compiler-rt: fix build on ARMv6

compiler-rt has accumulated several regressions that prevent it from building
on ARMv6. It is important to note that there are two major versions of ARMv6:
base ARMv6 and ARMv6K. ARMv6K includes several important new instructions,
such as non-word size atomic operations (ldrexd, strexd, etc.) and the yield
instruction. Most ARMv6 CPUs actually implement ARMv6K, including all those used
in Raspberry Pis, but nixpkgs' "raspberryPi" platform targets base ARMv6.

compiler-rt versions 8-14 fail to build on ARMv6 and ARMv6K. compiler-rt 15 (not
yet in nixpkgs) builds on ARMv6K but not ARMv6. This patch fixes versions 9-14
on both ARMv6 variants. The patches don't apply cleanly to version 8, and I
figured it wasn't worth carrying another version of the patches for such an old
version.

A total of five patches are required to get compiler-rt building on ARMv6:
* armv6-mcr-dmb.patch: use `mcr` to provide the equivalent of `dmb` on ARMv6.
  Included in LLVM 15.
* armv6-sync-ops-no-thumb.patch: prevent certain atomic operation functions
  from using Thumb mode. Included in LLVM 15.
* armv6-no-ldrexd-strexd.patch: don't use ldrexd or strexd, which are not
  available in base ARMv6. Submitted upstream by me.
* armv6-scudo-no-yield.patch: use nop instead of yield on ARMv6 in standalone
  scudo. Required by versions >=13, since they enable standalone scudo.
  Submitted upstream by me.
* armv6-scudo-libatomic.patch: link standlone scudo to libatomic on ARMv6 (and
  any other platforms that need it). Not yet submitted because the backport is
  a bit different from the upstream version and I need to test it.

12 files changed, 416 insertions, 1 deletions

diff --git a/pkgs/development/compilers/llvm/10/compiler-rt/default.nix b/pkgs/development/compilers/llvm/10/compiler-rt/default.nix
index f113e55f284..9af786c9604 100644
--- a/pkgs/development/compilers/llvm/10/compiler-rt/default.nix
+++ b/pkgs/development/compilers/llvm/10/compiler-rt/default.nix
@@ -61,6 +61,10 @@ stdenv.mkDerivation {
     ./gnu-install-dirs.patch
     ../../common/compiler-rt/libsanitizer-no-cyclades-11.patch
     ./X86-support-extension.patch # backported from LLVM 11
+    # Fix build on armv6l
+    ../../common/compiler-rt/armv6-mcr-dmb.patch
+    ../../common/compiler-rt/armv6-sync-ops-no-thumb.patch
+    ../../common/compiler-rt/armv6-no-ldrexd-strexd.patch
   ] ++ lib.optional stdenv.hostPlatform.isAarch32 ./armv7l.patch;
 
   # TSAN requires XPC on Darwin, which we have no public/free source files for. We can depend on the Apple frameworks
diff --git a/pkgs/development/compilers/llvm/11/compiler-rt/default.nix b/pkgs/development/compilers/llvm/11/compiler-rt/default.nix
index 979ec9e23f6..61ee5fefd26 100644
--- a/pkgs/development/compilers/llvm/11/compiler-rt/default.nix
+++ b/pkgs/development/compilers/llvm/11/compiler-rt/default.nix
@@ -66,6 +66,10 @@ stdenv.mkDerivation {
     ../../common/compiler-rt/libsanitizer-no-cyclades-11.patch
     ../../common/compiler-rt/darwin-plistbuddy-workaround.patch
     ./armv7l.patch
+    # Fix build on armv6l
+    ../../common/compiler-rt/armv6-mcr-dmb.patch
+    ../../common/compiler-rt/armv6-sync-ops-no-thumb.patch
