[glibc/release/2.34/master] riscv: align stack before calling _dl_init [BZ #28703]

[Aurelien Jarno]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=aa3a97496c82a8443039248ebee650322c9480f4

commit aa3a97496c82a8443039248ebee650322c9480f4
Author: Aurelien Jarno <aurelien@aurel32.net>
Date:   Thu Dec 16 00:06:28 2021 +0100

    riscv: align stack before calling _dl_init [BZ #28703]
    
    Align the stack pointer to 128 bits during the call to _dl_init() as
    specified by the RISC-V ABI [1]. This fixes the elf/tst-align2 test.
    
    Fixes bug 28703.
    
    [1] https://github.com/riscv-non-isa/riscv-elf-psabi-doc
    
    (cherry picked from commit 225da459cebef1037dcd78b56471edc0721e1c41)

Diff:
---
 NEWS                       | 1 +
 sysdeps/riscv/dl-machine.h | 6 ++++++
 2 files changed, 7 insertions(+)

diff --git a/NEWS b/NEWS
index 873491df1f..d9b344027b 100644
--- a/NEWS
+++ b/NEWS
@@ -25,6 +25,7 @@ The following bugs are resolved with this release:
   [28678] nptl/tst-create1 hangs sporadically
   [28700] "dns [!UNAVAIL=return] files" NSS default for hosts is not useful
   [28702] RISC-V: clone does not align stack
+  [28703] RISC-V: _dl_init might be called with unaligned stack
   [28704] elf/tst-cpu-features-cpuinfo fails for KVM guests on some AMD systems
 
 
diff --git a/sysdeps/riscv/dl-machine.h b/sysdeps/riscv/dl-machine.h
index aedf69fcdd..951268923d 100644
--- a/sysdeps/riscv/dl-machine.h
+++ b/sysdeps/riscv/dl-machine.h
@@ -127,8 +127,14 @@ elf_machine_load_address (void)
 	sll a3, a1, " STRINGXP (PTRLOG) "\n\
 	add a3, a3, a2\n\
 	add a3, a3, " STRINGXP (SZREG) "\n\
+	# Stash the stack pointer in s1.\n\
+	mv s1, sp\n\
+	# Align stack to 128 bits for the _dl_init call.\n\
+	andi sp, sp,-16\n\
 	# Call the function to run the initializers.\n\
 	jal _dl_init\n\
+	# Restore the stack pointer for _start.\n\
+	mv sp, s1\n\
 	# Pass our finalizer function to _start.\n\
 	lla a0, _dl_fini\n\
 	# Jump to the user entry point.\n\