FreeCalypso > hg > freecalypso-sw

annotate toolchain/binutils-patches/elf32-arm.patch @ 992:a7b0b426f9ca

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target-utils: boot ROM UART autodetection revamped The new implementation should work with both the familiar Calypso C035 boot ROM version found in our regular targets as well as the older Calypso F741979B version found on the vintage D-Sample board.
author Mychaela Falconia <falcon@ivan.Harhan.ORG>
date Wed, 30 Dec 2015 21:28:41 +0000
parents ebe258a85813
children
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
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ebe258a85813 toolchain: binutils patch to emit the "short" form of Thumb->ARM call veneers
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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1 # The present patch to the ARM ELF linking code in binutils (made against
ebe258a85813 toolchain: binutils patch to emit the "short" form of Thumb->ARM call veneers
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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2 # binutils-2.21.1a) is a hack that affects the generation of Thumb->ARM
ebe258a85813 toolchain: binutils patch to emit the "short" form of Thumb->ARM call veneers
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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3 # call veneers. The binutils linker can make these veneers in two forms:
ebe258a85813 toolchain: binutils patch to emit the "short" form of Thumb->ARM call veneers
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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4 #
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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5 # "Short" "Long"
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6 # (16-bit) bx pc (16-bit) bx pc
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7 # (16-bit) nop (16-bit) nop
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8 # (32-bit) b dest (32-bit) ldr pc, [pc, #-4]
ebe258a85813 toolchain: binutils patch to emit the "short" form of Thumb->ARM call veneers
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9 # (32-bit) .long target
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10 #
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11 # For code that's going to run on the Calypso ARM7 processor, the
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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12 # "short" form is the one we want: because of the way the address space
ebe258a85813 toolchain: binutils patch to emit the "short" form of Thumb->ARM call veneers
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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13 # is laid out, the range of an ARM branch instruction will always be
ebe258a85813 toolchain: binutils patch to emit the "short" form of Thumb->ARM call veneers
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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14 # sufficient for us, whereas the long version is more costly in terms
ebe258a85813 toolchain: binutils patch to emit the "short" form of Thumb->ARM call veneers
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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15 # of the number of cycles required, especially when executing from
ebe258a85813 toolchain: binutils patch to emit the "short" form of Thumb->ARM call veneers
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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16 # external memory.
ebe258a85813 toolchain: binutils patch to emit the "short" form of Thumb->ARM call veneers
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17 #
ebe258a85813 toolchain: binutils patch to emit the "short" form of Thumb->ARM call veneers
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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18 # Unfortunately, the code which decides between these two forms
ebe258a85813 toolchain: binutils patch to emit the "short" form of Thumb->ARM call veneers
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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19 # (located in the arm_type_of_stub() function in bfd/elf32-arm.c)
ebe258a85813 toolchain: binutils patch to emit the "short" form of Thumb->ARM call veneers
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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20 # is broken. The original code (which you can see below in the
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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21 # "before" part of the patch hunk) exhibits two problems:
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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22 #
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23 # 1. The distance that matters here is not from the original
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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24 # call point to the destination, but from the stub to
ebe258a85813 toolchain: binutils patch to emit the "short" form of Thumb->ARM call veneers
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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25 # the destination - and in this function we don't know
ebe258a85813 toolchain: binutils patch to emit the "short" form of Thumb->ARM call veneers
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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26 # where the stub will end up.
ebe258a85813 toolchain: binutils patch to emit the "short" form of Thumb->ARM call veneers
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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27 #
ebe258a85813 toolchain: binutils patch to emit the "short" form of Thumb->ARM call veneers
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28 # 2. Because it's an ARM branch, the limits should be
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29 # ARM_MAX_[BF]WD_BRANCH_OFFSET, not the THM_ ones.
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30 #
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31 # The 2nd problem would be trivial to fix, but the 1st one
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32 # much less so: this function doesn't know where the stub
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33 # will end up, and considering that for the present purpose
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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34 # of the FreeCalypso project always emitting the "short"
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35 # version would be perfect, there is no justification for
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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36 # expending the time and effort to restructure the linker
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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37 # to do the proper relaxation for the case at hand.
ebe258a85813 toolchain: binutils patch to emit the "short" form of Thumb->ARM call veneers
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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38 #
ebe258a85813 toolchain: binutils patch to emit the "short" form of Thumb->ARM call veneers
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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39 # Therefore, the patch we apply is a hack: we simply force the
ebe258a85813 toolchain: binutils patch to emit the "short" form of Thumb->ARM call veneers
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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40 # use of the "short" form unconditionally.
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41
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42 *** elf32-arm.c Wed May 11 07:29:12 2011
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43 --- elf32-arm-patched.c Mon Aug 19 03:24:38 2013
ebe258a85813 toolchain: binutils patch to emit the "short" form of Thumb->ARM call veneers
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44 ***************
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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45 *** 3203,3211 ****
ebe258a85813 toolchain: binutils patch to emit the "short" form of Thumb->ARM call veneers
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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46 : arm_stub_long_branch_v4t_thumb_arm);
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47
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48 /* Handle v4t short branches. */
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49 ! if ((stub_type == arm_stub_long_branch_v4t_thumb_arm)
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50 ! && (branch_offset <= THM_MAX_FWD_BRANCH_OFFSET)
ebe258a85813 toolchain: binutils patch to emit the "short" form of Thumb->ARM call veneers
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51 ! && (branch_offset >= THM_MAX_BWD_BRANCH_OFFSET))
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52 stub_type = arm_stub_short_branch_v4t_thumb_arm;
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53 }
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54 }
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55 --- 3203,3209 ----
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56 : arm_stub_long_branch_v4t_thumb_arm);
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57
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58 /* Handle v4t short branches. */
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59 ! if (stub_type == arm_stub_long_branch_v4t_thumb_arm)
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60 stub_type = arm_stub_short_branch_v4t_thumb_arm;
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61 }
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62 }