+    ../../common/compiler-rt/armv6-no-ldrexd-strexd.patch
   ];
 
   preConfigure = lib.optionalString stdenv.hostPlatform.isDarwin ''
diff --git a/pkgs/development/compilers/llvm/12/compiler-rt/default.nix b/pkgs/development/compilers/llvm/12/compiler-rt/default.nix
index 22e2ab9d5b2..8a9f878bc3a 100644
--- a/pkgs/development/compilers/llvm/12/compiler-rt/default.nix
+++ b/pkgs/development/compilers/llvm/12/compiler-rt/default.nix
@@ -66,6 +66,10 @@ stdenv.mkDerivation {
     ./normalize-var.patch
     ../../common/compiler-rt/darwin-plistbuddy-workaround.patch
     ./armv7l.patch
+    # Fix build on armv6l
+    ../../common/compiler-rt/armv6-mcr-dmb.patch
+    ../../common/compiler-rt/armv6-sync-ops-no-thumb.patch
+    ../../common/compiler-rt/armv6-no-ldrexd-strexd.patch
   ];
 
   # TSAN requires XPC on Darwin, which we have no public/free source files for. We can depend on the Apple frameworks
diff --git a/pkgs/development/compilers/llvm/13/compiler-rt/default.nix b/pkgs/development/compilers/llvm/13/compiler-rt/default.nix
index 02ddabad676..feae499b843 100644
--- a/pkgs/development/compilers/llvm/13/compiler-rt/default.nix
+++ b/pkgs/development/compilers/llvm/13/compiler-rt/default.nix
@@ -71,6 +71,12 @@ stdenv.mkDerivation {
     ./darwin-targetconditionals.patch
     ../../common/compiler-rt/darwin-plistbuddy-workaround.patch
     ./armv7l.patch
+    # Fix build on armv6l
+    ../../common/compiler-rt/armv6-mcr-dmb.patch
+    ../../common/compiler-rt/armv6-sync-ops-no-thumb.patch
+    ../../common/compiler-rt/armv6-no-ldrexd-strexd.patch
+    ../../common/compiler-rt/armv6-scudo-no-yield.patch
+    ../../common/compiler-rt/armv6-scudo-libatomic.patch
   ];
 
   # TSAN requires XPC on Darwin, which we have no public/free source files for. We can depend on the Apple frameworks
diff --git a/pkgs/development/compilers/llvm/14/compiler-rt/default.nix b/pkgs/development/compilers/llvm/14/compiler-rt/default.nix
index aff2722074e..021eba5a7b6 100644
--- a/pkgs/development/compilers/llvm/14/compiler-rt/default.nix
+++ b/pkgs/development/compilers/llvm/14/compiler-rt/default.nix
@@ -81,6 +81,12 @@ stdenv.mkDerivation {
     ./darwin-targetconditionals.patch
     ../../common/compiler-rt/darwin-plistbuddy-workaround.patch
     ./armv7l.patch
+    # Fix build on armv6l
+    ../../common/compiler-rt/armv6-mcr-dmb.patch
+    ../../common/compiler-rt/armv6-sync-ops-no-thumb.patch
+    ../../common/compiler-rt/armv6-no-ldrexd-strexd.patch
+    ../../common/compiler-rt/armv6-scudo-no-yield.patch
+    ../../common/compiler-rt/armv6-scudo-libatomic.patch
   ];
 
   # TSAN requires XPC on Darwin, which we have no public/free source files for. We can depend on the Apple frameworks
diff --git a/pkgs/development/compilers/llvm/9/compiler-rt/default.nix b/pkgs/development/compilers/llvm/9/compiler-rt/default.nix
index be7380470ce..7e24ab399a8 100644
--- a/pkgs/development/compilers/llvm/9/compiler-rt/default.nix
+++ b/pkgs/development/compilers/llvm/9/compiler-rt/default.nix
@@ -60,6 +60,10 @@ stdenv.mkDerivation {
     ./codesign.patch # Revert compiler-rt commit that makes codesign mandatory
