From 45116f342057b7facecd3d05c2091ce3a77eda59 Mon Sep 17 00:00:00 2001

From: Nelson Chu <nelson.chu@sifive.com>

Date: Mon, 29 Nov 2021 04:48:20 -0800

Subject: [PATCH] RISC-V: jal cannot refer to a default visibility symbol for

shared object.

This is the original binutils bugzilla report,

https://sourceware.org/bugzilla/show_bug.cgi?id=28509

And this is the first version of the proposed binutils patch,

https://sourceware.org/pipermail/binutils/2021-November/118398.html

After applying the binutils patch, I get the the unexpected error when

building libgcc,

/scratch/nelsonc/riscv-gnu-toolchain/riscv-gcc/libgcc/config/riscv/div.S:42:

/scratch/nelsonc/build-upstream/rv64gc-linux/build-install/riscv64-unknown-linux-gnu/bin/ld: relocation R_RISCV_JAL against `__udivdi3' which may bind externally can not be used when making a shared object; recompile with -fPIC

Therefore, this patch add an extra hidden alias symbol for __udivdi3, and

then use HIDDEN_JUMPTARGET to target a non-preemptible symbol instead.

The solution is similar to glibc as follows,

https://sourceware.org/git/?p=glibc.git;a=commit;h=68389203832ab39dd0dbaabbc4059e7fff51c29b

libgcc/ChangeLog:

* config/riscv/div.S: Add the hidden alias symbol for __udivdi3, and

then use HIDDEN_JUMPTARGET to target it since it is non-preemptible.

* config/riscv/riscv-asm.h: Added new macros HIDDEN_JUMPTARGET and

HIDDEN_DEF.

---

libgcc/config/riscv/div.S | 15 ++++++++-------

libgcc/config/riscv/riscv-asm.h | 6 ++++++

2 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/libgcc/config/riscv/div.S b/libgcc/config/riscv/div.S

index c9bd7879c1e36..723c3b82e48c6 100644

--- a/libgcc/config/riscv/div.S

+++ b/libgcc/config/riscv/div.S

@@ -40,7 +40,7 @@ FUNC_BEGIN (__udivsi3)

sll a0, a0, 32

sll a1, a1, 32

move t0, ra

- jal __udivdi3

+ jal HIDDEN_JUMPTARGET(__udivdi3)

sext.w a0, a0

jr t0

FUNC_END (__udivsi3)

@@ -52,7 +52,7 @@ FUNC_BEGIN (__umodsi3)

srl a0, a0, 32

srl a1, a1, 32

move t0, ra

- jal __udivdi3

+ jal HIDDEN_JUMPTARGET(__udivdi3)

sext.w a0, a1

jr t0

FUNC_END (__umodsi3)

@@ -95,11 +95,12 @@ FUNC_BEGIN (__udivdi3)

.L5:

ret

FUNC_END (__udivdi3)

+HIDDEN_DEF (__udivdi3)

FUNC_BEGIN (__umoddi3)

/* Call __udivdi3(a0, a1), then return the remainder, which is in a1. */

move t0, ra

- jal __udivdi3

+ jal HIDDEN_JUMPTARGET(__udivdi3)

move a0, a1

jr t0

FUNC_END (__umoddi3)

@@ -111,12 +112,12 @@ FUNC_END (__umoddi3)

bgtz a1, .L12 /* Compute __udivdi3(-a0, a1), then negate the result. */

neg a1, a1

- j __udivdi3 /* Compute __udivdi3(-a0, -a1). */

+ j HIDDEN_JUMPTARGET(__udivdi3) /* Compute __udivdi3(-a0, -a1). */

.L11: /* Compute __udivdi3(a0, -a1), then negate the result. */

neg a1, a1

.L12:

move t0, ra

- jal __udivdi3

+ jal HIDDEN_JUMPTARGET(__udivdi3)

neg a0, a0

jr t0

FUNC_END (__divdi3)

@@ -126,7 +127,7 @@ FUNC_BEGIN (__moddi3)

bltz a1, .L31

bltz a0, .L32

.L30:

- jal __udivdi3 /* The dividend is not negative. */

+ jal HIDDEN_JUMPTARGET(__udivdi3) /* The dividend is not negative. */

move a0, a1

jr t0

.L31:

@@ -134,7 +135,7 @@ FUNC_BEGIN (__moddi3)

bgez a0, .L30

.L32:

neg a0, a0

- jal __udivdi3 /* The dividend is hella negative. */

+ jal HIDDEN_JUMPTARGET(__udivdi3) /* The dividend is hella negative. */

neg a0, a1

jr t0

FUNC_END (__moddi3)

diff --git a/libgcc/config/riscv/riscv-asm.h b/libgcc/config/riscv/riscv-asm.h

index 8550707a4a26a..96dd85b0df2e5 100644

--- a/libgcc/config/riscv/riscv-asm.h

+++ b/libgcc/config/riscv/riscv-asm.h

@@ -33,3 +33,9 @@ see the files COPYING3 and COPYING.RUNTIME respectively. If not, see

#define FUNC_ALIAS(X,Y) \

.globl X; \

X = Y

+

+#define CONCAT1(a, b) CONCAT2(a, b)

+#define CONCAT2(a, b) a ## b

+#define HIDDEN_JUMPTARGET(X) CONCAT1(__hidden_, X)

+#define HIDDEN_DEF(X) FUNC_ALIAS(HIDDEN_JUMPTARGET(X), X); \

+ .hidden HIDDEN_JUMPTARGET(X)