Date: Tue, 14 Feb 2017 08:35:54 -0800 From: Mark Millard <markmi@dsl-only.net> To: andrew@freebsd.org, Shawn Webb <shawn.webb@hardenedbsd.org>, Tom Vijlbrief <tvijlbrief@gmail.com> Cc: freebsd-arm <freebsd-arm@freebsd.org> Subject: A potential fix for arm64's: sh`forkshell child-process path after fork sometimes has a bad stack pointer value Message-ID: <3BC697B9-4A3E-49FF-AB11-1106E2EF8399@dsl-only.net> In-Reply-To: <93064627-5F72-4167-90B1-0A98ABF4C99C@dsl-only.net> References: <DC3CC3BE-9D8C-41ED-ADD0-AFD4019B2E90@dsl-only.net> <2D04FF37-DEC8-42CE-961D-AE8CD58A0EAA@dsl-only.net> <93064627-5F72-4167-90B1-0A98ABF4C99C@dsl-only.net>
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The following change has let my test run for 8.5 hours so far without a
fork-failure in sh`forkshell :
# svnlite diff /usr/src/sys/arm64/arm64/swtch.S
Index: /usr/src/sys/arm64/arm64/swtch.S
===================================================================
--- /usr/src/sys/arm64/arm64/swtch.S (revision 312982)
+++ /usr/src/sys/arm64/arm64/swtch.S (working copy)
@@ -241,6 +241,12 @@
mov fp, #0 /* Stack traceback stops here. */
bl _C_LABEL(fork_exit)
+ /*
+ * Disable interrupts to avoid
+ * overwriting sp_el0 and spsr_el1 by an IRQ exception.
+ */
+ msr daifset, #2
+
/* Restore sp and lr */
ldp x0, x1, [sp]
msr sp_el0, x0
@@ -263,12 +269,6 @@
ldp x28, x29, [sp, #TF_X + 28 * 8]
/* Skip x30 as it was restored above as lr */
- /*
- * Disable interrupts to avoid
- * overwriting spsr_el1 by an IRQ exception.
- */
- msr daifset, #2
-
/* Restore elr and spsr */
ldp x0, x1, [sp, #16]
msr elr_el1, x0
I'm going to switch to attempting a self-hosted buildworld
buildkernel again.
===
Mark Millard
markmi at dsl-only.net
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