[PATCH 5.11 090/210] powerpc/ptrace: Dont return error when getting/setting FP regs without CONFIG_PPC_FPU_REGS

From: Greg Kroah-Hartman
Date: Mon Apr 12 2021 - 05:31:27 EST

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From: Christophe Leroy <christophe.leroy@xxxxxxxxxx>

commit 3618250c8399cb36f4a0fbc48610a178307e1c64 upstream.

An #ifdef CONFIG_PPC_FPU_REGS is missing in arch_ptrace() leading
to the following Oops because [REGSET_FPR] entry is not initialised in
native_regsets[].

[ 41.917608] BUG: Unable to handle kernel instruction fetch
[ 41.922849] Faulting instruction address: 0xff8fd228
[ 41.927760] Oops: Kernel access of bad area, sig: 11 [#1]
[ 41.933089] BE PAGE_SIZE=4K PREEMPT CMPC885
[ 41.940753] Modules linked in:
[ 41.943768] CPU: 0 PID: 366 Comm: gdb Not tainted 5.12.0-rc5-s3k-dev-01666-g7aac86a0f057-dirty #4835
[ 41.952800] NIP: ff8fd228 LR: c004d9e0 CTR: ff8fd228
[ 41.957790] REGS: caae9df0 TRAP: 0400 Not tainted (5.12.0-rc5-s3k-dev-01666-g7aac86a0f057-dirty)
[ 41.966741] MSR: 40009032 <EE,ME,IR,DR,RI> CR: 82004248 XER: 20000000
[ 41.973540]
[ 41.973540] GPR00: c004d9b4 caae9eb0 c1b64f60 c1b64520 c0713cd4 caae9eb8 c1bacdfc 00000004
[ 41.973540] GPR08: 00000200 ff8fd228 c1bac700 00001032 28004242 1061aaf4 00000001 106d64a0
[ 41.973540] GPR16: 00000000 00000000 7fa0a774 10610000 7fa0aef9 00000000 10610000 7fa0a538
[ 41.973540] GPR24: 7fa0a580 7fa0a570 c1bacc00 c1b64520 c1bacc00 caae9ee8 00000108 c0713cd4
[ 42.009685] NIP [ff8fd228] 0xff8fd228
[ 42.013300] LR [c004d9e0] __regset_get+0x100/0x124
[ 42.018036] Call Trace:
[ 42.020443] [caae9eb0] [c004d9b4] __regset_get+0xd4/0x124 (unreliable)
[ 42.026899] [caae9ee0] [c004da94] copy_regset_to_user+0x5c/0xb0
[ 42.032751] [caae9f10] [c002f640] sys_ptrace+0xe4/0x588
[ 42.037915] [caae9f30] [c0011010] ret_from_syscall+0x0/0x28
[ 42.043422] --- interrupt: c00 at 0xfd1f8e4
[ 42.047553] NIP: 0fd1f8e4 LR: 1004a688 CTR: 00000000
[ 42.052544] REGS: caae9f40 TRAP: 0c00 Not tainted (5.12.0-rc5-s3k-dev-01666-g7aac86a0f057-dirty)
[ 42.061494] MSR: 0000d032 <EE,PR,ME,IR,DR,RI> CR: 48004442 XER: 00000000
[ 42.068551]
[ 42.068551] GPR00: 0000001a 7fa0a040 77dad7e0 0000000e 00000170 00000000 7fa0a078 00000004
[ 42.068551] GPR08: 00000000 108deb88 108dda40 106d6010 44004442 1061aaf4 00000001 106d64a0
[ 42.068551] GPR16: 00000000 00000000 7fa0a774 10610000 7fa0aef9 00000000 10610000 7fa0a538
[ 42.068551] GPR24: 7fa0a580 7fa0a570 1078fe00 1078fd70 1078fd70 00000170 0fdd3244 0000000d
[ 42.104696] NIP [0fd1f8e4] 0xfd1f8e4
[ 42.108225] LR [1004a688] 0x1004a688
[ 42.111753] --- interrupt: c00
[ 42.114768] Instruction dump:
[ 42.117698] XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
[ 42.125443] XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
[ 42.133195] ---[ end trace d35616f22ab2100c ]---

Adding the missing #ifdef is not good because gdb doesn't like getting
an error when getting registers.

Instead, make ptrace return 0s when CONFIG_PPC_FPU_REGS is not set.

Fixes: b6254ced4da6 ("powerpc/signal: Don't manage floating point regs when no FPU")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/9121a44a2d50ba1af18d8aa5ada06c9a3bea8afd.1617200085.git.christophe.leroy@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/powerpc/kernel/ptrace/Makefile | 4 ++--
arch/powerpc/kernel/ptrace/ptrace-decl.h | 14 --------------
arch/powerpc/kernel/ptrace/ptrace-fpu.c | 10 ++++++++++
arch/powerpc/kernel/ptrace/ptrace-novsx.c | 8 ++++++++
arch/powerpc/kernel/ptrace/ptrace-view.c | 2 --
5 files changed, 20 insertions(+), 18 deletions(-)

