[PATCH 2/2] powerpc: fix inconsistencies in syscall error return handling
From: Dmitry V. Levin <hidden>
Date: 2025-01-27 18:14:25
Also in:
lkml
Subsystem:
linux for powerpc (32-bit and 64-bit), ptrace support, the rest · Maintainers:
Madhavan Srinivasan, Michael Ellerman, Oleg Nesterov, Linus Torvalds
Since the introduction of SECCOMP_RET_TRACE support, the kernel supports simultaneously both the generic kernel -ERRORCODE return value ABI and the powerpc sc syscall return ABI for PTRACE_EVENT_SECCOMP tracers. This change is an attempt to address the code inconsistencies in syscall error return handling that were introduced as a side effect of the dual ABI support. Signed-off-by: Dmitry V. Levin <redacted> --- arch/powerpc/kernel/ptrace/ptrace.c | 23 ++++++++++++++++++++--- arch/powerpc/kernel/signal.c | 11 +++-------- arch/powerpc/kernel/syscall.c | 6 +++--- 3 files changed, 26 insertions(+), 14 deletions(-)
diff --git a/arch/powerpc/kernel/ptrace/ptrace.c b/arch/powerpc/kernel/ptrace/ptrace.c
index 727ed4a14545..3778775bf6ba 100644
--- a/arch/powerpc/kernel/ptrace/ptrace.c
+++ b/arch/powerpc/kernel/ptrace/ptrace.c@@ -207,7 +207,7 @@ static int do_seccomp(struct pt_regs *regs) * syscall parameter. This is different to the ptrace ABI where * both r3 and orig_gpr3 contain the first syscall parameter. */ - regs->gpr[3] = -ENOSYS; + syscall_set_return_value(current, regs, -ENOSYS, 0); /* * We use the __ version here because we have already checked
@@ -215,8 +215,18 @@ static int do_seccomp(struct pt_regs *regs) * have already loaded -ENOSYS into r3, or seccomp has put * something else in r3 (via SECCOMP_RET_ERRNO/TRACE). */ - if (__secure_computing(NULL)) + if (__secure_computing(NULL)) { + + /* + * Traditionally, both the generic kernel -ERRORCODE return + * value ABI and the powerpc sc syscall return ABI is + * supported. For consistency, if the former is detected, + * convert it to the latter. + */ + if (!trap_is_scv(regs) && IS_ERR_VALUE(regs->gpr[3])) + syscall_set_return_value(current, regs, regs->gpr[3], 0); return -1; + } /* * The syscall was allowed by seccomp, restore the register
@@ -226,6 +236,13 @@ static int do_seccomp(struct pt_regs *regs) * allow the syscall to proceed. */ regs->gpr[3] = regs->orig_gpr3; + if (!trap_is_scv(regs)) { + /* + * Clear SO bit that was set in this function earlier by + * syscall_set_return_value. + */ + regs->ccr &= ~0x10000000L; + } return 0; }
@@ -315,7 +332,7 @@ long do_syscall_trace_enter(struct pt_regs *regs) * If we are aborting explicitly, or if the syscall number is * now invalid, set the return value to -ENOSYS. */ - regs->gpr[3] = -ENOSYS; + syscall_set_return_value(current, regs, -ENOSYS, 0); return -1; }
diff --git a/arch/powerpc/kernel/signal.c b/arch/powerpc/kernel/signal.c
index aa17e62f3754..1a38d6bcaed6 100644
--- a/arch/powerpc/kernel/signal.c
+++ b/arch/powerpc/kernel/signal.c@@ -19,6 +19,7 @@ #include <asm/unistd.h> #include <asm/debug.h> #include <asm/tm.h> +#include <asm/syscall.h> #include "signal.h"
@@ -229,14 +230,8 @@ static void check_syscall_restart(struct pt_regs *regs, struct k_sigaction *ka, regs_add_return_ip(regs, -4); regs->result = 0; } else { - if (trap_is_scv(regs)) { - regs->result = -EINTR; - regs->gpr[3] = -EINTR; - } else { - regs->result = -EINTR; - regs->gpr[3] = EINTR; - regs->ccr |= 0x10000000; - } + regs->result = -EINTR; + syscall_set_return_value(current, regs, -EINTR, 0); } }
diff --git a/arch/powerpc/kernel/syscall.c b/arch/powerpc/kernel/syscall.c
index be159ad4b77b..2fe47191e509 100644
--- a/arch/powerpc/kernel/syscall.c
+++ b/arch/powerpc/kernel/syscall.c@@ -122,7 +122,7 @@ notrace long system_call_exception(struct pt_regs *regs, unsigned long r0) if (unlikely(trap_is_unsupported_scv(regs))) { /* Unsupported scv vector */ _exception(SIGILL, regs, ILL_ILLOPC, regs->nip); - return regs->gpr[3]; + return regs_return_value(regs); } /* * We use the return value of do_syscall_trace_enter() as the
@@ -133,13 +133,13 @@ notrace long system_call_exception(struct pt_regs *regs, unsigned long r0) */ r0 = do_syscall_trace_enter(regs); if (unlikely(r0 >= NR_syscalls)) - return regs->gpr[3]; + return regs_return_value(regs); } else if (unlikely(r0 >= NR_syscalls)) { if (unlikely(trap_is_unsupported_scv(regs))) { /* Unsupported scv vector */ _exception(SIGILL, regs, ILL_ILLOPC, regs->nip); - return regs->gpr[3]; + return regs_return_value(regs); } return -ENOSYS; }
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