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RISC-V: preserve a1 in mcount 

The RISC-V ELF psABI states that both a0 and a1 are used for return
values so we should preserve them both in return_to_handler.  This is
especially important for RV32 for functions returning a 64-bit quantity
otherwise the return value can be corrupted and undefined behaviour
results.

Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Signed-off-by: Jamie Iles <jamie@jamieiles.com>
Link: https://lore.kernel.org/r/20221115200832.706370-4-jamie@jamieiles.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
This commit is contained in:
Jamie Iles 2022-11-15 20:08:31 +00:00 committed by Palmer Dabbelt
parent 3bd7743f8d
commit dc58a24db8
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1 changed files with 4 additions and 2 deletions
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6
arch/riscv/kernel/mcount.S
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@ -29,6 +29,7 @@
REG_S s0, 2*SZREG(sp)
REG_S ra, 3*SZREG(sp)
REG_S a0, 1*SZREG(sp)
REG_S a1, 0*SZREG(sp)
addi s0, sp, 4*SZREG
.endm
@ -42,6 +43,7 @@
REG_L ra, 3*SZREG(sp)
REG_L s0, 2*SZREG(sp)
REG_L a0, 1*SZREG(sp)
REG_L a1, 0*SZREG(sp)
addi sp, sp, 4*SZREG
.endm
@ -71,9 +73,9 @@ ENTRY(return_to_handler)
mv a0, t6
#endif
call ftrace_return_to_handler
mv a1, a0
mv a2, a0
RESTORE_RET_ABI_STATE
jalr a1
jalr a2
ENDPROC(return_to_handler)
#endif