--- a/arch/powerpc/kernel/ptrace/Makefile
+++ b/arch/powerpc/kernel/ptrace/Makefile
@@ -6,11 +6,11 @@
CFLAGS_ptrace-view.o += -DUTS_MACHINE='"$(UTS_MACHINE)"'

obj-y += ptrace.o ptrace-view.o
-obj-$(CONFIG_PPC_FPU_REGS) += ptrace-fpu.o
+obj-y += ptrace-fpu.o
obj-$(CONFIG_COMPAT) += ptrace32.o
obj-$(CONFIG_VSX) += ptrace-vsx.o
ifneq ($(CONFIG_VSX),y)
-obj-$(CONFIG_PPC_FPU_REGS) += ptrace-novsx.o
+obj-y += ptrace-novsx.o
endif
obj-$(CONFIG_ALTIVEC) += ptrace-altivec.o
obj-$(CONFIG_SPE) += ptrace-spe.o
--- a/arch/powerpc/kernel/ptrace/ptrace-decl.h
+++ b/arch/powerpc/kernel/ptrace/ptrace-decl.h
@@ -165,22 +165,8 @@ int ptrace_put_reg(struct task_struct *t
extern const struct user_regset_view user_ppc_native_view;

/* ptrace-fpu */
-#ifdef CONFIG_PPC_FPU_REGS
int ptrace_get_fpr(struct task_struct *child, int index, unsigned long *data);
int ptrace_put_fpr(struct task_struct *child, int index, unsigned long data);
-#else
-static inline int
-ptrace_get_fpr(struct task_struct *child, int index, unsigned long *data)
-{
- return -EIO;
-}
-
-static inline int
-ptrace_put_fpr(struct task_struct *child, int index, unsigned long data)
-{
- return -EIO;
-}
-#endif

/* ptrace-(no)adv */
void ppc_gethwdinfo(struct ppc_debug_info *dbginfo);
--- a/arch/powerpc/kernel/ptrace/ptrace-fpu.c
+++ b/arch/powerpc/kernel/ptrace/ptrace-fpu.c
@@ -8,32 +8,42 @@

int ptrace_get_fpr(struct task_struct *child, int index, unsigned long *data)
{
+#ifdef CONFIG_PPC_FPU_REGS
unsigned int fpidx = index - PT_FPR0;
+#endif

if (index > PT_FPSCR)
return -EIO;

+#ifdef CONFIG_PPC_FPU_REGS
flush_fp_to_thread(child);
if (fpidx < (PT_FPSCR - PT_FPR0))
memcpy(data, &child->thread.TS_FPR(fpidx), sizeof(long));
else
*data = child->thread.fp_state.fpscr;
+#else
+ *data = 0;
+#endif

return 0;
}

int ptrace_put_fpr(struct task_struct *child, int index, unsigned long data)
{
+#ifdef CONFIG_PPC_FPU_REGS
unsigned int fpidx = index - PT_FPR0;
+#endif

if (index > PT_FPSCR)
return -EIO;

+#ifdef CONFIG_PPC_FPU_REGS
flush_fp_to_thread(child);
if (fpidx < (PT_FPSCR - PT_FPR0))
memcpy(&child->thread.TS_FPR(fpidx), &data, sizeof(long));
else
child->thread.fp_state.fpscr = data;
+#endif

return 0;
}
--- a/arch/powerpc/kernel/ptrace/ptrace-novsx.c
+++ b/arch/powerpc/kernel/ptrace/ptrace-novsx.c
@@ -21,12 +21,16 @@
int fpr_get(struct task_struct *target, const struct user_regset *regset,
struct membuf to)
{
+#ifdef CONFIG_PPC_FPU_REGS
BUILD_BUG_ON(offsetof(struct thread_fp_state, fpscr) !=
offsetof(struct thread_fp_state, fpr[32]));

flush_fp_to_thread(target);

return membuf_write(&to, &target->thread.fp_state, 33 * sizeof(u64));
+#else
+ return membuf_write(&to, &empty_zero_page, 33 * sizeof(u64));
+#endif
}

/*
@@ -46,6 +50,7 @@ int fpr_set(struct task_struct *target,
unsigned int pos, unsigned int count,
const void *kbuf, const void __user *ubuf)
{
+#ifdef CONFIG_PPC_FPU_REGS
BUILD_BUG_ON(offsetof(struct thread_fp_state, fpscr) !=
offsetof(struct thread_fp_state, fpr[32]));

@@ -53,4 +58,7 @@ int fpr_set(struct task_struct *target,

return user_regset_copyin(&pos, &count, &kbuf, &ubuf,
&target->thread.fp_state, 0, -1);
+#else
+ return 0;
+#endif
}
--- a/arch/powerpc/kernel/ptrace/ptrace-view.c
+++ b/arch/powerpc/kernel/ptrace/ptrace-view.c
@@ -522,13 +522,11 @@ static const struct user_regset native_r
.size = sizeof(long), .align = sizeof(long),
.regset_get = gpr_get, .set = gpr_set
},
-#ifdef CONFIG_PPC_FPU_REGS
[REGSET_FPR] = {
.core_note_type = NT_PRFPREG, .n = ELF_NFPREG,
.size = sizeof(double), .align = sizeof(double),
.regset_get = fpr_get, .set = fpr_set
},
-#endif
#ifdef CONFIG_ALTIVEC
[REGSET_VMX] = {
.core_note_type = NT_PPC_VMX, .n = 34,

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