     ./gnu-install-dirs.patch
     ../../common/compiler-rt/libsanitizer-no-cyclades-9.patch
+    # Fix build on armv6l
+    ../../common/compiler-rt/armv6-mcr-dmb.patch
+    ../../common/compiler-rt/armv6-sync-ops-no-thumb.patch
+    ../../common/compiler-rt/armv6-no-ldrexd-strexd.patch
   ] ++ lib.optional stdenv.hostPlatform.isAarch32 ./armv7l.patch;
 
   # TSAN requires XPC on Darwin, which we have no public/free source files for. We can depend on the Apple frameworks
diff --git a/pkgs/development/compilers/llvm/common/compiler-rt/armv6-mcr-dmb.patch b/pkgs/development/compilers/llvm/common/compiler-rt/armv6-mcr-dmb.patch
new file mode 100644
index 00000000000..acdcc9e983b
--- /dev/null
+++ b/pkgs/development/compilers/llvm/common/compiler-rt/armv6-mcr-dmb.patch
@@ -0,0 +1,75 @@
+From a11d1cc41c725ec6dee58f75e4a852a658dd7543 Mon Sep 17 00:00:00 2001
+From: Khem Raj <raj.khem@gmail.com>
+Date: Thu, 10 Mar 2022 19:30:00 -0800
+Subject: [PATCH] [builtins] Use mcr for dmb instruction on armv6
+
+At present compiler-rt cross compiles for armv6 ( -march=armv6 ) but includes
+dmb instructions which are only available in armv7+ this causes SIGILL on
+clang+compiler-rt compiled components on rpi0w platforms.
+
+Reviewed By: MaskRay
+
+Differential Revision: https://reviews.llvm.org/D99282
+---
+ compiler-rt/lib/builtins/arm/sync-ops.h | 8 ++++----
+ compiler-rt/lib/builtins/assembly.h     | 8 ++++++++
+ 2 files changed, 12 insertions(+), 4 deletions(-)
+
+diff --git a/lib/builtins/arm/sync-ops.h b/lib/builtins/arm/sync-ops.h
+index c9623249e5d20..7a26170741ad2 100644
+--- a/lib/builtins/arm/sync-ops.h
++++ b/lib/builtins/arm/sync-ops.h
+@@ -19,14 +19,14 @@
+   .thumb;                                                                      \
+   .syntax unified;                                                             \
+   DEFINE_COMPILERRT_THUMB_FUNCTION(__sync_fetch_and_##op)                      \
+-  dmb;                                                                         \
++  DMB;                                                                         \
+   mov r12, r0;                                                                 \
+   LOCAL_LABEL(tryatomic_##op) : ldrex r0, [r12];                               \
+   op(r2, r0, r1);                                                              \
+   strex r3, r2, [r12];                                                         \
+   cmp r3, #0;                                                                  \
+   bne LOCAL_LABEL(tryatomic_##op);                                             \
+-  dmb;                                                                         \
++  DMB;                                                                         \
+   bx lr
+ 
+ #define SYNC_OP_8(op)                                                          \
+@@ -35,14 +35,14 @@
+   .syntax unified;                                                             \
+   DEFINE_COMPILERRT_THUMB_FUNCTION(__sync_fetch_and_##op)                      \
+   push {r4, r5, r6, lr};                                                       \
+-  dmb;                                                                         \
