000000ffffffffULL;
  
-	} else {
+	} else
+#endif /* CONFIG_COMPAT */

Same comment above braces and #ifdefs in the middle of an if/else

quoted hunk ↗ jump to hunk

  		f = (void *)sys_call_table[r0];
-	}
  
  	return f(r3, r4, r5, r6, r7, r8);
  }

diff --git a/arch/powerpc/kernel/vdso.c b/arch/powerpc/kernel/vdso.c
index d60598113a9f..a991b5d69010 100644
--- a/arch/powerpc/kernel/vdso.c
+++ b/arch/powerpc/kernel/vdso.c

@@ -667,7 +667,7 @@ static void __init vdso_setup_syscall_map(void)
  {
  	unsigned int i;
  	extern unsigned long *sys_call_table;
-#ifdef CONFIG_PPC64
+#ifdef CONFIG_COMPAT

It should be possible to get rid of that #ifdef completely.

quoted hunk ↗ jump to hunk

  	extern unsigned long *compat_sys_call_table;
  #endif
  	extern unsigned long sys_ni_syscall;

@@ -678,9 +678,11 @@ static void __init vdso_setup_syscall_map(void)
  		if (sys_call_table[i] != sys_ni_syscall)
  			vdso_data->syscall_map_64[i >> 5] |=
  				0x80000000UL >> (i & 0x1f);
+#ifdef CONFIG_COMPAT

Use if (IS_ENABLED(CONFIG_COMPAT && compat_sys_call_table[i] != 
sys_ni_syscall)

quoted hunk ↗ jump to hunk

  		if (compat_sys_call_table[i] != sys_ni_syscall)
  			vdso_data->syscall_map_32[i >> 5] |=
  				0x80000000UL >> (i & 0x1f);
+#endif /* CONFIG_COMPAT */
  #else /* CONFIG_PPC64 */
  		if (sys_call_table[i] != sys_ni_syscall)
  			vdso_data->syscall_map_32[i >> 5] |=

diff --git a/arch/powerpc/perf/callchain.c b/arch/powerpc/perf/callchain.c
index c84bbd4298a0..b3dacc8bc98d 100644
--- a/arch/powerpc/perf/callchain.c
+++ b/arch/powerpc/perf/callchain.c

@@ -15,7 +15,7 @@
  #include <asm/sigcontext.h>
  #include <asm/ucontext.h>
  #include <asm/vdso.h>
-#ifdef CONFIG_PPC64
+#ifdef CONFIG_COMPAT
  #include "../kernel/ppc32.h"
  #endif
  #include <asm/pte-walk.h>

@@ -165,6 +165,7 @@ static int read_user_stack_64(unsigned long __user *ptr, unsigned long *ret)
  	return read_user_stack_slow(ptr, ret, 8);
  }
  
+#ifdef CONFIG_COMPAT

Unneeded #ifdef

quoted hunk ↗ jump to hunk

  static int read_user_stack_32(unsigned int __user *ptr, unsigned int *ret)
  {
  	if ((unsigned long)ptr > TASK_SIZE - sizeof(unsigned int) ||

@@ -180,6 +181,7 @@ static int read_user_stack_32(unsigned int __user *ptr, unsigned int *ret)
  
  	return read_user_stack_slow(ptr, ret, 4);
  }
+#endif
  
  static inline int valid_user_sp(unsigned long sp, int is_64)
  {
@@ -341,6 +343,7 @@ static inline int valid_user_sp(unsigned long sp, int is_64)
  
  #endif /* CONFIG_PPC64 */
  
+#if !defined(CONFIG_PPC64) || defined(CONFIG_COMPAT)

You don't need to opt that out.

quoted hunk ↗ jump to hunk

  /*
   * Layout for non-RT signal frames
   */

@@ -482,12 +485,15 @@ static void perf_callchain_user_32(struct perf_callchain_entry_ctx *entry,
  		sp = next_sp;
  	}
  }
+#endif /* 32bit */
  
  void
  perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
  {
-	if (current_is_64bit())
-		perf_callchain_user_64(entry, regs);
-	else
+#if !defined(CONFIG_PPC64) || defined(CONFIG_COMPAT)
+	if (!current_is_64bit())
  		perf_callchain_user_32(entry, regs);
+	else
+#endif
+		perf_callchain_user_64(entry, regs);

Please rewrite using  IS_ENABLED() instead of #ifdefs.

Christophe

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