[PATCH v4 1/5] powerpc/rtas: Handle ibm,open-errinjct return format
From: Narayana Murty N <hidden>
Date: 2026-08-31 06:55:42
Also in:
lkml
Subsystem:
linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Madhavan Srinivasan, Linus Torvalds
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:
if (rtas_token_is_open_errinjct(token) && nret < 2) {
WARN_ON_ONCE(1);
return RTAS_INVALID_PARAMETER;
}
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: ibm,open-errinjct
places status at rets[1], so the -1 sentinel check must use rets[1]
for that function rather than always using rets[0].
Reference: OpenPOWER PAPR documentation
https://files.openpower.foundation/s/XFgfMaqLMD5Bcm8
Signed-off-by: Narayana Murty N <redacted>
---
arch/powerpc/kernel/rtas.c | 78 +++++++++++++++++++++++++++++++++-----
1 file changed, 68 insertions(+), 10 deletions(-)
diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c
index 8d81c1e7a8db..7131870655c6 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 RTAS_INVALID_PARAMETER; + } + 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 != NULL) { + 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);
@@ -1942,10 +1992,18 @@ 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) - errbuf = __fetch_rtas_last_error(buff_copy); + /* + * A -1 return code indicates that the last command couldn't + * be completed due to a hardware error. ibm,open-errinjct + * places status at rets[1] rather than rets[0]; check the + * correct position for the -1 sentinel. + */ + { + __be32 status_cell = (token == rtas_function_token(RTAS_FN_IBM_OPEN_ERRINJCT) && + nret >= 2) ? args.rets[1] : args.rets[0]; + if (be32_to_cpu(status_cell) == -1) + errbuf = __fetch_rtas_last_error(buff_copy); + } lockdep_unpin_lock(&rtas_lock, cookie); raw_spin_unlock_irqrestore(&rtas_lock, flags);
--
2.51.1