++  DMB;                                                                         \
+   mov r12, r0;                                                                 \
+   LOCAL_LABEL(tryatomic_##op) : ldrexd r0, r1, [r12];                          \
+   op(r4, r5, r0, r1, r2, r3);                                                  \
+   strexd r6, r4, r5, [r12];                                                    \
+   cmp r6, #0;                                                                  \
+   bne LOCAL_LABEL(tryatomic_##op);                                             \
+-  dmb;                                                                         \
++  DMB;                                                                         \
+   pop { r4, r5, r6, pc }
+ 
+ #define MINMAX_4(rD, rN, rM, cmp_kind)                                         \
+diff --git a/lib/builtins/assembly.h b/lib/builtins/assembly.h
+index 69a3d8620f924..06aa18162e3b4 100644
+--- a/lib/builtins/assembly.h
++++ b/lib/builtins/assembly.h
+@@ -189,6 +189,14 @@
+   JMP(ip)
+ #endif
+ 
++#if __ARM_ARCH >= 7
++#define DMB dmb
++#elif __ARM_ARCH >= 6
++#define DMB mcr p15, #0, r0, c7, c10, #5
++#else
++#error only supported on ARMv6+
++#endif
++
+ #if defined(USE_THUMB_2)
+ #define WIDE(op) op.w
+ #else
+
diff --git a/pkgs/development/compilers/llvm/common/compiler-rt/armv6-no-ldrexd-strexd.patch b/pkgs/development/compilers/llvm/common/compiler-rt/armv6-no-ldrexd-strexd.patch
new file mode 100644
index 00000000000..2537ae1fae1
--- /dev/null
+++ b/pkgs/development/compilers/llvm/common/compiler-rt/armv6-no-ldrexd-strexd.patch
@@ -0,0 +1,162 @@
+From 4fe3f21bf8b20c766877d2251d61118d0ff36688 Mon Sep 17 00:00:00 2001
+From: Ben Wolsieffer <benwolsieffer@gmail.com>
+Date: Wed, 7 Dec 2022 14:56:51 -0500
+Subject: [PATCH] [compiler-rt][builtins] Do not use ldrexd or strexd on ARMv6
+
+The ldrexd and strexd instructions are not available on base ARMv6, and were
+only added in ARMv6K (see [1]). This patch solves this problem once and for all
+using the __ARM_FEATURE_LDREX macro (see [2]) defined in the ARM C Language
+Extensions (ACLE). Although this macro is technically deprecated in the ACLE,
+it allows compiler-rt to reliably detect whether ldrexd and strexd are supported
+without complicated conditionals to detect different ARM architecture variants.
+
+[1] https://developer.arm.com/documentation/dht0008/a/ch01s02s01
+[2] https://arm-software.github.io/acle/main/acle.html#ldrexstrex
+
+Differential Revision: https://reviews.llvm.org/D139585
+---
+ compiler-rt/lib/builtins/arm/sync_fetch_and_add_8.S  | 2 +-
+ compiler-rt/lib/builtins/arm/sync_fetch_and_and_8.S  | 2 +-
+ compiler-rt/lib/builtins/arm/sync_fetch_and_max_8.S  | 2 +-
+ compiler-rt/lib/builtins/arm/sync_fetch_and_min_8.S  | 2 +-
+ compiler-rt/lib/builtins/arm/sync_fetch_and_nand_8.S | 2 +-
+ compiler-rt/lib/builtins/arm/sync_fetch_and_or_8.S   | 2 +-
+ compiler-rt/lib/builtins/arm/sync_fetch_and_sub_8.S  | 2 +-
+ compiler-rt/lib/builtins/arm/sync_fetch_and_umax_8.S | 2 +-
+ compiler-rt/lib/builtins/arm/sync_fetch_and_umin_8.S | 2 +-
+ compiler-rt/lib/builtins/arm/sync_fetch_and_xor_8.S  | 2 +-
