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riscv: replace use of callee-saved register in standalone

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Register x19 (s3) is a callee-saved register. It must not be used to
load and jump to exported functions without saving it beforehand.
Replace it with t0, a temporary and caller-saved register.

Change the code comment to reflect this and fix it to correctly list gp
as the register with the pointer to global data.

Signed-off-by: Lukas Auer <lukas.auer@aisec.fraunhofer.de>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Tested-by: Bin Meng <bmeng.cn@gmail.com>
This commit is contained in:
Lukas Auer 2019-01-04 01:37:32 +01:00 committed by Andes
parent 3c37278ff1
commit cbb860f2c8
1 changed files with 5 additions and 5 deletions
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10
examples/standalone/stubs.c
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@ -174,16 +174,16 @@ gd_t *global_data;
: : "i"(offsetof(gd_t, jt)), "i"(FO(x)) : "$r16");
#elif defined(CONFIG_RISCV)
/*
* t7 holds the pointer to the global_data. gp is call clobbered.
* gp holds the pointer to the global_data. t0 is call clobbered.
*/
#define EXPORT_FUNC(f, a, x, ...) \
asm volatile ( \
" .globl " #x "\n" \
#x ":\n" \
" lw x19, %0(gp)\n" \
" lw x19, %1(x19)\n" \
" jr x19\n" \
: : "i"(offsetof(gd_t, jt)), "i"(FO(x)) : "x19");
" lw t0, %0(gp)\n" \
" lw t0, %1(t0)\n" \
" jr t0\n" \
: : "i"(offsetof(gd_t, jt)), "i"(FO(x)) : "t0");
#elif defined(CONFIG_ARC)
/*
* r25 holds the pointer to the global_data. r10 is call clobbered.