From: Rich Felker <dalias@aerifal.cx>
Date: Fri, 13 Oct 2017 14:23:48 +0000 (-0400)
Subject: fix access by setjmp and longjmp to __hwcap on arm built as thumb2
X-Git-Tag: v1.1.17~6
X-Git-Url: https://git.librecmc.org/?a=commitdiff_plain;h=e364774d7ca0a78db1b8457d5094b747eb2df318;p=oweals%2Fmusl.git

fix access by setjmp and longjmp to __hwcap on arm built as thumb2

this is a subtle issue with how the assembler/linker work. for the adr
pseudo-instruction used to find __hwcap, the assembler in thumb mode
generates a 16-bit thumb add instruction which can only represent
word-aligned addresses, despite not knowing the alignment of the
label. if the setjmp function is assigned a non-multiple-of-4 address
at link time, the load then loads from the wrong address (the last
instruction rather than the data containing the offset) and ends up
reading nonsense instead of the value of __hwcap. this in turn causes
the checks for floating-point/vector register sets (e.g. IWMMX) to
evaluate incorrectly, crashing when setjmp/longjmp try to save/restore
those registers.

fix based on bug report by Felix Hädicke.
---

diff --git a/src/setjmp/arm/longjmp.s b/src/setjmp/arm/longjmp.s
index 6191ab26..76cc2920 100644
--- a/src/setjmp/arm/longjmp.s
+++ b/src/setjmp/arm/longjmp.s
@@ -39,4 +39,5 @@ longjmp:
 3:	bx lr
 
 .hidden __hwcap
+.align 2
 1:	.word __hwcap-1b
diff --git a/src/setjmp/arm/setjmp.s b/src/setjmp/arm/setjmp.s
index c6fe1bb2..011315b7 100644
--- a/src/setjmp/arm/setjmp.s
+++ b/src/setjmp/arm/setjmp.s
@@ -41,4 +41,5 @@ setjmp:
 3:	bx lr
 
 .hidden __hwcap
+.align 2
 1:	.word __hwcap-1b