ibm,open-errinjct uses a non-standard RTAS return layout:
rets[0] = session token (output parameter)
rets[1] = status code
Unlike all other RTAS functions which use:
rets[0] = status code
rets[1..] = output parameters
Add rtas_token_is_open_errinjct() to identify this call, and
rtas_status_from_args() to extract status from the correct position.
Add an early guard in rtas_call() that rejects ibm,open-errinjct
invocations where nret < 2, since reading rets[1] would be out of
bounds. This is a kernel-side call-convention error, so -EINVAL is
returned rather than an RTAS firmware status code:
if (rtas_token_is_open_errinjct(token) && nret < 2) {
WARN_ON_ONCE(1);
return -EINVAL;
}
Adjust the output-copy loop so that for ibm,open-errinjct:
return value = rets[1] (status)
outputs[0] = rets[0] (session token)
For all other functions the existing convention is preserved:
return value = rets[0] (status)
outputs[0..] = rets[1..] (non-status outputs)
Move the "/* A -1 return code... */" comment immediately before the
ret == -1 check so it documents the check it guards.
Also fix sys_rtas() last-error status detection: add the same early
nret < 2 validation at the syscall boundary (returning -EINVAL) to
avoid entering RTAS with an invalid ibm,open-errinjct return layout.
After that guard, use rtas_status_from_args() to obtain the RTAS
status for last-error handling.
The prominent user librtas already passes nret = 2 for this function
as required by PAPR, so well-formed callers are unaffected.
Reference: OpenPOWER PAPR documentation
https://files.openpower.foundation/s/XFgfMaqLMD5Bcm8
Signed-off-by: Narayana Murty N <[email protected]>
---
arch/powerpc/kernel/rtas.c | 78 +++++++++++++++++++++++++++++++++-----
1 file changed, 69 insertions(+), 9 deletions(-)
diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c
index 8d81c1e7a8db..38f3d08d4228 100644
--- a/arch/powerpc/kernel/rtas.c
+++ b/arch/powerpc/kernel/rtas.c
@@ -1117,6 +1117,28 @@ static bool token_is_restricted_errinjct(s32 token)
token == rtas_function_token(RTAS_FN_IBM_ERRINJCT);
}
+/*
+ * ibm,open-errinjct uses a non-standard return layout:
+ * rets[0] = session token (output parameter)
+ * rets[1] = status code
+ *
+ * All other RTAS functions use the standard layout:
+ * rets[0] = status code
+ * rets[1..] = output parameters
+ */
+static inline bool rtas_token_is_open_errinjct(int token)
+{
+ return token == rtas_function_token(RTAS_FN_IBM_OPEN_ERRINJCT);
+}
+
+static int rtas_status_from_args(int token, struct rtas_args *args, int nret)
+{
+ if (rtas_token_is_open_errinjct(token))
+ return be32_to_cpu(args->rets[1]);
+
+ return nret > 0 ? be32_to_cpu(args->rets[0]) : 0;
+}
+
/**
* rtas_call() - Invoke an RTAS firmware function.
* @token: Identifies the function being invoked.
@@ -1198,6 +1220,16 @@ int rtas_call(int token, int nargs, int nret, int
*outputs, ...)
return -1;
}
+ /*
+ * ibm,open-errinjct returns rets[0]=session_token, rets[1]=status.
+ * We need nret >= 2 to read status from rets[1]. Reject early if
+ * the caller forgot to account for the extra return cell.
+ */
+ if (rtas_token_is_open_errinjct(token) && nret < 2) {
+ WARN_ON_ONCE(1);
+ return -EINVAL;
+ }
+
if ((mfmsr() & (MSR_IR|MSR_DR)) != (MSR_IR|MSR_DR)) {
WARN_ON_ONCE(1);
return -1;
@@ -1213,15 +1245,33 @@ int rtas_call(int token, int nargs, int nret, int
*outputs, ...)
va_rtas_call_unlocked(args, token, nargs, nret, list);
va_end(list);
+ ret = rtas_status_from_args(token, args, nret);
+
/* A -1 return code indicates that the last command couldn't
- be completed due to a hardware error. */
- if (be32_to_cpu(args->rets[0]) == -1)
+ * be completed due to a hardware error.
+ */
+ if (ret == -1)
buff_copy = __fetch_rtas_last_error(NULL);
- if (nret > 1 && outputs != NULL)
- for (i = 0; i < nret-1; ++i)
- outputs[i] = be32_to_cpu(args->rets[i + 1]);
- ret = (nret > 0) ? be32_to_cpu(args->rets[0]) : 0;
+ /*
+ * Copy non-status outputs to the caller's buffer.
+ *
+ * For ibm,open-errinjct the layout is:
+ * rets[0] = session token -> outputs[0]
+ * rets[1] = status (returned, not copied)
+ *
+ * For all other RTAS functions:
+ * rets[0] = status (returned, not copied)
+ * rets[1..nret-1] -> outputs[0..nret-2]
+ */
+ if (outputs) {
+ if (rtas_token_is_open_errinjct(token)) {
+ outputs[0] = be32_to_cpu(args->rets[0]);
+ } else if (nret > 1) {
+ for (i = 0; i < nret - 1; ++i)
+ outputs[i] = be32_to_cpu(args->rets[i + 1]);
+ }
+ }
lockdep_unpin_lock(&rtas_lock, cookie);
raw_spin_unlock_irqrestore(&rtas_lock, flags);
@@ -1896,6 +1946,14 @@ SYSCALL_DEFINE1(rtas, struct rtas_args __user *, uargs)
if (block_rtas_call(func, nargs, &args))
return -EINVAL;
+ /*
+ * ibm,open-errinjct places status at rets[1]; reject calls with
+ * fewer than 2 return cells before entering RTAS, since reading
+ * rets[1] for the -1 sentinel would be out of bounds.
+ */
+ if (rtas_token_is_open_errinjct(token) && nret < 2)
+ return -EINVAL;
+
if (token_is_restricted_errinjct(token)) {
int err;
@@ -1942,9 +2000,11 @@ SYSCALL_DEFINE1(rtas, struct rtas_args __user *, uargs)
do_enter_rtas(&rtas_args);
args = rtas_args;
- /* A -1 return code indicates that the last command couldn't
- be completed due to a hardware error. */
- if (be32_to_cpu(args.rets[0]) == -1)
+ /*
+ * A -1 return code indicates that the last command couldn't
+ * be completed due to a hardware error.
+ */
+ if (rtas_status_from_args(token, &args, nret) == -1)
errbuf = __fetch_rtas_last_error(buff_copy);
lockdep_unpin_lock(&rtas_lock, cookie);
--
2.54.0
