Le 09/11/2025 à 01:35, Finn Thain a écrit :
From: Christophe Leroy <[email protected]>
Since Linux v6.7, booting using BootX on an Old World PowerMac produces
an early crash. Stan Johnson writes, "the symptoms are that the screen
goes blank and the backlight stays on, and the system freezes (Linux
doesn't boot)."
Further testing revealed that the failure can be avoided by disabling
CONFIG_BOOTX_TEXT. Bisection revealed that the regression was caused by
a patch which replaced the static btext font data with const data in a
different compilation unit. To fix this, access the font data at its
relocated address.
You can explain that characters start being displayed by bootx_init()
which is call very early in the boot before kernel text is relocated to
its final location. During that period, data is addressed with an offset
which is added to the Global Offset Table (GOT) entries at the start of
bootx_init() by fonction reloc_got2(). But the pointers that are located
inside a structure are not referenced in the GOT and are therefore not
updated by reloc_got2(). It is therefore needed to apply the offset
manually by using PTRRELOC() macro.
Cc: Cedar Maxwell <[email protected]>
Cc: Stan Johnson <[email protected]>
Cc: "Dr. David Alan Gilbert" <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: [email protected]
Link: https://lists.debian.org/debian-powerpc/2025/10/msg00111.html
Link:
https://lore.kernel.org/linuxppc-dev/[email protected]/
Reported-by: Cedar Maxwell <[email protected]>
Closes: https://lists.debian.org/debian-powerpc/2025/09/msg00031.html
Bisected-by: Stan Johnson <[email protected]>
Tested-by: Stan Johnson <[email protected]>
Fixes: 0ebc7feae79a ("powerpc: Use shared font data")
Signed-off-by: Finn Thain <[email protected]>
---
Christophe, as you're the author of this patch, this submission will
probably need your sign-off.
I only suggested it, you authored the patch. Add me as:
Suggested-by: Christophe Leroy <[email protected]>
---
arch/powerpc/kernel/btext.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/kernel/btext.c b/arch/powerpc/kernel/btext.c
index 7f63f1cdc6c3..ca00c4824e31 100644
--- a/arch/powerpc/kernel/btext.c
+++ b/arch/powerpc/kernel/btext.c
@@ -20,6 +20,7 @@
#include <asm/io.h>
#include <asm/processor.h>
#include <asm/udbg.h>
+#include <asm/setup.h>
#define NO_SCROLL
@@ -463,7 +464,7 @@ static noinline void draw_byte(unsigned char c, long locX, long locY)
{
unsigned char *base = calc_base(locX << 3, locY << 4);
unsigned int font_index = c * 16;
- const unsigned char *font = font_sun_8x16.data + font_index;
+ const unsigned char *font = PTRRELOC(font_sun_8x16.data) + font_index;
int rb = dispDeviceRowBytes;
rmci_maybe_on();
