Re: [musl] remove SIGSTKFLT on mips?

[Rich Felker <dalias@libc.org>]

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On Thu, May 21, 2020 at 09:51:29AM -0700, enh wrote:
> (context: https://github.com/landley/toybox/issues/194)
> 
> seems like musl defines SIGSTKFLT for mips as signal 7. the kernel
> disagrees and says SIGEMT is 7, and that mips doesn't have a
> SIGSTKFLT:
> 
> arch/mips/include/uapi/asm/signal.h:#define SIGEMT 7
> 
> git blame says SIGSTKFLT was introduced in the original commit:
> 
> commit 6315004f6102dca44c4ba50654a36967b8b9c2a6
> Author: Rich Felker <dalias@aerifal.cx>
> Date:   Wed Jul 11 04:22:13 2012 -0400
> 
>     initial version of mips (o32) port, based on work by Richard
> Pennington (rdp)
> 
>     basically, this version of the code was obtained by starting with
>     rdp's work from his ellcc source tree, adapting it to musl's build
>     system and coding style, auditing the bits headers for discrepencies
>     with kernel definitions or glibc/LSB ABI or large file issues, fixing
>     up incompatibility with the old binutils from aboriginal linux, and
>     adding some new special cases to deal with the oddities of sigaction
>     and pipe syscall interfaces on mips.
> 
>     at present, minimal test programs work, but some interfaces are broken
>     or missing. threaded programs probably will not link.

I have the two attached patches pending push if there's no objection.

Rich

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From a19640a8912e9876f293267986875742867faa54 Mon Sep 17 00:00:00 2001
From: Rich Felker <dalias@aerifal.cx>
Date: Thu, 21 May 2020 13:14:40 -0400
Subject: [PATCH 1/2] handle possibility that SIGEMT replaces SIGSTKFLT in
 strsignal

presently all archs define SIGSTKFLT but this is not correct. change
strsignal as a prerequisite for fixing that.
---
 src/string/strsignal.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/string/strsignal.c b/src/string/strsignal.c
index 96bfe841..922d3271 100644
--- a/src/string/strsignal.c
+++ b/src/string/strsignal.c
@@ -31,7 +31,11 @@ static const char map[] = {
 	[SIGPIPE]   = 13,
 	[SIGALRM]   = 14,
 	[SIGTERM]   = 15,
+#if defined(SIGSTKFLT)
 	[SIGSTKFLT] = 16,
+#elif defined(SIGEMT)
+	[SIGEMT]    = 16,
+#endif
 	[SIGCHLD]   = 17,
 	[SIGCONT]   = 18,
 	[SIGSTOP]   = 19,
@@ -70,7 +74,11 @@ static const char strings[] =
 	"Broken pipe\0"
 	"Alarm clock\0"
 	"Terminated\0"
+#if defined(SIGSTKFLT)
 	"Stack fault\0"
+#elif defined(SIGEMT)
+	"Emulator trap\0"
+#endif
 	"Child process status\0"
 	"Continued\0"
 	"Stopped (signal)\0"
-- 
2.21.0


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From 8a9b96b328f084cc7a824174378643d2402b8dfb Mon Sep 17 00:00:00 2001
From: Rich Felker <dalias@aerifal.cx>
Date: Thu, 21 May 2020 13:06:21 -0400
Subject: [PATCH 2/2] fix incorrect SIGSTKFLT on all mips archs

signal 7 is SIGEMT on Linux mips* ABI according to the man pages and
kernel. it's not clear where the wrong name came from but it dates
back to original mips commit.
---
 arch/mips/bits/signal.h    | 2 +-
 arch/mips64/bits/signal.h  | 2 +-
 arch/mipsn32/bits/signal.h | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/mips/bits/signal.h b/arch/mips/bits/signal.h
index e1d97ac7..1b69e762 100644
--- a/arch/mips/bits/signal.h
+++ b/arch/mips/bits/signal.h
@@ -93,7 +93,7 @@ typedef struct __ucontext {
 #define SIGTRAP   5
 #define SIGABRT   6
 #define SIGIOT    SIGABRT
-#define SIGSTKFLT 7
+#define SIGEMT    7
 #define SIGFPE    8
 #define SIGKILL   9
 #define SIGBUS    10
diff --git a/arch/mips64/bits/signal.h b/arch/mips64/bits/signal.h
index c31ad07e..4f91c9fc 100644
--- a/arch/mips64/bits/signal.h
+++ b/arch/mips64/bits/signal.h
@@ -112,7 +112,7 @@ typedef struct __ucontext {
 #define SIGTRAP   5
 #define SIGABRT   6
 #define SIGIOT    SIGABRT
-#define SIGSTKFLT 7
+#define SIGEMT    7
 #define SIGFPE    8
 #define SIGKILL   9
 #define SIGBUS    10
diff --git a/arch/mipsn32/bits/signal.h b/arch/mipsn32/bits/signal.h
index c31ad07e..4f91c9fc 100644
--- a/arch/mipsn32/bits/signal.h
+++ b/arch/mipsn32/bits/signal.h
@@ -112,7 +112,7 @@ typedef struct __ucontext {
 #define SIGTRAP   5
 #define SIGABRT   6
 #define SIGIOT    SIGABRT
-#define SIGSTKFLT 7
+#define SIGEMT    7
 #define SIGFPE    8
 #define SIGKILL   9
 #define SIGBUS    10
-- 
2.21.0