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.
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)
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)
.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)
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)
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:
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)
#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)