+ 10 files changed, 10 insertions(+), 10 deletions(-)
+
+diff --git a/lib/builtins/arm/sync_fetch_and_add_8.S b/lib/builtins/arm/sync_fetch_and_add_8.S
+index 18bdd875b8b7..bee6f7ba0f34 100644
+--- a/lib/builtins/arm/sync_fetch_and_add_8.S
++++ b/lib/builtins/arm/sync_fetch_and_add_8.S
+@@ -13,7 +13,7 @@
+ 
+ #include "sync-ops.h"
+ 
+-#if __ARM_ARCH_PROFILE != 'M'
++#if __ARM_FEATURE_LDREX & 8
+ #define add_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI) \
+     adds rD_LO, rN_LO, rM_LO ; \
+     adc rD_HI, rN_HI, rM_HI
+diff --git a/lib/builtins/arm/sync_fetch_and_and_8.S b/lib/builtins/arm/sync_fetch_and_and_8.S
+index 3716eff809d5..b4e77a54edf6 100644
+--- a/lib/builtins/arm/sync_fetch_and_and_8.S
++++ b/lib/builtins/arm/sync_fetch_and_and_8.S
+@@ -13,7 +13,7 @@
+ 
+ #include "sync-ops.h"
+ 
+-#if __ARM_ARCH_PROFILE != 'M'
++#if __ARM_FEATURE_LDREX & 8
+ #define and_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI) \
+     and rD_LO, rN_LO, rM_LO ; \
+     and rD_HI, rN_HI, rM_HI
+diff --git a/lib/builtins/arm/sync_fetch_and_max_8.S b/lib/builtins/arm/sync_fetch_and_max_8.S
+index 06115ab55246..1813274cc649 100644
+--- a/lib/builtins/arm/sync_fetch_and_max_8.S
++++ b/lib/builtins/arm/sync_fetch_and_max_8.S
+@@ -13,7 +13,7 @@
+ 
+ #include "sync-ops.h"
+ 
+-#if __ARM_ARCH_PROFILE != 'M'
++#if __ARM_FEATURE_LDREX & 8
+ #define max_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI)         MINMAX_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI, gt)
+ 
+ SYNC_OP_8(max_8)
+diff --git a/lib/builtins/arm/sync_fetch_and_min_8.S b/lib/builtins/arm/sync_fetch_and_min_8.S
+index 4f3e299d95cc..fa8f3477757b 100644
+--- a/lib/builtins/arm/sync_fetch_and_min_8.S
++++ b/lib/builtins/arm/sync_fetch_and_min_8.S
+@@ -13,7 +13,7 @@
+ 
+ #include "sync-ops.h"
+ 
+-#if __ARM_ARCH_PROFILE != 'M'
++#if __ARM_FEATURE_LDREX & 8
+ #define min_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI)         MINMAX_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI, lt)
+ 
+ SYNC_OP_8(min_8)
+diff --git a/lib/builtins/arm/sync_fetch_and_nand_8.S b/lib/builtins/arm/sync_fetch_and_nand_8.S
+index 425c94474af7..fb27219ee200 100644
+--- a/lib/builtins/arm/sync_fetch_and_nand_8.S
++++ b/lib/builtins/arm/sync_fetch_and_nand_8.S
+@@ -13,7 +13,7 @@
+ 
+ #include "sync-ops.h"
+ 
+-#if __ARM_ARCH_PROFILE != 'M'
++#if __ARM_FEATURE_LDREX & 8
+ #define nand_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI) \
+     bic rD_LO, rN_LO, rM_LO ; \
+     bic rD_HI, rN_HI, rM_HI
+diff --git a/lib/builtins/arm/sync_fetch_and_or_8.S b/lib/builtins/arm/sync_fetch_and_or_8.S
+index 4f18dcf84df9..3b077c8737b1 100644
+--- a/lib/builtins/arm/sync_fetch_and_or_8.S
++++ b/lib/builtins/arm/sync_fetch_and_or_8.S
+@@ -13,7 +13,7 @@
+ 
+ #include "sync-ops.h"
+ 
+-#if __ARM_ARCH_PROFILE != 'M'
++#if __ARM_FEATURE_LDREX & 8
+ #define or_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI) \
+     orr rD_LO, rN_LO, rM_LO ; \
+     orr rD_HI, rN_HI, rM_HI
+diff --git a/lib/builtins/arm/sync_fetch_and_sub_8.S b/lib/builtins/arm/sync_fetch_and_sub_8.S
+index 25a4a1076555..c171607eabd8 100644
+--- a/lib/builtins/arm/sync_fetch_and_sub_8.S
