This reverts commit 8875f47b7681 ("powerpc/syscall: Save r3 in regs->orig_r3
").
Save caller's original r3 state to the kernel stackframe before entering
system_call_exception. This allows for user registers to be cleared by
the time system_call_exception is entered, reducing the influence of
user registers on speculation within the kernel.
Prior to this commit, orig_r3 was saved at the beginning of
system_call_exception. Instead, save orig_r3 while the user value is
still live in r3.
Also replicate this early save in 32-bit. A similar save was removed in
commit 6f76a01173cc ("powerpc/syscall: implement system call entry/exit
logic in C for PPC32") when 32-bit adopted system_call_exception. Revert
its removal of orig_r3 saves.
Signed-off-by: Rohan McLure <rmcl...@linux.ibm.com>
Reviewed-by: Nicholas Piggin <npig...@gmail.com>
---
V3: New commit.
V5: New commit message, as we do more than just revert 8875f47b7681.
---
arch/powerpc/kernel/entry_32.S | 1 +
arch/powerpc/kernel/interrupt_64.S | 2 ++
arch/powerpc/kernel/syscall.c | 1 -
3 files changed, 3 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index 1d599df6f169..44dfce9a60c5 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -101,6 +101,7 @@ __kuep_unlock:
.globl transfer_to_syscall
transfer_to_syscall:
+ stw r3, ORIG_GPR3(r1)
stw r11, GPR1(r1)
stw r11, 0(r1)
mflr r12
diff --git a/arch/powerpc/kernel/interrupt_64.S
b/arch/powerpc/kernel/interrupt_64.S
index ce25b28cf418..71d2d9497283 100644
--- a/arch/powerpc/kernel/interrupt_64.S
+++ b/arch/powerpc/kernel/interrupt_64.S
@@ -91,6 +91,7 @@ _ASM_NOKPROBE_SYMBOL(system_call_vectored_\name)
li r11,\trapnr
std r11,_TRAP(r1)
std r12,_CCR(r1)
+ std r3,ORIG_GPR3(r1)
addi r10,r1,STACK_FRAME_OVERHEAD
ld r11,exception_marker@toc(r2)
std r11,-16(r10) /* "regshere" marker */
@@ -275,6 +276,7 @@ END_BTB_FLUSH_SECTION
std r10,_LINK(r1)
std r11,_TRAP(r1)
std r12,_CCR(r1)
+ std r3,ORIG_GPR3(r1)
addi r10,r1,STACK_FRAME_OVERHEAD
ld r11,exception_marker@toc(r2)
std r11,-16(r10) /* "regshere" marker */
diff --git a/arch/powerpc/kernel/syscall.c b/arch/powerpc/kernel/syscall.c
index 81ace9e8b72b..64102a64fd84 100644
--- a/arch/powerpc/kernel/syscall.c
+++ b/arch/powerpc/kernel/syscall.c
@@ -25,7 +25,6 @@ notrace long system_call_exception(long r3, long r4, long r5,
kuap_lock();
add_random_kstack_offset();
- regs->orig_gpr3 = r3;
if (IS_ENABLED(CONFIG_PPC_IRQ_SOFT_MASK_DEBUG))
BUG_ON(irq_soft_mask_return() != IRQS_ALL_DISABLED);
--
2.34.1
