Fix overwriting first byte in THR register during send #8
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commit 0afbb0e |
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Is this commit from u-boot mainline identical to your patch ? |
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I think so |
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Yes, it is identical. |
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Do you need that commit from mainline cherry-picked into our branch? Or any other reason ? |
ehristev
pushed a commit
that referenced
this pull request
Apr 5, 2021
Atish reports that on RISC-V, accessing the EFI variables causes
a kernel panic. An objdump of the file verifies that, since the
global pointer for efi_var_buf ends up in .GOT section which is
not mapped in virtual address space for Linux.
<snip of efi_var_mem_find>
0000000000000084 <efi_var_mem_find>:
84: 715d addi sp,sp,-80
* objdump -dr
0000000000000086 <.LCFI2>:
86: e0a2 sd s0,64(sp)
88: fc26 sd s1,56(sp)
8a: e486 sd ra,72(sp)
8c: f84a sd s2,48(sp)
8e: f44e sd s3,40(sp)
90: f052 sd s4,32(sp)
92: ec56 sd s5,24(sp)
94: 00000497 auipc s1,0x0
94: R_RISCV_GOT_HI20 efi_var_buf
98: 0004b483 ld s1,0(s1) # 94 <.LCFI2+0xe>
98: R_RISCV_PCREL_LO12_I .L0
98: R_RISCV_RELAX *ABS*
* objdump -t
0000000000000084 g F .text.efi_runtime 00000000000000b8 efi_var_mem_find
With the patch applied:
* objdump -dr
0000000000000086 <.LCFI2>:
86: e0a2 sd s0,64(sp)
88: fc26 sd s1,56(sp)
8a: e486 sd ra,72(sp)
8c: f84a sd s2,48(sp)
8e: f44e sd s3,40(sp)
90: f052 sd s4,32(sp)
92: ec56 sd s5,24(sp)
94: 00000497 auipc s1,0x0
94: R_RISCV_PCREL_HI20 .LANCHOR0
94: R_RISCV_RELAX *ABS*
98: 00048493 mv s1,s1
98: R_RISCV_PCREL_LO12_I .L0
98: R_RISCV_RELAX *ABS*
* objdump -t
0000000000000008 l O .data.efi_runtime 0000000000000008 efi_var_buf
On arm64 this works, because there's no .GOT entries for this
and everything is converted to relative references.
* objdump -dr (identical pre-post patch, only the new function shows up)
00000000000000b4 <efi_var_mem_find>:
b4: aa0003ee mov x14, x0
b8: 9000000a adrp x10, 0 <efi_var_mem_compare>
b8: R_AARCH64_ADR_PREL_PG_HI21 .data.efi_runtime
bc: 91000140 add x0, x10, #0x0
bc: R_AARCH64_ADD_ABS_LO12_NC .data.efi_runtime
c0: aa0103ed mov x13, x1
c4: 79400021 ldrh w1, [x1]
c8: aa0203eb mov x11, x2
cc: f9400400 ldr x0, [x0, #8]
d0: b940100c ldr w12, [x0, #16]
d4: 8b0c000c add x12, x0, x12
So let's switch efi_var_buf to static and create a helper function for
anyone that needs to update it.
Fixes: e01aed4 ("efi_loader: Enable run-time variable support for tee based variables")
Reported-by: Atish Patra <[email protected]>
Tested-by: Atish Patra <[email protected]>
Signed-off-by: Ilias Apalodimas <[email protected]>
Reviewed-by: Heinrich Schuchardt <[email protected]>
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During send on TWI the first byte is lost because there is not TWI_SR_TXRDY check and THR register is immediately overwritten.