++++ b/lib/builtins/arm/sync_fetch_and_sub_8.S
+@@ -13,7 +13,7 @@
+ 
+ #include "sync-ops.h"
+ 
+-#if __ARM_ARCH_PROFILE != 'M'
++#if __ARM_FEATURE_LDREX & 8
+ #define sub_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI) \
+     subs rD_LO, rN_LO, rM_LO ; \
+     sbc rD_HI, rN_HI, rM_HI
+diff --git a/lib/builtins/arm/sync_fetch_and_umax_8.S b/lib/builtins/arm/sync_fetch_and_umax_8.S
+index aa5213ff1def..d1224f758049 100644
+--- a/lib/builtins/arm/sync_fetch_and_umax_8.S
++++ b/lib/builtins/arm/sync_fetch_and_umax_8.S
+@@ -13,7 +13,7 @@
+ 
+ #include "sync-ops.h"
+ 
+-#if __ARM_ARCH_PROFILE != 'M'
++#if __ARM_FEATURE_LDREX & 8
+ #define umax_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI)         MINMAX_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI, hi)
+ 
+ SYNC_OP_8(umax_8)
+diff --git a/lib/builtins/arm/sync_fetch_and_umin_8.S b/lib/builtins/arm/sync_fetch_and_umin_8.S
+index 8b40541ab47d..595444e6d053 100644
+--- a/lib/builtins/arm/sync_fetch_and_umin_8.S
++++ b/lib/builtins/arm/sync_fetch_and_umin_8.S
+@@ -13,7 +13,7 @@
+ 
+ #include "sync-ops.h"
+ 
+-#if __ARM_ARCH_PROFILE != 'M'
++#if __ARM_FEATURE_LDREX & 8
+ #define umin_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI)         MINMAX_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI, lo)
+ 
+ SYNC_OP_8(umin_8)
+diff --git a/lib/builtins/arm/sync_fetch_and_xor_8.S b/lib/builtins/arm/sync_fetch_and_xor_8.S
+index 7436eb1d4cae..9fc3d85cef75 100644
+--- a/lib/builtins/arm/sync_fetch_and_xor_8.S
++++ b/lib/builtins/arm/sync_fetch_and_xor_8.S
+@@ -13,7 +13,7 @@
+ 
+ #include "sync-ops.h"
+ 
+-#if __ARM_ARCH_PROFILE != 'M'
++#if __ARM_FEATURE_LDREX & 8
+ #define xor_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI) \
+     eor rD_LO, rN_LO, rM_LO ; \
+     eor rD_HI, rN_HI, rM_HI
+-- 
+2.38.1
+
diff --git a/pkgs/development/compilers/llvm/common/compiler-rt/armv6-scudo-libatomic.patch b/pkgs/development/compilers/llvm/common/compiler-rt/armv6-scudo-libatomic.patch
new file mode 100644
index 00000000000..13b67eb2a41
--- /dev/null
+++ b/pkgs/development/compilers/llvm/common/compiler-rt/armv6-scudo-libatomic.patch
@@ -0,0 +1,65 @@
+From a56bb19a9dc303a50ef12d83cd24c2395bf81076 Mon Sep 17 00:00:00 2001
+From: Ben Wolsieffer <benwolsieffer@gmail.com>
+Date: Wed, 7 Dec 2022 21:25:46 -0500
+Subject: [PATCH] [scudo][standalone] Use CheckAtomic to decide to link to
+ libatomic
+
+Standalone scudo uses the atomic operation builtin functions, which require
+linking to libatomic on some platforms. Currently, this is done in an ad-hoc
+manner. MIPS platforms always link to libatomic, and the tests are always linked
+to it as well. libatomic is required on base ARMv6 (but not ARMv6K), but it is
+currently not linked, causing the build to fail.
+
+This patch replaces this ad-hoc logic with the CheckAtomic CMake module already
+used in other parts of LLVM. The CheckAtomic module checks whether std::atomic
+requires libatomic, which is not strictly the same as checking the atomic
+builtins, but should have the same results as far as I know. If this is
+problematic, a custom version of CheckAtomic could be used to specifically test
+the builtins.
