soc: apple: rtkit: Do not copy the reg state structure to the stack

The register state struct is 848 bytes, which ends up bloating the
apple_rtkit_crashlog_dump_regs stack frame beyond 1024 on some
32-bit platforms, triggering compile warnings.

This doesn't matter for 64BIT/ARM64, but there's also no good reason to
copy the structure to the stack in this case. We can use __packed to
avoid alignment issues, there are no double-read hazards, and this is a
fatal error path so performance does not matter.

Fixes: 22991d8d5725 ("soc: apple: rtkit: Add register dump decoding to crashlog")
Signed-off-by: Asahi Lina <lina@asahilina.net>
Reviewed-by: Eric Curtin <ecurtin@redhat.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

diff --git a/drivers/soc/apple/rtkit-crashlog.c b/drivers/soc/apple/rtkit-crashlog.c
index dfa74b3..8319e36 100644 (file)
--- a/drivers/soc/apple/rtkit-crashlog.c
+++ b/drivers/soc/apple/rtkit-crashlog.c
@@ -57,7 +57,7 @@ struct apple_rtkit_crashlog_regs {
        u64 unk_X;
        u64 esr;
        u64 unk_Z;
-};
+} __packed;
 static_assert(sizeof(struct apple_rtkit_crashlog_regs) == 0x350);
 
 static void apple_rtkit_crashlog_dump_str(struct apple_rtkit *rtk, u8 *bfr,
@@ -126,18 +126,18 @@ static void apple_rtkit_crashlog_dump_mailbox(struct apple_rtkit *rtk, u8 *bfr,
 static void apple_rtkit_crashlog_dump_regs(struct apple_rtkit *rtk, u8 *bfr,
                                           size_t size)
 {
-       struct apple_rtkit_crashlog_regs regs;
+       struct apple_rtkit_crashlog_regs *regs;
        const char *el;
        int i;
 
-       if (size < sizeof(regs)) {
+       if (size < sizeof(*regs)) {
                dev_warn(rtk->dev, "RTKit: Regs section too small: 0x%zx", size);
                return;
        }
 
-       memcpy(&regs, bfr, sizeof(regs));
+       regs = (struct apple_rtkit_crashlog_regs *)bfr;
 
-       switch (regs.psr & PSR_MODE_MASK) {
+       switch (regs->psr & PSR_MODE_MASK) {
        case PSR_MODE_EL0t:
                el = "EL0t";
                break;
@@ -160,11 +160,11 @@ static void apple_rtkit_crashlog_dump_regs(struct apple_rtkit *rtk, u8 *bfr,
 
        dev_warn(rtk->dev, "RTKit: Exception dump:");
        dev_warn(rtk->dev, "  == Exception taken from %s ==", el);
-       dev_warn(rtk->dev, "  PSR    = 0x%llx", regs.psr);
-       dev_warn(rtk->dev, "  PC     = 0x%llx\n", regs.pc);
-       dev_warn(rtk->dev, "  ESR    = 0x%llx\n", regs.esr);
-       dev_warn(rtk->dev, "  FAR    = 0x%llx\n", regs.far);
-       dev_warn(rtk->dev, "  SP     = 0x%llx\n", regs.sp);
+       dev_warn(rtk->dev, "  PSR    = 0x%llx", regs->psr);
+       dev_warn(rtk->dev, "  PC     = 0x%llx\n", regs->pc);
+       dev_warn(rtk->dev, "  ESR    = 0x%llx\n", regs->esr);
+       dev_warn(rtk->dev, "  FAR    = 0x%llx\n", regs->far);
+       dev_warn(rtk->dev, "  SP     = 0x%llx\n", regs->sp);
        dev_warn(rtk->dev, "\n");
 
        for (i = 0; i < 31; i += 4) {
@@ -172,12 +172,12 @@ static void apple_rtkit_crashlog_dump_regs(struct apple_rtkit *rtk, u8 *bfr,
                        dev_warn(rtk->dev,
                                         "  x%02d-x%02d = %016llx %016llx %016llx %016llx\n",
                                         i, i + 3,
-                                        regs.regs[i], regs.regs[i + 1],
-                                        regs.regs[i + 2], regs.regs[i + 3]);
+                                        regs->regs[i], regs->regs[i + 1],
+                                        regs->regs[i + 2], regs->regs[i + 3]);
                else
                        dev_warn(rtk->dev,
                                         "  x%02d-x%02d = %016llx %016llx %016llx\n", i, i + 3,
-                                        regs.regs[i], regs.regs[i + 1], regs.regs[i + 2]);
+                                        regs->regs[i], regs->regs[i + 1], regs->regs[i + 2]);
        }
 
        dev_warn(rtk->dev, "\n");