Re: [PATCH] powerpc/chrp: Revert "Move PHB discovery" and "Make hydra_init() static"

Sat, 17 Jul 2021 08:56:26 -0700 

Christophe Leroy <[email protected]> a écrit :


Guenter Roeck <[email protected]> a écrit :


This patch reverts commit 407d418f2fd4 ("powerpc/chrp: Move PHB
discovery") and commit 9634afa67bfd ("powerpc/chrp: Make hydra_init()
static").

Running the upstream kernel on Qemu's brand new "pegasos2" emulation
results in a variety of backtraces such as

Kernel attempted to write user page (a1) - exploit attempt? (uid: 0)
------------[ cut here ]------------
Bug: Write fault blocked by KUAP!
WARNING: CPU: 0 PID: 0 at arch/powerpc/mm/fault.c:230 do_page_fault+0x4f4/0x920 
CPU: 0 PID: 0 Comm: swapper Not tainted 5.13.2 #40
NIP:  c0021824 LR: c0021824 CTR: 00000000
REGS: c1085d50 TRAP: 0700   Not tainted  (5.13.2)
MSR:  00021032 <ME,IR,DR,RI>  CR: 24042254  XER: 00000000
GPR00: c0021824 c1085e10 c0f8c520 00000021 3fffefff c1085c60 c1085c58 00000000 GPR08: 00001032 00000000 00000000 c0ffb3ec 44042254 00000000 00000000 00000004 GPR16: 00000000 ffffffff 000000c4 000000d0 0188c6e0 01006000 00000001 40b14000 GPR24: c0ec000c 00000300 02000000 00000000 42000000 000000a1 00000000 c1085e60 
NIP [c0021824] do_page_fault+0x4f4/0x920
LR [c0021824] do_page_fault+0x4f4/0x920
Call Trace:
[c1085e10] [c0021824] do_page_fault+0x4f4/0x920 (unreliable)
[c1085e50] [c0004254] DataAccess_virt+0xd4/0xe4

and the system fails to boot. Bisect points to commit 407d418f2fd4
("powerpc/chrp: Move PHB discovery"). Reverting this patch together with
commit 9634afa67bfd ("powerpc/chrp: Make hydra_init() static") fixes
the problem.
Isn't there more than that in the backtrace ? If there is a fault blocked by Kuap, it means there is a fault. It should be visible in the traces.
Should we fix the problem instead of reverting the commit that made the problem visible ?
Also, as it is a KUAP fault, did you test without CONFIG_PPC_KUAP ? Does it boot ? 





Cc: Oliver O'Halloran <[email protected]>
Cc: Geert Uytterhoeven <[email protected]>
Fixes: 407d418f2fd4 ("powerpc/chrp: Move PHB discovery")
Signed-off-by: Guenter Roeck <[email protected]>
---
arch/powerpc/include/asm/hydra.h    |  2 ++
arch/powerpc/platforms/chrp/pci.c   | 11 ++---------
arch/powerpc/platforms/chrp/setup.c | 12 +++++++++++-
3 files changed, 15 insertions(+), 10 deletions(-)
diff --git a/arch/powerpc/include/asm/hydra.h b/arch/powerpc/include/asm/hydra.h 
index d024447283a0..ae02eb53d6ef 100644
--- a/arch/powerpc/include/asm/hydra.h
+++ b/arch/powerpc/include/asm/hydra.h
@@ -94,6 +94,8 @@ extern volatile struct Hydra __iomem *Hydra;
#define HYDRA_INT_EXT7          18      /* Power Off Request */
#define HYDRA_INT_SPARE         19

+extern int hydra_init(void);
+
#endif /* __KERNEL__ */

#endif /* _ASMPPC_HYDRA_H */
diff --git a/arch/powerpc/platforms/chrp/pci.c b/arch/powerpc/platforms/chrp/pci.c 
index 76e6256cb0a7..b2c2bf35b76c 100644
--- a/arch/powerpc/platforms/chrp/pci.c
+++ b/arch/powerpc/platforms/chrp/pci.c
@@ -131,7 +131,8 @@ static struct pci_ops rtas_pci_ops =

volatile struct Hydra __iomem *Hydra = NULL;

-static int __init hydra_init(void)
+int __init
+hydra_init(void)
{
        struct device_node *np;
        struct resource r;
@@ -313,14 +314,6 @@ chrp_find_bridges(void)
                }
        }
        of_node_put(root);
-
-       /*
-        *  "Temporary" fixes for PCI devices.
-        *  -- Geert
-        */
-       hydra_init();           /* Mac I/O */
-
-       pci_create_OF_bus_map();
}

/* SL82C105 IDE Control/Status Register */
diff --git a/arch/powerpc/platforms/chrp/setup.c b/arch/powerpc/platforms/chrp/setup.c 
index 3cfc382841e5..c45435aa5e36 100644
--- a/arch/powerpc/platforms/chrp/setup.c
+++ b/arch/powerpc/platforms/chrp/setup.c
@@ -334,11 +334,22 @@ static void __init chrp_setup_arch(void)
        /* On pegasos, enable the L2 cache if not already done by OF */
        pegasos_set_l2cr();

+       /* Lookup PCI host bridges */
+       chrp_find_bridges();
+
+       /*
+        *  Temporary fixes for PCI devices.
+        *  -- Geert
+        */
+       hydra_init();           /* Mac I/O */
+
        /*
         *  Fix the Super I/O configuration
         */
        sio_init();

+       pci_create_OF_bus_map();
+
        /*
         * Print the banner, then scroll down so boot progress
         * can be printed.  -- Cort
@@ -571,7 +582,6 @@ define_machine(chrp) {
        .name                   = "CHRP",
        .probe                  = chrp_probe,
        .setup_arch             = chrp_setup_arch,
-       .discover_phbs          = chrp_find_bridges,
        .init                   = chrp_init2,
        .show_cpuinfo           = chrp_show_cpuinfo,
        .init_IRQ               = chrp_init_IRQ,
--
2.25.1

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