+---
+ compiler-rt/lib/scudo/standalone/CMakeLists.txt       | 7 +++++++
+ compiler-rt/lib/scudo/standalone/tests/CMakeLists.txt | 4 +---
+ 2 files changed, 8 insertions(+), 3 deletions(-)
+
+diff --git a/lib/scudo/standalone/CMakeLists.txt b/lib/scudo/standalone/CMakeLists.txt
+index ae5c354768c8..eb27374ca520 100644
+--- a/lib/scudo/standalone/CMakeLists.txt
++++ b/lib/scudo/standalone/CMakeLists.txt
+@@ -1,5 +1,8 @@
+ add_compiler_rt_component(scudo_standalone)
+ 
++include(DetermineGCCCompatible)
++include(CheckAtomic)
++
+ include_directories(../.. include)
+ 
+ set(SCUDO_CFLAGS)
+@@ -34,6 +37,10 @@ list(APPEND SCUDO_LINK_FLAGS -Wl,-z,defs,-z,now,-z,relro)
+ 
+ list(APPEND SCUDO_LINK_FLAGS -ffunction-sections -fdata-sections -Wl,--gc-sections)
+ 
++if(HAVE_CXX_ATOMICS_WITH_LIB OR HAVE_CXX_ATOMICS64_WITH_LIB)
++  list(APPEND SCUDO_LINK_FLAGS -latomic)
++endif()
++
+ # We don't use the C++ standard library, so avoid including it by mistake.
+ append_list_if(COMPILER_RT_HAS_NOSTDLIBXX_FLAG -nostdlib++ SCUDO_LINK_FLAGS)
+ 
+diff --git a/lib/scudo/standalone/tests/CMakeLists.txt b/lib/scudo/standalone/tests/CMakeLists.txt
+index 6d0936cbb5c1..70a5a7e959c1 100644
+--- a/lib/scudo/standalone/tests/CMakeLists.txt
++++ b/lib/scudo/standalone/tests/CMakeLists.txt
+@@ -38,9 +38,7 @@ set(LINK_FLAGS
+   ${SANITIZER_TEST_CXX_LIBRARIES}
+   )
+ list(APPEND LINK_FLAGS -pthread)
+-# Linking against libatomic is required with some compilers
+-check_library_exists(atomic __atomic_load_8 "" COMPILER_RT_HAS_LIBATOMIC)
+-if (COMPILER_RT_HAS_LIBATOMIC)
++if(HAVE_CXX_ATOMICS_WITH_LIB OR HAVE_CXX_ATOMICS64_WITH_LIB)
+   list(APPEND LINK_FLAGS -latomic)
+ endif()
+ 
+-- 
+2.38.1
+
diff --git a/pkgs/development/compilers/llvm/common/compiler-rt/armv6-scudo-no-yield.patch b/pkgs/development/compilers/llvm/common/compiler-rt/armv6-scudo-no-yield.patch
new file mode 100644
index 00000000000..2fd48eda651
--- /dev/null
+++ b/pkgs/development/compilers/llvm/common/compiler-rt/armv6-scudo-no-yield.patch
@@ -0,0 +1,34 @@
+From ff0b373b959165477f45d9f5f9a8da471ae111ab Mon Sep 17 00:00:00 2001
+From: Ben Wolsieffer <benwolsieffer@gmail.com>
+Date: Wed, 7 Dec 2022 18:03:56 -0500
+Subject: [PATCH] [scudo][standalone] Only use yield on ARMv6K and newer
+
+The yield instruction is only available in ARMv6K and newer. It behaves as a
+nop on single threaded platforms anyway, so use nop instead on unsupported
+architectures.
