5.10-stable patches

added patches:
	powerpc-update-ppc_save_regs-to-save-current-r1-in-pt_regs.patch

diff --git a/queue-5.10/powerpc-update-ppc_save_regs-to-save-current-r1-in-pt_regs.patch b/queue-5.10/powerpc-update-ppc_save_regs-to-save-current-r1-in-pt_regs.patch
new file mode 100644 (file)
index 0000000..a62c345
--- /dev/null
+++ b/queue-5.10/powerpc-update-ppc_save_regs-to-save-current-r1-in-pt_regs.patch
@@ -0,0 +1,101 @@
+From b684c09f09e7a6af3794d4233ef785819e72db79 Mon Sep 17 00:00:00 2001
+From: Aditya Gupta <adityag@linux.ibm.com>
+Date: Thu, 15 Jun 2023 14:40:47 +0530
+Subject: powerpc: update ppc_save_regs to save current r1 in pt_regs
+
+From: Aditya Gupta <adityag@linux.ibm.com>
+
+commit b684c09f09e7a6af3794d4233ef785819e72db79 upstream.
+
+ppc_save_regs() skips one stack frame while saving the CPU register states.
+Instead of saving current R1, it pulls the previous stack frame pointer.
+
+When vmcores caused by direct panic call (such as `echo c >
+/proc/sysrq-trigger`), are debugged with gdb, gdb fails to show the
+backtrace correctly. On further analysis, it was found that it was because
+of mismatch between r1 and NIP.
+
+GDB uses NIP to get current function symbol and uses corresponding debug
+info of that function to unwind previous frames, but due to the
+mismatching r1 and NIP, the unwinding does not work, and it fails to
+unwind to the 2nd frame and hence does not show the backtrace.
+
+GDB backtrace with vmcore of kernel without this patch:
+
+---------
+(gdb) bt
+ #0  0xc0000000002a53e8 in crash_setup_regs (oldregs=<optimized out>,
+    newregs=0xc000000004f8f8d8) at ./arch/powerpc/include/asm/kexec.h:69
+ #1  __crash_kexec (regs=<optimized out>) at kernel/kexec_core.c:974
+ #2  0x0000000000000063 in ?? ()
+ #3  0xc000000003579320 in ?? ()
+---------
+
+Further analysis revealed that the mismatch occurred because
+"ppc_save_regs" was saving the previous stack's SP instead of the current
+r1. This patch fixes this by storing current r1 in the saved pt_regs.
+
+GDB backtrace with vmcore of patched kernel:
+
+--------
+(gdb) bt
+ #0  0xc0000000002a53e8 in crash_setup_regs (oldregs=0x0, newregs=0xc00000000670b8d8)
+    at ./arch/powerpc/include/asm/kexec.h:69
+ #1  __crash_kexec (regs=regs@entry=0x0) at kernel/kexec_core.c:974
+ #2  0xc000000000168918 in panic (fmt=fmt@entry=0xc000000001654a60 "sysrq triggered crash\n")
+    at kernel/panic.c:358
+ #3  0xc000000000b735f8 in sysrq_handle_crash (key=<optimized out>) at drivers/tty/sysrq.c:155
+ #4  0xc000000000b742cc in __handle_sysrq (key=key@entry=99, check_mask=check_mask@entry=false)
+    at drivers/tty/sysrq.c:602
+ #5  0xc000000000b7506c in write_sysrq_trigger (file=<optimized out>, buf=<optimized out>,
+    count=2, ppos=<optimized out>) at drivers/tty/sysrq.c:1163
+ #6  0xc00000000069a7bc in pde_write (ppos=<optimized out>, count=<optimized out>,
+    buf=<optimized out>, file=<optimized out>, pde=0xc00000000362cb40) at fs/proc/inode.c:340
+ #7  proc_reg_write (file=<optimized out>, buf=<optimized out>, count=<optimized out>,
+    ppos=<optimized out>) at fs/proc/inode.c:352
+ #8  0xc0000000005b3bbc in vfs_write (file=file@entry=0xc000000006aa6b00,
+    buf=buf@entry=0x61f498b4f60 <error: Cannot access memory at address 0x61f498b4f60>,
+    count=count@entry=2, pos=pos@entry=0xc00000000670bda0) at fs/read_write.c:582
+ #9  0xc0000000005b4264 in ksys_write (fd=<optimized out>,
+    buf=0x61f498b4f60 <error: Cannot access memory at address 0x61f498b4f60>, count=2)
+    at fs/read_write.c:637
+ #10 0xc00000000002ea2c in system_call_exception (regs=0xc00000000670be80, r0=<optimized out>)
+    at arch/powerpc/kernel/syscall.c:171
+ #11 0xc00000000000c270 in system_call_vectored_common ()
+    at arch/powerpc/kernel/interrupt_64.S:192
+--------
+
+Nick adds:
+  So this now saves regs as though it was an interrupt taken in the
+  caller, at the instruction after the call to ppc_save_regs, whereas
+  previously the NIP was there, but R1 came from the caller's caller and
+  that mismatch is what causes gdb's dwarf unwinder to go haywire.
+
+Signed-off-by: Aditya Gupta <adityag@linux.ibm.com>
+Fixes: d16a58f8854b1 ("powerpc: Improve ppc_save_regs()")
+Reivewed-by: Nicholas Piggin <npiggin@gmail.com>
+Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
+Link: https://msgid.link/20230615091047.90433-1-adityag@linux.ibm.com
+Cc: stable@vger.kernel.org
+Signed-off-by: Aditya Gupta <adityag@linux.ibm.com>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ arch/powerpc/kernel/ppc_save_regs.S |    6 +++---
+ 1 file changed, 3 insertions(+), 3 deletions(-)
+
+--- a/arch/powerpc/kernel/ppc_save_regs.S
++++ b/arch/powerpc/kernel/ppc_save_regs.S
+@@ -58,10 +58,10 @@ _GLOBAL(ppc_save_regs)
+       lbz     r0,PACAIRQSOFTMASK(r13)
+       PPC_STL r0,SOFTE-STACK_FRAME_OVERHEAD(r3)
+ #endif
+-      /* go up one stack frame for SP */
+-      PPC_LL  r4,0(r1)
+-      PPC_STL r4,1*SZL(r3)
++      /* store current SP */
++      PPC_STL r1,1*SZL(r3)
+       /* get caller's LR */
++      PPC_LL  r4,0(r1)
+       PPC_LL  r0,LRSAVE(r4)
+       PPC_STL r0,_LINK-STACK_FRAME_OVERHEAD(r3)
+       mflr    r0

diff --git a/queue-5.10/series b/queue-5.10/series
index 011345566502256b7a58a31ad0d5af4bbc87bc57..581743385d6821d85ce2a99e615ee29bad7226bc 100644 (file)
--- a/queue-5.10/series
+++ b/queue-5.10/series
@@ -33,3 +33,4 @@ mmc-meson-mx-sdhc-fix-initialization-frozen-issue.patch
 mmc-rpmb-fixes-pause-retune-on-all-rpmb-partitions.patch
 mmc-core-cancel-delayed-work-before-releasing-host.patch
 mmc-sdhci-sprd-fix-emmc-init-failure-after-hw-reset.patch
+powerpc-update-ppc_save_regs-to-save-current-r1-in-pt_regs.patch