+
+Differential Revision: https://reviews.llvm.org/D139600
+---
+ compiler-rt/lib/scudo/standalone/common.h | 5 +++++
+ 1 file changed, 5 insertions(+)
+
+diff --git a/lib/scudo/standalone/common.h b/lib/scudo/standalone/common.h
+index bc3dfec6dbba..862cda1d4bc4 100644
+--- a/lib/scudo/standalone/common.h
++++ b/lib/scudo/standalone/common.h
+@@ -109,7 +109,12 @@ inline void yieldProcessor(u8 Count) {
+ #elif defined(__aarch64__) || defined(__arm__)
+   __asm__ __volatile__("" ::: "memory");
+   for (u8 I = 0; I < Count; I++)
++#if __ARM_ARCH >= 6 && !defined(__ARM_ARCH_6__)
++    // yield is supported on ARMv6K and newer
+     __asm__ __volatile__("yield");
++#else
++    __asm__ __volatile__("nop");
++#endif
+ #endif
+   __asm__ __volatile__("" ::: "memory");
+ }
+-- 
+2.38.1
+
diff --git a/pkgs/development/compilers/llvm/common/compiler-rt/armv6-sync-ops-no-thumb.patch b/pkgs/development/compilers/llvm/common/compiler-rt/armv6-sync-ops-no-thumb.patch
new file mode 100644
index 00000000000..098a155d448
--- /dev/null
+++ b/pkgs/development/compilers/llvm/common/compiler-rt/armv6-sync-ops-no-thumb.patch
@@ -0,0 +1,52 @@
+From 5017de8ba4b1fe985169cf54590e858a9019a91f Mon Sep 17 00:00:00 2001
+From: Khem Raj <raj.khem@gmail.com>
+Date: Fri, 11 Mar 2022 16:25:49 -0800
+Subject: [PATCH] [builtins] Do not force thumb mode directive in
+ arm/sync-ops.h
+
+.thumb_func was not switching mode until [1]
+so it did not show up but now that .thumb_func (without argument) is
+switching mode, its causing build failures on armv6 ( rpi0 ) even when
+build is explicitly asking for this file to be built with -marm (ARM
+mode), therefore use DEFINE_COMPILERRT_FUNCTION macro to add function
+header which considers arch and mode from compiler cmdline to decide if
+the function is built using thumb mode or arm mode.
+
+[1] https://reviews.llvm.org/D101975
+
+Note that it also needs https://reviews.llvm.org/D99282
+
+Reviewed By: peter.smith, MaskRay
+
+Differential Revision: https://reviews.llvm.org/D104183
+---
+ compiler-rt/lib/builtins/arm/sync-ops.h | 6 ++----
+ 1 file changed, 2 insertions(+), 4 deletions(-)
+
+diff --git a/lib/builtins/arm/sync-ops.h b/lib/builtins/arm/sync-ops.h
+index 7a26170741ad2..d914f9d3a1093 100644
+--- a/lib/builtins/arm/sync-ops.h
++++ b/lib/builtins/arm/sync-ops.h
+@@ -16,9 +16,8 @@
+ 
+ #define SYNC_OP_4(op)                                                          \
+   .p2align 2;                                                                  \
+-  .thumb;                                                                      \
+   .syntax unified;                                                             \
+-  DEFINE_COMPILERRT_THUMB_FUNCTION(__sync_fetch_and_##op)                      \
++  DEFINE_COMPILERRT_FUNCTION(__sync_fetch_and_##op)                            \
+   DMB;                                                                         \
+   mov r12, r0;                                                                 \
+   LOCAL_LABEL(tryatomic_##op) : ldrex r0, [r12];                               \
+@@ -31,9 +30,8 @@
+ 
+ #define SYNC_OP_8(op)                                                          \
+   .p2align 2;                                                                  \
+-  .thumb;                                                                      \
+   .syntax unified;                                                             \
+-  DEFINE_COMPILERRT_THUMB_FUNCTION(__sync_fetch_and_##op)                      \
++  DEFINE_COMPILERRT_FUNCTION(__sync_fetch_and_##op)                            \
+   push {r4, r5, r6, lr};                                                       \
+   DMB;                                                                         \
+   mov r12, r0;                                                                 \
+
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index ba48c480a54..6cf32a80561 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -15348,7 +15348,6 @@ with pkgs;
       /**/ if platform.isDarwin then 11
       else if platform.isFreeBSD then 12
       else if platform.isAndroid then 12
-      else if platform.system == "armv6l-linux" then 7  # This fixes armv6 cross-compilation
       else if platform.isLinux then 11
       else if platform.isWasm then 12
       else latest_version;